If we should try many experiments of neutralizing alkalis with acids, we would discover these general rules:

1 All acids contain hydrogen.

2 All alkalis contain oxygen and hydrogen in equal proportions.

3 When these substances react, the hydrogen of the acid joins the hydrogen of the base or alkali, forming water, H20.

4 The metal of the base always replaces the hydrogen of the acid.

2K0H +H2SO4 = K2S04 +2H20

Potassium Sulfuric Potassium hydroxid + acid = Sulfate + Water (alkali or base) (acid) (Salt)

(In the above equation the potassium (K) of the potassium hydroxid replaces the Hydrogen (H) in the sulfuric acid.).

5 The other elements of the original compounds unite to form a new substance, which is neither acid nor alkali, but which is termed a salt.

The names of a few common acids, bases and salts, and their chemical formulas, are given here, as many of them will be important in the pursuance of this work.

Acids

HC1 ......Hydrochloric (in gastric juice)

HN03.....Nitric

H2S04 ....Sulfuric C2H402 ... Acetic (vinegar) C6H8O7 .. .Citric (lemon juice)

Bases

NaOH ... .Sodium hydroxid (caustic soda)

KOH .....Potassium hydroxid (caustic potash)

Ca(OH)2.. .Calcium hydroxid (slaked lime) NH4OH ... Ammonium hydroxid

(Ammonia gas dissolved in water produces this alkali.) The equation for this is as follows: NH3 + H20 + NH4OH

(Ammonia) gas + Water + Ammonium hydroxid.

Salts

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)

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.

Fonnation of salts in the human body.

When sulfur is burned in air it forms sulfur dioxid, SO2, which is used for the purpose of fumigation or destroying alleged disease 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 elments, 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, 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.

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.

Importance of metals to digestive juices.

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.

Iron in patent medicines.