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SELECTED ARTICLES. 
the addition of nitric acid or fresh crystals, as recommended by 
some, such addition being liable to render the product of an 
Isabella yellow; then let it be poured into a warm silver 
mould. When nitrate of silver is prepared in this manner, it 
is perfectly white, and does not, as the Pharmacopoeia misin- 
forms us, become blackened in the sunshine. The test given 
for its purity in the Pharmacopoeia is perfectly fallacious; for 
when chloride of silver is thrown down from a concentrated 
solution by an excess of chloride of sodium, some of the pre- 
cipitate is always re-dissolved, and the supernatant liquid will 
consequently become discoloured by sulphuretted hydrogen. 
But nitrate of silver is not a solitary instance of the insuffi- 
ciency of this book, for enabling an inexperienced person to 
prepare a chemical. No one, not previously conversant with 
chemical manipulation, could prepare sulphuric ether by the 
formula here presented. Even the directions for rectifying 
it are utterly insufficient, no clue being given to the proper 
temperature. The varieties of apparatus necessary for the 
different preparations, are passed over in the most dignified 
silence. 
We now proceed to prove our second proposition — that the 
chemical processes are not calculated to yield either the 
cheapest or the purest products. In some instances, the pro- 
cess, not recommended, but commanded to be pursued, is not 
at all adapted for obtaining the intended product. Protoxide 
of mercury is desired to be prepared by agitating together a 
gallon of lime water with an ounce of calomel. We prepared 
some in the above manner, and when heat was applied to a 
portion, were edified with the spectacle of five-sixths sublim- 
ing in the form of a protochloride of mercury; yet we are 
gravely told in the notes, that we may ascertain its purity by 
its not dissolving in muriatic acid — (how could it?) — by its 
completely subliming — (no doubt; but what are its pro- 
ducts?) — and by its dissolving in acetic acid. We question 
whether the College applied this last test. 
In other instances, preparations are directed which have 
not the slightest use in medical practice. Acetic acid is, for 
