Tin. 
395 
ver white but without gloss, so that the mixture above 
mentioned is found to produce the most desirable hue* 
In a chemical point of view this operation is curious, 
and appears to present a contradiction to the usual laws 
of affinity, for when tin is immersed in a common solu- 
tion of copper, it precipitates most of the copper in the 
metallic state. 
The circumstances requisite to produce a precipitate 
of metallic tin on copper, have been examined in an able 
set of experiments by Professor Gadolin, a Swedish che- 
mist, an account of which is inserted in the Stockholm 
Transactions for 1788, to which are added some other 
experiments and remarks by Baron de Gedda. It is to 
be observed, that the circumstances relating to the oxy- 
genation of metals in their solutions in acids were very in- 
completely known at that time, so that we may now ac- 
count for phenomena which must have been inexplicable 
at that period* The facts however cannot vary, and are 
always valuable. This chemist chiefly confined himself 
to the action of a single salt, namely tartar, or its acid* 
We shall select and give in a few words some of the ex- 
periments. 
1. Tartriteof potash was added to nitromuriat of tin, 
which caused a white precipitate of tartrite of tin, which 
was edulcorated and dried. Some of this precipitate was 
boiled with water, and copper was immersed, but the 
copper was in no degree altered. 
2. Some of the above tartrite of tin was acidulated with 
tartareous acid and copper was boiled in it, but with no 
effect. 
3. Some of the same tartrite of tin was treated as in the 
last experiment, but with the addition of some leaf- tin and 
the copper was now completely tinned. 
4. The last experiment was repeated, but without an 
excess of acid, and no effect was produced on the copper. 
Vol. 1IL 3 C 
