86 



E. DIVERS AND T. HAGA. 



actually is the reading of other chemists before us, that property, 

 which Hantzsch regards as, above all, characteristic of Pelouze's salts, 

 has no existence in fact. 



Hantzsch says, further, that the greater decomposability of his 

 own potassium salt stands in striking contrast with the relatively 

 great stability of Pelouze's salt, which, according to the latter, can be 

 purified by dissolving it in boiling water and then recrystallising, with 

 loss only of a small part of it through decomposition. The greater 

 instability of Hantzsch's preparation is seen, according to him, in the 

 fact that its solution in water decomposes somewhat quickly even at 

 the common temperature, and with effervescence when gently heated. 



But we find both descriptions to be true of one and the same 

 preparation. Any sample of the salt, as obtained by us in a strongly 

 alkaline mother-liquor, following Pelouze's directions, which has been 

 thoroughly well drained on a tile, so as to be almost pure and, though 

 alkaline to litmus, yet without the least caustic taste, can be purified, 

 as Pelouze says, by dissolution in the proper quantity of boiling water 

 and quick cooling of the solution. There will, it is true, be brisk 

 effervescence, but the greater part of the salt will be recovered and 

 will be free from sulphate, after draining on a tile. Then, again, the 

 pure salt can be dissolved in just sufficient boiling water, with but 

 little effervescence and quite small loss, if only to the water has been 

 added a few drops of dilute solution of potassium hydroxide, and that 

 the hot solution is cooled quickly by immersion in cold water. The 

 same crystals may then be redissolved in their mother-liquor, and the 

 solution brought to full ebullition over a naked flame, and, yet, much of 

 the salt be recovered, provided the solution is quickly cooled. Further, 

 using each time water at 50° with no alkali at all, the pure salt may be 

 dissolved and recrystallised four times over, collecting and draining 

 the crystals each time, and testing them for purity, though there is 



