ELISHA MITCHELL SCIENTIFIC SOCIETY. 13 



The third crop are white in color and yield <>n analysis 54.19 

 and 54.34 per cent. Ph. The calculated percentages for a sub- 

 stance of the composition 6PbBr 2 .PbI 2 are=54.34 per cent. Ph. 



The fourth crop are also white, and gave only a slight reaction 

 for iodine. They contained 50.12 per cent. PI), and are there- 

 fore nearly pure lead bromide. In form these crystals are all 

 alike, closely resembling ordinary lead bromide. 



Lead ehlorobromiodide. — Lead chloride, lead bromide and lead 

 iodide were dissolved together in hot water and allowed to crys- 

 tallize. No special proportions were taken, though in the first 

 experiment an excess of lead iodide was probably present. In 

 the second, more lead bromide and lead chloride were present, 

 with the bromide probably in excess. In both cases the iodide 

 crystallized out abundantly, immediately on cooling-. The sec- 

 ond, third and fourth crops of crystals were taken separately. 

 They were like one another in appearance, forming masses of 

 long silky yellowish white needles. Thev combined chlorine, 

 bromine, and iodine. Analyses of the three last fractions in the 

 second experiment gave the following percentages of lead: 



I. Pb=60.34; II. Pb=61.48; III. Pb=61.32. Analysis 

 of the fourth fraction gave, IV. Pb=61.57. 



There seems to be only one compound formed, as in I. the 

 analysis was probably defective. 



From these experiments it is evident that lead has quite a 

 facility for forming double compounds with the halogens and 

 analogous radicals, forming probably in many cases a series of 

 such salts with various ratios between the halogens, all being 

 (piite stable and crystallizing nicely. 



