PHARMACEUTICAL NOTICES. 
261 
the receiver, add to it a slight excess of solution of nitrate 
of silver, and wash the precipitated cyanuret until pure. It 
is then dried by pressure between paper and exposure to a 
heat of 212° Fah. and weighed. Every ten grains of this 
precipitate is equivalent to two per cent, of anhydrous prus- 
sic acid, and the amount of water of dilution is readily ob- 
tained by a simple sum of proportion, viz. : Suppose the 
precipitate weighs 1 34 grains, proceed thus: if 13-5 grains of 
cyanuret are produced by 100 grains of the stronger acid, 
10 grains of cyanuret will be produced by 74 grains of it, 
hence every 74 parts of the solution of prussic acid in the 
receiver requires 26 parts of water of dilution, which is 
readily converted into fluid ounces by the following state- 
ment : 74 : 26 : : f. ^14 f.§4 f. 37 21, which is nearly 
that stated in the formula. 
As there is great liability to variation in the strength of 
the product of the distillation, this experimental essay is 
always necessary, and hence the language of the Pharma- 
copoeia — "five fluid ounces, or as much as may be sufficient." 
The above directions are chiefly intended for those who 
manipulate with the small quantities of the officinal recipe ; 
but, in making large quantities of the acid, it is better to 
use less water with the materials in the retort, which de- 
mands a smaller amount of distilled liquid, and yields a 
a stronger acid. I am in the practice of obtaining an acid 
of 5 or 6 per cent., and diluting in accordance with the above 
mentioned plan. 
If any of the acid contents of the retort are thrown over 
into the receiver by concussion, the! subsequent testing 
cannot be depended on, as a portion of the precipitate will 
be sulphate of silver. To prevent this, a deep retort should 
be used. 
A word in relation to stopping the vials : These should 
be of the capacity of one fluid ounce, glass stopped, and 
after introducing the acid, the cavity of the neck should be 
wiped dry, and the stopper pressed firmly into its place, 
