402 Analysis of Scientific Books. 



We have frequently tried this method, and have not been 

 able to obtain the pure prussic acid by means of it, though 

 we cannot pretend to say with what other compounds it is 

 blended. 



M. Magendie prepares prussic acid for pharmaceutical use 

 by diluting Gay-Lussac's acid, for which, however, the formula 

 is not given. In this paragraph Dr. G. falls into some sad 

 errors respecting the specific gravities of the pure and diluted 

 prussic acid. He tells us that M. Magendie employs Gay- 

 Lussac's acid, diluted with six times its volume, or eight times 

 and a half its weight of distilled water. *' The density of the 

 pure hydrocyanic acid at the temperature of 45° being=70.583, 

 (that of water being = 1,) it follows that the weight of the di- 

 luted acid will be 9.20583, since the weight of fluids are equal 

 to their volumes multiplied by their densities," p. 20. We do 

 not profess to understand this sentence, but we believe it will 

 be found that the specific gravity of Gay-Lussac's liquid acid is 

 0.70583, and that the liquid acid of the above strength has not 

 the medium density of 0.920583, (which Doctor G. probably 

 means,) but that its specific gravity is 0.99000, or thereabouts, 

 great increase of density resulting from the mixture of the pure 

 acid with water. 



This brings us to the Apothecaries' Company's process, which 

 Dr. Granville speaks of in the following terms : — 



" The formula they employ has been supplied by Professor 

 Brande, as he himself informed me, and is the following : prussi- 

 ate of mercury Ibj., muriatic acid Ibj., water Ibv. Draw off four 

 pints, and rectify through chalk. I have not had an oppor- 

 tunity of trying this acid, as I am satisfied with that which Mr. 

 Garden prepares for my patients*, but I should conceive that the 

 same objections which exist respecting Scheele's process, may 



* " Mr. Garden, Chemist, of Oxford-street, is the only person, to my 

 knowledge, who has prepared the medicinal prussic acid, according to both 

 the above methods, (meaning Scheele's and Vauquelin's,) each of which is 

 perfectly good for the purpose of practice, and I have satisfied myself by 

 ocular demonstration, that every precaution was taken to ensure the accu- 

 rate result of the operations." Note at p. 19. 



