NaCl .......Sodium chlorid (table salt)
KNO₃ .......Potassium nitrate (salt-peter)
CuSO₄ ......Copper sulfate (blue vitriol)
Ca₃(PO₄)₂ ..Calcium phosphate (normal)
(The mineral of bones)
[Sidenote: Formation of salts in the human body]
FLUORIN, BROMIN, IODIN--These three elements are in many respects like
chlorin. The first is a gas, the second a heavy, reddish-brown liquid
at ordinary temperature, and the third a dark, grayish crystalline
solid. These elements all form acids just as chlorin forms hydrochloric
acid. These acids produce salts, and these various salts exist in small
quantities in the human body.
MINERAL SULFUR--This element is of no particular importance or use to
the body, as it is insoluble and cannot be digested. The compounds of
sulfur, however, are numerous and important. Sulfuric acid, sometimes
called oil of vitriol, is one of the most active chemicals known, and
is especially destructive to living tissue, as it combines with the
water in the tissue so rapidly as to char or burn it.
When sulfur is burned in air it forms sulfur dioxid, SO₂, which is used
for the purpose of fumigation or destroying alleged dis-ease germs.
This SO₂ dissolved in water gives H₂SO₃, sulfurous acid. By oxidizing
this another part of oxygen is added, forming H₂SO₄. All three of these
compounds are poisonous and harmful.
HYDROGEN SULFID, H₂S, is a poisonous gas with a bad odor. It is formed
by the decay of certain food substances, such as eggs. Sometimes this
gas occurs in intestinal fermentation.
CARBON DISULFID, CS₂, is used extensively to kill insects. The salts
of sulfuric acid, or sulfates, are quite important, and many of them
are poisonous. Glauber's salt (sodium sulfate Na₂SO₄) and Epsom salts
(magnesium sulfate MgSO₄) are extensively used by the medical profession
as purgatives. These poisons cause the intestines to act violently in an
effort to throw out the offending substances.
VEGETABLE SULFUR IN THE HUMAN BODY--I have herein mentioned a number
of sulfur compounds which are foreign or harmful to animal life. In
wonderful contrast to this is the fact that sulfur is an essential
constituent of the human body, and in certain complex compounds with
nitrogen and other elements, forms the brain, nerves, and many other
body-tissues.
PHOSPHORUS--This element is useful in the manufacture of common matches
because it possesses the power to ignite by friction. The things of
interest to the food scientist, however, are the salts of phosphoric
acid. These enter largely into the bones, and to some extent into the
nerves and other organs of the body.
SILICON is the element which, combined with oxygen, forms the greatest
part of the rocks and the sand of the solid earth. It forms the shell of
certain sea-animals. In the human body it is found in the teeth and in
the bones in very small quantities.
METALS--Metals, when united with oxygen and hydrogen, form the bases of
nearly all the substances studied in this lesson. When these act with
acids they produce the salts. It is these salts of the metals that are
of most interest to us. The salts of common metals, such as copper, tin,
lead, and iron do not enter into the composition of the human body, and
many of these are decidedly poisonous, especially those of copper, lead,
mercury, and arsenic.
[Sidenote: Importance of metals to digestive juices]
The metals whose salts are found in the body are sodium, potassium,
calcium, and magnesium. These metals in their elementary state are
seldom seen outside a chemist's laboratory, but we can judge of their
importance when we remember that the digestive juices contain these
metals. The teeth and all bony substances are formed from these
compounds, and the ability of all body-fluids to carry food material
in solution depends upon a definite per cent of these metal salts. The
study of minerals, or of mineral salts contained in food, together with
their uses in the body, forms an important subdivision of food chemistry.
IRON--Iron is mentioned separately from other metals because it not only
yields salts that occur in small quantities in the body, but because,
like sulphur, it enters into the complex nitrogenous portions of the
body to form part of the living substance itself.
[Sidenote: Iron in patent medicines]
This organic iron, as it is sometimes called, occurs chiefly in the red
blood-corpuscles. The patent medicines which are exploited for the iron
they contain, are frauds so far as nourishing the body is concerned. The
popular deception is caused by the general belief that all compounds
containing the same elements are alike in their uses. One might as well
swallow iron filings as to endeavor to build red blood corpuscles out of
the mineral solution of iron.