234 .Scientific Noticea-^Chemistry, [M'AftCll, 



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 intro- 

 duce into it, when melted, a little of the mixture which contains 

 the sulphuret of arsenic. It is oxidized with effervescence, 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 blowpipe ; 

 and a small quantity of this mixture is allowed to fall to the 

 small end of the above-mentioned tube. It is now gradually 

 heated to expel all humidity which tends to throw it into the 

 wide part of the tube, and when it is very dry, heat, at the 

 flame of the blowpipe, the part of the tube which contains the 

 mixture. The arsenic will be disengaged, and be sublimed at 

 a distance from the heated part. An addition of vitrified boracic 

 acid greatly promotes the decomposition which then takes place 

 at a less elevated temperature ; but the acid frequently contains 

 water, and produces a bubbling of the melted matter, which 

 raises it in the tube, and causes the vapours to issue by perfo- 

 rating the softened part of the glass. 



M. Berzelius maintains, that the sixth part of a grain of st</- 

 phuret of arsenic is sufficient to make three different trials: but he 

 adds, that when we have discovered only very small traces of 

 arsenic, we must take care not to introduce any by means of 

 re-agents, among which, both the sulphuric and the hydrochloric 

 acid may contain it. The first almost always contains some 

 arsenic when it is manufactured from volcanic sulphur, and the 

 second in consequence of sulphuric acid being used in the pre- 

 paration of hydrochloric acid, yields the arsenic which it contains 

 in separating it from soda. We must, therefore, be certain of 

 the purity of these re-agents. 



When death has been caused by the arsenic, and not by the 

 arsenious acid, the process must be modified, because the sul- 

 phuretted hydrogen gas decomposes the arsenic acid too slowly. 

 In this case, we must add hydrosulphuret of ammonia, which 

 reduces the arsenic acid to the state of sulphuret, which is after- 

 wards precipitated by the hydrochloric acid.* — (Edin. Phil. Jour.) 



* It is obv-ious that Berzelius has not seen Dr. Christison's paper on the " Detection 

 of minute Quantities of Arsenic in mixed Fluids." These gentlemen agree in precipi- 

 tating arsenious acid by sulphuretted hydrogen, so as to obtain the yellow sulphuret ; 

 but their subsequent methods differ. Berzelius adopts a process which requires all the 

 dexterity of as expert a chemist as himself for conducting it with success. Dr. Christi- 

 son, on the contrary, scrapes the sulphuret from the filtre with a knife, which may be 

 done though a very minute portion of it is present, and obtains metallic arsenic at once 

 by heating it with black ihix. We refer for particulars to his paper in the EdicbnTgh 

 and Surgical Journal.— (xYo<e by the Editor.) . ; 



