346 HYDRO-SULPHURETS. 



2. GENERAL PROPERTIES. 



(a.) Soluble in water, recent solution colorless, by exposure to the 

 air become greenish or yellowish, and deposit sulphur on the sides 

 of the vessel. 



(b.) If the bottle in which they are kept contains lead, it is redu- 

 ced, and coats the interior with a metallic lining, probably a sulphuret. 



(c.) By long exposure to the air, and even by long keeping, they 

 pass to the state of sulphites, and ultimately to that of sulphates, which 

 are sometimes precipitated, and sometimes remain, in part or in whole, 

 in solution. 



(d.) Acids liberate sulphuretted hydrogen, but do not precipitate 

 sulphur ; 



(e.) Except* the nitric acid, which combines with the hydrogen 

 to form water, and thus liberate sulphur ; 



(f.) Except also when the hydro-sulphurets have been partially 

 decomposed by careless keeping, when they throw down sulphur. 



(g.) Precipitate all metallic solutions, and also alumina and zir- 

 conia, but no other earths. 



(A.) Generally crystallizable. 



(t.) Take up an additional dose of sulphur, by digestion, upon it, 

 but do not suffer it to be again precipitated by a stream of sulphuret- 

 ted hydrogen. 



(/.) After exposure, for some time, to the air, exhale sulphurous 

 acid gas along with sulphuretted hydrogen, and precipitate sulphur. 



(k.) Absorb oxygen, and therefore used in eudiometry. 



(I.) If there is no more sulphuretted hydrogen than is necessary to 

 saturate the base, they are inodorous ; but they usually have the odor 

 of sulphuretted hydrogen, because it not only saturates the base, but 

 combines with the water of the solution, which after the superfluous 

 gas is expelled, by heat, will no longer have any odor. 



(m.) The hydro-sulphurets are decomposed by heat, and the base 

 remains ; ammonia excepted, which is exhaled. 



(w.) It is said that sulphuretted hydrogen combines with alkalies, 

 in a double proportion, forming bi-hydro-sulphurets. 



HYDRO-SULPHURET OF POTASS A. 



1. Crystallizes in large transparent crystals, similar to those of sul- 

 phate of soda ; four sided prisms acuminated by four planes, or six 

 sided prisms with six planes, at the ends. 



2. Taste alkaline and bitter, inodorous when dry, but becomes 

 odorant by moisture ; is deliquescent. 



3. Forms a syrupy liquor, which imparts a green color to bodies 

 in contact with it. 



4. Dissolves, not only in water but in alcohol, producing cold. 



* Chlorine produces the same effect by seizing the hydrogen. 



