ON ARSENIC 131 



took place, and some regulus of arsenic was sublimed, (d) 

 Lead dissolved in nitrous or muriatic acid or vinegar is 

 precipitated by the acid of arsenic. This precipitate shows 

 the phenomena mentioned at (c). 



SECTION XXIX. UPON TIN. 



(a) Tin digested with acid of arsenic grows at first black, 

 and is afterwards covered with a white powder ; at last the 

 whole mass grows gelatinous, (b) One part of tin filings 

 was mixed with two parts of acid of arsenic and distilled. 

 When the mass became red hot, it took fire in the retort, 

 and immediately after both arsenic and a little regulus of 

 arsenic were sublimed. The tin was dissolved, and formed 

 a limpid flux, which, after growing cold, was of a milky 

 colour. Upon this mass I poured water, and exposed it to 

 heat, in order to dissolve the acid. A quantity of white 

 powder was separated, which was insoluble in any acid, and 

 contained very little acid of arsenic, (c) The solutions of 

 tin in mineral acids are not precipitated by the acid of 

 arsenic, but its solution in vinegar is. Neutral arsenical 

 salts precipitate the solutions of tin. This precipitate is 

 very difficult of fusion. When it is mixed with charcoal 

 powder, regulus of arsenic is sublimed. 



SECTION XXX. UPON ZINC. 



This is the only one of all the metals and semimetals 

 that effervesces when digested with acid of arsenic, (a) 

 The zinc grows black, and the transparency of the acid is 

 destroyed by a quantity of black powder. If this powder 

 be separated, edulcorated, and dried, and then put upon an 



