122 DETECTION OF ARSENIC. 



precipitate, ammoniacal of sulphate of copper an apple green 

 precipitate. 



The sulphurreted hydrogen gas, the solution being first 

 slightly acidulated with a drop or two of muriatic or acetic 

 acid, produces a bright yellow precipitate, which subsides 

 upon the liquid being boiled. If these experiments be per- 

 formed with due care, his mind in an ordinary case would be 

 satisfied with the confirmation of his suspicions, but as his 

 testimony may involve the fate of a fellow-creature, he pro- 

 ceeds to investigate still further the character of his newly 

 formed compounds. Either one or all the precipitates are care- 

 fully separated from the fluid in which they are enveloped, by 

 a filter, are dried, and being mixed with black flux, the mixture 

 is introduced into the reducing tube, the powder adhering to 

 its sides is carefully wiped away, and the end containing the 

 mixture is heated in the flame of a spirit lamp to redness, this 

 process as has been already said causes a decomposition of the 

 arsenical salt if it be present; the metal is reduced and sub- 

 limed within one half an inch above the flux, forming a bril- 

 liant ring of a steel gray lustre ; when examined with a lens 

 the inner crust appears a group of minute shining crystals. 

 This crust may be sublimed higher up in the tube, and if the 

 heat be adroitly applied the metal is converted into octahedral ' 

 crystals of white oxide of arsenic. His opinion may be still 

 further confirmed by re-dissolving the crystals last obtained, 

 and applying the fluid re-agents de novo, when if the charac- 

 teristic precipitates be again produced, no doubt can possibly 

 exist of the identity of the subject of his examination with 



-ARSENIC. 



The process here related is a general sketch of a mode of 

 procedure proper to be pursued in the examination of a simple 

 colourless fluid, suspected of containing arsenic in some one of 

 its forms ; but should it be required to examine a mass of solid 

 organic matter under the same suspicions, some preparatory 

 means must be employed to render the arsenic sensible to re- 

 agents. The organic matter which has a tendency to embar- 

 rass the experiments, and invalidate our confidence in the 

 results must be destroyed, and this may be best accomplished 

 by treating it with muriatic acid, boiling and evaporating to 

 dryness repeatedly, until all appearance of organic structure 



