126 H. L. Wells — Ccesium- and Potassium- Lead Halides. 



crucible and the whole was weighed and calculated as lead 

 oxide. A different method was selected for the determination 

 of lead in the potassium compounds, for the reason that some 

 of them could not be readily dissolved in hot water, and it was 

 found to be more convenient and expeditious than the other. 

 About one gram of substance was dissolved in about 10 cc 

 nitric acid (sp. gr. 1*20), about 2 C0 concentrated sulphuric 

 acid, previously diluted with water were then added and the 

 nitric acid was removed by evaporation. After diluting with 

 about 25 ec of water and cooling, the lead sulphate was collected 

 in a Gooch crucible, washed with very dilute sulphuric acid, 

 ignited and weighed. 



In order to determine caesium, the alkaline solution from 

 which the lead had been removed was concentrated until the 

 ammonium carbonate, hydroxide and sulphide had been nearly 

 or quite removed, a small excess of sulphuric acid was added, 

 and, after evaporation and ignition, normal caesium sulphate 

 was obtained by igniting in a current of air containing am- 

 monia and this was weighed. 



The filtrates from the lead sulphate did not contain an 

 appreciable amount of lead. Normal potassium sulphate was 

 obtained from these solutions by evaporating, igniting and 

 heating in an ammoniacal atmosphere. 



The halogens were determined as silver halides. Where 

 the substance could be completely dissolved in hot water, an 

 excess of silver nitrate was added to the hot solution and it 

 was afterwards acidified with nitric acid. When it happened 

 that the lead halide remained partly undissolved, the nitric 

 acid was not added until this had been completely decomposed 

 by long digestion on the water-bath with an excess of silver 

 nitrate. The precipitates were collected and weighed in Gooch 

 crucibles. 



The Caesium-Lead Chlorides ; by G. F. Campbell. 



Cs^PbCl^. — When lead chloride is dissolved, by the aid of 

 heat, in a solution of caesium chloride which is so concentrated 

 as to be nearly saturated when cold, this salt is deposited on 

 cooling in the form of brilliant, white rhombohedrons. Crys- 

 tals having a diameter of 2 or 3 mm were sometimes obtained. 

 Two entirely separate crops were analyzed, both of which 

 were undoubtedly free from other compounds. 



Calculated 

 Found. for Cs 4 PbCl 6 . 



Caesium 55-60 56-03 55-90 



Lead 21-63 2T75 



Chlorine..- 21-97 22-23 2235 



99-89 100-00 



