98 TINNING COPPER, &.C. 



Weight of a cubic foot of English tin, according to different 

 authors. 



Cotes, Ferguson, Emerson 7320 oz. avoir. 

 Boerhaavt-'s Chem. by Shaw 7311 

 Musschenbroeck & Wallerius 7471 

 Martin 7550 



From the following experiments it may appear probable, that 

 not one of these authors, in estimating the specific gravity of tin, 

 has used the purest sort, but rather a mixture of that with lead, or 

 some other metal. 



A block of tin, when it is heated till it is near melting, or after 

 being melted, and before it becomes quite fixed, is so brittle that 

 it may be shattered into a great many long pieces like icicles, by a 

 smart blow of a hammer* : tin in this form is called by our own 

 manufacturers grain tin, by foreigners virgin tin, or tears of tin ; 

 and they tell us, that its exportation from Britain is prohibited 

 under pain of deatht. The tin which I used in the following ex- 

 periments, was of this sort, but I first melted it, and let it cool gra- 

 dually ; a circumstance, I suspect, of some consequence in de. 

 determining the specific gravity not only of tin, but of other me. 

 tals. I have put down in the following table., the specific gravity 

 of this tin, and of the lead I mixed with it by fusion, and of the 

 several mixtures when quite cold ; the water in which they were 

 weighed was fiO p . 



Weight of a cubic foot of lead, tin, &c. 



Lead 1 1270 oz. avoir. 



Tin - 7170 



Tin 32 parts, lead 17321 



Tin 16 lead 17438 



Tin 10 lead 17492 



Tin 8 lead 17560 



Tin 5 lead 17645 



Tin 3 lead 17940 



Tin 2 lead 18160 



Tin 1 lead 18817 



This property is riot peculiar to tin; 1 have seen masses of lead which, 

 nnder similar circumstances, exhibited similar .-ipp. -arancjcs ; and it has been 

 observed, that zinc, when heated till it is just ready to be fn-ol, i- brittle. 



f Ency. Fran, and Mr. Baumc calls it " etain en roche, a cau c qne sa forme 



