108 NON-METALS AND THEIR COMBINATIONS. 



Tests for hydrogen sulphide or sulphides. 



1. Hydrogen sulphide or soluble sulphides (ammonium sulphide 

 may be used), when added to soluble salts of lead, copper, mercury, 

 etc., give black precipitates of the sulphides of those metals. 



2. From insoluble sulphides (ferrous sulphide, FeS, may be used) 

 liberate the gas by sulphuric or hydrochloric acid, and test as above, 

 or suspend a piece of filter-paper, moistened with solution of lead 

 acetate, in the liberated gas, when the paper turns dark. Some sul- 

 phides, for instance those of mercury, gold, platinum, as also FeS 2 , 

 and a few others, are not decomposed by the acids mentioned, unless 

 zinc be added. 



Carbon disulphide, Carbonii bisulphidum, CS 2 = 76. This 

 compound is obtained by passing vapors of sulphur over heated 

 charcoal. It is a colorless, highly refractive, very volatile, and 

 inflammable neutral liquid, having a characteristic odor and a sharp, 

 aromatic taste. It boils at 46 C. (115 F.) ; it is almost insoluble 

 in water, soluble in alcohol, ether, chloroform, fixed and volatile oils ; 

 for the latter two it is an excellent solvent, but dissolves, also, many 

 other substances, such as sulphur, phosphorus, iodine, many alka- 

 loids, etc. 



Selenium, Se, and Tellurium, Te, are but rarely met with. Both elements 

 show much resemblance to sulphur ; both are polymorphous ; both combine 

 with hydrogen, forming H 2 Se and H 2 Te, gaseous compounds having an odor 

 more disagreeable even than that of H 2 S. Like sulphur, they form dioxides, 

 Se0 2 and TeO 2 , which combine with water, forming the acids H 2 SeO 3 and 

 H 2 Te0 3 , analogous to H 2 S0 3 . The acids H 2 Se0 4 and H 2 Te0 4 , corresponding 

 to H 2 S0 4 , also are known. 



QUESTIONS. 131. How is sulphur found in nature? 132. Mention of sul- 

 phur: atomic weight, valence, color, odor, taste, solubility, behavior when 

 heated, and allotropic modifications. 133. State the processes for obtaining 

 sublimed, washed, and precipitated sulphur. 134. State composition and mode 

 of preparing sulphur dioxide and sulphurous acid; what are they used for, 

 and what are their properties ? 135. Explain the process for the manufacture 

 of sulphuric acid on a large scale. 136. Mention of sulphuric acid : color, 

 specific gravity, its action on water and organic substances. 137. Give tests 

 for sulphates and sulphites, sulphuric and sulphurous acids. 138. What is the 

 difference between sulphates, sulphites, and sulphides? 139. How is hydro- 

 sulphuric acid formed in nature, and by what process is it obtained artificially? 

 What are its properties, and what is it used for? 140. Mention antidotes in 

 case of poisoning by sulphuric and hydrosulphuric acids. 



