404 Anaiysis of Scientific Books. 



the filtered liquor deposits on cooling ; evaporate the mother 

 liquor to half its bulk, and set aside to crystallize, repeating 

 this operation as long as crystals form. Take 1 lb. of crystal- 

 lized cyanuret of mercury in powder, 1 lb. of muriatic acid, 

 (specific gravity 1.150,) and 6 pints of water ; introduce this 

 mixture into a tubulated retort, and distil 6 pints by mea- 

 sure. If these proportions be observed, the prussic acid, dis- 

 solved in water, will pass over free of muriatic acid, and of a 

 specific gravity of 0.995." 



We allow, with Dr. Granville, that this process has no 

 merit on account of novelty, but we aver, in opposition to the 

 Doctor, that it affords a very uniform and a very pure pro- 

 duct, of a good strength for pharmaceutical use, which the 

 other processes do not; and therefore that the acid which 

 Dr. G. administers is open to the objections which he errone- 

 ously urges against the improved formula above given. But 

 the Doctor insinuates, though he must know better, that the 

 acid sold at Apothecaries' Hall is always turbid, yellowish, and 

 impure ; this we deny, and if occasionally yellow and turbid, it 

 is in consequence of age, and rather an indication of its purity 

 than otherwise, for dilute hydrocyanic acid, when free from iron, 

 sulphur, and chlorine, deposits, upon long keeping, a yellowish 

 powder, which we believe to be a solid carburet of nitrogen, con- 

 sisting, perhaps, of I atom of carbon and one of nitrogen ; for 

 when collected, dried, and burned in oxygen, it affords carbonic 

 acid and nitrogen anly; this, however, we merely throw out by 

 the way, not having hitherto examined it with due precision. 



One word more with respect to the Apothecaries' Company : 

 we beheve ourselves correct in stating that their Laboratories at 

 Blackfriars are always open to the inspection of members of the 

 College of Physicians, upon proper application ; that they have 

 no secrets, but on the contrary, solicit inspection ; that they 

 are at all times ready to adopt any real improvements and neces- 

 sary alterations in their processes ; and that they implicitly fol- 

 low the directions of the London Pharmacopoeia in the prepa- 

 rations therein contained, excepting that they have the sanction 

 of the proper officers of the college for certain modifications ren- 



