While air is merely a mixture of oxygen and nitrogen, this does not prove that these two elements cannot unite. In fact they do unite in five different proportions so as to form five different substances. These are given below to illustrate how different substances can be formed from Importance of proportioning food the same things, by merely combining them in different proportions. This example is also given to impress upon the mind of the practitioner the great importance of proportioning nutritive elements in diet so that the patient will not be overfed on some elements while underfed on others. It is absolutely essential, in order to know what effect a substance will have in the laboratory, or in the body, to know not only of what it is composed, but with what substances and in what proportions it is combined.
| Nitrous oxid | N2O |
| Nitric oxid | NO or N2O2 |
| Nitrogen trioxid | N2O3 |
| Nitrogen peroxid | NO2 or N2O4 |
| Nitrogen pentoxid | N2O5 |
To further illustrate the wonders of chemical combinations, we give the properties of two of these oxygen and nitrogen compounds:
Properties and uses of nitrous oxid
Nitrous oxid, N2O, is colorless, transparent, and has a slightly sweetish taste. When inhaled it causes a kind of intoxication which manifests itself in the form of hysterical laughing, hence it is commonly called "laughing gas." Inhaled in larger quantities it causes unconsciousness and insensibility to pain. It is, therefore, used in many surgical operations, particularly by dentists in extracting teeth.
Nitrogen peroxid, NO2, is a reddish-brown gas. It has an extremely disagreeable odor and is very poisonous.
Composition of nitric acid
By oxidation the nitrogen of animal substances is converted into nitric acid, HNO3. Furthermore, the silent, continuous action of minute living organisms in the cell is always tending to transform the waste-products of animal life into compounds closely related to nitric acid. This acid, as its chemical formula indicates, is formed by the combination of the three elements we have just studied, namely, hydrogen, nitrogen, and oxygen. Pure nitric acid is a colorless liquid. It gives off colorless, irritating fumes, when exposed to the air. Strong nitric acid acts violently upon many substances, particularly those of animal and Properties of nitric acid vegetable origin, decomposing them very rapidly. Nitric acid burns the flesh, eats through clothing, disintegrates wood, and dissolves metals. It is one of the most active of chemical substances.
The compounds of nitrogen that occur in food are very numerous and of complex composition. They will be discussed in Lessons III and IV, pages [99] and [125] respectively.
CHLORIN