ARSENIC. 



311 



humid way. The powder must be dried by a gentle heat, and a 

 portion of it mixed with two or three parts of the black flux, con- 

 sisting of one part of finely powdered charcoal, and two parts of 

 dry carbonate of potash. The mixture is then to be put into a 

 glass tube, open at one end : the open end is now to be loosely 

 closed by a piece of wood or soft paper, while the other is heated 

 by placing it in red-hot coals, or in the flame of a spirit lamp, 

 when, if arsenic be present, a thin brilliant metallic crust will be 

 found lining the upper part of the tube, and which, when placed on 

 a bar of hot iron, will exhale dense white fumes, and a strong 

 smell of garlic. In order to detect the presence of the white oxide 

 of arsenic by re-agents, the suspected powder should be boiled in 

 distilled water, the solution filtered, and a portion of it put into 

 three test tubes, a, b, and c, as recommended by Mr. Brande. 

 " To a, add a drop or two of solution of potassa, and then a 

 similar quantity of solution of sulphate of copper : an apple-green 

 precipitate indicates arsenic ; if the precipitate be sky-blue, no 

 arsenic is present. To the liquid h, add a drop or two of solution 

 ammonia, and then the same quantity of nitrate of silver; if 

 white arsenic be present, a yellow precipitate is formed ; if not, 

 there is no change, or only a white cloudiness. To c, add a drop 

 or two of liquid potassa, evaporate to dryness, and having added a 

 morsel of wax, heat the residue to redness. Metallic arsenic will 

 sublime, and the garlic smell will be very perceptible upon opening 

 the lower end of the tube, and holding it inclined, so that a current 

 of air may pass through it. The precipitates from a and b, heated 

 with a little wax, should give similar indications of metallic arsenic. 

 Of the above tests, the first was contrived by Scheele, and the 

 second by Mr. Hume ; and, with the corroboration afforded by the 

 third method, they are effectual and satisfactory." 



"The medical treatment," continues Mr. Brande, "which should 

 be adopted for the relief or cure of persons poisoned by arsenic, 

 may be summed up in a few words. The vomiting excited by the 

 poison should be encouraged by a dose or two of sulphate of zinc, 

 in preference to ipecacuanha, and copious draughts of mucilaginous 

 liquors, such as barley-water and gruel. The bowels should be 

 emptied by the least irritating means, as by castor oil, or a mixture 



