PATENT INKS, AND SALTS OF GOLD. 
69 
of nitrogen. This iodine solution is a very speedy solvent 
of gold. If gold leaf be placed upon it without the addition 
of water, a black oxide of gold is formed, which immedi- 
ately dissolves, but if it be diluted with water, the process 
of oxidation is less rapid, and the gold leaf assumes a fine 
purple colour (not black) before solution. This salt of gold 
crystallizes in four-sided prisms, which are soluble in water. 
A few drops of this solution placed on a slip of glass, gene- 
rally form microscopic arborescent crystals, from which, 
under the application of heat, both the iodine and ammonia 
may be volatilized, and arborescent metallic gold alone 
remains. If a moderate heat only is employed, one equiva- 
lent only of iodine is dispelled, and white crystals of am- 
monio-iodide of gold remain. 
Blue Printing Ink^ No. 2, 
9th. I manufacture a blue printing ink by taking the 
soluble precipitate of cyanogen and iron, obtained by the 
process described under the first head of this specification, 
and rubbing up the same in oil, after the manner ordinarily 
followed in the manufacture of printing inks; or by boiling 
down the blue writing ink produced by the said process, to 
a sufficient consistence, and then rubbing up the same in 
oil. 
Black Printing Ink, No. 1. 
10th. I manufacture a black printing ink by boiling down 
the black writing ink produced from the materials, and by 
the process described under the fifth head of this specifica- 
tion, and rubbing it up in oil as aforesaid. 
Red Printing Ink. 
11th. I manufacture a red printing ink by taking the 
ammoniacal solution of cochineal, obtained by the process 
described under the sixth head of this specification, and 
rubbing it up in oil, adding protiodide of tin according to 
the degree of lustre required ; or by boiling down the red 
