The
Science Notebook
Gilbert Chemistry - Part 8
NOTE: This book was published in 1936 as a manual
to accompany several Gilbert Chemistry sets of the time.
While some of the experiments and activities here
may be safely done as written, a number of them use chemicals
and methods no longer considered safe. In
addition, much of the information contained in this book about
chemistry and other subjects is outdated and inaccurate.
Therefore, this book is probably best appreciated for
its historical value rather than as a source for current
information and good experiments. If you try
anything here, please understand that you do so at
your own risk. See our Terms of Use.
Pages 141 - 160
GILBERT
CHEMISTRY 141
TESTING FOODS
TESTING FOR STARCH
EXPERIMENT 421 - How to make a
solution for testing starch
Put one-half measure of tartaric acid and one-half measure of
bleaching powder (calcium hypochlorite) in a test tube two-thirds
full of water Shake the contents of the tube until the solids
are dissolved. Then add 10 or 12 drops of sodium iodide solution and
shake again. Notice the brown solution which is formed.
This is free iodine in solution and was formed by the action of
chlorine gas on the sodium iodide solution. The chlorine gas
was liberated by the action of the tartaric acid on the bleaching
powder or calcium hypochlorite.
Save this solution and use it in the following experiments for
testing for starch in food and other substances.
EXPERIMENT 422 - Testing for starch
in rice
Put three or four grains of rice in a test tube half full of water
and boil the water for three or four minutes. Allow the test tube to
cool and then add one or two drops of the iodine solution prepared
in the preceding experiment. Notice the blue color which is
formed. This is the test for starch.
EXPERIMENT 423 - Testing for starch
in potatoes
Boil a small piece of potato about the size of a pea in a test tube
half full of water for three or four minutes. Allow the test tube to
cool, then add one or two drops of iodine solution. Notice the
formation of a blue color, showing that potatoes contain starch.
EXPERIMENT 424 - Testing for starch
in flour
Put one measure of flour in a test tube half full of water and boil
the solution for one or two minutes. Allow the solution to cool and
then add one or two drops of iodine solution. Notice the blue
color which is formed, showing that flour contains starch.
EXPERIMENT 425 - Testing for starch
in corn
Break one or two kernels of corn into small pieces and boil them in
a test tube half full of water for three or four minutes. Allow the
solution to cool and add one or two drops of iodine solution. Notice
the formation of a blue color, showing that corn also contains
starch.
EXPERIMENT 426 - Testing for starch
in apples
Green fruit contains starch, which is converted into sugar when the
fruit becomes ripe.
Satisfy yourself that this is true by boiling a small piece of a
green apple and of a ripe apple in separate test tubes half full of
water for one or two minutes and adding one or two drops of iodine
solution to the cool solutions. Notice that the blue color was
formed only in the case of the green apple, showing that starch is
present in green fruit.
142
GILBERT CHEMISTRY
THE FOOD CHEMIST
- JACK HORNER
"Little Jack Horner, he sat in a corner,
Eating a piece of Mother's Thanksgiving pie,
He stuck in his finger and pulled out a raisin
And applied Gilbert's iron test to satisfy his imagination."
EXPERIMENT 427-Testing a raisin for
iron
Select a raisin and wash it with water. Then incinerate the raisin
in a porcelain crucible by heating the crucible over your alcohol
lamp until the raisin is reduced to an ash. This ash contains only
inorganic matter. Digest the ash in diluted boiling
hydrochloric acid solution and filter. The insoluble residue
will be silica. The iron content of the ash will be dissolved,
forming iron chloride. Apply the characteristic test for iron
by adding some of the iron solution to the reagent sodium
thiocyanate. If iron is present red iron thiocyanate will be
formed. Also add some of the iron solution to a mixture of
potassium ferro- and potassium ferricyanide solutions. A blue
color will be formed if iron is present.
EXPERIMENT 428 - Testing raisin
seeds
Take a clean raisin and remove all of the seeds from the pulp. Then
incinerate the washed seeds, and the pulp separately in porcelain
crucibles. Test the ash in each crucible for iron. Which contains
the most iron, the seeds or the pulp?
EXPERIMENT 429 - Apple seeds
Apply the iron test to the ash of apple seeds.
EXPERIMENT 430 - Quince seeds
Apply the iron test to the ash of quince seeds.
EXPERIMENT 431 - Turnip seeds
Apply the iron test to the ash of turnip seeds.
EXPERIMENT 432 - Cabbage seeds
Apply the iron test to the ash of cabbage seeds.
EXPERIMENT 433 - Beans
Incinerate a bean after grinding to a powder and test the ash for
iron.
EXPERIMENT 434 - Sunflower seeds
Apply the iron test to the ash of sunflower seeds.
EXPERIMENT 435 - Lettuce seeds
Apply the iron test to the ash of lettuce seeds.
EXPERIMENT 436 - Wheat kernel
Apply the iron test to the ash of kernels of wheat.
EXPERIMENT 487 - "Tums for your
Tummy"
Procure in the drug store a small package of "Tums."
Incinerate one of the "tums" and test the ash for iron.
Dissolve some of the ash from "tums" in water and determine whether
the water solution is alkaline or acid by testing with
indicators. Test a "tum" for the presence of sugar.
EXPERIMENT 438 - Popcorn
Apply an iron test to the ash of incinerated popcorn.
GILBERT
CHEMISTRY 143
EXPERIMENT 439 - Popcorn balls
Pop some dry popcorn in a corn popper. Then separate some of
the white fluffy material and incinerate. Test the resulting ash for
iron.
EXPERIMENT 440 - Grape seeds
Apply an iron test to the ash of some grape seeds.
STARCH
AND SUGAR INDUSTRY
before we say anything about this industry, we will discuss briefly
how starch and sugar are being made every day by nature in plant
life and the changes these substances undergo in animal life.
The carbon dioxide which is always found in the air is made by the
heat of the sun to combine with water in the plant tissues to
produce a compound formaldehyde. Formaldehyde in turn
undergoes what is known as polymerization in the plant to form
sugars. By polymerization we mean several molecules of the
substances combining to form a more complex compound. The
sugar is changed to starch by plant ferments or enzymes. In
the process of converting carbon dioxide and water by the plants
into sugar and starch, oxygen is liberated and given off into the
air. This process may be expressed very clearly as follows:
1. CO2
+
H2O
Sunlight -->
CH2O
+
O2
carbon dioxide
Water in presence
Formaldehyde
Oxygen
of chlorophyll
2. 6CH2O
-->
C6H12O6
Enzyme
-->
C6H10O5
Formaldehyde
Dextrose
(sugar)
Starch
Man is dependent upon plants for starches and sugar. When
these foods are taken into the body they are changed back again with
the aid of the oxygen which we breathe into the lungs from the air
into water and carbon dioxide. The carbon dioxide is constantly
being passed out of the body when we breathe the air out of our
lungs.
To summarize, then, we can say that carbon dioxide of the air is
taken up by plants and oxygen given off. In animal life oxygen
is removed from the air and carbon dioxide given off. In other
words, carbon dioxide sustains plant life but destroys animal life.
Nearly all plant and vegetable matter contains starch - potatoes,
corn, wheat and rice containing a large percentage of this
substance. Sugar cane and beets on the other hand are the chief
sources of sugar and contain large amounts of this substance.
Starch and sugar come under the class of compounds known as
carbohydrates. That is, they are compounds of carbon with
hydrogen and oxygen. In the United States starch is obtained
chiefly from corn, while in Europe potatoes are the chief
source. Starch consists of minute granules. These
granules are composed of a substance known as granulose, which
is surrounded by a membrane composed principally of
cellulose. Starch does not dissolve in cold water because the
granulose which is soluble in water is protected from the action of
water by insoluble cellulose membrane. When heated with water the
granules burst and the granulose dissolves, forming the well-known
starch paste.
Besides its commercial use in the laundry, starch is manufactured
for the purpose of making the commercial products known as glucose,
grape sugar, malt glucose, dextrin, British gums and soluble starch.
These compounds are all formed from starch
144
GILBERT CHEMISTRY
by hydrolysis with suitable reagents. They are all important
compounds and are widely used. Corn syrup is nothing more than
glucose which originally came from starch.
Cane sugar or ordinary household granulated sugar is obtained from
the sugar cane through a process of refining. It is the sweetest of
all natural sugars and is called sucrose. It has the formula C12H22O11.
On hydrolysis with acids this sucrose may be broken down into
two other sugars, dextrose and levulose, having the same formula C6H12O6,
but differing in physical properties. Levulose is sweeter than
dextrose and is the chief component of honey. Dextrose is
found in commercial glucose or corn syrup. Maltose is the
sugar that is formed by the action of enzymes, such as diastase on
starch. It has the same formula as dextrose and levulose and
is the sugar from which alcohol and most of the alcoholic liquors
are prepared.
EXPERIMENT 441 - How to make potato
starch
Peel a fresh potato and after washing it with water cut a piece of
it up into very small slices. Place these slices in a mortar, or
cup, add a little water, about a test tube full and grind the pieces
into a fine pulp by means of a pestle or spoon. Now add a
little more water and after stirring a little with a stirring rod
strain the mixture through a coarse cloth, catching the liquid
in a glass. Fill the glass half full of water, stir a few
times and allow the liquid to stand quietly for several minutes.
Notice that a white sediment settles out in the bottom of the glass.
This sediment is the starch originally contained in the potato. The
liquid contains a little of the fibrous material which passed
through the cloth on straining.
The principle involved in the manufacture of starch from potatoes in
Europe is similar to this, although complicated machinery is used in
the manufacture of large quantities and in the purification and
separation of starch.
EXPERIMENT 442 - How to make
cornstarch
Place about 15 kernels of corn in a mortar, or cup, add a test tube
full of water and allow the corn to soften somewhat in the water for
several hours. Then grind the kernels up into a pulp by means of a
pestle or spoon.
Add a little more water and after stirring a few times, strain the
mixture through a coarse cloth into a a glass. Fill the glass
half full of water, stir the mixture a few times and allow the
liquid to stand quietly for a few minutes. Notice the sediment
in the bottom of the glass. This is starch originally contained in
the corn.
Cornstarch is manufactured extensively in the United States by a
method similar to this.
EXPERIMENT 443 - How to make starch
from flour
Besides starch, flour contains an organic compound called
gluten. In order to separate the starch from gluten proceed as
follows:
Put two tablespoonfuls of flour in a cup and add just enough water
to make the flour into a stiff dough. This can be done by
working the moist flour with the fingers until it is kneaded into a
round ball the same as your mother does when she prepares bread
dough for making bread. Now take this ball of dough and holding it
in a glass half full of water work it with the fingers so that all
portions of it will come in contact with the water. Notice
that the starch separates from the dough and settles in the water,
leaving a very sticky mass of gluten in the fingers.
EXPERIMENT 444 - Changing starch
into glucose (sugar)
Put 12 measures of starch and three measures of sodium bisulphate in
a test tube half full of water and boil the mixture for 10 or 15
minutes. The starch has now been hydrolyzed by the acid to form
glucose.
GILBERT
CHEMISTRY 145
In order to tell whether the starch has been completely changed over
into glucose pour 4 or 5 drops of the above solution into another
test tube, add 2 or 3 drops of sodium iodide solution and 1 measure
of bleaching powder. if the mixture turns blue, there is still
some starch present, and it will be necessary to heat the starch and
sodium bisulphate solution a little longer, adding a little more
sodium bisulphate. If no color is produced when a portion of this
solution is tested with sodium iodide and bleaching powder, all the
starch is converted over into glucose.
When bleaching powder is added to some of the acid solution
containing starch and sodium bisulphate, chlorine gas is liberated
which, in turn, reacts with the sodium iodide, liberating iodine.
Iodine in the presence of starch gives a blue color.
In order to obtain solid glucose from the above solution of starch
and sodium bisulphate, pour the solution into a saucer and allow it
to evaporate slowly. Solid glucose will soon separate out.
EXPERIMENT 445 - Making starch from
Bantam sweet corn
Obtain a good ear of Golden Bantam corn. Use a grater to make a pulp
and do not use the cobs. Put an equal amount of water with
this pulp. Put the solution in a fine cotton cloth (a linen
cloth will do) and squeeze the juice into another pan. Allow
this to set for 12 hours and pour the water off. A white paste will
be left. Dry this in the sun and you will have a good grade of
corn starch.
EXPERIMENT 446 - Manufacture
of potato starch
Obtain quite a large potato and by scraping reduce it to pulp.
Mix this pulp with an equal amount of water and then squeeze through
a cotton cloth (linen is also good). Repeat the squeezing
operation several times until the pulp is quite free of all
water. The pulp (which we can now call cellulose) remains on
the cloth and the starch and water goes through into a container.
Allow the solution of water-starch to set for some time and then
pour the water off. The white compound in the bottom of the
container is potato starch. By drying this starch of all water
a good quality dry starch will be obtained.
EXPERIMENT 447 - Changing
starch into sugar in the body
The starch in foods we eat is converted into sugars in the body
during digestion by the action of acids contained in the stomach and
in the saliva.
Make a little starch paste by mixing one measure of starch in a test
tube with eight or 10 drops of water. Fill the test tube half full
of hot water and boil the mixture for several minutes. Now to
the warm starch paste add a test tube one-quarter full of saliva
from the mouth. Shake the contents of the tube and allow the
test tube to stand in a warm place, preferably on the back of the
stove for a half hour.
Test a few drops of this mixture from time to time in a test tube by
adding one measure of tartaric acid and one measure of bleaching
powder and two or three drops of sodium iodide solution. When
you fail to get the blue color, the starch is all converted into
glucose.
In the United States most of the granulated sugar or sucrose is
obtained from the sugar cane which is imported into this country
from Cuba. Most of the sugar in Europe, on the other hand, is
obtained from the sugar beet.
The process of refining or obtaining sugar from these substances is
rather simple. These substances are first cut up and moistened
with water. They are then passed through heavy rollers which squeeze
out all the soluble juice. These juices are then filtered to remove
any fibrous material, after which they are treated with dry slaked
lime which neutralizes the acids contained in the juices and
precipitates impurities such as albumens. The mixture is then
filtered and the juice concentrated or evaporated
146
GILBERT CHEMISTRY
in large vacuum evaporators to a heavy syrup. It is then allowed to
stand until the sugar crystallizes out. This is removed and
after further purification is ready for the market. The liquid
remaining contains much sugar in solution and is usually
very dark. This is sold on the market as molasses.
EXPERIMENT 448-Sugar as a reducing
agent
Put two measures of sodium carbonate and two measures of calcium
oxide in a test tube one-third full of water. Shake thoroughly
and warm for a few minutes over a flame. Now filter off the
precipitate of calcium carbonate which is formed in the reaction,
catching the sodium hydroxide solution in another test tube.
Now to the test tube containing the sodium hydroxide solution add
one-half measure of copper sulphate and shake thoroughly. This gives
a green precipitate of copper hydroxide.
To this test tube containing copper hydroxide and sodium hydroxide
add eight or 10 drops of corn syrup or honey and heat the solution
nearly to boiling. Notice that the solution turns brown and a
red precipitate forms on the bottom of the test tube. This
precipitate is cuprous oxide.
The corn syrup contains a sugar dextrose which reduces the copper
hydroxide to cuprous oxide and water. Several of the sugars have
this property of reduction and this is due to the aldehyde group
(CHO) contained in the sugar molecule.
TESTING
FOR PROTEINS
Proteins of which we already have spoken is the class of substances
containing nitrogen such as lean meat, the whites or albumen of
eggs; the albumen and casein of milk and that part of dry vegetables
which is not carbohydrate, oil or mineral matter. Let us
examine a few of these substances for proteins. When proteins
are treated with a base, or alkali, the nitrogen is given off in the
form of ammonia.
EXPERIMENT 449 - How to test for
proteins in eggs
Put half a spoonful of the white of an egg in a test tube, add 2
measures of calcium oxide and 3 or 4 drops of water. Warm the
test tube over a flame for a few minutes then remove the test tube
from the flame and smell at the mouth of the tube. Do you recognize
the odor of ammonia? Hold a piece of moistened red litmus paper over
the mouth of the tube and notice that it turns blue.
EXPERIMENT 450 - How to test for
proteins in milk
Put five or six drops of milk in a test tube, add one measure of
calcium oxide and warm the test tube over a flame. Remove the
test tube from the flame and smell at the mouth of the tube.
Notice the odor of ammonia.
EXPERIMENT 451 - How to test for
proteins in meat
Put a piece of lean meat about the size of a pea in a test tube, add
one measure of calcium oxide and 3 or four drops of water.
Warm the test tube over a flame for a few moments. Remove the
test tube from the flame and smell at the mouth of the tube.
Do you recognize the odor of ammonia? Potato, although a
vegetable, contains a certain amount of protein.
EXPERIMENT 452 - How to test for
proteins in beans
Crush two beans in small pieces and place them in a test tube.
Add one measure of calcium oxide and four or five drops of
water. Warm the test tube over a flame for a few
moments. Remove the test tube from the flame and smell at the
mouth of the tube. Do you recognize the odor of ammonia?
GILBERT
CHEMISTRY 147
Beans contain about 22 per cent protein material.
EXPERIMENT 453 - Testing for
sulphur in proteins
Put a half spoonful of the white of an egg into a test tube and add
one measure of copper sulphate and two measures of calcium
oxide. Heat the test tube over a flame and allow the mixture
to boil for two or three minutes. Notice the black precipitate
of copper sulphide which is formed, showing that proteins contain
sulphur.
BREAD
MAKING AND BAKING POWDER
In making bread, baking powder is thoroughly mixed with the dry
flour. Water is then added, the flour is kneaded into a dough
and put in a warm place to rise. Heat nearly always hastens a
chemical reaction; that is why dough rises quicker in a warm place
than in a cool place.
The moisture plus the tartaric acid act upon the sodium bicarbonate
and start the formation of carbon dioxide. Soon the dough begins to
rise, due to the gas being liberated. The powder has been
distributed through the mass, so that a million gas bubbles are
formed which puff out the dough, making it porous. During the
process of baking, the gas and the remaining constituents of the
baking powder are converted into harmless substances. Most of
the carbonates are insoluble compounds and can therefore be
precipitated from solutions of their soluble salts by carbon dioxide
or a soluble carbonate. Some of these insoluble carbonates are
beautifully colored and make very interesting experiments.
EXPERIMENT 454 - How to make baking
powder
Put two measures of sodium bicarbonate and two measures of tartaric
acid into a test tube. Mix thoroughly by closing the mouth of
the tube with your thumb and shaking back and forth. Notice that
nothing happens. Now add a half test tube full of water and notice
the sudden reaction. These are the two active constituents of
baking powder. The gas liberated is carbon dioxide.
Baking powder is composed of two or sometimes more chemicals which,
when dry, are not reactive. When water or moisture is applied the
tartaric acid and sodium bicarbonate are put into forms whereby they
react readily upon each other, the sodium bicarbonate giving
up its carbon dioxide. This gas is the same as that formed in
the lungs or in soda water.
Baking powders found on the market are of three kinds, named from
the kind of acid salt used. For example, tartrate powders have
tartaric acid or acid potassium tartrate (cream of tartar);
phosphate powders have an acid phosphate such as lime or potassium;
and alum powders have as an acid aluminum sulphate.
The reactions which take place in these different baking powders may
be expressed as follows;
1. Acid potassium tartrate + sodium bicarbonate = carbon
dioxide + sodium potassium tartrate (Rochelle Salts).
2. Acid potassium phosphate + sodium bicarbonate = carbon
dioxide + sodium potassium phosphate.
3. Aluminum sulphate + sodium bicarbonate = carbon dioxide +
aluminum hydroxide + sodium sulphate (Glauber°s Salt).
EXPERIMENT 455--How to test for
starch in baking powder
Put one measure of baking poweder in a test tube one-half full of
water and heat the solution to boiling. Allow the solution to
cool, then add one or two drops of iodine solution. Notice the
formation of a blue color, showing that baking powder contains
starch.
148
GILBERT CHEMISTRY
Starch is put into baking powder for the purpose of taking up
moisture, thereby preventing the acid salt in the baking powder from
reacting with the sodium bicarbonate.
EXPERIMENT 456 - How to test for
alum in baking powder
Make a solution of logwood by putting one measure of logwood in a
test tube half full of water and heating the solution to
boiling. Allow the liquid to cool, then pour the clear red
liquid into another test tube.
Put three measures of baking powder in a test tube half full of
water and add one-half measure of tartaric acid. Notice the violent
effervescence due to the liberation of carbon dioxide gas. When the
reaction has stopped add two or three drops of the red logwood
solution. If the solution turns reddish-blue, alum is present
in the baking powder. Apply this same test for detection of
alum in bread, biscuits, doughnuts and loaf cake.
EXPERIMENT 457 - How to test for
copper sulphate in bread
Dissolve one-third measure of tartaric acid and one measure of
sodium ferrocyanide in a test tube half full of water. Then put into
the test tube three or four pieces of bread to be tested and allow
the bread to stand in this solution for one or two hours. If
the solution becomes reddish-brown the bread contains copper
sulphate.
Copper sulphate is very seldom used as an adulterant in bread.
TESTING
MILK
EXPERlMENT 458 - How to test for
coloring matter in milk
Put one measure of sodium bicarbonate in a test tube one third full
of milk and, putting the thumb over the mouth of the test tube,
shake the contents thoroughly.
Now place a piece of filter paper in this solution and allow the
paper to remain in this solution for 10 to 12 hours. At the end of
this time remove the paper and examine it. If it is colored a
reddish yellow the milk contains some artificial coloring
matter.
EXPERIMENT 459 - How to test for
starch in milk
Heat a half test tube full of milk to boiling and allow the test
tube to cool. Then add one or two drops of iodine solution. lf
the milk turns blue, it contains starch.
EXPERIMENT 460 How to test butter
Place a small piece of butter about the size of a pea in your spoon
and heat it slowly over a flame. If the butter foams and
froths on boiling the butter is fresh. On the other hand, if
it sputters or pops it is either oleomargarine or renovated butter.
Another test that may be applied to butter to show whether it is
adulterated is as follows:
Heat a half test tube of milk until it is very hot. Then put
into the milk a piece of butter about a half inch square to be
tested and stir until it is all melted. Now place the cup in a
pan of cold water containing a little ice and stir the milk
continually until the milk becomes cold and the butter
solidifies. If the butter is pure or renovated it will
solidify into small particles throughout the milk. If it
is oleomargarine it will solidify into one solid cake.
Pure fresh butter contains water and butter fat. Butter fat
consists principally of the fats olein, palmitin and stearin.
The flavor of the butter is due to the presence of a small amount of
butyrin, which is an ester of butyric acid and glycerine.
GILBERT
CHEMISTRY 149
Oleomargarine is made from the fat of cattle and hogs, together with
small amounts of cotton seed oil and milk or butter. The milk or
butter is added to furnish enough butyrin to give the butter flavor.
Renovated butter is stale or rancid butter made over by chemical
treatment.
EXPERIMENT 461 - How to make casein
Put three measures of sodium bisulphate in a test tube one-third
full of water and shake until it dissolves. Now add a few drops at a
time with constant shaking some of this solution to a half test tube
full of milk. Notice that suddenly a white curdy precipitate
is formed. This precipitate is casein. This is the same
precipitate that is formed when milk turns sour or curdles. The
souring of milk is brought about by the formation of lactic acid due
to the fermentation of the milk.
Casein besides being used as a food in cheese has many other
important uses today. It is used in the manufacture of
adhesives, paints, in dyeing, in medicine, as electrical insulators
and in making plastic masses as in stoneware, toys, etc. In
the manufacture of these things the casein is put through a certain
chemical treatment.
SOAP
Most of us are familiar with soap and its cleansing properties but
how few of us understand the chemistry of soap making and the part
soap plays in cleansing. Soap was made in early history by
treating fat with the lye obtained by extracting wood ashes with
water and lime. What really happens when ashes are treated in this
way is that potassium carbonate which occurs in wood ashes is
dissolved by the water. This water solution of potassium
carbonate then reacts with the lime or calcium oxide to form an
insoluble compound of calcium carbonate and a soluble compound of
caustic potash, potassium hydroxide or lye as it is commonly
called. Fats or grease, which are compounds of glycerine with
fatty acids, are then boiled with the proper proportion of
lye. During the reaction the glycerine of the fat is set free
and a compound of the fatty acid with the lye is formed, which is
the soap.
If too much alkali is used in making a soap, the soap will contain
free alkali which is bad. If not enough alkali is used the
soap will be greasy which is also bad. It is up to the chemist
in a soap factory to determine what the suitable proportions are for
every sample of soap to be made. In making fine soaps, such as
Castile soap and the high grade toilet soaps, olive oil is used
instead of common fats and in the manufacture of many soaps,
perfumes and coloring matters are mixed with the other
materials. Ordinary white soaps are made from cotton seed oil.
Cheap laundry soaps are made from impure fats obtained from kitchen
grease, bones, etc. Glycerine soaps are made by melting hard
soap and adding an equal amount of glycerine.
The difference between hard and soft soaps is due to the materials
contained in them. Soaps made from caustic potash, or
potassium soaps, are soft, while those made from caustic soda or
sodium soaps, are hard.
In making hard soap, caustic soda and fat are boiled together and
when the contents of the vessel are thoroughly united a strong
solution of sodium chloride or common salt is added and the mixture
heated again. The heating is then stopped and the contents
allowed to stand for several hours. During this time the
contents of the vessel separate into two portions, the lower one
consisting of glycerine, salt and all impurities and the upper one
soap. The glycerine is separated from the water and used in
medicine and in the manufacture of high explosives such as
nitroglycerine and dynamite.
Did you ever stop to think what happens when you wash your hands
with soap?
150
GILBERT CHEMISTRY
The soap removes grease or oil from your hands by breaking it up
into tiny droplets that are washed away by the water. ln other
words, when you produce a lather on the hands with soap you emulsify
the oil or grease and in this condition it is easily removed.
EXPERIMENT 462 - Making soap
Make a solution of caustic soda or lye by putting three measures of
sodium carbonate and four measures of calcium oxide into a test tube
half full of water and boil for two or three minutes. Allow the tube
to cool and when the liquid has settled pour the clear liquid into
another test tube. Now add a piece of lard or butter about the
size of a marble and boil the liquid again for a few minutes, being
careful that the liquid does not bump out of the test tube. You can
prevent this by shaking the tube in the flame while heating.
Notice that the lard or butter dissolves very readily in the hot
alkali. Now add three measures of common salt and heat the mixture
again for two or three minutes. Allow the contents of the tube
to cool and notice that the soap separates out as the upper
layer. The liquid layer below contains glycerine, salt and
impurities. Try washing your hands with the soap you have
made.
EXPERIMENT 463 - Why soap cleanses
Put a little kerosene oil into a test tube one-third full of water
and shake the contents of the tube. Notice that the oil has
been broken up into minute droplets. Allow the tube to stand"
and now notice that the oil runs together and rises to the top of
the water.
Repeat this experiment, using the white of an egg in place of the
water. Notice that this time the oil is broken up into minute
droplets as before, but remains in this condition and does not run
together and rise to the top of the water. This forms what is called
an emulsion, the oil being emulsified.
Repeat this experiment, using a soap solution in place of the white
of an egg and convince yourself that the soap forms a true emulsion
with the oil. It is due to this fact that oil, grease and dirt
are easily removed from the hands when washed with soap.
EXPERIMENT 464 - Making liquid soap
Put a piece of toilet soap about the size of a marble in a test tube
and add twice the amount of glycerine. Heat the test tube over
a flame until the mixture is all melted together. When this mixture
is melted together pour the contents of the test tube into a small
bottle and fill the bottle with water. This will give you a liquid
soap which can be used on the hands the same as ordinary soap.
EXPERIMENT 465-Chemical films and
bubbles
Many times you will have the occasion to use films or bubbles in
your laboratory. You may desire to fill a soap bubble with
hydrogen gas. You may wish to use films of soap for defraction
experiments. The common soap bubble will not stand up well, so
below we are giving a formula of a soap that will give a good bubble
and that will stand up well.
Pure Castile Soap - 1 oz. (Palm-0il soap is also good)
Distilled Water - 8 oz.
Pure Glycerine - 4 oz.
Cut the soap into thin shavings. Dissolve in the water.
When the solution is complete as possible, add the glycerine and
stir well. On standing, the mixture becomes clear at the bottom. The
clear portion is removed and used.
GILBERT
CHEMISTRY 151
DETERGENTS
Ordinary soap is a detergent and is made by the action of alkali on
fats. During the World War several of the countries of Europe,
especially Germany, were cut off from the outside world and as a
result, fats became so scarce that they could not be used for making
soap This shortage stimulated a search for other kinds of detergent
agents. This led to the discovery of a new type of valuable
washing agents. These are designated by the class name “Hymolal
Salts," and are alkali salts of sulfated alcohols of high molecular
weight. The organic chemist prepares his higher alcohols by
application of catalytic hydrogenation to higher fatty acids which
are widely distributed in nature. Lauric acid, for example,
which is obtained commercially from cocoanut oil gives, on reduction
lauryl alcohol. Sulfation of this alcohol gives lauryl
sulphuric acid, and when this last acid is neutralized with alkali a
practical detergent is formed (sodium lauryl sulphate.) These salts
are more powerful sudsing agents than the ordinary soaps, they are
not affected by hard water, and can be us in both acid and alkaline
solutions. The hymolal salts are manufactured in the form of
powders, flakes, bars and liquids. These detergents are being
introduced to the trade in this country by Proctor and Gamble
Company of Cincinnati, Ohio. The greatest advantage for these
detergents over soaps is that they are affected very little by the
hardness of water.
SOLVING
THE HARD WATER PROBLEM IN THE KITCHEN, LAUNDRY AND BATHROOM
EXPERIMENT 466 - Action of ordinary
soap on hard water
Place some very hard water in a basin and try to make a good washing
solution by sudsing with some of your mother’s kitchen soap. Note
that a large portion of your dissolved soap is used up by the hard
water and is turned into insoluble calcium and magnesium soap.
These insoluble metallic soaps are sticky and heavy and settle on
clothes, your face and hands, in your hair, and on the surface of
your wash bowl and bathtub. They cannot be removed by rinsing.
EXPERIMENT 467 - Action of ordinary
soap on sea water
Secure a bottle of salt water at the sea shore and shake with some
ordinary soap. Note the result.
EXPERIMENT 468 - Soap in acid
solutions
Prepare a dilute solution of hydrochloric acid as directed in a
previous experiment and treat this acid solution with some ordinary
soap. Note the result.
EXPERIMENT 469 - Treating hard
water with a hymolal salt
Repeat experiment 468 and treat your hard water with a hymolal salt
detergent.
EXPERIMENT 470 - Treating sea water
with a hymolal salt
Repeat experiment 468 and treat sea water with a hymolal salt
detergent. Note the difference in behavior.
EXPERIMENT 471 - Action of
hydrochloric acid solution on soap
Mix a hymolal salt detergent solution with dilute hydrochloric acid
solution. Compare with the results obtained with soap under
the same conditions.
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GILBERT CHEMISTRY
EXPERIMENT 472 - Action of calcium
chloride solution on soap
Dissolve some calcium chloride in water and then try to dissolve
some common soap in the solution. Note the formation of an
insoluble calcium soap.
EXPERIMENT 473 - Action of calcium
chloride on a hymolal salt
Repeat the previous experiment but instead of using soap, stir into
the calcium chloride solution a hymolal salt. Note the
difference in behavior.
EXPERIMENT 474 - Action of barium
chloride on a hymolal salt
Repeat experiment 473 using barium chloride.
EXPERIMENT 475 - Action of
strontium chloride on a hymolal salt
Repeat experiment 473 using strontium chloride.
ALKALINE
DETERGENTS AND THEIR BEHAVIOR TOWARDS METALS
Alkaline detergents are used commercially for cleaning metal
surfaces. Chemicals which find wide use for this purpose are
sodium hydroxide, sodium carbonate, trisodium phosphate, sodium
stearate and sodium metasilicate. A very interesting and
instructive series of experiments can be carried out with these
salts as follows: Perform a series of immersion treatment tests with
the following metals in sheet form, namely, tin, aluminum, zinc and
copper.
IMMERSION
TESTS
EXPERIMENTAL PROCEDURE 476 -
Immersion test with metal strip
Suspend a small sheet of the metal strip in a one to two per cent
solution of the different detergents mentioned above and let the
metal remain in contact with the detergent solution for four to five
hours at ordinary temperature. The strip of metal should be
weighed before and after immersion. These experiments will
offer an opportunity of using your gravimetric balance and
weights. Note the loss or icrease in weight of each strip.
EXPERIMENT 477 - Tin and sodium
hydroxide
Tin and sodium hydroxide
EXPERIMENT 478- Tin and sodium
carbonate
Tin and sodium carbonate
EXPERIMENT 479 ~ Tin and trisodium
phosphate
Tin and trisodium phosphate
EXPERIMENT 480 - Tin and sodium
silicate
Tin and sodium silicate. Strips of tin may be cut from e clean
tomato can. Strips of metal two inches by one-half inch are
large enough for experimental purposes.
EXPERIMENT 48l - Copper sheet
Apply the same series of four experiments using thin copper sheet.
EXPERIMENT 482 - Zine sheet
Apply the same series of four experiments using zinc sheet.
GILBERT
CHEMISTRY 153
EXPERIMENT 483 - Sheet
aluminum
Apply the same series of four experiments using sheet aluminum.
Observe which one of the different metals dissolves in any of the
detergent solutions. Also observe whether gas bubbles are
generated. If gas is generated try to identify it.
GUMS,
ADHESIVES AND GLUES
Gum arabic, a natural occurring substance, is the essential
constituent in the manufacture of gums and adhesive for envelopes
and stamps. However, a very good substitute known as dextrin or
British gum is now made in large quantities both in this country and
in Europe by heating starch and subjecting it to the proper
treatment.
Glues are manufactured by boiling with water properly prepared
animal matter, such as skins, bones and fish stock, and drying the
solution.
A very good household cement for mending crockery, glass, etc., can
be made by using water glass or sodium silicate as the binding
agent.
EXPERIMENT 484 - How to cement
broken glass
By means of a small camel‘s hair brush, paint the broken surfaces of
the glass with water glass. After the water glass starts to
harden, which will require a few minutes, press the two broken
surfaces together and allow the glass to remain this way for a day
or two. If on pressing the two surfaces together a little of
the water glass squeezes out, rub this off with a damp cloth.
Notice after a day or two that the pieces are held very firmly
together. Glass mended with water glass will not hold together
in contact with water, since water glass is soluble in water.
EXPERIMENT 485 - How to mend broken
china or porcelain
Make a paste by putting a half spoonful of waterglass and six
measures of calcium carbonate in a mortar or cup and mixing with a
pestle or spoon. Now mend the pieces of china or porcelain by
painting with a brush the broken surfaces with this paste.
This paste when dry is white and resembles exactly the color of the
china or porcelain.
EXPERIMENT 486 - How to mend black
crockery
To cement together pieces of black chinaware or porcelain make a
paste, using a half spoonful of water glass and six measures of
manganese dioxide. Then mend the broken pieces together, using this
cement the same way as described in the previous experiment.
EXPERIMENT 487 - How to mend blue
chinaware
To mend broken pieces of blue chinaware make a paste, using one-half
teaspoonful of water glass, four measures of sodium ferrocyanide and
two measures of ferric ammonium sulphate. Then proceed exactly
as before in applying the cement. The blue color is formed by
the action of sodium ferrocyanide on ferric ammonium sulphate.
How could you make a red cement, a brown cement, or a green cement?
EXPERIMENT 488-Another household
cement
A very good cement for mending chinaware may be made by making a
paste, using a half teaspoonful of the white of a fresh egg and six
measures of calcium carbonate. To mend pieces of broken china
with this paste brush some of it on the broken surfaces of the china
and quickly press the broken edges together and allow the
mended pieces to stand for a day or two.
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GILBERT CHEMISTRY
EXPERIMENT 489 - How to make
envelope or postage stomp mucilage
Put five measures of sugar, two measures of gum arabic and two
measures of starch in a test tube one-half full of water. Shake the
contents of the tube and allow the tube to stand for five or six
hours. Then heat the contents of the tube to boiling and allow the
tube to cool. With a soft brush paint some of this mucilage on
a piece of paper and allow it to dry. Now when moistened with water
you will be able to stick the paper to any surface. Postage stamp
and envelope mucilage is made similar to this. In order to
keep this mucilage from going bad, a drop or two of some
preservative, such as oil of sassafras or wintergreen, must be
added.
EXPERIMENT 490 - A common household
adhesive paste
Make a starch paste by shaking 12 measures of powdered starch in a
test tube one-fourth full of water. Stir a little with a stirring
rod if necessary. Now to this paste add half a test tube full of
boiling water containing three measures of calcium chloride.
Pour this solution into the test tube containing the starch paste
and heat the contents of the test tube to boiling. Allow the
test tube to cool. This gives a paste which is very good
for ordinary household use, such as pasting on labels.
EXPERIMENT 491 - Another household
adhesive paste
Another practical adhesive paste can be made from wheat flour, water
and calcium chloride.
Put eight measures of ordinary wheat flour and two measures of
calcium chloride in a test tube one-half full of water. Heat the
test tube over a flame and boil the contents of the tube until it
becomes thick and pasty. Then stop heating and allow the test
tube to cool.
In order to keep the pastes prepared in the last two experiments for
any length of time one or two drops of a preservative, such as oil
of sassafras or wintergreen oil must be added.
EXPERIMENT 492 - Labels for your
bottles
Cut small pieces of adhesive tape from the roll and stick on the
bottles. Then write the name of the chemicals or the formula on the
tape with a pen and ink and varnish the label. However, you
can purchase gummed labels at your local drug store quite cheaply.
LABEL ALL POISON
BOTTLES WITH POISON!
INK
Most of the common black inks are made from nut galls and ferrous
(iron) sulphate. The nut-galls are rich in tannic acid and
this with ferrous sulphate gives a black precipitate. Colloidal or
jelly-like substances, such as gum arabic or dextrin are sometimes
added, as these substances delay the precipitation, although the
very black color is produced at once. Some preservative is
usually added to prevent the ink from moulding.
Today very good black inks are made from derivatives of the organic
compound aniline. Aniline is a compound obtained indirectly
from coal tar.
Much time has been devoted to finding an ink that would be permanent
and resist all attempts to remove it from paper. Most inks can be
erased from paper without much difficulty. Printer's ink,
however, which is made from lampblack has been found to be the most
permanent, as the finely divided carbon which is held firmly within
the pores of the paper is insoluble in all liquid solvents
so it cannot be removed by washing. lt is also very
difficult to erase it without destroying the paper.
GILBERT
CHEMISTRY . 155
Silver nitrate, when in contact with an oxidizable material such as
cloth, is reduced in the presence of light to black metallic silver.
Because of this fact it is used in the manufacture of indelible
inks.
Quite often it is desirous of making several copies from a single
document. In order to do this an exact copy of the document is made
on heavy paper, using copying ink. The desired copies are then
made by using very thin unsized paper and placing them on the copy
prepared with copying ink. Pressure is then applied to the
copies so that the inks penetrate through the duplicates. It is
possible by this method to prepare as many as a dozen duplicate
copies at one time from the original copy.
EXPERIMENT 493 - How to make black
writing ink
Dissolve one measure of tannic acid in a test tube one-third full of
water. Then in another test tube one-third full of water dissolve
one measure of ferric ammonium sulphate. Now mix the two
solutions and notice the intense dark black color formed by the
reaction of the two substances. The black color and
precipitate is due to the formation of iron tannate. Try
writing with this ink, using a clean pen.
If you wish to make up a bottle of black ink to use permanently
proceed as follows: Dissolve four measures of tannic acid in a
test tube three~quarters full of water. Pour this solution
into a glass containing six test tubes full of water. In
another test tube three-quarters full of water dissolve four
measures of ferric ammonium sulphate and one measure of gum
arabic. Heat the test tube in order to dissolve these
substances. Then pour the contents of this tube into the glass
and stir well with a stirring rod. Add one or two drops of oil
of wintergreen to keep the ink from moulding and pour the
ink into a bottle. This will give a black writing ink
that can be used from time to time.
EXPERIMENT 494 - How to make blue
ink
Prussian blue ink may be made by dissolving two measures of ferric
ammonium sulphate in a test tube one-third full of water and adding
this solution to a solution of sodium ferrocyanide made by
dissolving two measures of sodium ferrocyanide in a in a test tube
one-quarter full of water. The blue precipitate formed in the
reaction is a compound of ferro-ferricyanide. Write with the
ink.
EXPERIMENT 495 - How to make purple
ink
Put three measures of logwood into a test tube one-third full of
water and boil for several minutes until the solution is deeply
colored. Then add 1 measure of aluminum sulphate and heat to
boiling again. Notice the beautiful dark colored purple
ink which is formed. Write with the ink using a clean
pen. By repeating this experiment and adding one measure of
sodium bisulphate in addition to the other compounds, it is possible
to make a red ink. Write with an ink made in this way, using a
clean pen.
EXPERIMENT 496 How to make carmine
ink
Put two measures of cochineal in a test tube one-third full of water
and boil for several minutes until the solution is deeply
colored. Cool the solution, and, using a clean pen, write with
it. Notice that this gives a crimson or purplish-red ink. This
color is due to carminic acid occurring in cochineal.
EXPERIMENT 497 - How to make a
green ink
Put two measures of nickel ammonium sulphate and one measure of
sodium ferrocyanide in a test tube one-third full of water and shake
well. Now add one-half measure of ferric ammonium sulphate and
shake well again. Notice the formation of a deep green color
and precipitate. Write with this solution using a clean pen.
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GILBERT CHEMISTRY
EXPERIMENT 498 - How to make a
commercial blue-black ink
Put one measure of ferric ammonium sulphate and one measure of
tannic acid into a test tube one-third full of water and shake well.
In another test tube one~quarter full of water add one measure of
sodium ferrocyanide and one measure of ferric ammonium sulphate and
shake thoroughly. Mix the two solutions and notice the
bluish-black ink produced. Write with this ink, using a clean
pen. Notice that the writing is blue. After two or three days
the writing will turn black.
EXPERIMENT 499-How to make
printer's ink
Put a spoonful of water glass (sodium silicate) in a test tube and
add two measures of powdered charcoal or better, lampblack. By
means of the stirring rod, stir the mixture until it is quite
uniform. Then fill the test tube one-third full of water and
shake thoroughly.
Now add one measure of ferric ammonium sulphate and one measure of
tannic acid. Shake thoroughly for several minutes and notice
the heavy dark black liquid produced. Printer's ink is made
similar to this. Writing done with this ink will last for a
long time and is very difficult to remove. This is because the
charcoal or lampblack gets into the pores of the paper where it is
held fast.
EXPERIMENT 500 - A commercial ink
powder
Mix together on a sheet of paper three measures of tannic acid, six
measures of ferric ammonium sulphate, and six measures of sodium
ferrocyanide. Place this mixture in a small dry bottle and
whenever you wish to make a good blue-black ink add water to the
bottle and shake thoroughly.
EXPERIMENT 501 - A red ink powder
Crush into the form of a powder a little cochineal by grinding it in
the mortar and put five or six measures of the powder into a small
dry bottle. Whenever you wish red ink simply add water to the
bottle and shake thoroughly for several minutes.
EXPERIMENT 502 - An ink remover
Dissolve one measure of tartaric acid and one measure of calcium
hypochlorite (bleaching powder) in a test tube one-third full of
water.
By means of a small camel’s hair brush, paint the ink to be removed
with some of the solution just prepared and notice that the ink
disappears. The bleaching powder and tartaric acid react to form
chlorine gas, which in the presence of water bleaches the ink or
makes it colorless. Not all inks can be bleached in this
manner. Prussian blue for example is not affected by this
solution.
EXPERIMENT 503 - Ink powder
Mix together one measure of tannic acid and one measure of ferric
ammonium sulphate. Place the powder thus formed in a small bottle,
and when you need ink simply add some of this powder to a little
water.
EXPERIMENT 504 - Blue ink powder
Blue ink powder may be made by mixing together two measures of
sodium ferrocyanide and one measure of ferric ammonium
sulphate. When this powder is mixed with water you have blue
ink all ready to write with.
EXPERIMENT 505 - Red ink powder
Put two or three measures of cochineal in your mortar and grind the
material up to a fine powder. When this powder is mixed with
water it will make red ink. Ink powders are sometimes very
convenient to use.
GILBERT
CHEMISTRY 157
EXPERIMENT 506 - How to make carbon
paper
Obtain a cake of Ivory soap and by scraping the soap with a knife,
make a pile of fine soap shavings. Put 15 measures of the soap
shavings in a glass or cup. In a test tube one-third full of water,
put one measure of sodium ferrocyanide and one measure of ferric
ammonium sulphate and shake thoroughly until the solids are all
dissolved. Pour this blue solution into the glass or cup with
the soap shavings and stir thoroughly for five minutes until the
mixture forms a smooth thick paste.
Now using a small brush or piece of absorbent cotton spread this
paste smoothly over a piece of paper. Set the paper away to
dry for a day and then use it like you would ordinary carbon paper.
EXPERIMENT 507 - How to make blue
typewriter ribbon
Obtain a quantity of soap shavings by scraping a piece of Ivory soap
with a knife. Put 15 measures o these shavings in a glass or
cup and add four or five drops of glycerine.
Now dissolve one measure of ferric ammonium sulphate and one measure
of sodium ferrocyanide in a test tube one~half full of water.
Shake this solution well so that the solids will be entirely
dissolved and then pour it into the glass or cup containing the soap
shavings and glycerine. Stir this mixture with your stirring
rod until it forms a smooth paste.
Now get a piece of cloth or tape about the width and thickness of a
typewriter ribbon and apply the paste which you have made evenly to
the cloth or tape. Now hang the tape up to dry for half an
hour or so and then roll it up into a roll just like a ribbon. In
order to use it on a typewriter you will of course have to roll it
on to an empty spool of the same kind used on your typewriter.
EXPERIMENT 508 - A finger print
record
Prepare some blue ink as in the experiment "Blue Ink." Paint
the thumb or finger with the blue solution. Do not get too
much solution on the finger, but just cover it thinly. Now
press the finger against a clean sheet of white paper being careful
not to smear, and there you have your finger print. An album
can be made by taking the finger prints of all your friends and
marking them. Wash your hands after taking your finger print.
EXPERIMENT 509 - Detecting finger
prints
Obtain a smooth piece of white paper, breathe on one of your fingers
a few times and press it on the paper. Prepare a mixture of
one measure of sulphur and one measure of powdered charcoal.
Put this mixture on the paper which you have touched with your
finger and tap the underneath side of the paper gently so that the
powder will be spread over the part of the paper where you have
pressed your finger. Shake the excess powder off the paper and
you will find that the finger prints instead of being invisible are
now plainly seen.
EXPERIMENT 510 - Blue Ink
Dissolve two measures of sodium ferrocyanide in a test tube
one-quarter full of water. In another test tube dissolve one
measure of ferric ammonium sulphate. Pour the second solution
into the first. Prussian blue will be formed. Try to
write with the ink. Prussian blue is used in laundry blueing.
EXPERIMENT 511 - Violet ink
Put two measures of logwood in a test tube one-quarter full of
water. Warm to extract color and then add one-half measure of
aluminum sulphate to the hot solution.
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GILBERT CHEMISTRY
EXPERIMENT 512 - Lemon ink
Dip your pen into a container of lemon juice and write as if with
regular ink. Upon heating the paper, your writing will become
visible.
EXPERIMENT 513 - Red ink
Put two measures of logwood in a test tube and fill tube one-quarter
full of water. Warm to extract color and add one-half measure
of aluminum sulphate and one-half measure of sodium bisulphate.
EXPERIMENT 514 - Safety ink
Put one spoonful of water glass in a mortar or cup and stir in one
measure of powdered charcoal. Stir for some time to properly
mix. Keep bottled up in a tight stoppered bottle if it is
desired to keep for any length of time. Writing done with this
ink is very hard to remove.
EXPERIMENT 515 - Copying ink
Place in a test tube one measure of sodium ferrocyanide and one-half
measure of ferric ammonium sulphate. Fill test tube
one-quarter full of water and shake to dissolve salts. Blue
ink is formed.
Now add to this 10 drops of glycerine. Shake. Write on paper with
this mixture making your letters very large. Lay the copy on a flat
surface and spread over it a piece of soft tissue paper and
then a piece of damp blotting paper and over the blotting paper
place a board. Press down on the board an then remove the board and
blotting paper and see if you have produced a readable copy. The
copying ink should have penetrated through the tissue paper so that
writing will appear on reverse side.
EXPERIMENT 516 - Making a camphor
ball float
Fill a wide mouth bottle with vinegar and drop some camphor balls
into the vinegar and sodium bicarbonate. Carbon dioxide will be
generated and little bubbles of gas will collect on the camphor
balls. Soon the camphor balls will become "lighter" and will
float to the top of the vinegar and sink again. This process
is repeated several times.
EXPERIMENT 517-Formation of lead
iodide
In a convenient sized test tube place two spoonfuls of water and add
six drops of sodium iodide solution. In another test tube
place about one measure of lead nitrate or lead acetate obtainable
at any drug store and dissolve by adding about one test tube of
water. Now pour the lead nitrate solution into the sodium
iodide solution. A heavy bright yellow precipitate of lead
iodide will form. Now heat until it begins to boil, then set
aside to cool. On cooling watch closely what happens.
Most of the iodide will have settled to the bottom, but there also
appears above it, numerous little scales or specks of all colors, -
some golden, some silver, blue, green, red, pink, orange, and violet
which sparkle beautifully. The lead iodide, which by this time
has all settled to the bottom of the test tube, leaves the most
beautiful colored specks in the clear liquid above it. Its
beauty cannot be very easily described but soon the beautiful specks
settle to the bottom of the test tube leaving only a few lingering
above them. Even at the bottom they produce a striking effect.
It is very interesting to watch the colored particles.
EXPERIMENT 518 - Magic transfer
solution
This solution transfers pictures to cloth, paper dishes, etc., in
their original color. The solution is made as follows: common
castile soap, half bar; turpentine, quarter pint; water, half
gallon. Dissolve the soap in the water and then add the
turpentine. To use, apply with a small brush to any printed
page or picture and the lay a clean
GILBERT
CHEMISTRY 159
paper or cloth over the picture and rub quite hard with the back of
a spoon. To transfer to glass or or to dishes use white varnish and
do the same as above. You can make up a few bottles of this
solution and sell some to your friends at school.
EXPERIMENT 519 - Partition
solubility of iodine
To a half test tube of water add about ten drops of tincture of
iodine (this you will find in the medicine closet.) The
solution in the test tube will be of a reddish-brown color.
Add to this an eighth test tube of carbon tetrachloride. The carbon
tetrachloride will sink to the bottom. Shake the test tube and
then let the carbon tetrachloride layer settle to the bottom of the
tube. The bottom layer will be of a rich violet color.
Reaction: Tincture of iodine is a solution of iodine and potassium
iodide in water and alcohol. When carbon tetrachloride is
added, it dissolves the free iodine. The carbon tetrachloride
settles to the bottom of the test tube because it is heavier than
the water and it is not miscible with water.
FERMENTATION
Fermentation is the decomposition or breaking down of complex
organic compounds into simpler substances by certain living
organisms called ferments. There are many different kinds of
fermentation depending on the different kinds of organisms or
ferments. The most familiar illustration of fermentation is
the fermentation of fruits or fruit juices, the decay of vegetable
matter or nitrogenous matter, the souring of cider or of milk and
that taking place in bread making by action of yeast. Most
organic substances, especially the complex substances, are subject
to fermentation changes. The chemical changes brought about by
ferments consist in the breaking down of complex molecules to form
simple groups of atoms. In some cases it consists in a rearrangement
of the atoms in the molecule to form a compound with different
properties. There are many kinds of living organisms or
ferments, each of which produces its special change. Most ferments
are microscopic plants of simple structure which multiply very
rapidly when placed in the proper medium or substance. They
are variously known as microbes, germs and bacteria. Yeast which is
used so commonly in bread making is a microscopic plant found in the
air and about certain fruit trees. The yeast cakes which you
buy in the store are these same living organisms which have been
grown in some suitable culture medium as the potato or corn
meal. The above class of ferments are known as organized
ferments. The other class of ferments are called chemical or
unorganized ferments and are known as enzymes. Examples of these are
pepsin, trypsin and diastase.
The action of ferments on organic substances always works best at
definite temperatures. Above these temperatures the ferments
or organisms are destroyed or their action delayed.
EXPERIMENT 520 - Changing sugar
into carbon dioxide
Put two spoonfuls of corn syrup or molasses in a tumbler half full
of water and stir it up. Then dissolve one~quarter of a cake
of yeast in a small tea cup full of lukewarm water. This is best
done by allowing the yeast to stand in the water for about a half
hour and then stirring. Now pour the solution of yeast into
the tumbler containing the syrup and set the tumbler aside in a warm
place for several hours. Notice that after some time a
reaction is taking place, small bubbles of gas being agiven off.
Hold a lighted match over the surface of the liquid in the tumbler
an notice that it goes out, due to the carbon dioxide gas which is
given off. The syrup or molasses contains a large amount of
sugar and during the fermentation produced by the yeast this sugar
is changed into carbon dioxide gas.
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GILBERT CHEMISTRY
EXPERIMENT 521 - Changing starch
into sugar and carbon dioxide
Put a half teaspoonful of starch in a tea cup and add a spoonful of
water. Stir the starch in the water until it is in the form of a
paste and then fill the teacup three-quarters full of boiling water
and stir for a few moments. Now dissolve one-quarter of a cake of
yeast in a teacup One-quarter full of luke warm water and put this
solution into teacup containing the starch. Set the teacup away in a
warm place and examine it carefully from time to time. Notice
the formation of bubbles of gas, due to the liberation of carbon
dioxide gas. It will require several days before the starch will be
converted into sugar and carbon dioxide.
This illustrates the way starchy foods are converted in the body
into sugars which, in turn, are burned up through the process of
assimilation into carbon dioxide and water.
EXPERIMENT 522 - The formation of
mould
Mould is another form of ferment. You have probably noticed the
formation of mould on such substances as sour milk, vinegar and
starch which have been exposed to the air for some time. These
substances contain the proper food material for certain bacteria in
the air. As a result these bacteria, under proper condition of
heat get into these substances and multiply very rapidly, producing
the mould.
Prepare a starch solution as follows: Put a half spoonful of starch
in a tea cup and add one spoonful of water. Stir until the starch
forms a paste with the water. Then fill the cup with boiling
water and stir until the starch forms a very gelatinous paste.
It may be necessary to boil this mixture in a tin cup or pan for a
few minutes to form a heavy paste.
Now set the starch solution aside in a warm place for a few days and
notice after some time the formation of mould on the surface of the
starch.
EXPERIMENT 523 - Growth of mould
Place one-half teaspoonful of ordinary starch in a small pan and add
to this a small amount of water. Stir to form a perfect paste
and then add about one-third of a cup of boiling water. Set
the pan on a stove and continue to boil until a perfect paste is
formed. This paste is now bacteria free. Finally pour
the paste into an ordinary tumbler and set it away in a warm place.
It will soon become infected with bacteria from the air.
Examine it from time to time and notice when mould begins to
form. After some mould has formed examine its appearance under
a microscope.
EXPERIMENT 524 - Composition of
mould
Carefully remove some mould from the surface of the starch mixture
and test it for sugar, starch, protein and ammonia.
EXPERIMENT 525 - Sugar fermentation
Dissodve one spoonful of ordinary sugar in about one~half cup of
water, using an ordinary tumbler for the experiment. Place in
the sugar solution a small piece of yeast, which has first been
masticated with water to form a paste and set aside in a warm place
to stand. Notice what happens after a few hours. Test
the gas that is generated. Will it burn? Will it
dissolve in water, in sodium hydroxide solution?
EXPERIMENT 526 - Fermentation of
corn syrup
Apply the previous experiment using commercial corn syrup or
ordinary molasses.
EXPERIMENT 527 - Making vinegar
Take about one cup of freshly made sweet cider and add to this two
or three drops of strong vinegar. Place the mixture in an
ordinary tumbler and set aside, after covering with a plate or piece
of cardboard to keep the dust out. At the end
"The Science Notebook"
Copyright 2008-2018 - Norman Young