306 



Dr. E. Frankland. Contributions to [June 20, 



Calculated. 



A 



^ Found. 



3SO s 240 17-71 17-61 



5PbO 1115 82-29 81*96 



1355 100-00 99-57 

 These analytical results suggest the following graphic formula : — 



Pb0 2 PbO, 



II II " 



s=o 2 =s=o 2 =s . 



Pb0 2 Pb0 2 Pb0 2 



The formation of this salt may be represented by the following 

 equation : — 



5PbO+3S0 4 H 3 = S 3 Pb 5 14 + 30H 2 . 



Litharge. Sulphuric Buff lead Water, 

 acid. salt. 



Action of Dilute Sulphuric Acid on Minium. 



Minium was treated with dilute sulphuric acid in exactly the same 

 way as litharge, and the resulting brownish red compound dried, first 

 at 100° C, and afterwards at 150 — 160°. The loss at this higher 

 temperature was again less than 0'2 per cent. 



PbO, SO g , and excess of oxygen were then determined in this salt 

 in the following manner : — The salt was first treated with concen- 

 trated hydrochloric acid in order to reduce all the lead to the mon- 

 oxide stage. The resulting mixture was then dissolved in caustic 

 potash and treated as already described. The excess of oxygen was 

 determined by finding the loss of weight which resulted from the 

 evolution of C0 2 when the salt was treated with oxalic acid and 

 dilute nitric acid. 



2*1136 grams of the salt gave 1*1978 grams baric sulphate and 

 2*2710 grams lead sulphate. 



1*5110 gram treated with oxalic acid and dilute nitric acid evolved 

 0*0910 gram C0 2 . 



These numbers correspond to the following percentages : — 



80 8 19*46 



PbO 7908 



1*09 



99*63 



which agree with the formula — 



SoPboO 



105 



