68 
PATENT INKS, AND SALTS OF GOLD. 
Marking Ink, JVo. 1. 
7th. I manufacture, by the improved process following, a 
marking ink, which may be used with steel pens, and is not 
only of great intensity of colour, but comes out most readily 
on the application of heat. I rub together in a mortar 
nitrate of silver, and the proper equivalent of tartaric acid 
in a dry state. I then add water, on which crystals of tar- 
trate of silver are formed and the nitric acid set free. I next 
neutralize this acid by adding liquor ammoniae, which also 
dissolves the tartrate of silver. I finally add gum, colouring 
matter and water, in the usual way, and in quantities 
which may be varied at pleasure. By this process the 
nitric acid, which is essential to a good marking ink, is re- 
tained, and the tartrate of silver formed is soluble in less 
than half the quantity of liquor ammonios ordinarily required 
when tartrate of silver is the basis of the ink. The tedious 
operation of filtering and washing the carbonate of silver, 
in order to form the tartrate, is also thereby entirely dis- 
pensed with. 
Marking Ink., No. 2. 
8th. I manufacture, in manner following, a marking ink, 
differing from the preceding, and all other marking inks 
containing salts of silver only, in this respect, that it cannot 
be acted on by the common solvents of salts of silver, as 
cyanide of potassium or chloride of lime, and is so far, 
therefore, more indelible. I take the ink, as it has been 
formed by the process last described, and add to it an am- 
moniacal solution of an oxide, or salt of gold. 1 have used 
for this purpose, the purple of Cassius, the hydrosulphite of 
gold, the ammonio-iodide of gold, and the ammonio-per- 
iodide of gold. The two last salts, which I believe to be new 
salts, I obtain by dissolving iodme in liquor ammonise under 
the application of heat; an operation, however, which re- 
quires to be conducted with great caution, in order to pre- 
vent the formation of the explosive compound, the teriodide 
