1821.] r The Edinburgh Pharmacopaia, 61 



decomposable by very little more than half its weight of lime ; 

 the quantity ordered is once and a half its weight. I have tried 

 the process, and found it extremely inconvenient ; it is a most 

 pungent operation to mix, as here directed, hme and muriate of 

 ammonia, the quantity of hme being so very large, much delays 

 the getting it into the retort, to the great annoyance of the 

 operator. I confess I prefer the modification of the London 

 process of 1787, which 1 have recommended, and which, with a 

 slight variation, the London College have now adopted. 1 found 

 the specific gravity of the aqua ammonise of the Edinburgh 

 Pharmacopceia to be 0*936, agreeing very nearly with their 

 statement; viz. 0*939. 



Estimating by the strength of the products merely, the pro- 

 cess of the Edinburgh College is more economical than the 

 London in the proportion of 16 to 10. As, however, the former 

 order the large quantity of hme, which they employ with the 

 muriate of ammonia, to be made red-hot, the retort generally 

 breaks ; and as this does not follow as a matter of course in the 

 London process, I consider it to be really most economical j and 

 having tried both, it is certainly more easily managed. 



Tartras Antimoniij incorrectly so called, instead of Tartras 

 Antimonii et Potassae. This salt is directed to be prepared by 

 the old mode of boihng crocus of antimony in a solution of 

 tartar. The objections to this process I have stated at length 

 in my remarks on the London Pharmacopoeia. I shall, there- 

 fore, only repeat, that it is an extremely inconvenient one on ac- 

 count of the difficult solubihty of the crocus, unless it has gone 

 through the troublesome process of levigation or elutriation. 



Carbonas Ferri Prcccipiiatus. — Four parts of sulphate of iron 

 are directed to be decomposed by five parts of carbonate of soda. 

 Scarcely 4^^ parts of the alkaline salt are requisite. 



Tartras Potasses et Ferri, — This salt is correctly named ; 

 whereas, as already observed, the potash has been omitted in 

 the chemical name for tartarized antimony. 



Acetas Hydrargyri, — This salt, which is not contained in the 

 London Pharmacopoeia, is directed to be prepared by dissolving 

 three parts of mercury in four and a half of diluted nitric acid, or 

 in a little more than is required to dissolve it. This solution is 

 to be decomposed by three parts of acetate of potash dissolved 

 in about 42 times its weight of water. 



It is of importance in making this salt, that the mercury 

 should be as nearly as possible in the state of protoxide, other- 

 wise but little acetate of mercury will be obtained ; for if the 

 peracetate be formed, it is a very soluble salt, and protoacetate 

 on]k is deposited in crystals. 



On this account I do not see why the College has ordered 

 rather more nitric acid than is required to dissolve the mercury* 

 The excess, which in this case amounts to about one-ninth part, 

 is extremely Habk to be decomposed by, and to convert the 



