POTASSIUM NITROSOSULPHATE. g 7 



here, such great loss, from one cause and another, that from ten grams 

 the quantity of pure salt recovered the fourth time amounts to only a 

 fraction of one gram. Now, such a salt as this, fully coming up, as 

 it does, to every expectation based on Pelouze's description, will quite 

 freely effervesce in its solution at 60° or above, and will all decompose 

 in a day or two, even at common temperatures, thus behaving in 

 accordance with Hantzsch's description. Pelouze, we may add, found 

 the less stable ammonium nitrososulphate to decompose slowly in 

 solution even at 0°, and quickly with effervescence at 40°. 



Another point of contrast noticed by Hautzsch in the effect of 

 heat on the two salts is that, while the salt he can prepare is gradually 

 but fully decomposed when heated up to about 90°, into sulphate and 

 nitrous oxide, Pelouze states that he found his salt not to lose weight 

 and not to decompose at 110°- 115°. 



We find the salt prepared by us to behave conformably with 

 Hantzsch's account, and feel ourselves justified in setting down 

 Pelouze's contrary statement to some oversight on his part, not 

 ourselves meeting in his description of his salts with that exactness, 

 which Hantzsch speaks of. Our own observations amount to what 

 follows. At the bottom of a test-tube, immersed in oil, the pure salt, 

 on two occasions, exploded at 91°, when heated in well-dried air. In 

 a capsule in the ordinary air-bath, some of the same pure salt reached 

 108° before it exploded. Again, at the bottom of a test-tube in oil, 

 in a gentle current of well-dried hydrogen, the salt exploded also at 

 108°. The decomposition is an exothermic one, and we are disposed to 

 attribute this difference from the tube experiments in air to the well- 

 known great cooling effect of the hydrogen being about equal in the 

 test-tube to that of the use of an open vessel in a capacious air-bath, 

 rather than to the exclusion of air by the hydrogen. In another 

 experiment made in dried hydrogen, the salt lost only 10 °/ , that is, 



