SULPHURETTED HYDROGEN. 141 



soda crystals, a parallel action will take place; the solution of 

 carbonate of potash (effervescing vigorously with acids) will 

 become converted by boiling with lime into " liquor potassse," or 

 solution of caustic potash, which will not effervesce with acids, but 

 will be far more corrosive and biting to the taste than the original 

 solution of mild alkali. 



Expt. 145. To dissolve Sulphuretted Hydrogen Gas in 

 Water and in Ammonia. Place in the gas generator used in 

 Expt. 143 some lumps of sulphide of iron, and then, after inserting 

 the cork and tubes, pour hydrochloric acid down the thistle funnel ; 

 the chemical action taking place (Expt. 13) causes sulphuretted 

 hydrogen gas to escape. Pass the gas through distilled water, 

 just as the carbonic acid gas was passed into the caustic soda solu- 

 tion in the last experiment ; the water will dissolve some of the 

 gas, thereby furnishing the solution of sulphuretted hydrogen 

 referred to in some of the preceding experiments (Nos. 12, 95, 

 121, 125, 126). 



Pass the sulphuretted hydrogen gas into solution of ammonia 

 instead of water ; the sulphuretted hydrogen will dissolve and will 

 act chemically on the ammonia at the same time, producing a 

 compound called sulpliydrate of ammonium ; this being soluble in 

 water, is formed without any visible action taking place ; but its 

 formation is easily rendered evident by the great alteration pro- 

 duced in the properties of the fluid when the gas has been passed 

 through for some time. Thus, into each of two test-tubes pour a 

 few drops of solution of copper sulphate, and to the one add some 

 of the original ammonia solution, and to the other some of the 

 sulphydrate of ammonium solution ; the first will act as in Expt. 

 124, producing a blue precipitate, dissolving to a deep blue clear 

 fluid on adding more ammonia ; the secood will produce a black 

 precipitate, soluble neither in ammonia solution nor in excess of 

 sulphydrate of ammonium. If a little solution of perchloride of 

 iron (ferric chloride) be used instead of sulphate of copper, the 

 ammonia solution will produce a red-brown precipitate, and the 

 sulphydrate of ammonium solution a black one ; whilst if chloride 

 of cadmium solution be employed, the former reagent will throw 

 down a white precipitate, and the latter a yellow one. 



Caution. Sulphuretted hydrogen is a poisonous gas, though not 

 so dangerous to breathe in small quantities as some others; 

 moreover, on account of its chemical action on many metallic 

 compounds, and especially on lead paint, it is apt to stain and 

 discolour many ordinary articles of furniture and painted goods. 



down the filtered liquor to dryness ; a strongly alkaline mass results. Pearl- 

 ash is this crude substance somewhat purified and refined. 



