SULFUR AND ITS COMPOUNDS IOI 



form ? (9) Why is nitric oxid used in the manufacture of H 2 SO 4 ? 

 (10) What are the physical properties of H 2 SO 4 ? (n) Of what 

 agricultural value is H. 2 SO 4 ? (12) Does H 2 SO 4 dissolve lead ? (13) 

 Why does commercial H 2 SO 4 often appear dark-colored or deposit 

 a fine white sediment ? 



119. Sulfates. Sulfuric acid is a dibasic acid, and 

 hence may form two series of salts, as NaHSO 4 , primary 

 sodium sulfate (acid sodium sulfate) , and Na 2 SO 4 , second- 

 ary sodium sulfate (normal sodium sulfate). The sul- 

 fates of the metals form a large class of compounds which 

 vary in chemical and physical properties according to the 

 metal that is present. The sulfates as a class are fairly 

 stable compounds ; some, as sodium and potassium sul- 

 fates, are soluble ; others, as calcium sulfate, are sparingly 

 so while barium sulfate is one of the most insoluble sub- 

 stances in nature. Many of the sulfates contain water of 

 crystallization. Some, as calcium and potassium sulfates, 

 are valuable as fertilizers, while others, as copper sulfate, 

 are used as fungicides. 



120. Sulfids. Sulfids are compounds of the metals 

 with sulfur, as K 2 S, FeS, and CuS. When a sulfid, as 

 FeS, is treated with a dilute acid, H 2 S, hydrogen sulfid, 

 is liberated. FeS + 2HC1 = FeCl 2 + H 2 S. 



The differences in solubility and other properties of the 

 sulfids are taken advantage of in the separation and 

 identification of the metals. H 2 S is formed when albu- 

 minous matter, as the white of an egg, decays. It is also 

 present as one of the gases given off from sewers. It is a 

 poisonous, suffocating gas. 



Experiment 22. Hydrogen sulfid, (This experiment should 



