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An Introduction to Chemical Science

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The FeS is revivified by exposure to the air. 2 FeS + O3 = Fe2O3
+ 2S. It can then be used again. H2S, if not separated, burns
with the gas, forming H2S03, which oxidizes in the air to H2SO4;
hence the need of removing it. CO2 diminishes the illuminating
power.

306. Composition.--Even when freed from its impurities coal-gas
is a very complex mixture, the chief components being nearly as
follows:--


Percent Diluents, having little C, give
H 45) very little light. Notice the small
CH, 41) diluents. percentage of luminants, or light-
CO 5 ) giving compounds, also the proportion
C,HB 1.3) of C to H in them.
C,H6 1.2)luminants.
CZH4 2.5) Cannel coal contains more of
C02 2) impurities. the heavy bydro-carbons, CnH2n,
N, etc. 2) etc., than the ordinary bituminous
100 coal. Ten per cent of the coal should be
cannel; naphtha is, however, often employed to subserve the same
purpose, one ton of ordinary bituminous coal requiring four gallons
of oil.

In Boston, 7,000,000 cubic feet of gas have been burned in one
day, consuming 500 tons of coal; the average is not more than
half that quantity. Of the other products, coke is employed for
heating purposes, gas carbon is used to some extent in electrical
work, and coal-tar is the source of very many artificial products
that were formerly only of natural origin. NH3, is the main
source of ammonium salts, and S is made into H2SO4.

307. Natural Gas occurs near Pittsburg, Pa., and in many other
places, in immense quantities. It is not only employed to light
the streets and houses, but is used for fires and in iron and
glass manufactories. It is estimated that 600,000,000 cubic feet
are burned, saving 10,000 tons of coal daily in Pittsburg, Only
half a dozen factories now use coal. More than half the gas is
wasted through safety valves, on account of the great pressure on
the pipes as it issues from the earth.

These reservoirs of natural gas very frequently occur in
sandstone, usually in the vicinity of coal-beds, but sometimes
remote from them. In all cases the origin of the gas is thought
to be in the destructive distillation, extending through long
geological periods, of coal or of other vegetable or animal
matter in the earth's interior.

Natural gas varies in composition, and even in the same well,
from day to day; it consists chiefly of CH4, with some other
hydro-carbons.

CHAPTER LVI.

ALCOHOL.

308. Fermented Liquor.

Experiment 130.--Introduce 20 cc.of molasses into a flask of 200
cc, fill it with water to the neck, and put in half a cake of
yeast. Fit to this a d.t., and pass the end of it into a t.t.
holding a clear solution of lime water. Leave in a warm place for
two or three days. Then look for a turbidity in the lime water,
and account for it. See whether the liquid in the flask is sweet.
The sugar should be changed to alcohol and CO2. This is fermented
liquor; it contains a small percentage of alcohol.

309. Distilled Liquor. Experiment 131.--Attach the flask used in
the last experiment to the apparatus for distilling water (Fig.
32), and distil not more than one-fifth of the liquid, leaving
the rest in the flask. The greater part of the alcohol will pass
over. To obtain it all, at least half of the liquid must be
distilled; what passes over towards the last is mostly water.
Taste and smell the distillate. Put some into an e.d. and touch a
lighted match to it. If it does not burn, redistil half of the
distillate and try to ignite the product. Try the combustibility
of commercial alcohol; of Jamaica ginger, or of any other liquid
known to contain alcohol.

310. Effect on the System.

Experiment 132.--Put a little of the white of egg into an e.d. or
a beaker; cover it with strong alcohol and note the effect.
Strong alcohol has the same coagulating action on the brain and
on the tissues generally, when taken into the system, absorbing
water from them, hardening them, and contracting them in bulk.

311. Affinity for Water.

Experiment 133.--To show the contraction in mixing alcohol and
water, measure exactly 5cc.of alcohol and 5cc.of water. Pour them
together, and presently measure the mixture. The volume is
diminished. A strip of parchment soaked in water till it is limp,
then dipped into strong alcohol, becomes again stiff, owing to
the attraction of alcohol for water.

312. Purity.--The most important alcohols are methyl alcohol and
ethyl alcohol. The former, wood spirit, is obtained in an impure
state by distilling wood; it is used to dissolve resins, fats,
oils, etc., and to make aniline. It is poisonous, as are the
others.

Ethyl alcohol, spirit of wine, is the commercial article. It is
prepared by fermenting glucose, and distilling the product. It
boils at 78 degrees, vaporizing 22 degrees lower than water, from
which it can be separated by fractional distillation. By
successive distillations of alcohol ninety-four per cent can be
obtained, which is the best commercial article, though most
grades fall far below this. Five per cent more can be removed by
distilling with CaO, which has a strong affinity for water. The
last one per cent is removed by BaO. One hundred per cent
constitutes absolute alcohol, which is a deadly poison. Diluted,
it increases the circulation, stimulates the system, hardens the
tissues by withdrawing water, and is the intoxicating principle
in all liquors.--It is very inflammable, giving little light, and
much heat, and readily evaporates.

Beer has usually three to six per cent of alcohol; wines, eight
to twenty per cent. The courts now regard all liquors having
three per cent, or less, of alcohol, as not intoxicating. In
Massachusetts it is one per cent.

CHAPTER LVII.

OILS, FATS, AND SOAPS.

313. Sources and Kinds of Oils and Fats.--Oils and fats are
insoluble in water; the former are liquid, the latter solid. Most
fats are obtained from animals, oils from both plants and
animals. Oils are classified as fixed and essential. Castor oil
is an example of the former and oil of cloves of the latter.
Fixed oils include drying and non-drying oils. They leave a stain
on paper, while essential, or volatile oils, leave no trace, but
evaporate readily. Essential oils dissolved in alcohol furnish
essences. They are obtained by distilling with water the leaves,
petals, etc., of plants. Drying oils, as linseed, absorb O from
the air, and thus solidify. Non-drying ones, as olive, do not
solidify, but develop acids and become rancid after some time.

Oils and fats are salts of fatty acids and the base glycerin. The
three most common of these salts are olein, found in olive oil,
palmitin, in palm oil and human fat, and stearin, in lard. The
first is liquid, the second semi-solid, the last solid. Most fats
are mixtures of these and other salts.


Olefin = Glyceryl) ( oleic)
oleate ) ( )
Pahnitin = Glyceryl)salts from (palmitic)acid and glyceryl hydrate.
palmitate) ( )
Stearin = Glyceryl) (stearic )
stearate)


314. Saponification consists in separating these salts
into their acids and the base glycerin; soap-making is the best
illustration. To effect this separation, a strong soluble base is
used, KOH for soft, and NaOH for hard soap. Study this reaction:


Glyceryl oleate ) (sodium ) (oleate )
Glyceryl palmitate) + (hydrate) = sodium (palmitate) + (glyceryl
Glyceryl stearate ) (stearate ) (hydrate


Soaps are thus salts of fatty acids and of K or Na.

315. Soap is soluble in soft water, but the sodium stearate
probably unites with water to form hydrogen sodium stearate and
NaOH. The grease which exudes from the skin, or appears in
fabrics to be washed, is attacked by this NaOH and removed,
together with the suspended dirt, and a new soap is formed and
dissolved in the water. Hard water contains salts of Ca and Mg,
and when soap is used with it the Na is at once replaced by these
metals, and insoluble Ca or Mg soaps are formed. Hence in hard
water soap will not cleanse till all the Ca and Mg compounds have
combined.

316. Glycerin, C3H5(OH)3, is a sweet, thick, colorless, unctuous
liquid, used in cosmetics, unguents, pomades, etc. It is prepared
in quantity by passing superheated steam over fats when under
pressure.

317. Dynamite.--Treated with HNO3 and H2SO4 glycerin forms the
very explosive and poisonous liquid nitro-glycerin. In this
process the C3H5(OH)3 becomes C3H5(NO3)3. C3H5(OH)3 + 3HNO3 =
C3H5(NO3)3+3 H2O. H2SO4 is used to absorb the H2O which is
formed. Nitro-glycerin, absorbed by gunpowder, diatomaceous
earth, sawdust, etc., forms dynamite. For obvious reasons the
pupil should not experiment with these substances.

318. Butter and Oleomargarine.--Milk contains minute particles of
fat, about 1/500 of an inch in diameter, which give it the
whitecolor. These particles are lighter than the containing
liquid, and rise to the top as cream. Churning unites the
particles more closely, and separates them from the buttermilk.
The flavor of butter is due to the presence of five or ten per
cent of butyric and other acids of the same series.

It was found that cows gave milk after they ceased to have food;
hence it was inferred that the milk was produced at the expense
of the cows' fat. Why could not butter be artificially made from
the same fat? It was but a step from fat to milk, as it was from
milk to butter. Oleomargarine, or butterine, was the result. Beef
fat, suet, is washed in water, ground to a pulp, and partially
melted and strained, the stearin is separated from the filtered
liquid and made into soap, and an oily liquid is left. This is
salted, colored with annotto, mixed with a certain portion of
milk, and churned. The product is scarcely distinguishable from
butter, and is chemically nearly identical with it, though less
likely to become rancid from the absence of certain fatty acids;
its cost is perhaps one-third as much as that of butter.

Chapter LVIII

CARBO-HYDRATES.

319. Carbon and Water.--Some very important organic compounds
have H and O, in the proper proportion to form water, united with
C. The three leading ones are sugar, C12H22O11 or C12(H2O)11,
starch, C6H10O6, or ?, and cellulose, C18H30O15 or ?. Note the
significance of the name carbo-hydrates as applied to them.

320. Sugars may be divided into two classes,--the sucroses,
C12H22O11, and the glucoses, C6H12O6. Sucrose, the principal
member of the first class, is obtained from the juice of the
maple, the palm, the beet and the sugarcane; in Europe largely
from the beet, in America from cane. Granulated sugar is that
which has been refined; brown sugar is the unrefined. From the
sap evaporated by boiling, brown sugar crystallizes, leaving
molasses, which contains glucose and other substances. Good
molasses has but a small percentage of glucose. To refine brown
sugar it is dissolved in water, a small quantity of blood is
added to remove certain vegetable substances, after which it is
filtered through animal charcoal, i.e. bone-black, a process
which takes out the coloring-matter. The water is then evaporated
in vacuum-pans, so as to boil at about 74 degrees and to prevent
conversion into grape sugar. By this process much glucose or
syrup is formed, which is separated from the crystalline sucrose
by rapidly revolving centrifugal machines. Great quantities of
sucrose are used for food by all civilized nations. A single
refinery in New York purifies 2,000,000 pounds per day.

321. Glucose, or invert sugar, the principal member of the second
class, consists of two distinct kinds of sugar, --dextrose and
levulose. These differ in certain properties, but have the same
symbol. Both are found in equal parts in ripe fruits, while
sucrose occurs in the unripe. Honey contains these three kinds of
sugar.

Sucrose, by the action of heat, weak acids, or ferments, may be
resolved into the other two varieties. C12H22O11 + H2O = C6H12O6
+ C6H12O6. No mode of reversing this process, or of transforming
glucose into sucrose is known. Glucose is easily made from starch
or from the cellulose in cotton rags, sawdust, etc. If boiled
with dilute H2SO4 starch takes up water and becomes glucose.
C6H10O5 + H2O = C6H12O6.

CaCO3 is added to precipitate the H2SO4, which remains unchanged.
State the reaction. The product is filtered and the filtrate is
evaporated. Much glucose is made from the starch of corn and
potatoes.

322. Starch is found in all plants, especially in grains, seeds,
and tubers. Green plants--those containing chlorophyll--
manufacture their own starch from CO2 and H2O. These chlorophyll
grains are the plant's chemical laboratories, and hundreds of
thousands of them exist in every leaf. CO2 and a very little H2O
enter the leaf from the air, H2O being also drawn up through the
root and stem from the earth. In some unknown way in the leaf,
light has the power of synthesizing these into starch and setting
free O, which is returned to the atmosphere.6 CO2 + 5 H2O =
C6H10O5 + 12 O. As no such change takes place in darkness, all
green plants must have light. Parasitic plants, which are usually
colorless, obtain starch ready-made from those on which they
feed.

323. Uses.--Glucose is used in the manufacture of alcohol and
cheap confectionery, and in adulterating sucrose. It is only two-
thirds as sweet as the latter. The seeds of all plants contain
starch for the germinating sprout to feed upon; but starch is
insoluble, and hence useless until it is converted into glucose.
This is effected by the action of warmth, moisture, and a ferment
in the seed. Glucose is soluble and is at first the plant's main
food.

Commercial starch is made in the United States chiefly from corn;
in Europe, from potatoes. Differences in the size of starch
granules enable microscopists to determine the plant to which
they belong.

324. Cellulose, or woody fiber, is the basis of all vegetable
cell walls. Cotton fiber represents almost pure cellulose. From
it are made paper and woven tissues. In paper manufacture, woody
fiber is made into a pulp, washed, bleached, filtered, hot-
pressed, and sometimes glazed. Parchment paper, vegetable
parchment, is made by dipping unglazed paper for half a minute
into cold dilute H2SO4, 1 part H2O, 2 1/2 parts H2SO4, and then
washing. The fiber, by chemical change, is thus toughened. The
cell walls of wood are impure cellulose; hence the inferior
quality of paper made from wood-pulp. Paper is now employed for a
large number of purposes for which wood has heretofore been used,
such as for barrels, pails, and other hollow ware, wheels,
etc.

325. Gun-cotton is made by treating cotton fiber with H2SO4
and HNO3, washing and drying. To all appearances no change has
taken place, but the substance has become an explosive compound.

326. Dextrin, a gummy substance used for the backs of postage
stamps, is a carbo-hydrate, as in fact are gums in general.
Dextrin is made by heating starch with H2SO4 at a lower
temperature than for dextrose.

327. Zylonite and Celluloid. -These two similar substances embody
the latest use of cellulose in manufactured articles. For
zylonite, linen paper is cut into strips two feet by one inch,
soaked ten minutes in a mixture of H2SO4 and HNO3, a process
called nitration, washed for several hours, then ground to a fine
pulp, and thoroughly dried. It is then similar to pyroxiline.
Aniline coloring-matter of any desired shade is added, after
which it is dissolved by soaking some hours in alcohol and
camphor, the liquid is evaporated, and the substance is kneaded
between steam-heated iron rollers, dried with hot air, and
finally subjected to great pressure, to harden it, and cut into
sheets. Zylonite is combustible at a low temperature, and when in
the pyroxiline stage, explosively so. Ivory, coral, amber, bone,
tortoise shell, malachite, etc., are so closely imitated that the
imitation can only be detected by analysis. Collars, combs,
canes, piano-keys, and jewelry, are manufactured from it, and it
can be made transparent enough for windows.

CHAPTER LIX

CHEMISTRY OF FERMENTATION.

328. Ferments.--A large number of chemical changes are brought
about through the direct agency of bodies called ferments; their
action is called fermentation. Ferments are sometimes lifeless
chemical products found in living bodies; but in other cases they
are humble plants.

329. Yeast is one of the most common of living ferments, wild
yeast being a microscopic plant found on the ground near apple-
trees and grape-vines, and often in the air. The cultivated
variety is sold by grocers. The temperature best suited to the
rapid multiplication of the germs forming the ferment plant is 25
degrees to 35 degrees.

330. Alcoholic and Acetic Fermentation.--The changes which the
juice of the apple undergoes in forming cider and vinegar are a
good illustration of fermentation by a living plant. Apple-juice
contains sucrose. Yeast germs from the air, getting into this
unfermented liquor, cause it to "work." This process changes
sucrose to glucose, and glucose to alcohol and CO2, and is known
as alcoholic fermentation. The latter reaction, C6H12O6 = 2 C2H6O
+ 2 CO, is only partially correct, as other products are formed.
The juice has now become cider; the sugar alcohol. After a time,
if left exposed, another organism finds its way to the alcohol,
and transforms it into acetic acid, HC2H8O2, and H2O. This
process is called acetic fermentation. C2H6O + O2 = HC2H3O2 +
H2O. For this fermentation, a liquor should not have over ten per
cent of alcohol. Mother of vinegar consists of the germs that
caused the fermentation. Still a third species of ferment may
cause another action, changing acetic acid to H2O and CO2. The
vinegar then tastes flat. HC2H3O2 + 4 O = 2H2O + 2 CO2.

Some mineral acids, as H2SO4 and HCl, and some organic acids, are
regarded as lifeless ferments. To this class are thought to
belong the diastase of malt and the pepsin of the stomach. This
variety of ferments exists in the seeds of all plants, and
changes starch to glucose.

331. Bread which is raised by yeast is fermented, the object
being to produce CO2, bubbles of which, with the alcohol, cause
the dough to rise and make the bread light.

Grapes and other fruits ferment and produce wines, etc., from
which distilled liquors are obtained.

332. Lactic Fermentation changes the sugar of milk, lactose, to
lactic acid, i.e. sour milk. In canning fruit, any germs present
are killed by heating, and those from the air are excluded by
sealing the can. Milk has been kept sweet for years by boiling,
and tightly covering the receptacle with two or three folds of
cotton cloth.

333. Putrefaction is fermentation in which the products of decay
are ill-smelling. Saprophytes attack the dead matter, feed on it,
and cause it to putrefy. This action, as well as that of ordinary
fermentation, used to be attributed solely to oxygen. Germs bring
back organic matter to a more elementary state, and so have a
very important function. By some scientists, digestion is
regarded as a species of fermentation, probably due to the action
of lifeless ferments; e.g. sucrose cannot be taken into the
system, but is first fermented to glucose.

334. Most Infectious Diseases are now thought to be due to
parasites of various kinds, such as bacteria, microbes, etc.,
with which the victim often swarms, and which feed on his
tissues, multiplying with enormous rapidity. Such diseases are
small-pox, intermittent and yellow fevers, etc. Consumption, or
tuberculosis, is believed to be caused by a microbe which
destroys the lungs. In some diseases not less than fifteen
billions of the organisms are estimated to exist in a cubic inch.
These multiply so rapidly that from a single germ in forty-eight
hours may be produced nearly three hundred billions. These germs
do not spring into life spontaneously from inorganic matter, but
come from pre-existent similar forms. Parasites are not so rare
in the system even of a healthy person as is generally supposed.
They are found on our teeth and in many of the tissues of the
body.

Several infectious diseases are now warded off or rendered less
virulent by vaccination, the philosophy of which is that the
organisms are rendered less dangerous by domestication; several
crops, or generations, are grown in a prepared liquid, each less
injurious than its parent. Some of the more domesticated ones are
introduced into the system, and the person has only a modified
form of the disease, often scarcely any at all, and is for a more
or less limited time insured against further danger.

Dust particles and motes floating in the air are in part germs,
living or dead, often requiring only moisture and mild
temperature for resuscitation. Most of these are harmless.

Chapter LX.

CHEMISTRY OF LIFE.

335. Growth.--The chemistry of organic life is very complex, and
not well understood. A few of the principal points of distinction
between the two great classes of living organisms, plants and
animals, are all that can be noted here. Minerals grow by
accretion, i.e. by the external addition of molecules of the same
material as their interior. A crystal of quartz grows by the
addition of successive molecules of SiO2, arranged in a
symmetrical manner around its axis. The growth of crystals can be
seen by suspending a string in a saturated solution of CuSO4, or
of sugar. In plants and animals the growth is very much more
complex, but is from the interior, and is produced by the
multiplication of cells. To produce this cell-growth and
multiplication, food-materials must be furnished and assimilated.
In plants, sap serves to carry the food-materials to the parts
where they are needed. In the higher animals, vari- ous fluids,
the most important of which is the blood, serve the same purpose.

336. Chemistry of Plants.--In ultimate analysis, plants consist
mainly of C, H, O, N, P, K. In proximate analysis, as it is
called, they are found to contain these elements combined to form
substances like starch, sugar, etc. Water is the leading compound
in both animals and plants. One of the most important differences
between animals and plants is, that all plants, except parasitic
ones, are capable of building up such compounds as starch from
mineral food-stuffs, while animals have not that power, but must
have the products of proximate analysis ready prepared, as it
were, by the plant. Hence plants thrive on minerals, whereas
animals feed on plants or on other animals. The power which
plants have of transforming mineral matter is largely due to
sunlight, the action of which in separating CO, was described.
The reaction in the synthesis of starch from CO2 and H2O in the
leaf, is thought to be as follows: 6 CO2 + 5 H2O = C6H10O5 + 12
O. C6H10O5 is taken into the tree as starch; 12 O is given back
to the air. All the constituents, except CO2 and a very small
quantity of H2O, are absorbed by the roots, from the soil, from
which they are soon withdrawn by vegetation. To renew the supply,
fertilizers or manures are applied to the soil. These must
contain compounds of N, P, and K. N is usually applied in the
form of ammonium compounds, e.g. (NH4)2SO4, (NH4)2CO3, and
NH4NO3. The reduction and application of Cas(PO4)2 for this
purpose was described. K is usually applied in the form of KCl
and K2SO4.

337. Food of Man.--In the higher animals the object is not so much
to increase the size as to supply the waste of the system. The
principal elements in man's body are C, H, O, N, S, P.

An illustration of the transformation of mineral foods by plants
before they can be used by animals is found in the Ca3(PO4)2 of
bones. This is rendered soluble; plants absorb and transform it;
animals eat the plants and obtain the phosphates. Thus man is
said to "eat his own bones." The food of mankind may be divided
into four classes (1) proteids, which contain C, H, O, N, and
often S and P; (2) fats, and (3) amyloids, both of which contain
C, H, O; (4) minerals. Examples of the first class are the gluten
of flour, the albumen of the white of egg, and the casein of
cheese. To the second class belong fats and oils; to the third,
starch, sugar, and gums; to the fourth, H2O, NaCl and other
salts. Since only proteids contain all the requisite elements,
they are essential to human food, and are the only absolutely
essential ones, except minerals; but since they do not contain
all the elements in the proportion needed by the system, a mixed
diet is indispensable. Milk, better than any other single food,
supplies the needs of the system. The digestion and assimilation
of these food-stuffs and the composition of the various tissues
is too complicated to be taken up here; for their discussion the
reader is referred to works on physiological chemistry.

338. Conservation.--Plants, in growing, decompose CO2, and
thereby store up energy, the energy derived from the light and
heat of the sun. When they decay, or are burned, or are eaten by
animals, exactly the same amount of energy is liberated, or
changed from potential to kinetic, and the same amount of CO2 is
restored to the air. The tree that took a hundred years to
complete its growth may be burned in an hour, or be many years in
decaying; but in either case it gives back to its mother Nature,
all the matter and energy that it originally borrowed. The ash
from burning plants represents the earthy matter, or salts, which
the plant assimilated during its growth; the rest is volatile. In
the growth and destruction of plants or of animals, both energy
and matter have undergone transformation. Animals, in feeding on
plants, transform the energy of sunlight into the energy of
vitality. Thus "we are children of the sun."

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