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PATENT INKS, AND SALTS OP GOLD. 65 
ART. XVUL— PATENT INKS, AND NEW SALTS OF GOLD. 
Patentee, Rev. J. B. Reade, of Stone Vicarage, Aylesbury. 
Blue Writing Ink. 
1st. I manufacture, in manner following, a blue writing 
ink, which is wholly free from acid, and therefore well 
adapted for use with steel pens. I first obtain a solution of ' 
iodide of iron by the process ordinarily followed for that 
purpose, and then dissolve therein half the weight of iodine 
already employed. I next pour this mixture into a semi- 
saturated solution of yellow prussiate of potash, employing 
a weight of this salt nearly equal to the whole weight of 
iodine used in the above iodine solution. A decomposition 
of the materials thus brought together immediately takes 
place, when the cyanogen (of the prussiate of potash) and 
iron combine, and are precipitated in a solid form, and the 
potassium (of the prussiate) and iodine combine to form a 
neutral iodide of potassium, which remains in solution with 
a little excess of iodide of iron. I next filter and wash the 
solid precipitate of cyanogen and iron (which is soluble 
Prussian blue,) and finally dissolve it in water, which forms 
the blue ink required. In this process, it will be observed 
that neither any acid nor persalt of iron is employed, as is 
usual in the formation of Prussian blue. 
. I was led to these results by a microscopical examination 
of the metallic colours in salts of the ashes of plants. I em- 
ployed iron and iodine to produce the same effects on pure 
salts ; and in the course of my experiments I ascertained that 
these two substances (iron and iodine) have so great an af- 
finity for each other, that when placed together without any 
water, or when rubbed together, they very speedily form a 
liquid, containing an excess of iodine in solution, which, 
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