Analysis of Scientific Books. 403 



be urged likewise in the present case ; for the acid cannot by 

 this process be obtained in an uniform and well-known degree 

 of concentration. I know besides that the acid, thus prepared, 

 is of a turbid yellowish colour, instead of being colourless and 

 transparent, and that it deposits a considerable sediment, both 

 which circumstances seem greatly to militate against its purity .. 

 there is, moreover, no novelty in the process itself, being, in fact, 

 that of Gay-Lussac, changing unnecessarily the proportions, and 

 omitting two or three essential precautions, proposed as indis- 

 pensable by that chemist in the preparation of the acid." 



We should have conceived it more decorous on the part of 

 Dr. Granville, finding the above preparation objectionable, as 

 he has asserted it to be, (but which we shall presently show it is 

 not,) to have stated the objections to the Apothecaries' Com- 

 pany, instead of publishing their process with a view to depre- 

 ciate it, and to employ it as a vehicle of a puff oblique in favour 

 of the Doctor's chemist, Mr. Garden. But let us see how the 

 matter really stands. On making inquiry at Apothecaries' Hall, 

 we find that in consequence of the occasional demand for prussic 

 acid, and the want of any official directions for its preparation 

 in the London Pharmacopaeia, Mr. Brande, who holds the office 

 of Professor of Chemistry, and Materia Medica to the Society, 

 received orders from the Laboratory Committee, to examine the 

 various processes for preparing that acid, and to make a report 

 accordingly. That this report was nearly as follows : — 



" Having tried the methods of Scheele and Vauquelin, I find 

 them uncertain as to the products, and more especially in the 

 latter case, the specific gravity of Vauquelin's acid always ex- 

 ceeding that of distilled water, probably from the presence of 

 sulphocyanic acid ; I consequently recommend to the Com- 

 mittee the following process, founded on Gay-Lussac's method 

 of obtaining the pure acid : 



" Prepare a cyanuret of mercury as follows : — ^Take 1 lb. 

 of finely levigated peroxide of mercury, (the hydrargyri 

 oxidum rubrunif of the PharmacopcBia,) and 2 lbs. of powdered 

 Prussian blue ; boil them in a glass vessel in 8 pints of dis- 

 tilled water for one hour, filter and collect the crystals which 



