n ATOMIC WEIGHTS OF THE METALS 377 



LEAD SULPHATE = 



Formula PbSO 4 . 



The corresponding formula for lead sulphite is PbSO 3 . 



2. Potassium Chlorate. In this case Berzelius weighed 

 the oxygen directly (by loss of weight) and the chlorine as 

 silver chloride, and determined the metal by difference. 



(1) 3*9850 grams of potassium chlorate, heated in a small 

 retort, lost i'5475 grams of oxygen and left 2*4375 of potass- 

 ium chloride (Klassiker, XXXV. 122). 



(2) 10 grams of potassium chloride, precipitated with silver 

 nitrate, gave 19*21 grams of fused "horn-silver" (silver 

 chloride) (Klassiker, XXXV. 93). 



(3) 3 grams of pure silver, dissolved in nitric acid, pre- 

 cipitated with muriatic acid, evaporated and fused, gave 

 3*98 grams of " horn-silver " (Klassiker, XXXV. 24). 



It follows 



(4) From (i), that 3*9850 grams of potassium chlorate con- 

 tain 1'5475 grams of oxygen. 



(5) From (2) and (3), that since 3*98 grams of silver 

 chloride contain 3 grams of silver and 3*98-3*00 = 0*98 

 grarn of chlorine, therefore 19*21 grams of horn-silver con- 



tain - .-4- x '98 = 473 grams of chlorine, derived from 



10 grams of potassium chloride ; thus, 3*9850 grams of 

 potassium chlorate or 2*4375 grams of potassium chloride 



contain x ^^ _ 1*1529 grams of chlorine. 



10 



(6) Finally, 3*9850 grams of potassium chlorate must con- 

 tain 3*9850- 1*5475 - 1*1529 = 1*2846 grams of potassium. 



