VARIOUS DECOMPOSITIONS OF POTASSIUM CARBONATE. 483 



oxysalts of sulphur intervene ; compounds of which, in fact, 

 traces may be found by moderating the action. 



The well-known reaction of carbon disulphide on potassium 

 sulphate, which it changes into sulphide, may be roughly 

 regarded as the sum of those of sulphur and carbon. But 

 according to Schone it is also preceded by intermediate com- 

 pounds, such as sulphocarbonate. 



14. Sulphur and potassium carbonate. This is among the 

 number of reactions which have received the greatest amount 

 of investigation. At a red heat it yields polysulphide, sulphate, 

 and carbonic acid 



4C0 3 K 2 + 168 = 3K 2 S 5 + S0 4 K 2 + 4C0 2 . 



But these are also the extreme terms of successive reactions, 

 hyposulphite, for instance, forming at 250, according to 

 Mitscherlich. 



15. Carbon and potassium carbonate. This reaction yields at a 

 red heat carbonic oxide and potassium oxide, not without there 

 being formed various secondary compounds, such as the acety- 

 lides. The dissociation of potassium carbonate also intervenes 

 (Deville). 



16. Potassium carbonate and sulphurous acid. If the gas 

 passes rapidly, the red-hot salt changes into sulphate, with only a 

 trace of sulphide. If the current is slow the sulphide increases. 



17. Carbonic acid and sulphite. Sulphate, polysulphide, 

 and a little carbonate are formed. Metasulphite (anhydrous 

 bisulphite) gives the same products. 



18. Carbonic acid and potassium polysulphide. In a red-hot 

 tube some sulphur is sublimed, and the gas liberated contains 

 about three per cent, of a mixture of carbonic oxide, sulphurous 

 acid, and oxysulphide. It is the same reaction as that of sulphur 

 on carbonic acid, which is attributable to the dissociation of 

 the latter compound. A small quantity of alkaline carbonate 

 appears also to result from this dissociation ; the oxygen 

 supplied by the latter concurring with the excess of carbonic 

 acid to displace the sulphur. 



19. From these facts, there result several consequences con- 

 nected with the study of the reactions produced during the 

 explosion of powder. 



For example, if potassium carbonate subsists in any consider- 

 able amount in presence of sulphur resulting from the dissocia- 

 tion of the simultaneously produced polysulphide, it is apparently 

 because both salts do not form at the same spot of the substance 

 in ignition. The same sulphur would also attack the potassium 

 sulphate if both bodies were kept together at the same point. 

 The carbonic oxide would also destroy the sulphate if it were 

 formed at the same spot, or if it remained for some time in 

 contact with the melted salts, etc. 



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