ON LIQUOR HYDRARGYRI PERCHLORIDI, B.P. 
545 
advantageously employed as a solvent for the mercurial salt, instead of a mix¬ 
ture of water and spirit of wine. A deposit was formed in the solution, appa¬ 
rently from the decomposition of the bichloride and a remark, appended to 
the formula, says:—“ In the former Pharmacopoeia the solvent power of 
water was increased by spirit of wine, instead of hydrochlorate of ammonia as 
now directed.” Now the solution made according to his process does not 
contain a trace of perchloride of mercury as such. Mr. Phillips, in trying to 
obtain a stable solution, seems purposely to have overlooked the fact, that a 
solution of a double salt is formed, although the quantity of chloride of am¬ 
monium be much in excess of that necessary for its production. This salt is 
the ammonio-mercuric chloride, or sal alembroth of the alchemists, a definite 
compound, crystallizing in flattened rhombic prisms, and having the compo¬ 
sition of, 
2NTff 4 Cl. HgCh. H 2 0. 
There is a corresponding double salt formed with iodine, the iodo-hydrar- 
gyrate of ammonia of Boullay. 
2NH 4 I. HgI 2 3H 2 0. 
Two other salts of the perchloride of mercury and chloride of ammonium, 
are known, one having the composition of, 
NH 4 C1. HgClo. 
And the same with | at. of water, 
2(NH 4 C1. HgCl 2 )H 2 0. 
As we are directed in making the solution to use equal quantities by weight 
of chloride of ammonium and perchloride of mercury,—that is, about five equi¬ 
valents of the former to one of the latter,—the following equation will pro¬ 
bably show the result:—• 
5NII 4 Cl+HgCl 2 +H 2 0=2NPI 4 Cl. HgCl 2 . H 2 0+3NH 4 C1. 
There may possibly be a salt with more atoms of the ammonium salt, but 
such a salt is not at present known, and reasons can be assigned for its non¬ 
existence. Under any circumstance the solution will not contain perchloride 
of mercury as such, and this can be proved by experiment. 
In the first place, the perchloride in the Pharmacopoeia solution is rendered 
much more soluble. A solution of the double salt, containing, of the per¬ 
chloride, equivalent to one part in two of water kept at a temperature of 100° 
F. showed no tendency to crystallize. 
There is likewise a well-known powerful chemical affinity existing between 
perchloride of mercury and albumen. In the Pharmacopoeia solution this 
affinity is lessened, and combination does not take place when it is mixed with 
a solution of albumen until some time has elapsed—until in fact the albumen 
has split up the double salt. 
Again, and this is the most important, perchloride of mercury is soluble at 
ordinary temperatures in 16 parts and upwards, of common water, forming a 
clear solution, but if we attempt to make the Pharmacopoeia solution with 
common water, a dense, and at first, flocculent, white precipitate is formed. 
If even tlie solution be made with distilled water, and then diluted further 
with common water, the same precipitate occurs. 
This precipitate, collected by filtration, washed, carefully dried,and digested 
with liquor potass£e, changes to a yellow colour, forming mercuric oxide ; 
ammonia is evolved, as a piece of moistened turmeric paper, laid over the 
mouth of the test-tube containing it, is turned brown, it can likewise be de¬ 
tected by its odour; and the fluid, filtered and acidulated with nitric acid, 
