290 REVIEWS — Taylor's treatise on poisons. 



B I. The carbonaceous mass is evaporated (carefully) to dryness, 

 which operation will certainly occupy some hours. 



II. The solution is filtered, and the residue washed out, which 

 requires one hour at most. 

 C I. The carbonaceous mass is heated with nitric acid, which must of 

 course be free from arsenic, and, as Dr. Taylor recommends, also 

 free from hydrochloric acid. 

 II. Hydro-sulphuric acid is passed through the solution. No impu- 

 rities can get into the mixture. 

 D I. The ash is washed with water, filtered, and washed out. 

 II. The precipitate is thrown onto a filter, and washed out. 

 E I. The solution is evaporated to dryness, treated with nitric acid, and 

 evaporated several times (the term several may be assumed to 

 mean three or four). 

 II. The precipitate is treated with ammonia, and the filtrate evapo- 

 rated to dryness. Here we have an extra chemical, which must 

 be proved to be free from arsenic. There does not seem, however, 

 to be any possibility of its containing that substance ; and among 

 the numerous bodies in which that poison has been detected, to 

 the best of the writer's recollection, ammonia has never been 

 mentioned, although this of course does not preclude the neces- 

 sity of proving its purity. 

 F I. The acid residue is neutralized with pure carbonate of potassa. 

 II. The residue is dissolved in nitric acid ; long digestion is not 

 necessary, and the operation is finished in a few minutes. Here 

 the salt of potassa on the one hand, and the nitric acid on the 

 other, must be free from arsenic. 

 G I. The solution is evaporated to dryness. 



II. The solution is neutralized with carbonate of soda. The car- 

 bonate of soda used in the second process must be free from 

 arsenic and from chlorine, which the ordinary pure salt used by 

 chemists almost always is. 

 H I. The dry mass is washed with a little water, to extract the 

 arseniate of potash (and filtered?). 

 II. The solution is evaporated to dryness. 



In I. a loss of arsenic may ensue from imperfect washing ; it 

 would be better to dissolve the whole. 



