SULPHUR. 101 



Washed sulphur, Sulphur lotum, is sublimed sulphur washed 

 with a very dilute ammonia water, and then with pure water ; the 

 object of this treatment being to free the sulphur from all adhering 

 sulphurous and sulphuric acid, as also from arsenic compounds which 

 are sometimes present. 



Precipitated sulphur, Sulphur prsecipitatum (Milk of sulphur). 

 Made by boiling one part of calcium hydroxide with two parts of 

 sulphur and thirty parts of water, filtering the solution, adding to it 

 dilute hydrochloric acid until nearly neutral, washing and drying the 

 precipitated sulphur. 



By the action of sulphur on calcium hydroxide are formed calcium polysul- 

 phide, calcium hyposulphite, and water : 



3(Ca20H) + 12S : : 2CaS 5 + CaS 2 O 3 + 3H 2 O. 

 Calcium Sulphur. Calcium Calcium Water, 



hydroxide. Polysulphide, Hyposulphite. 



On adding hydrochloric acid to the solution, both substances are decomposed 

 and sulphur is liberated : 



2CaS 5 + CaS 2 3 + 6HC1 = 3CaCl 2 + 3H 2 O + 12S. 



Precipitated sulphur differs from sublimed sulphur by being in a more finely 

 divided state, and by having a much paler yellow, almost white color. 



Sulphur dioxide, SO 2 = 64 (Sulphurous anhydride, improperly 

 also called sulphurous acid). 



Two combinations of sulphur and oxygen are known; they are 

 sulphur dioxide, SO 2 , and sulphur trioxide, SO 3 . 



Sulphur dioxide is formed always when sulphur or substances con- 

 taining it in a combustible form (H 2 S, CS 2 , etc.) burn in air. It is 

 formed also by the action of strong sulphuric acid on many metals 

 (Cu, Hg, Ag, etc.), or on charcoal : 



2H 2 SO 4 + Cu : : CuSO 4 + 2H 2 O + SO 2 . 

 Sulphuric Copper. Cupric Water. Sulphur 



acid. sulphate. dioxide. 



2H 2 SO 4 + C = CO 2 + 2H 2 O + 2SO 2 . 



Sulphur dioxide is a colorless gas, having a suffocating, disagreeable 

 odor ; it liquefies at a temperature of 10 C. (14 F.), and solidifies 

 at 60 C. ( 76 F.) ; it is very soluble in water, forming sulphur- 

 ous acid ; it is a strong, deoxidizing, bleaching, and disinfecting 

 agent ; when inhaled in a pure state it is poisonous ; when diluted 

 with air it produces coughing and irritation of the air-passages. 



