SULPHURETTED HYDROGEN. 341 



2. Properties. 



(a.) All soluble; decomposed by a moderate heat, sulphurous 

 acid gas being exhaled and sulphates remaining. 



(b.) Strong sulphuric acid decomposes the acid of the hypo-sul- 

 phates, at the instant when it is decomposing the salts which contain 

 it ; a weak acid, applied cold, separates the hypo-sulphuric acid with- 

 out decomposition. 



(c.) Not changed by the air, or only slightly absorb oxygen. 

 The hypo-sulphate of baryta crystallizes in square prisms of pecul- 

 iar brilliancy ; that of potassa in a cylindroidal form ; that of lime in 

 hexagonal, and that of strontia in very small hexahedral laminae. 

 Composition of the acids of sulphur. 



Sulphur. Oxygen. 



Hypo-sulphurous acid, - 16 -f 8 1 and 1 proper* 



Sulphurous acid, - 16 -f 16 1 and 2 " 



Sulphuric acid, - 16 + 24 1 and 3 " 



Hypo-sulphuric acid, - 32 + 40 2 and 5 " 



Thus these compounds beautifully illustrate the laws of definite 

 and multiple proportions. 



COMPOUNDS FORMED BETWEEN SULPHUR, HYDROGEN, AND THE AL- 

 KALIES AND EARTHS. 

 SULPHURETTED HYDROGEN. 



1. NOMENCLATURE. The termination uret is appropriated to 

 combinations of simple combustible, non-metallic* bodies, with each 

 other and with the metals, alkalies, and earths. Thus, in the case 

 of sulphur and phosphorus, we have sulphuret of phosphorus, or 

 phosphuret of sulphur, sulphuret or phosphuret of lime, and of calci- 

 um, of potassa, and of potassium, of iron, &tc. To denote different 

 proportions of the principles, terms are derived either from some 

 sensible property, usually the color ; e. g. we have a black and red 

 sulphuret of mercury, yellow and red sulphuret of arsenic, &tc. ; or 

 it is now more usual to prefix the same terms that are applied to the 

 oxides, as proto-sulphuret, deuto-sulphuret, &c. implying one or two- 

 proportions of sulphur, &c. 



Where the compound is gaseous, it is usual to add ted to the ter- 

 mination uret ; as sulphuretted hydrogen and phosphuretted hydro- 

 gen, instead of sulphuret and phosphuret of hydrogen. 



2. HISTORY. Known to Rouelle, but first investigated by Scheele, 

 A. D. 1777 ; afterwards by many distinguished chemists. 



3. PROCESSES. 



(a.) By heating sulphur in hydrogen gas, by the solar rays ; or 

 by subliming sulphur, repeatedly, in hydrogen gas ; or, by passing 

 this gas over sulphur heated in a porcelain or coated glass tube. 



* The compounds of metallic bodies with each other are called alloys. 



