3JS On the Tinnhig of Copper , 



in precipitating, inight 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 consamcd, confirmed the preceding facts ; with this 

 only ditference, that the tinning assumed the colour of lead, 

 and readily yielded to the friction of the finger, coming off 

 in the form of a gray powder, which was nothing else than 

 very fine particles of lead. This phaenomenon was more 

 remarkable in the pan No. 8, though the quantity 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 quan- 

 tity of lead and tin contained in tinning. 



The vinegar formed zones of a very beautiful colour on. 

 the tinning of the pan No. 1. These facts may still ser\'e 

 to enable one to distinguish the quality of tinning. These 

 experiments evidently prove that lead, which is very soluble 

 in vineorar, loses that property when alloyed with tin. This 

 is agreeable to chemical facts already known ; for tin is 

 more oxidable and soluble than lead, and the latter is pre- 

 cipitated from its solutions by tin, and this is the cause of 

 the presence of the gray powder above mentioned ; for vi- 

 negar, indeed, dissolves inmicdiatcly a few particles of the 

 lead in the tinning, but it is afterwards precipitated by the 

 tin, and forms gray dust. All these facts, and many others 

 explained by the author, prove that tinning, the half even 

 of which is lead, cannot be dangerous in domestic purposes; 

 and that, to be hurtful to the health by the contact of ali- 

 mentary acids, it would be necessary that the pans should 

 be pure lead, or tinned with that metal only, which is im- 

 possible. 



Paragraph W. 



On Tin Vessels. 



It was iKcessary to examine the action of vegetable acids 

 on vessels of tin. For this purpose the author caused the 

 following vessels to be made : 

 1st, Pure tin. 



All 



