PHARMACOPCEIA OP ROYAL COLLEGE OF PHYSICIANS. 325 
until the excess of acid is expelled. This is a most awkward 
method; besides, that this residual salt is much sought after in 
the arts. A much preferable method, is the direct addition of 
strong sulphuric acid to a concentrated solution of carbonate 
of potash. The acid will require to be added cautiously in a 
large vessel, on account of the violent effervescence; but the 
sulphate is thrown down in the form of minute, easily-powder- 
ed crystals, which, by those who are acquainted with the diffi- 
culty of pulverizing this salt, will be esteemed an advantage. 
Iodide of mercury is directed to be prepared by rubbing 
together an ounce of mercury with five drachms of iodine; 
a little alcohol being added during the trituration. We pre- 
pared some in this way, and mixing it with a solution of 
chloride of sodium, allowed it to filter; upon the addition of 
nitrate of silver, a copious precipitate was thrown down, 
which only partially dissolved in water of ammonia. The 
iodide of mercury evidently contained a large quantity of 
biniodide. 
It is quite unnecessary to multiply instances. We think 
we have sufficiently proved both our propositions; and that it 
will be generally allowed that the chemical processes of the 
Pharmacopoeia are insufficient, and incapable of producing 
pure or cheap articles. Is it not a gross perversion of power, 
thus to dictate to manufacturers the method and the materials 
they are to use, in preparing things about which they must 
necessarily know most. The College have placed themselves 
in this predicament: either to oblige compounders to use no 
chemicals, except those that are made " nostro more," and so 
inflict a grievous hardship; or to connive at the use of com- 
pounds prepared very differently from their commands, and 
so dishonour the king's warrant. Leaving the College to 
wriggle, as well as they can, from between the horns of this 
dilemma, we proceed to examine the remainder of their 
preface. 
The next subject of importance referred to, is the change 
of names, which, they assert, is one of considerable difficulty; 
but it appears that they have made up their minds, for they 
VOL. III. — NO. IV. 41 
