186 Mr. Cooper's Remarks on Hydrocyanic Acid. 



you have brought forward, I am sure you will excuse the li- 

 berty I have taken in thus addressing you. 



Yours very truly, 

 25 Great George-street, Feb. 18, 1839. Thomas WebsTER. 



XXXIV. Some remai'Jcs on Hydrocyanic Acid. 

 By J. T. Cooper, Esq., Lecturer on Chemistry^ SfC* 



IN the month of November 1831 I prepared some anhydrous 

 hydrocyanic acid, by passing a current of dry sulphuretted 

 hydrogen through a tube containing dry cyanide of mercury, 

 and condensed the product by a freezing mixture surrounding 

 the receivers ; almost immediately after its preparation its 

 specific gravity was taken at the temperature of 37° Fahr., 

 which was found to be 0'706 ; and in two hours and a half 

 after its preparation, I proceeded to determine its refractive 

 index, by inclosing a portion of the acid in a perfectly air- 

 tight hollow prism, whose refracting angle was 49° 15' 40", 

 which, adopting the notation of Sir J. F. W. Herschel, we 

 will call Z I ; then by a \evy simple instrument which 1 am 

 in the habit of using for these purposes, the angle D, or that 

 made by the incident and refracted ray, was found to be for 

 Frauenhofer's ray A 14° 41', and for ray H 15° 13' 30". Hence 



(M) 



by adopting Sir J. Herschel's formula, viz. /x = sin j 



sin — 



2 



in which expression /x represents the refractive index, we have 



for ray A — = V° 20' 30" 



•' 2 



extreme red — = 24 37 50 log. sin. 9*61989 



(M)= 



31 58 20 log. sin. 9'72387 



Temp. 37° < 



and for ray H 

 extreme violet 



/* = 1-2705 log. 



D 



-= 7 36 45 



•10398 



= 24 37 50 log. sin. 9*61989 



(M) 



= 32 14 35 log. sin. 9*72714 

 /x = 1*2801 log. 



•10725 



* Communicated by the Author, from whom it was received in the course 

 of last month. — Edit. 



