Proceedings of the British Association. 323 



tations. Experiments are now in progress to determine this ques- 

 tion. 



New extemporaneous process for the 'production of Hydrocyanic 

 Add for medical use, by R. D. Thomson, M. D. The importance 

 of this acid as a remedial agent, induced the author to bestow 



' much attention upon a mode of producing it always of uniform 

 ■strength. Having tried all the processes for this purpose, proposed 

 in this country, he was satisfied that none of them afforded an acid 

 of uniform strength. The process recommended by Dr. Clark of 

 Aberdeen, was superior to every other, but an objection to it is 

 the great difliculty of procuring pure cyanide of potassium. 'The 

 author believes the following process to be less liable to objection 

 than any at present used. The first step consists in forming a 

 pure cyanide of lead. This may be done in various ways, either 

 by precipitating acetate of lead bjr hydrocyanic acid,'-as prepared 

 from the ferrocyanide of potassium and sulphuric acid, in a stop- 

 pered bottle, or by distilling the mixed materials into a Wolff's 

 bottle containing a solution of acetate of lead. In either case a 

 definite compound of cyanogen and lead will be obtained, which 

 is to be carefully washed and gently heated. The next step in 

 the process is to decompose it by means of sulphuric acid. In 



^order to obtain an acid of the strength of the Acidum Hydro- 

 cyanicum dilutum of the London Pharmacopoeia, or containing 

 about two per cent, of absolute acid, the following formula is re- 

 commended. 



46.36 grains of cyanide of lead. 



2 fluid drachms of dilute sulphuric acid. Lend. Pharm. 



6 fluid drachms of pure distilled water. 



Introduce the cyanide of lead into a stoppered bottle ; mix the 

 acid and water in a glass vessel ; allow the mixture to cool, and 

 then pour upon it the cyanide of lead. Close the stopper, and 

 agitate the fluid and salt together. After standing for some time, 

 pour off the supernatant liquor from the precipitated sulphate of 

 lead, and preserve it in a stoppered bottle. This formula is 

 founded upon the circumstance that the dilute sulphuric acid of 

 the London Pharmacopoeia contains in each fluid drachm about 

 9.5 grains of oil of vitriol (SO^^HO). Two drachms will there- 

 fore contain nineteen grains of oil of vitriol. The quantity re- 

 quired for saturating 43.36 grains of cyanide of lead, is only 17.4 

 grains ; but the small excess is useful in preserving the acid. 



