132 Prof. Berzelius's Method of' detecting Arsenic, &c. 



In the case where the solid arsenic cannot be found, we 

 must collect as much as possible of the contents of the sto- 

 mach and the intestines, or even cut the stomach in pieces, 

 and mix it with its contents. The whole is then to be di- 

 gested with a solution of hydrate of potash. Hydrochloric 

 acid is then added in excess. The whole is filtered, and, if 

 the liquid is too much diluted, it is concentrated by evaporation. 

 A current of sulphuretted hydrogen is then passed through it, 

 which precipitates the arsenic in the form of the yellow sulphu- 

 ret. If the quantity of arsenic is very small, the liquid will 

 become yellow without giving a precipitate. It must then be 

 evaporated, and, in proportion as the hydrochloric acid be- 

 comes more concentrated, the sulphuret of arsenic will begin 

 to be deposited. It is then filtered. If the sulphuret re- 

 maining on the filter is in too small a quantity to be taken 

 from the paper, add some drops of caustic ammonia, which 

 will dissolve it. Then put the liquid which passes the filter 

 into a watch-glass, and evaporate it. The ammonia will be 

 Volatilized, and will leave as a residue the sulphuret of arsenic. 

 If it shall still be difficult to collect the sulphuret, we must 

 put into the watch-glass a litttle pulverized nitrate of potash, 

 and, with the finger, mix the sulphuret with the nitrate of 

 potash, which detaches it from the glass. At the bottom of a 

 small phial, or a piece of glass tube, shut at one end, melt a 

 little nitrate of potash at the flame of a spirit-lamp, and in- 

 troduce into it, when melted, a little of the mixture which 

 contains the sulphuret of arsenic. It is oxidized with efferves- 

 cence, but without fire, or detonation, and without loss of 

 arsenic. The melted salt is then to be dissolved in water, and 

 lime added in excess, and the liquid boiled. The arseniate 

 of lime will then be deposited, and may be collected. When 

 dried, it is mixed with charcoal, and then brought to a red 

 heat by the blow-pipe, and a small quantity of this mixture 

 is allowed to fall to the end B of the above tube. It is now 

 gradually heated to expel all humidity which tends to throw 

 it into the wide tube A C, and when it is very dry, heat at 

 the flame of the blow-pipe, the part of the tube which con- 

 tains the mixture. The arsenic will be disengaged, and be 

 sublimed, at a distance from the heated part. An addition of 



