1862.] 187 



sulphocyanide of ammonia is formed ; yet it is well known that both 

 are formed when bisulphide of carbon is added to ammoniacal alcohol. 

 The erroneous view of the action of heated hydrate of lime upon the 

 sulphur-compounds in gas arose, I think, from the generally received 

 opinion that the blackening of lead-salts by a gas is a proof that that 

 gas is sulphide of hydrogen joined to the fact that sulphide of hy- 

 drogen is one of the compounds produced by the action of the heated 

 lime. If the sulphide of hydrogen had been separated from the 

 mixture of gaseous compounds produced, the truth would have been 

 apparent ; but as, I believe, all experimenters have failed to separate 

 them, the subject was obscure. After having failed in many pro- 

 cesses devised by myself and suggested by others, I at last removed 

 the sulphide of hydrogen, and showed that the blackening of lead- 

 salts is no proof of the presence of sulphide of hydrogen. Ordinary 

 purified gas was passed over heated hydrate of lime, then through a 

 considerable quantity of well-washed hydrated peroxide of iron, over 

 lead-paper, and subsequently through moist slaked lime. The per- 

 oxide of iron was slightly blackened, and withdrew every trace of sul- 

 phide of hydrogen : the lead-paper became black, and the slaked 

 lime yellow. This yellow lime gave a primrose- coloured solution 

 with water, which precipitated lead- and silver-salts brownish red, 

 thus showing the presence of impure hydrosulphocarbonate of lime. 



To be certain of the absence of sulphide of hydrogen, some of the 

 yellow lime was treated with hydrochloric acid, and the gases evolved 

 thereby were conducted into a solution of potash. The potash solu- 

 tion gave no reaction with nitroprusside of sodium, showing the 

 absence of sulphide of hydrogen, and when boiled with nitric acid 

 gave no precipitate with a salt of baryta. 



The hydrochloric solution of the lime contained a sulphur-salt, 

 which was obtained as sulphate of lime when nitric acid was added 

 and the whole was boiled. 



The blackening of the lead-paper in this case could not be due to 

 sulphide of hydrogen, as that compound was absent. Nor I think is 

 it due to the hydrosulphocarbonic acid which passed over, and in 

 contact with, the lead-paper, and was arrested by the lime. The red 

 compound which this acid produces with lead-salts is said to turn 

 black rapidly ; and the red compound produced by a lead salt, and 

 those of Berzelius and Zeise, undoubtedly does so blacken, as also 



