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.
Importance of metals to digestive juices