100 ANSWERS TO PRACTICAL QUESTIONS 



(3.) CaSO 4 , 2H 2 O = 172, 



'2H 2 O = 36. 

 Hence, -^ = .20 = 20 % of gypsum is water. 



(4.) A1 2 K 2 , 4SO 4 +24H 2 O = 949. 

 24H 2 O = 432. 

 Hence, $ff = .45 45 % of potash alum is water. 



45. What is the test for Ay ? Ca ? 



Ag can be easily detected when in solution by the precipi- 

 tation of the white, curdy chloride, insoluble in H 2 O and 

 HNO 3 , and soluble in H 3 N : the metal can be obtained in 

 malleable globules before the blowpipe, and is reduced from its 

 solutions by Fe, Cu, P, and Hg. Ag is estimated quantita- 

 tively either as the chloride or as the metal. 



Copper may be tested (1) by the black insoluble sulphide ; 

 (2) by the blue hydrate turning black on heating ; (3) by the 

 deep-blue coloration with ammonia ; (4) by the deposition of 

 red metallic copper upon a bright surface of iron placed in the 

 solution. 



40. What weight of crystallized "tin salts" (SnCl 2 , 

 2H 2 O) can be prepared from one ton of metallic tin ? 



Sn : SnCl 2 , 2H 3 O : : 2,000 Ibs. : x. 

 118 : 225 :: 2,000 Ibs. : x. 



118 x = 450,000 Ibs. 



x = 3813.56 Ibs. (SnCU, 2H 2 O). 



47. 1OO parts by weight of silver yield 132.87 parts of 

 silver chloride. Given the atomic iveiyht of chlorine (35.4], 

 required that of silver. 



32.87 : 100 : : 35.4 : x. 



48. What is the composition of slacked lime ? 



(See Chemistry, p. 139.) 

 OaO,H 2 0. 



49. How is ferrous sulphate obtained? How many 

 tons of crystals can be obtained by the slow oxidation of 



