Note 40 — Chapter XX · SULPHUR, SELENIUM, AND TELLURIUM

The instability of this salt is very great, and may be compared to that of the compound of ferrous sulphate with nitric oxide, for when heated under the contact influence of spongy platinum, charcoal, &c., it splits up into potassium sulphate and nitrous oxide. At 130° the dry salt gives off nitric oxide, and re-forms potassium sulphite. The free acid has not yet been obtained. These salts resemble the series of sulphonitrites discovered by Frémy in 1845. They are obtained by passing sulphurous anhydride through a concentrated and strongly alkaline aqueous solution of potassium nitrite. They are soluble in water, but are precipitated by an excess of alkali. The first product of the action has the composition K3NS3HO9. It is then converted by the further action of sulphurous anhydride, cold water, and other reagents into a series of similar complex salts, many of which give well-formed crystals. One must suppose that the chief cause of the formation of these very complex compounds is that they contain unsaturated compounds, NO, KNO2, and KHSO3, all of which are subject to oxidation and further combination, and therefore easily combine among each other. The decomposition of these compounds, with the evolution of ammonia, when their solutions are heated is due to the fact that the molecule contains the deoxidant, sulphurous anhydride, which reduces the nitrous acid, NO(OH), to ammonia. In my opinion the composition of the sulphonitrites may be very simply referred to the composition of ammonia, in which the hydrogen is partly replaced by the radicle of the sulphates. If we represent the composition of potassium sulphate as KO.KSO3, the group KSO3 will be equivalent (according to the law of substitution) to HO and to hydrogen. It combines with hydrogen, forming the potassium acid sulphite, KHSO3. Hence the group KSO3 may also replace the hydrogen in ammonia. Judging by my analysis (1870) the extreme limit of this substitution, N(HSO3)3, agrees with that of the sulphonitrite, which is easily formed, simultaneously with alkali, by the action of potassium sulphite on potassium nitrite, according to the equation 3K(KSO3) + KNO2 + 2H2O = N(KSO3)3 + 4HKO. The researches of Berglund, and especially of Raschig (1887), fully verified my conclusions, and showed that we must distinguish the following types of salts, corresponding with ammonia, where X stands for the sulphonic group, HSO3, in which the hydrogen is replaced by potassium; hence X = KSO3: (1) NH2X, (2) NHX2, (3) NH3, (4) N(OH)XH, (5) N(OH)X2, (6) N(OH)2X, just as NH2(OH) is hydroxylamine, NH(OH)2, is the hydrate of nitrous oxide, and N(OH)3 is orthonitrous acid, as follows from the law of substitution. This class of compounds is in most intimate relation with the series of sulphonitrous compounds, corresponding with ‘chamber crystals’ and their acids, which we shall consider later.