Taking as types hydrogen, hydrochloric acid, water and ammonia, he postulated that all organic compounds were referable to these four forms: the hydrogen type included hydrocarbons, aldehydes and ketones; the hydrochloric acid type, the chlorides, bromides and iodides; the water type, the alcohols, ethers, monobasic acids, acid anhydrides, and the analogous sulphur compounds; and the ammonia type, the amines, acid-amides, and the analogous phosphorus and arsenic compounds.
For instance, constant differences are found between the chlorides, bromides and iodides of sodium and potassium According to H.
With ammonia and alkaline bromides and iodides double salts are formed.
The bromides and iodides resemble the chlorides.
The anhydrous chlorides of nickel, cobalt, cadmium, barium, iron and lead act in the same way as catalysts at about 300° C., and the bromides of lead, cadmium, nickel and barium at about 320° C.