312 Parkes's History of Literuiy Joninah. 



than Forty years, I apprehend I can form a tolerably correct 

 opinion of the general merits of the work and of the manner 

 in which it has usually been conducted — and I do conceive that 

 I am justified in saying that I know of no publication in the 

 English Language, that is better calculated to give young 

 persons a general knowledge of men and of books, provided 

 they acquire the habit of frequently consulting it by means of 

 the General Indexes. 



Although I never had any intercourse with the late Dr. 

 Griffiths, nor have any personal knowledge of the present 

 Editor of the work, I feel pleasure in availing myself of the 

 opportunity which this History of the British Literary Journals 

 affords me of expressing my approbation of a Book which I con- 

 sider in the light of an old acquaintance from whom I have de- 

 rived much valuable information, and to whom I am under no 

 small degree of obligation. 



Mecklenburg h-sqvare, Samuel Parkes. 



March 20 th, 1822. ^ 



Art. VIII. On Prussic Acid. By Andrew Ure, M.D., 

 F.R.S., ^c. 



Having been frequently consulted by physicians and apothe- 

 caries concerning the strength of the dilute prussic or hydro- 

 cyanic acid employed in medicine, I instituted a series of ex- 

 periments, to determine the relation between its specific gravity 

 and quantity of real acid. The acid which I prepared with this 

 view, had a specific gravity=0.957. 



The following table comprehends their results. 



Quantity of above liquid Acid, Specific Gravity. Real Acid pr. Ct. 



TooTo 0.9570 T6~ 



66.6 0.9768 10.6 



57.0 0.9815 9.1 



50.0 0.9840 8.0 



44.4 0.9870 7.3 



40.0 0.9890 6.4 



36.4 0.9900 5.8 



