On some ComUnations qfPlatina. 2l3 



previously attached ; the retort was exhausted twice, and" 

 ilU-d with hydrogen or carbonic acid gas. It was exposed 

 to the heat of a sand-hath, and the stop-cock opened under 

 water. After some time the vapour of the water expelled 

 the gas in the retort; when this was eiFected, the stop-cock 

 was closed, and the neck of the retort kept cold by wet 

 cloths. When the hydrosulphuret had been thus heated 

 in a partial vacuum for about 10 hours, it appeared to be 

 quite dry, and no indications of moisture could be per- 

 ceived in the bulb of the retort. When cold it was slowly 

 opened over hydrogen gas. In one experiment in which 

 ihe retort had been previously filled with hydrogen gas, 

 nearly a half of a cubical inch of water was obtained, which 

 had the smell of sulphuretted h\drogen gas, and produced a 

 dark-coloured precipitate with nitrate of lead. I intended 

 to have examined this water more minutely, but was pre- 

 Tcnted by an accident. It seems probable that it was 

 merely impregnated with a little sulphuretted hydrogen 

 gas, expelled by the agency of heat. In another instance 

 when the hydrosulphuret was procured, the retort being 

 previously filled with carbonic acid gas, the water that came 

 over did not contain any sulphuretted hydrogen gas. I 

 cannot with certainty state the greatest temperature to 

 which the hydrosulphuret had been exposed in these ex- 

 periments; it was necessarily variable ; but from some trials 

 I made with- the thermometer, I have reason to think it 

 could scarcely at any time have exceeded the boiling point 

 o4^ water. A well stoppered bottle was filled with the dry 

 hydrosulphuret, and it was immediately^ examined. 



Physical and Chemical Properties. 



Its colour was dark brown. It was in small flat lumps, 

 which were readily reduced to powder. Its external sur- 

 face exhibited a feeble lustre, which was no longer apparent 

 when pulverized. Its lustre was scarcely infeiior to plum- 

 bago when it was rubbed on the fingers or paper. Jt had 

 no smell. It was insipid when first brought in contact 

 with the tongue ; but as it became divided in the mouth, a 

 tolerably strong saline taste was perceived. It scarcely 

 afl'ected litmus paper. When it was put into water, a 

 sliglil crackling noise was produced, and small bubbles of 

 ^a» were disengaged. 3 2 grains of hydrosulphuret afforded 

 in this vtay -f>^\- of a cubical inch oi gas, which diminished 

 Considerably with nitrous gas, and did not burn or explode 

 with a taper. 1 expected \o have found this gas hydrogen, 

 3 ami 



