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SELECTED ARTICLES. 
grains of nitrate of silver, washing and drying at 212°. It 
yields 201.6 grains of white cyanide. I should recommend 
that the bottle containing this salt be accompanied by a small 
stoppered phial with dilute hydrochloric acid of such strength 
that one minim will exactly decompose one grain of the 
cyanide: thus, suppose one corked phial having 200 grains of 
cyanide, with an half ounce stoppered bottle with hydrochloric 
acid of specific gravity 1.129, this would be enough to make 
five fluid ounces of dilute hydrocyanic acid of the Dublin 
strength, if the following formula be followed: — Into a phial 
capable of holding rather more than one fluid ounce, put 40 
grains of the cyanide, add 7 fluid ounces, 20 minims of water, 
and 40 minims of the dilute hydrochloric acid; cork closely, 
shake several times for the first quarter of an hour, set aside 
to allow the chloride of silver to fall, decant the clear liquid 
into another bottle to be preserved for use: every fluid drachm 
will contain one grain of real hydrocyanic acid. 
The only objection I had a priori to this process was the 
liability of a little free hydrochloric acid remaining in the 
solution, since all books echo that the presence of a minute 
quantity of the mineral acids very much hastens the decom- 
position of this acid: a statement perfectly opposite to fact, 
at least as far as concerns hydrochloric acid. I prepared 4 
ounces of hydrocyanic acid perfectly pure by distillation of 
chalk; to 2 ounces I added 5 drops of hydrochloric acid; 
the other 2 ounces in another phial were left perfectly pure, 
both inverted and placed in a glass case so as to have diffused 
light during the day. After three weeks the pure acid had 
become quite brown, and a considerable quantity of solid de- 
posit had formed; the other remained quite limpid and co- 
lourless, and, on actual trial, was found to contain 19.20ths of 
the acid which it had at first. Mr. Barry also informed me 
that his fourteen years' experience led to the same result; 
and that being aware of this, he adds purposely a little hydro- 
chloric acid to all his medicinal acid. Perhaps some may 
object to the price of the preparation: a case containing the 
two bottles with 200 grains of the cyanide would leave one- 
