396 
Tin . 
5. Cream of tartar, tin filings, and a piece of copper, 
were boiled together, and the copper was completely tin- 
ned. 
These experiments shew that in order to precipitate 
tin upon copper by means of tartar, it is necessary, both 
that some metallic tin should be present in the solution, 
and that the solution should contain an excess of acid. 
6. Some oxyd of copper arising from the decomposi- 
tion of blue vitriol by an alkali, was first boiled in a solu- 
tion of cream of tartar, after which both tin-leaf and cop- 
per were introduced, and the whole boiled together for 
three hours. Both the copper and tin were covered with 
a crust of blackish metallic alloy. 
7. Some copper w^s tinned by boiling with tin and a 
solution of tartar. The liquor after the copper was with- 
drawn was not changed to blue by volatile alkali, and 
hence was inferred to contain no copper, though when ex- 
posed to the light some faint blue streaks were observa- 
ble. 
8. The same experiment was repeated with tartar, 
alum, and salt, (the usual mode of tinning) and no indica- 
tions of copper were furnished by the volatile alkali. 
9. Copper was tinned with each of the above three 
salts singly, and in neither instance did the volatile alkali 
give any indications of dissolved copper in the liquor. 
10. Tin- leaf was boiled for an hour with a solution of 
cream of tartar. The tin was then withdrawn and a bar 
of iron introduced, and the boiling continued. The iron 
was soon blackened at its surface, and after three quarters 
of an hour, was covered with a mixture of reduced metal- 
lic tin and oxyd of tin, and the iron had lost weight in 
the process. 
Hence as iron was found to precipitate tin in a metallic 
state from its solution, it was conjectured that iron added 
to a solution of tin, in which copper was immersed, might 
