156 Wells, Wheeler and Penfeld — Doable Hal ides of 



subject,* Hemsen states that the exceptions to his law are " not 

 more than three or four oat of over four hundred." The work 

 here described confirms the result of Boullay, adds two more 

 exceptions to the law and points to the existence of a greater 

 number of compounds of the same type. It may be men- 

 tioned that a considerable number of other exceptions to this 

 law have recently been established in this laboratory and will 

 soon be described. 



Preparation and properties. — The salts are made by satu- 

 rating a very concentrated, hot solution of an alkaline halide 

 with the corresponding silver halide, filtering, cooling to crys- 

 tallization and, if necessary, evaporating the mother-liquor at 

 ordinary temperatures. If the solutions are too dilute, in some 

 cases at least, the 1 : 1 salts are formed. The compounds have 

 little tendency to crystallize well and many trials are usually 

 necessary in order to obtain satisfactory products. The salts 

 are all white. They are readily decomposed by water. 



Method of analysis. — The products analyzed were in the 

 form of crystals of such size that it was certain that they were 

 not mixed with other substances. In preparing them for 

 analysis the mother liquor was removed rapidly and completely 

 by pressing them between smooth filter-papers and great care 

 was. taken to avoid any evaporation of the liquid which ad- 

 hered to them. The analyses were made by treating them 

 with a sufficient amount of water acidified with nitric acid and 

 weighing the silver halide thus separated. The filtrate from 

 this was used for determining the remaining halogen or the 

 alkali- metal. 



Analyses. 



Calculated for 

 Found. 2CsCl . AgCl. 



Caesium 55-38 



Silver , 24-85 22-47 



Chlorine 22-15 



Calculated for 

 Found. 2RbI.AgI. 



Rubidium 25-05 25-91 



Silver 17-32 16-36 



Iodine 57'53 57/73 



99-90 



100-00 



Found. 



Potassium.. 



Silver 18-73 



Iodine 



* Am. Chem. Jour., xiv, 8*7. 



Calculated for 

 2KI . Agl. 



13-79 

 19-04 



67-17 



