12 JOURNAL OF THE 



soluble powder was washed and (hen dried at 100°. The analy- 

 ses gave the following results, the CN being found by difference: 



Lead ferrocyanide could not be induced to crystallize with lead 

 chloride. It is so insoluble that few of the methods of forma- 

 tion used in this research could be put into practice. On cover- 

 ing lead chloride with a solution of potassium ferrocyanide, the 

 lead gave up its chlorine completely. The resulting lead ferro- 

 cyanide persistently retained some potassium ferrocyanide. 

 Again, when lead ferrocyanide was boiled for some time with 

 potassium chloride, neither filtrate nor residue contained the 

 desired double salt. 



Lead ferrocyanide covered with ammonia water for several 

 weeks vields a brownish-^rav white mass which was free of am- 

 monia and contained 12.42 per cent, of ferroeyanic acid and .45 

 per cent, of ferric oxide. It is a basic ferrocyanide. 



Of course the attempt to crystallize lead ferrocyanide from 

 hydrochloric acid ended in the decomposition of the ferrocyanide 

 with the formation of lead chloride and separation of Prussian 

 blue. 



Lead bromiodide. When lead iodide is dissolved in hvdro- 

 bromic acid, the first crystals are of a deep yellow tint, approach- 

 ing orange. The crystals on analysis yielded 49.75 per cent. 

 Pb. Calculated for PbBr 2 .PbI 2 , Pb=49.93 per cent. These crys- 

 tals then have the composition represented by the formula 

 PbBr.Pbl. 



2 2 



The second crop of crystals have a straw-yellow color and 

 gave 52.99 and 52.57 percent. Pb, 30.61 percent, Br, and 16.20 

 per cent, I. Calculated for 3PbBr 2 .PbI 2 , 52.94 per cent, Pb, 

 30.77 per cent. Br, and 16.32 per cent. I. 



