1 98 Effects of the Prussic Jicid. 



VI. A useful little volume has been published in New- 

 Haven,* containing a transcript of Dn Magendie's memoirs 

 on the prussic acid, with prefatory remarks by the trans- 

 lator, Dr. J. G. Percival, with some additional cases of the 

 use of the acid, and an appendix by Dr. Alfred S. Monson 

 It will afford much useful information to those who wish to 

 employ this acid. 



The following is Dr. Monson's process for preparing the 

 acid : 



Pour into a glass retort, eighteen fluid ounces of a satu- 

 rated solution of prussiate of mercury, at the temperature 

 of 65° of Fahrenheit ; add to it two ounces and an half of 

 iron filings ; pour upon these, two ounces by weight, of 

 strong sulphuric acid, and distil off two fluid ounces into a 

 receiver containing one fluid ounce of distilled water. The 

 receiver must be surrounded with ice, and covered with a 

 cloth to render it dark. 



To get rid of the colouring matter, together with some 

 sulphuric acid, and iron that come over, it may be redistilled 

 from dry carbonate of lime. 



A tubulated receiver is employed: this is connected with 

 the retort by means of one or two adapters of common 

 length ; the junctures are made perfectly tight, a tube of 

 safety leads from the tubulure of the receiver into a httle 

 water, and a tube descends from the retort to the bottom of 

 the receiver. 



Remarks. 



Dr. Monson, in the volume mentioned above, observes: 

 " In forming the prussiate of mercury, I have observed^ 

 (and the same fact was noticed by Professor Silliman ) that 

 if only half as much of red oxid of mercury as of Prus- 

 sian blue be used, as directed by Scheele, the whole of the 

 Prussian blue is not decomposed, and more of the prussiate 

 of mercury is obtained, by adding more of the red oxid, 

 and boiling them again. 



To ascertain the precise quantity required to produce a 

 saturation, I have employed several proportions, Fi-om 

 ^hese experiments it results, that where the materials are of 



* By Howe & Spalding, and A. H. Maltby & Co. 



