of Arsenic from other Substances. 2S1 



in the wooden block c for the reception of the lower part of the 

 pillar c/, and a groove is cut in the top of the same block to re- 

 ceive the bend of the tube a a. Two elastic slips e e, cut from 

 the neck of a common bottle of India rubber, keep the tube 

 firm in its place. 



The matter to be submitted to examination, and supposed to 

 contain arsenic, if not in the fluid state, such as pastry, pudding, 

 or bread, &c., must be boiled with two or three fluid ounces of 

 clean water, for a sufficient length of time. 



The mixture so obtained must then be thrown on a filter to 

 separate the more solid parts : thick soup, or the contents of the 

 stomach, may be diluted with water and also filtered ; but water- 

 gruel, wine, spirits, or any kind of malt-liquor, and such like, 

 or tea, coffee, cocoa, &c., can be operated on without any pre^ 

 vious process. 



When the apparatus is to be used, a bit of glass rod about 

 an inch long, is to be dropped into the shorter leg, and this is 

 to be followed by a piece of clean sheet zinc, about an inch and 

 a half long and half an inch wide, bent double, so that it will 

 run down the tube till it is stopped by the piece of glass rod 

 first put in. The stopcock and jet are now to be inserted, and 

 the handle is to be turned so as to leave the cock open. The 

 fluid to be examined, having been previously mixed with from 

 a drachm and a half to three drachms of dilute sulphuric acid 

 (1 acid and 7 water), is to be poured into the long leg, till it 

 stands in the short one about a quarter of an inch below the 

 bottom of the cork. Bubbles of gas will soon be seen to rise 

 from the zinc, which are pure hydrogen, if no arsenic be pre- 

 sent ; but, if the liquor holds arsenic in any form in solution, 

 the gas will be arsenuretted hydrogen. The first portions are 

 to be allowed to escape, in order that they may carrj*^ with them 

 the small quantity of common air left in the apparatus ; after 

 which the cock is to be closed, and the gas will be found to ac- 

 cumulate in the shorter leg, driving the fluid up the longer one, 

 till the liquor has descended in the short leg below the piece of 

 zinc, when all further production of gas will cease. There is 

 thus obtained a portion of gas subject to the pressure of a co- 

 lumn of fluid of from seven to eight inches high : when, there- 

 fore, the stop-cock is opened, the gas will be propelled with some 



