Chap. 30.3 Aftion cf Acids on Tin. 177 



hardened, is called a block of tin ; each block of tin is 

 coined in the following manner : the officers appointed 

 by the duke of Cornwall affay it, by taking off a piece 

 of one of the under corners of the block, partly by 

 cutting and partly by breaking, and if well purified, 

 they (lamp the face of the block with the imprelTion 

 of the feal of the duchy, which (lamp is a permiffion 

 for the owner to fell, and at the fame time an afiurance 

 that the tin fo marked has been purpofely examined, 

 and found merchantable *. 



The concentrated vitriolic acid aces on tin with the 

 production of fulphuf eous vapours, part of the oxygen 

 of the acid, as is ufual in the folutions of metals in their 

 reguline ftate, being abftra6ted; The acid diflblves 

 about half its weight of tin, but not without the af- 

 fiftance of heat. The iblution is very cauftic. The. 

 nitrous acid is decompofed by tin, as it is by moft of 

 the metals, with great rapidity. The tin is converted 

 into a white calx, which it is very difficult to reduce. 

 M. de Morveau has remained the formation of a 

 quantity of volatile alkali during the folution of tin 

 in the nitrous acid. This is probably owing to a 

 combination of the azote, produced by the acid, with 

 the hydrogen, derived from the decompofition of the 

 water contained in the menftruum. The advocates 

 for the phlogiftic hypothecs, however, fay, that the hy- 

 drogen is the phlogidon of the tin fet at liberty during 

 the folution. 



The fuming muriatic acid acts ftrongly on 'tin, in- 

 ftantly lofing its colour and its property of emitting 

 fumes. The muriatic acid diffolves more than half 

 its weight of tin, and does not let it fall by repofe. By 

 evaporation it produces brilliant and very regularly 



* Borlafe's Hiftory of Cornwall, p. 183. 



VOL. II. N funned 



