82 



M. CHIKASHIGE. 



per cent, and then ceases. This loss, though mainly that of water, 

 includes also that of a little acid. A loss of half its water would 

 amount to 5*36 per cent, of its weight. At 100°, in a current of dry 

 air, it loses about 2 per cent, of water in six hours, a mere trace of 

 acid also escaping, as was proved by placing litmus-paper in the 

 issuing current of air. In another six hours it loses about 2 per cent. 

 more in weight, including now a notable amount of acid. 



As already stated, the salt is gradually decomposed by water. 

 The white basic salt thus produced becomes, when washed with water, 

 black from loss of acid. Alcohol decomposes the solid salt into soluble 

 acid -salt and white basic-salt, which is also blackened by washing with 

 water, but not by alcohol. Alcohol, added to an aqueous solution of 

 the salt, has no immediate effect. 



In analysing the salt, the perchloric acid was determined in 

 the same way as in the mercuric salt, after removal of the mercury 

 as sulphide. The mercury was estimated in a separate portion of 

 the salt by precipitation as mercurous chloride. The composition 

 of the salt has been given by Roscoe as that expressed by the 

 formula, (HgCJ0 4 ),,6H 2 0, he having found the mercury to be 56*60 

 per cent., in perfect agreement with the calculation for that formula. 

 Nevertheless I have assured myself, by examining different prepara- 

 tions, that the crystals I can obtain hold always, when not visibly 

 moist, only four mois, water — (HgCl0 4 ),,4H 2 0. 



Calc. I. II. III. IV. 



Mercury 59*61 59*00 58*90 — — 



Perchlorate radical 29*66 — — 29*60 29*50 



Water 10*73 — — — — 



It might seem from our respective results, that we had examined 

 different hydrates, but in the several preparations I made of the salt, I 

 never met with but one form of crystal which, with rapid evaporation 



