| NH2(C2H5) | + | CS2 | = | CS=N-C2H5 | + | H2S. |
| Ethylamine. | Ethylmustard oil. | |||||
Where a sufficient quantity of an amine is obtained, the primary, secondary, or tertiary character of the amine may be deduced with certainty by treating it with methyl or ethyl iodide.
A molecule of the base is digested with a molecule of methyl iodide and distilled with potash; the distillate is in the same manner again treated with methyl iodide and again distilled; and the process is repeated until an ammonium base is obtained, which will take up no more iodide. If three methyl groups were in this way introduced, the original substance was primary, if two, secondary, if one, tertiary.
The quaternary bases, such as tetraethyl ammoniumoxhydrate, decompose, on heating, into triethylamine and ethylene; the corresponding methyl compound in like manner yields trimethylamine and methyl-alcohol.
On the other hand, the primary, secondary, and tertiary bases do not decompose on heating, but volatilise without decomposition.
The chief distinctions between these various amines are conveniently put into a tabular form as follows:—
| Primary, NH2R. | Secondary, NHR2. | Tertiary, NR3. | Quaternary, NR4(OH). | |
|---|---|---|---|---|
| On treating with methyl iodide it takes up the following number of methyl groups, | 3 | 2 | 1 | ... |
| Reaction with nitrous acid, | Decomposes with evolution of nitrogen gas. | Formation of nitrosamine. | ... | ... |
| Mustard oil, &c., on treatment with CS2 and sublimate, | Mustard oil formed. | ... | ... | ... |
| Chloroform and alcoholic potash, | Formation of carbylamine. | ... | ... | ... |
| Effect of strong heat, | Sublimes. | Sublimes. | Sublimes. | Decomposes. |
| On addition of acids, | Combines to form salts. | Combines to form salts. | Combines to form salts. | ... |
§ 653. Methylamine, CH3NH2.—This is a gas at ordinary temperatures; it is inflammable, and possesses a strong ammoniacal odour. It has been found in herring brine, and is present in cultures of the comma bacillus; it has also been found in poisonous sausages, but it is not in itself toxic.
It forms crystalline salts, such as, for example, the hydrochloride, the platinochloride (Pt = 41·4 per cent.), and the aurochloride (Au = 53·3 per cent. when anhydrous). The best salt for estimation is the platinochloride, insoluble in absolute alcohol and ether.