Full text: Vol. II (2)

636 COPPER—IN NITRIC,—IN MURIATIC ACID. 
mical change that we obferve is a nitrate of tin in the place of a nitrate 
of copper, and the eruption of nitrous fumes. Some more oxygen 
ſeems, therefore, to be necefsary for the new compound; and we ſhould 
rather have looked for a diminution than an increase of heat ; unless 
we admit the heat to be produced in the fame way as when alcohol 
or sugar is added to nitric acid. 
Paper, moistened with a solution of this nitrate, when held before 
the fire, catches fire at a very low temperature,—not fufficient to melt 
tin. 
Theſe cryſtals are very fuſible, but it is a fort of watery fusion they 
undergo ; for they are very retentive of water; and if we increase 
the heat a little too high, the acid begins to evaporate, and carries 
away a ſmall portion of the copper. 
The muriatic acid diffolves this metal flowly. The colour of the 
solution is at first dark brown, but becomes green by keeping. Sym 
pathetic, or rather changeable ink, of Mr. Macquer, is prepared from 
this solution. 
The solution, when duly diluted, has a light blue colour, and when 
spread on paper, exhibits the fame hue as long as any moisture ad 
heres to it. But when flowly dried before the fire, and allowed to 
attract the moisture again, it returns to its former state of an almost 
imperceptible blue. In order to infure the disappearance when cold, 
dip a pencil in the solution (very weak) of muriat of lime. Paſs this 
over the copper solution,—it will not decompose it, but, by attracting 
moiſture, will cauſe the colour to vaniſh almoſt entirely. Care must 
be taken with this, and indeed with all thofe fympathetic inks, not to 
let the paper become too hot. This scorches that part on which the 
solution is spread, and makes it a permanent brown. 
The scales of copper, formed by calcination, exhibit nearly the 
fame appearances in solution in this acid. A recent and brown solu 
tion of the scales, if largely diluted with water, deposits part of the 
copper in the form of a white precipitate, super-saturated with cop¬
	        
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