ELI8HA MITCHELL SCIENTIFIC SOCIETY. 83 



LEAD chloro-bromidp:s. 



BY F. P. VENABLE. 



The double coinpounds of the lialogen salts of lead have com- 

 monly very, simple and regular formulas assigned to them, often 

 as if they occurred only with equal proportions of the constitu- 

 ents. In some previous work upon these compounds* it was 

 seen that in several classes of compounds, at least, this was not 

 the case. As a contribution to our knowledge of this combining 

 power of lead some further experiments were tried upon the 

 chloro- bromides of lead and the results are given in detail. 



First Experiment. In the first experiment 13.2 gm. of lead bro- 

 mide and 5 gm. of lead chloride were dissolved in hot water. 

 This is in the proportion of two parts of bromide to one of 

 chloride. A very small portion, less than one-tenth of a gram 

 remained undissolved. Three crops of crystals were gotten from 

 this. The following percentages of lead were obtained on 

 analysis: 



1st Fraction 62.48: 3 Pb Br,. 2 Pb Cl^ has 62.41 p. c. lead. 

 2d Fraction 64.80: Pb Br,. Pb CU lias 64.14 p. c. lead. 

 3d Fraction 62.50: 3 Pb Br,. 2 Pb CI2 has 62.41 p. c. lead. 



On evaporating further on a water bath three more crops of 

 (•rystals were gotten. 



4th Fraction contained 60.26: 3 Pb Bra. Pb CI2 lias 60.42 p. c. lead. 

 5th Fraction contained 59.48: 4 Pb Br2. Pb CI2 has 59.26 p. c. lead. 

 6th Fraction contained 59.09: 5 Pb Brg. Pb CI 2 has 58.71 p. c. lead. 



The next cro}) of crystals gotten on furtiier evaporation was 

 very evidently lead bromide mixed with a few crystals similar 

 to fractions 5th and 6th. 



Second Experiment. Two parts of chloride were taken to one 

 of bromide. Four fractions of crystals were gotten and the per- 

 centage of lead in them determined. 



*This Journal, V, 10. 



