WITH THE MARINE ACID. 349 



folid and uniform mafs aflumed a dark and ra- 

 ther an afh colour, but not in the lead a black. 

 But further, I diilolvcd fophirticated corrofivc 

 fu'oliinatc in diflillcd \vatcr of a boiling heat; 

 which folution, \vhen 1 added to it the cauftic 

 fpirit of ful ammoniac, dcpolitcd thin flakes, and 

 in a f/iort time aftcnvard* fccmcd here and there 

 to become of a green colour. The change of 

 colour \vis ftili lefs when I employed the fpirit 

 of luirtfliorn. The trial with ilie volatile alka- 

 li is therefore uncertain ; but we can determine 

 much more eafily, and with greater prccifion, 

 the prefen.cc of arfenic, if a finell of garlic is e- 

 inittiHl from corrofivc fublimate fprinklcd upon 

 burning coals. 



5 xvn. IV bite Mercurial Precipitate. 



THE white powder clcpofiterl in the nitrous 

 folution of mercury, on tiie admixture of com- 

 mon fait or muriatic acid, is named white mer- 

 curial precipitate. By fomc it is called cofinc- 

 tic mercury, or milk of mercury ; and Potter 

 gives it the appellation of the cakinatum wajiif. 

 Its colour, and the mzihod of ufing and prepa- 

 ring it have given rife to various names, which 

 were for the moft part very imliftincl, and have 

 been transferred to fubftanccs of a very different 

 nature. The preparation of it fcems to have 



been 



