54 REMARKS ON SOME OF THE MERCURIAL COMPOUNDS. 
composed by hydrochloric acid in excess, the residue will be 
found to darken on the addition of ammonia, &c. indicating 
the union of the acid with the protoxide of mercury. By this 
it is not intended to deny that the greater part of the mercury 
is in a minute state of division, but to assert that in this con- 
dition it is inert, and only owes its activity to the portion 
which is oxidized. As this compound is generally obtained, 
it is from manufacturers in London, where it is made on a 
large scale, and hence always contains more protoxide of mer- 
cury than when prepared according to the directions of the 
United States Pharmacopoeia. This must be evident, inas- 
much as in the preparation of eight ounces (the quantity re- 
commended by the United States,) the mercury is not sub- 
jected necessarily to the same action and exposure as when 
prepared by machinery on a larger scale, and is proved by 
the result that the English article, when given to children, 
will generally act as an emetic, and occasionally violently so, 
whereas when prepared in smaller quantities, it exerts an op- 
posite effect, and even will allay vomiting. Numerous cases 
have confirmed the truth of these remarks, and a compound 
like this which is generally used in the diseases of children, 
where the stomach is generally irritable, should always be 
prepared by the vender; when properly prepared there is no 
mercurial compound of a milder character, less liable to ob- 
jection, better suited to the diseases of children, and proves at 
the same time the fallacy of the idea which attributes its,ac- 
tion to aught else than the protoxide of mercury, 
UNGUENTA HYDRARGYRI. 
In these preparations the mercury is gradually extinguished 
by trituration with lard, suet, and other oleaginous com- 
pounds, and the different varieties only depend on the relative 
quantity of each ingredient. To enter into any minute in- 
vestigation as to the cause of their activity is deemed unne- 
cessary, as, if the principles which have been already men- 
tioned be correct, (and they are justified both by chemical 
