Potatoes, for example, from which most of the starch of commerce is
manufactured, after being pared, are grated to a pulp. This pulp is put
upon a sieve and stirred about, while at the same time a little stream
of water is made to flow upon it. A milky liquid runs through the sieve,
but the fibrous portion of the potato, the vegetable tissue, remains
behind. This liquid, after a short interval, deposits a white powder,
which is the starch. By the simple process of tearing up the vegetable
tissue, and removing the inclosed starch by washing, this substance may
be procured from a great variety of plants.
_Why do potatoes, beans, rice, and most of the common vegetables,
swell up when boiled with water?_
Because the _starch absorbs water_ at the boiling temperature, which
causes the _cells to swell_, thereby giving to the vegetable a rounded
appearance.
_What is the composition of wheat flour?_
_Starch_ is one of the principal constituents of wheat flour, as well as
of all other kinds of meal. The other principal constituent is a gray,
tough, viscous substance, called _gluten_.
_To what does paste, made of wheat or rye flour, owe its
adhesiveness?_
In some measure to the _starch_, but principally to the _gluten_
contained in it.
_Can starch be converted into gum and sugar?_
It _can_; _fruits and plants effect this change naturally_: we can also
produce the change artificially by chemical processes.
_Why are potatoes frozen and thawed sweet?_
Because by the _freezing action_ the starch of the potato is in part
converted into sugar.
_Why are apples, pears, grapes, etc., in their unripe state sour,
and in their ripe condition sweet?_
In the unripe fruits mentioned _starch is present_; in the ripe fruits
it is _absent_; in the process of ripening the starch is _converted into
sugar_, and the fruit becomes sweet.
_What are acids?_
Acids are substances which excite the _taste of sourness_ when applied
to the tongue; they change the _blue juices_ of vegetables to _red_, and
combine with alkalies to form neutral compounds.
_What is an alkali?_
An _alkali_ is a body that possesses properties the _converse of those
of an acid_. It has a _highly bitter, acrid taste_, changes the _blue
juices_ of vegetables to _green_, or the juices of vegetables which have
been changed red by an acid, back again to blue. Potash and soda are the
representatives of the alkalies.
_When sulphur is burned in the air what is the product formed?_
_Sulphurous acid._
_What causes the suffocating odor of a lighted brimstone match?_
The _sulphurous acid_ generated by the combustion of the sulphur.
_What is sulphuric acid or oil of vitriol?_
It is a compound of _sulphur and oxygen_, containing one-third more
oxygen than sulphurous acid.
_What is sulphuretted hydrogen?_
A _gas_ formed by the union of _sulphur and hydrogen_. It possesses an
offensive odor, and is very poisonous.
_How is sulphuretted hydrogen formed in nature?_
Principally from the _decomposition of animal substances_, as blood,
flesh, hair, etc.
_Why does the yolk of an egg tarnish a silver spoon?_
Because it contains a _little sulphur_, which, at the temperature of an
egg just boiled, will decompose the water or moisture upon the spoon,
and produce _sulphuretted hydrogen gas_, which will tarnish silver.
Both the white and the yolk contain sulphur, but the latter the most
abundantly.
_What is it that makes an open or foul sewer so destructive of
health to any district in which it may be situated?_
The evolution of _sulphuretted hydrogen_. When inhaled, it acts directly
upon the blood, thickening it, and turning it black.
_Why do surfaces painted with lead paints, in the vicinity of
sewers, soon turn black, or become discolored?_
Through the action of _sulphuretted hydrogen_.
_What is nitric acid?_
Nitric acid, or aqua-fortis, is a compound of five parts of oxygen and
one of nitrogen.
It is _liquid_; when pure, _colorless_, and highly _corrosive_; it
attacks almost all dead, unorganized substances, and destroys living
tissues.
_What is muriatic, or, more properly, hydrochloric acid?_
A compound of _hydrogen and chlorine_ usually prepared from salt. It is
an acid much used in the arts.
_What is “lunar caustic”?_
A compound of _nitric acid_ and _oxide of silver_.
_Why, when lunar caustic is applied to the flesh, does it burn and
destroy it?_
Through the agency of the _nitric acid_ contained in it.
_Do plants produce acids?_
Acids are formed in the _vegetable kingdom_ in _great abundance_; they
especially exist in unripe fruits, imparting to them a sour taste.
Acids formed from mineral substances are called “mineral acids”; acids
formed by or from vegetable substances are called “organic acids.”
_Why does tanning hides convert them into leather?_
Hides are steeped in water, with ground bark of the oak, hemlock, or
other trees; these barks contain large quantities of _tannic acid_,
which combine with the skin of animals, and form a combination which is
insoluble in water and not subject to putrefaction--viz., leather.
_What is ordinary vinegar?_
An acid, called _acetic acid_, and water.
_If wine or beer be imperfectly corked, why does it rapidly turn
sour?_
Because air gets into the liquor, and the oxygen of the air combining
with the alcohol of the liquor produces acetic acid, or _vinegar_.
_What is alcohol?_
Alcohol is the _spirit_ existing in wine, beer, cider, etc., _obtained
in the process of fermentation_.
_What is a ferment?_
A ferment is a substance containing _nitrogen_ in a state of
_decomposition_, which is able to excite fermentation in solutions of
sugar; old cheese, putrefying flesh, blood, etc., all of them are
ferments.
_What is yeast?_
We apply the term yeast to a particular species of ferment; the _foam of
beer_ (or of some similar liquor), produced by _fermentation_.
_Can you explain why it is that a body in a state of fermentation or
putrefaction should cause unlimited quantities of similar matter to
pass into the same state?_
We only _know the fact_: the reason we are _ignorant of_. The most
minute portion of milk, paste, juice of grapes, flesh, or blood, in a
state of fermentation or putrefaction, causes fresh milk, paste, grape
juice, flesh, or blood, to pass into the same condition, when in contact
with them.
_In storing or packing fruit for future use why is it necessary to
carefully remove every decayed specimen?_
Because the decayed portions of one specimen will quickly _communicate
decay to the fresh fruit in contact_ with it, and soon the whole mass of
fruit will become putrescent.
_If in a vessel, or any other structure, one timber becomes decayed
what course ought to be adopted?_
It should be removed _immediately_, or the decomposition once commenced
will in time affect the whole structure.
It sometimes happens that physicians, in dissection, are seriously
poisoned by the slightest cut of a knife which has been used upon the
dead body. The knife introduces to the healthy blood, through the wound,
a _minute portion of matter in the state of decomposition or
putrefaction_. This acts as a _ferment_, and causes the healthy matter
in contact with it to pass into the same decomposed state. The action
once commenced rapidly extends, until the whole body becomes affected,
and death ensues. It is almost impossible to heal wounds of this
character.
_Why is it especially dangerous to eat fruit or meats partially
decayed?_
Because the _decayed portions_ of the substance eaten are liable to
induce the _same condition_ in the healthy organs of the stomach with
which they may come in contact.
_Why do fruit preserves frequently turn sour?_
Because, owing to the action of some fermenting substance present either
in the fruits themselves or in the air, the sugar used in preserving is
_converted into alcohol_, and the alcohol into vinegar.
_Why does the housewife scald her preserved fruits to prevent their
turning sour?_
Because fermenting substances and fermenting action are _destroyed_ by a
boiling temperature.
_Why do we keep preserves, beer, cider, or other substances liable
to turn sour, in a cool place?_
Because a depression of temperature _arrests fermentation_, though it
does not prevent its renewal when the temperature in increased.
_What is ether?_
Ether is a product obtained by _distilling strong alcohol_ and
_sulphuric acid_. The product is called sulphuric ether, but it does not
contain sulphuric acid, nor has it any sulphur in its composition.
_What are the properties of ether?_
It is an _exceedingly volatile, inflammable_ body, producing
insensibility when inhaled, and readily dissolving all fatty and oily
bodies.
_Why will ether remove spots of oil, paint, or grease from
garments?_
Because it is a _solvent_ for all greasy, oily matters.
_What are the best agents for depriving putrid and decaying animal
and vegetable substances of their offensive odors?_
_Chloride of lime_ is the most effectual agent; and _chloride of zinc_
and _sulphate of iron_ (green vitriol) are also exceedingly efficient.
On a large scale, as in the sanatory cleansing of towns, pulverized
charcoal, burnt clay, and quicklime are to be recommended.
_What effect does the use of perfumes or the burning of pastiles
have upon offensive odors?_
They merely _disguise_ the odor, but do _not remove or destroy it_.
_By adopting what precautions may a person safely enter sick rooms,
or visit, without risk, the most dangerous receptacles of filth?_
By moistening a linen cloth with vinegar, and sprinkling over it
finely-powdered chloride of lime.
Air breathed through this, applied to the mouth and nostrils, will enter
the lungs charged with a minute quantity of chlorine, which will
effectually destroy any noxious vapors or miasms that escape from
diseased bodies, or from decaying animal and vegetable substances.
_What three conditions are requisite to produce putrefaction in
animal and vegetable substances?_
It is necessary that they should be exposed to the combined influence of
_air_, _heat_, and _moisture_.
_Why is a substance preserved from decay by drying, or by the
exclusion of air from it?_
Because by so doing we _remove_ the _moisture_ and _air_ essential to
the process of decay.
_Why does the smoking of fish or flesh contribute to their
preservation?_
Because the volatile matters of the smoke, such as creosote,
pyroligneous acid, and the like, effect a species of _chemical
combination_ with the fiber of the meat, and with the substances
contained in the natural juices of the flesh, which combinations are
_less liable_ to decay than the substances themselves.
_What is albumen?_
Albumen is an _animal substance_ as well as _vegetable_. It exists most
abundantly, and in its purest natural state, in the _white of an egg_,
from whence it derives its name (_album ovi_), which is the Latin for
the white of an egg.
The serum or fluid portion of the blood (which, after exposure to the
air, is separated from the more solid part), the vitreous and
crystalline humors of the eye, the brain, the spinal marrow, and nerves,
all contain albumen.
_What is the yolk of an egg?_
This also consists of _albumen_, but contains in addition a _yellow
oil_, which imparts to it its color.
_Why is meat tough which has been boiled too long?_
Because the _albumen_ becomes hard, like the white of a hard-boiled egg.
The best way of boiling meat to make it tender is this: Put your joint
in very brisk boiling water; after a few minutes add a little cold
water. The boiling water will _fix_ the albumen, which will prevent the
water from soaking into the meat, keep all its juices in, and prevent
the muscular fiber from contracting. The addition of cold water will
secure the cooking of the _inside_ of the meat, as well as of the
surface.
_Why is meat always tough if it be put into the boiler before the
water boils?_
Because the water is not hot enough to _coagulate_ the albumen between
the muscular fibers of the meat, which therefore runs into the water,
and rises to the surface as scum.
_Why is the flesh of old animals tough?_
Because it contains _very little_ albumen, and much muscular fiber.
_What is a poison?_
A poison is any agent capable of producing a dangerous effect upon
anything endowed with life.
_In cases of poisoning by substances taken into the stomach, what
course should be pursued, in the absence of medical attendance?_
The first step is to evacuate the stomach by means of powerful emetics,
and when vomiting has taken place, warm water and the white of eggs may
almost always be given with advantage.
_Can poisons administered for criminal purposes be almost certainly
detected?_
They can; chemical science within the last few years has made such
advances that the most minute quantities of all the best known poisons
can be detected with certainty long after death.
There is no poison _so liable_ and _certain_ to be found as _arsenic_,
and in almost every case of poisoning with mineral poisons, science is
enabled to detect the substance, even when life has been extinct for
years, and the body nearly decomposed.
_What is arsenic?_
Metallic arsenic is an _exceedingly brittle metal_, of a _steel-gray
color_. It vaporizes, when heated, with a strong odor of garlic, a
property not possessed by any other metal.
The substance used as poison, and sometimes known as ratsbane, is
arsenious acid, a compound of arsenic and oxygen. Arsenious acid has the
form and appearance of a fine white powder.
_What is the best remedy in cases of poisoning with arsenic?_
The _hydrated peroxide of iron_ (iron rust) is considered the best
remedy.
The following is the best method for preparing this substance: Take
common copperas (sulphate of iron) four ounces; dissolve in warm water
in a glass, or porcelain dish, and add a small quantity of sulphuric
acid, and afterwards ammonia solution, so long as a dense red
precipitate is formed. This precipitate carefully strained off, and
thoroughly washed in a filter with water, is hydrated peroxide of iron.
So long as kept moist, it may be preserved for a great length of time.
_Is lead a poison?_
Lead and nearly all its compounds are _dangerous_ and _secret poisons_;
when received into the system, it frequently remains dormant for years,
and then suddenly manifests itself in various forms of disease.
_What is the disease called “painter’s colic”?_
A disease to which painters and others _working in lead are liable_, in
consequence of receiving into their system, imperceptibly, portions of
lead.
_Is it dangerous to sleep in, or breathe the air of, a room newly
painted with paints containing lead?_
It is _highly dangerous_, since the air is filled with a vapor of the
lead compound used as paint.
_Why are some waters, when conveyed through lead pipe, poisonous?_
Waters which are _very pure_ and contain _much oxygen_ dissolved in
them; waters which contain _nitric acid_ compounds, such as those
flowing from the vicinity of barn-yards, manure heaps, and those which
contain _common salt_ or _organic matter_, as water flowing from swamps
and fields; waters containing soluble _carbonates_--all dissolve lead
from the pipes through which they may be made to pass. Constant use of
such waters, in the process of time, will introduce sufficient lead into
the system to produce disease, which is often attributed to other
causes.
_What is verdigris?_
Verdigris is a compound of copper, oxygen, and acetic acid. This, and
all the compounds of copper, are _very poisonous_. The most efficacious
antidotes for poisoning with copper are white of eggs and milk.
_What is calomel?_
It is a compound of _two parts of mercury_ united to one of _chlorine_,
forming the sub-chloride of mercury. The preparation, commonly known in
medicine as “blue pill,” is a preparation of calomel.
_What is corrosive sublimate?_
A compound of _mercury and chlorine_ united in equal proportions,
forming the perchloride of mercury.
_Are both these compounds, calomel and corrosive sublimate,
poisons?_
They _are_; corrosive sublimate, especially, is a most _deadly poison_.
In case of poisoning by it, the most effectual antidote is white of
eggs.
_What is the process of preserving wood from decay, commonly termed
“kyanizing”?_
It consists in _saturating_ the fibers of the wood with a _solution of
corrosive sublimate_.
Poisonous substances, and corrosive sublimate especially, have the
property of protecting animal and vegetable substances from decay. The
skins of stuffed birds and animals, and the plants of a herbarium, may
be protected from insects and decay, by washing them with a solution of
corrosive sublimate. It should not, however, be forgotten that these
substances by such treatment become themselves poisonous.
_Give a list of the chief antidotes for poisons._
(See Book of the Human Body.)
_What are the common names of familiar chemical substances?_