Brass* 
m 
ment, nvhich indicated the existence of tin. The sedi» 
ments of the third row did not change colour, whence it 
was concluded that there did not exist in them any me- 
tallic substances. The vinegar, then, boiled in the tin- 
ned pans did not dissolve lead, but only a very small 
quantity of tin. 
The sediments of the third row were, for the most part, 
composed of tartar and sulphat of lime. These two salts, 
in precipitating, might have carried with them a little 
lead ; but they did not contain an atom of it. 
The same experiments being repeated with very strong 
white wine vinegar, which was boiled till three parts of it 
were consumed, confirmed the preceding facts ; with this 
only difference, that the tinning assumed the colour of 
lead, and readily yielded to the friction of the finger, com® 
ing off in the form of a gray powder, which was nothing 
else than very fine particles of leach This phenomenon 
was more remarkable in the pan No. 8, though the quan- 
tity of that powder did not weigh half a grain. These 
facts were the less remarkable the nearer to the pan No. 1 ; 
so that with a little practice one might judge by these 
means of the quantity of lead and tin contained in tinning. 
The vinegar formed zones of a very beautiful colour 
on the tinning of the pan No. L These facts may still 
serve to enable one to distinguish the quality of tinning. 
These experiments evidently prove that lead, which is 
very soluble in vinegar, loses that property when alloyed 
with tin. This is agreeable to chemical facts already 
known ; for tin is more oxydable and soluble than lead, 
and the latter is precipitated from its solutions by tin, 
and this is the cause of the presence of the gray powder 
above mentioned; for vinegar, indeed, dissolves irnmedi- 
ately a few particles of the lead in the tinning, but it is 
afterwards precipitated by the tin, and forms gray dust* 
Aft these facts^ and many others explained by the author^ 
