AMMONIUM SULPHITES, THIOSULPIIATE AND TRITHIONATE. 205 



in the inverse order of that followed above, in accordance with 

 usage. This is done because of the nature of the products. 



Ammonium trithionate. — This salt is hardly affected until the 

 temperature is above 150°, and at 160-170° it steadily decom- 

 poses into sulphur dioxide and a residue of ammonium sulphate 

 and unfused sulphur. The non-fusion of the sulphur is remark- 

 able and only to be referred to the presence of minute quantitities 

 of impurities. It all dissolved readily in carbon bisulphide, and 

 crystallised out on evaporating the solvent. 



It can hardly be doubted but that ammonium tetrathionate 

 (and peniathionate, if it can exist) would decompose in the same 

 way as trithionate. Ammonium hyposulphate (dithionate) has been 

 shown by Heeren {Pogg., 1826, 7, 55), and more definitely by 

 Kluess {Ann., 1888, 246, 194) to first become anhydrous, if not 

 already so when heated, and then to decompose at about 130° 

 into sulphur dioxide and a residue of ammonium sulphate. 



Anwioniuvi thiosulphaie. — Zeise, in 1824 {Gm. Hbh) found 

 this salt to be converted by heat into water, ammonia, and a sub- 

 limate of sulphur, much thiosulphate again and sulphite, and a 

 little sulphate. This result must have been obtained by rough 

 heating. A much more weighty statement is that made by 

 Spring {Ber., 1874, 7, 1159), namely, that the dry salt can be 

 sublimed unchanged, intermediate dissociation being admitted. 

 We have found it to decompose very slowly at 150°, the main 

 products being a sublimate of anhydrous normal sulphite and 

 a residue of sulphur unfused, as in the case of the trithionate. 

 But, also very small quantities of hydrogen sulphide and am- 

 monia passed off in the current of nitrogen, and the sublimate 

 contained a very little of a salt having some of the properties 

 of trithionate and which did not strike the violet colour with 



