73 M. CHIKASHIGE. 



Mercuric perch lorate. 



Mercuric perchlorate is obtained when mercuric oxide is triturated 

 with aqueous perchloric acid until the resulting solution begins to 

 grow turbid from the presence of basic salt. The solution is filtered, 

 preferably through asbestus, mixed with a few drops of perchloric acid, 

 and evaporated at a gentle heat to a small volume. Evaporation is 

 then continued at the common temperature, over sulphuric acid, until 

 the salt crystallises out. If necessary, it may be recrystallised after dis- 

 solving it in a very little water. It is quite stable, but needs some 

 care to dry it, for in a desiccator it slowly effloresces, and in the air it 

 very quickly deliquesces (Serullas), while by slight rise of temperature 

 it melts. Preserved for a day or two in bottles, however, its upper 

 layers become dry by draining, and may then be quickly pressed 

 between folds of paper. 



Mercuric perchlorate crystallises in slender rectangular prisms, 

 as described by Serullas. Being exceedingly soluble in water, as well 

 as very hygroscopic, its slender crystals rapidly liquefy when exposed 

 to the air. It reddens litmus (Serullas), but its freedom from acid 

 can be shown by adding excess of sodium chloride to its solution, 

 which renders?it neutral. 



It shows a slight tendency to decompose with water. In absence 

 of any excess of acid, its solution deposits basic salt during evaporation 

 by heat. Also, its slow efflorescence in the desiccator is the result of 

 loss of acid as well as of water; so that the effloresced salt leaves some 

 insoluble basic salt when dissolved in water. 



Alcohol decomposes it more freely. The effect of this agent has 

 been described by Serullas, but I will here give a more definite state- 

 ment of its action, as observed by myself, than I find given in the hand- 

 books. Alcohol at once decomposes the crystals of the salt, leaving 



