OBSERVATIONS ON MURIATIC ACID. 24«1 



it does not feem to differ chemically ; nor does it contain any 



fenfible portion of" water of cryftallization. The fame may be 



faid of corrofive fublimate. 



It nOvv remains to fpeak of the real hyperoxtgenized muriate Hyper-ox. mur. 



of mercury. I paffed a current of oxigenized muriatic acid o bt ™ed U by paf- 



gas through fome water, in which there was red oxide of mer- ring ox. m. gas 



cury *. After a fhort time, the oxide became of a very dark thr ° u S h wat « 

 J ' J containing red 



brown colour ; and a folution appeared to have taken place, oxide of mer- 



The current was continued for fome time ; and, when I thought cur y* 



that a fufficient quantity of the oxide had been diffolved, I 



flopped the operation. The liquor was evaporated to drynefs; 



and the fait was thus obtained. There evidently was in the 



mafs a great proportion of corrofive fublimate, as might be 



expected, from what I had obferved to take place in the forma- It is more foluble 



tion of the other falts of this acid ; but, by carefully Separating ** n .*°£ Jjj^ 



the laft formed cryftals, I could pick out fome hyperoxigenized by cryftalliza- 



muriate of mercury* I then cryflallized it over again; and, tl0n * 



in this manner, I obtained it nearly pure. This fait is more 



foluble than corrofive fublimate : about four parts of water 



retain it in folution. The fhape of its cryftals, I cannot well 



gas ; yet more mercury is diffolved. The nitrate of mercury, there- 

 fore, rather contains an oxide lefs oxidized after ebullition than be- 

 fore it. The true difference is in the fub-nitrate of mercury, pre- 

 cipitated, as I before faid, by the water in which the muriate of foda 

 was diffolved. And the orange-coloured powder, which remains 

 after an attempt to fublime Scheele's calomel, is to be attributed to 

 the fame caufe. To prepare calomel in the humid way, uniform as Preparation of 

 to itfelf, and in all refpects fimilar-to that prepared in the dry way, calomel in the 

 it is neceffary, either to ufe the nitric folution before it has boiled, numid wa y* 

 or to pour fome muriatic acid into the folution of muriate of foda, 

 previoufly to mixing it with the boiled folution of nitrate of mer- 

 cury. In the fir ft cafe, no precaution is neceffary; and, in the lat- 

 ter, the oxide of mercury, which the nitrate of mercury has, by 

 boiling, taken up in excefs, finds an acid which is ready to faturate 

 it. All the mercurial oxide being thus converted into calomel, none 

 of that fub-nitrate of mercury can be prefent. 



The objections made by a medical gentleman againft Scheele's 

 calomel, when this paper was read before the Royal Society, led me 

 to reconfider the fubjeel, and to undertake the inveftigation detailed 

 in this note. 



* I ufed either of the red oxides of mercury indifcriminately. 



Vol. III. — December, 1802. R determine. 



