42 MANUFACTURE OF PROTOCHLORIDE OF TIN. 
plan is entirely reversed. The tin is not dissolved in dilute 
muriatic acid, and the saturation effected by repeatedly 
pouring the ley over granulated tin ; but earthenware re- 
cipients, filled with granulated tin, are adapted to the retorts 
from which the muriatic acid is disengaged, by which a 
highly concentrated solution is obtained, with the advan- 
tage, moreover^ that the muriatic acid is instantly absorbed 
by the tin ; thus avoiding all loss of muriatic acid and its 
destructive effects upon the building and vegetation. Nor 
are the workmen at all inconvenienced by the vapours. 
The concentrated solution of tin is now evaporated, not in 
earthenware or copper vessels, but in a tin pan, which is 
easily constructed ; and the evaporation must always be 
conducted as in a copper pan with a large excess of granu- 
lated tin ; for even though the solution contain free muriatic 
acid, the granulated tin and not the pan is acted upon, the 
tin of the pan becoming electro-negative, while the granu- 
lated tin in the pan becomes electro-positive. All the cop- 
per contained in the liquid is deposited upon the granulated 
tin as a black powder, while pure tin, in bright metallic 
layers, is deposited upon the tin pan itself at the surface of 
the evaporating solution ; so that if such a tin pan, after 
daily use for several years, should be worn into a hole, it 
may easily be mended by stopping it first with a tin nail, 
and keeping the surface of the evaporating tin solution for 
a length of time at that spot, when it is gradually stopped, 
being as it were soldered in the moiat way. — Chem. Gaz, 
from Liebig^s Annalen, 
