162 
ON MARKING INKS. 
nating; if any of the crystals dry on the surface of the vessel, 
a slight touch will produce an explosion !" 
Mr. Smee's very alarming statement made me determine 
no longer either to make or sell my ink ; and I am now, and 
have been ever" since, selling an article made by another 
party, with whose mode of preparation I am unacquainted. 
The foregoing remarks, of course, apply to only such inks 
as are composed of the triple salts of silver with ammonia. 
I do not deny the possibility of some of them being other- 
wise constituted, but in every sample which has come under 
my notice, ammonia is palpably perceptible by its odor, and 
I cannot conceive any thing which would answer the purpose 
of a marking ink, and which should contain ammonia, un- 
less it be one of the triple salts of silver, gold, or platinum. 
The two latter metals, from their great expense, would hardly 
be employed I should imagine, and would be open also to the 
same objections, on the score of their dangerous tendency, as 
the salts of silver. My impression that this is the constitu- 
tion of most of these inks is heightened by the fact 
that I had, some time back, an assistant who had previously 
lived with a druggist, who not only retailed but supplied 
many members of the trade with marking ink. His mode of 
preparation was to precipitate the chloride of silver by the ad- 
dition of a solution of chloride of sodium to a solution of ni- 
trate of silver ; to dissolve the chloride in liquor ammoniac 
and add gum and lamp black. Further also, by my having 
seen the following formula given in the Chemist, by a cor- 
respondent subscribing himself "A Retail Chemist — Take 
§j. of nitrate of silver, which dissolve in ^vj. of water; add to 
this solution as much liquid ammonia as will dissolve the pre- 
cipitated oxide, with sap green to color it, and mucilage to 
make the quantity amount to one ounce. 
It is evident that this retail Chemist thus prepares a mark- 
ing ink for sale, and doubtless the publication of the form, un- 
der the sanction of the Messrs Watts, would induce many 
others to do likewise. 
