viii. a, 6 West: Analysis and Composition of Red Lead 437 



Table III. — Analyses and composition of red lead. 



Sample. 



A. 



B. 



C. 



D. 



E. 



F. 



G. 



H. 



Insoluble matter 



none 

 18.64 



0.51 

 23.76 



24.53 

 60.92 



65.08 

 20.37 



none 

 27.74 



24.76 

 47.82 



66.05 

 6.53 



none 

 6.66 



31.28 

 62.02 



78.37 

 14.93 



none 

 29.22 



23.18 

 46.74 



55. 94 

 13.98 



0.08 

 41.36 



19.80 

 38.46 



51.85 

 6.41 



none 

 21.54 



26.30 

 52.18 



65.92 

 12.66 



none 

 6.36 



81.96 

 62.52 



83.14 

 11.34 



FreePbO - 



Red lead: 



Pb0 2 



27.02 

 64.52 



65.23 

 16.31 



Combined PbO 



Red lead as obtained from Table I: 



Pb 3 4 



Pb 4 6 _ 



Total Pb determined 



Total Pb calculated 



91.37 

 91.21 



100.08 



89.90 

 90.55 



99.72 



91.20 

 91.58 



100.32 



90.65 

 90.74 



99.96 



90.86 

 90.58 



99.14 



91.11 

 91.23 



99.70 



91.13 

 91.20 



100.02 



90.83 

 90.68 



99.84 



Total (insoluble matter + free 

 PbO + Pb 3 4 + Pb 4 5 ) 



As shown by the figures, there is a close agreement between 

 the calculated total lead content and that obtained by direct 

 determination. 



As shown by the data presented in Table III, the method of 

 analysis and calculation gives very accurate results. 



Although many investigations on red lead have been carried 

 out, its exact composition is still in doubt. The formula is 

 usually written Pb 3 4 . Several investigators regarded it as a 

 mixture of Pb 3 4 and Pb 4 B . Lowe considered it a mixture of 

 Pb 4 B and PbO. Milbauer 11 calculated his results on the sup- 

 position that it is only Pb 3 4 . 



According to the results, it would appear that red lead as or- 

 dinarily prepared consists of a mixture of the oxides Pb s 4 , 

 P^Og, and PbO, and the exact composition of any particular 

 sample depends upon the conditions of manufacture which estab- 

 lish the equilibrium of the various component oxides. 



Chem. Zeitg. (1909), 33, 513. 



