Classification of the War Gases

The classification of the war gases is particularly difficult because of the many aspects which these substances, some similar to one another, some completely different, present. The number of methods of classification which have been proposed are an indication of this difficulty. 

The physical classification of the war gases has often been proposed by taking as criterion either their state of aggregation, or their boiling point. 

The physiopathological classification of the war gases, though used very widely, is even less exact than the others mentioned. In point of fact the biological action of these substances is extremely complex and in certain concentrations a gas may change its action to that of another group. 

Classification of the war gases according to the characteristic chemical groups in their molecules has been almost completely neglected. It is only by taking the chemical characteristics of the substances as the sole criterion that it will be possible to elaborate a precise and complete classification of the war gases, and these chemical characteristics must be quite definite both as to the nature and the number of atoms in the molecule. 

The first attempts at a chemical classification of the war gases were those of Chugaev in 1918 and of Zitovic. These classifications are, however, merely schematic and are particularly lacking in precise and distinctive characteristics. 

This classification is based on the criterion of the tactical emplo5unent of the war gases. From this view-point they are divided into two groups ... 

The method of classification most used to-day is based on their state of aggregation at ordinary temperatures. According to this classification the war gases are divided as follows into three groups ... 

Meyer s Theory. According to this theory, the physiopathological action of war gases is attributed to certain atoms or radicles which have a tendency to react easily with other substances by addition. This classification on the basis of their ease of reaction should be determined by their combination with the various biological entities or tissues (as the blood, the nerve cells, the respiratory epithelia, etc.) which undergo specific and characteristic alterations. 

This classification is based on the most characteristic action of each war gas on the living organism. Various classifications have been made on this basis (German, English, American, etc.). The usual method is to divide the gases into the following classes ... 

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