486 POWDERS WITH A NITRATE BASE. 



Further, the neutral sulphite should be decomposed in its 

 turn into sulphate and sulphide. 



'Now, the author has ascertained, operating in a very confined 

 space filled with dry nitrogen, with a progressive heating, and 

 collecting the gases as they were formed, to prevent their 

 further reactions on the remaining salts 



1st. That the volume of the sulphurous gas is exactly the 

 half of the volume required by the second formula (normal 

 bisulphite). 



2nd. That the salt residuum consists of almost pure sulphate, 

 only exercising an insignificant action on an iodine solution. 



The transformation is perfectly definite when the metasulphite 

 alone is heated. In a current of an inert gas, such as nitrogen, 

 or even in a considerable space filled with this gas, metasulphite 

 commences to be decomposed into sulphurous acid, which is 

 carried off, and neutral sulphite, which afterwards yields a 

 certain amount of sulphide. But these complications may be 

 avoided by operating as has been described. These reactions 

 characterise metasulphite most distinctly. 



4. DECOMPOSITION BY HEAT OF THE ALKALINE HYPOSULPHITES. 



1. On the occasion of the discussion which was raised some 

 years since on the composition of the products of explosion of 

 powder, the author showed that potassium hyposulphite, shown 

 by former analyses to the extent of 34 per cent., does not in 

 reality pre-exist in any appreciable proportion among these 

 products, but is introduced during the analytical manipulations. 

 This demonstration is based on the fact that potassium hypo- 

 sulphite is entirely destroyed near 500, a temperature far lower 

 than that of the explosion of powder. It was finally accepted, 

 not without opposition at the outset, by Noble and Abel, after 

 the experiments of Debus, who proved that the hyposulphite 

 found in the analysis resulted from the use of cupric oxide to 

 eliminate the alkaline polysulphides. 



The author since proved the same with zinc oxide. This 

 oxide, acting on potassium polysulphide, yields besides zinc 

 sulphide some hyposulphite, sulphate, and hyposulphate, the 

 relative proportion of sulphur contained in the three latter 

 bodies being 1118 and 8 in one experiment. The presence of 

 the hyposulphite in particular had escaped notice previously ; 

 it is probable that this body is produced also with cupric oxide. 

 It is even formed, though only in small quantities, when 

 polysulphide is destroyed by zinc acetate. 



2. These facts being ascertained, it seemed desirable to 

 determine more accurately the temperatures of decomposition 

 of the alkaline hyposulphites. The experiments were made 



