244 AMINES. 



incinerating a portion of the dried residue, and calculating from 

 the carbonate of soda in the ash. In many analyses made in my 

 laboratory, the amovmt of soda in solution has been found to be 

 much smaller than was expected from calculation ; part of it was 

 evidently retained in the insoluble residue, 



§ 238. Other Nitrogenous Substances. — We possess hardly any 

 knowledge at all of the nitrogenous substances that are not dis- 

 solved by tvafer, alcohol, or alkali. I have already stated (§ 234) that 

 they may sometimes be extracted by hydrochloric acid and pepsin, 

 but TrefFner's researches on the chemical composition of the 

 mosses, alluded to in § 106, prove that this is not always the case. 

 I will here only remark that, in estimating the nutritive value of 

 a plant, such substances cannot, without further consideration, be 

 considered as albuminoids. 



AMINES AND THEIR COMPOUNDS. 



§ 239. Monamines. — According to A. W. Hofmann, monamines 

 may be distinguished from other amines by means of the isonitrile- 

 reaction, as the latter do not evolve the characteristic odour of 

 that compound when warmed with alcoholic potash and chloro- 

 form. 



Another reaction for monamines consists in warming an alcoholic 

 solution with bisulphide of carbon, by which a sulphocarbamide of 

 the base is produced. This compound, when heated with an 

 aqueous solution of mercuric chloride (not in excess) develops an 

 odour of oil of mustard. ^ 



§ 240. For the separation of ethylamine from diethyl- and triethyl- 

 amine by means of anhydrous ethyloxalate, see A. W. Hofmann f 

 the author subsequently availed himself of the method in separ- 

 ating the methyl bases. Carey Lea^ recommends picric acid for 

 the ethyl l)ases. 



In Hofmann's method the ethylamine is converted into diethyl- 

 oxamide, which can be recrystallizcd from water, and yields 

 ethylamine by distillation with potash. 



Diethylamine yields under the same conditions oily ethylic di- 

 ethyloxamate, Avhich can be purified by distillation (boils at 260°), 

 and converted by potash into diethylamine. 



^ Ber. d. d. chem. Gcs. iii. 767, 1870. 



2 Journ. f. pract. Chem. Ixxxiii. 191, 1861 ; Comptes rendus, Iv. 749, 1862. 



^ Chem, Centralblatt, 76, 1863. 



