32 Mr. R. Phillips on the [Jan. 



which it may at first be subjected is a solution of sulphuretted 

 hydrogen gas in water. This is to be preferred to any coloured 

 fluid containing sulphuretted hydrogen, such as the hydrosul- 

 phuret, or, perhaps more properly, hydroguretted sulphuret of 

 ammonia ; for this fluid possesses the colour when diluted, 

 which we expect to produce by the action of sulphuretted 

 hydrogen upon arsenious acid. The method of preparing this 

 solution of the gas is perfectly simple. Put into an oil flask 

 about two ounces of muriatic acid undiluted with water, and an 

 ounce and a half of powdered sulphuret of antimony ; fit a cork 

 to the flask, and pass through it the shorter leg of a small hollow 

 glass tube twice bent at right angles ; pass the longer leg of the 

 tube into a vial containing distilled water, and then by the heat 

 of a spirit-lamp applied to the flask, sulphuretted hydrogen gas 

 will be readily procured, and though much of it will escape, yet 

 a sufficient quantity will be dissolved by the water. If distilled 

 water cannot be procured, then rain water may be used, or if 

 that be not at the moment obtainable, water, which has been 

 boiled and become clear, must be substituted. The annexed cut 

 will sufficiently explain this apparatus. 



A\ 



d_o 



X 



If a glass tube is not at hand , one may be readily formed of 

 tin plate soldered. I have employed one for the purpose of 

 trying the experiment, which was made in about an hour; the 

 shorter leg may be about two inches and a half to three inches 

 long ; the intermediate space, and the longer leg, each six inches 

 in length ; the diameter may be about one-fourth of an inch ; 

 this passed through the cork, and used instead of the glass one, 

 answers the purpose perfectly, notwithstanding the tin is 

 slightly acted upon by the gas during its passage, and by the 

 solution in which it is immersed. 



To this solution, clear and colourless, add, in a wine glass, or 

 a vial, some of the suspected fluid ; if it contain arsenious acid, 

 a yellow-coloured fluid will be produced, and, after the lapse of 

 £ome hours, a yellow precipitate will fall down. It has been 

 objected to this test, that antimony produces a similar appear- 



