ELISHA MITCIIPn.L SCIENTIFIC SOCIETY. 85 



Atteni[)ts wore then made to prepare tliis compound and so by 

 determining its nietliod of ])re[)aration and by fnrtlier analyses 

 to decide whether it could be called a definite compound or 

 not. Three grams of lead nitrate were dissolved in hot water 

 and ten y:rams of lead bromide added. Tiie whole was filtered 

 hot and allowed to cool. The bromide (as judged by the appear- 

 ance of the crystals) crystallized out with very little admixture 

 of nitrate. 



Next a saturated solution of lead nitrate was taken and lead 

 bromide dissolved in it while hot in such amount that it did not 

 crystalize out immediately on cooling. Four crops of crystals 

 were gotten from this mixture on its slow evaporation. These 

 presented very much the same appearance, that of stellated groups 

 of needle-like crystals. 



On analyzing these after drying at 100° the following results 



were obtained : 



1st Cnip percentage bromine 41.23. 

 2d '' " " 36.75. 



3d " " " 33.40. 



4th " ** " 34.68. 



There are reasons for thinking this last analysis faulty as the 

 amount of substance at command was insufficient. 



The percentage of bromine in lead bromide is 43.58; in 

 Pb (N03),. 5 Pb Br, it is 36.92, in Pb (^03)^. 3 Pb Br, it is 33.50. 



The first crop of crystals then contained only a small amount 

 of lead nitrate and this amount increases with each subsequent 

 crop, approaching nearly to two definite compounds as far as the 

 analyses can point out. It is of course highly improbable tliat 

 one could secure pure compounds by one such fractional crystal- 

 lazation, but the fact that figures approximately correspcjuding 

 to Pb (Nog)^. (Pb Brjg were obtained in each of the two experi- 

 ments certainly affords ground for believing that such a com- 

 })ound is formed. 



Chemical Laboratory U. N. C, Ma.y, 1890. 



