IOWA ACADEMY OF SCIENCES. 127 



SOME NEW DOUBLE BROMIDES AND THEIR DIS- 

 SOCIATION IN AQUEOUS SOLUTION. 



BY NICHOLAS KNIGHT. 



The purpose of this investigation is to study the condi- 

 tion of double bromides in the presence of varying amounts 

 of water. The substances herein described are well 

 defined compounds, having a composition as definite and 

 a crystalline form as characteristic as any group of chem- 

 ical substances. 



The question as to the way these substances break down 

 in aqueous solution is an interesting one. Are they first 

 decomposed into their constituent molecules, and then 

 these molecules dissociated electrolytically by the water, 

 as a mixture of the two substances would be, or do the 

 molecules of the double salts exist as such in aqueous solu- 

 tion ? No satisfactory answer has yet been received. 



The application of the conductivity method to the 

 problem of the existence of double salts in solution has 

 been made by a number of investigators. The conductivity 

 of solutions of the double salts, and also the conductivity 

 of solutions of the constituent were determined. On com- 

 paring the sum of the conductivities of the constituents 

 with the conductivity of the double salt at the same dilu- 

 tion, it is usually found that the conductivity of the double 

 salt is very much less than the sum of the constituents in 

 concentrated solution. Hence it is concluded that in such 

 solutions the double salt is only partially broken down into 

 the constituent substances. As the dilution increases the 

 differences become smaller and hnally disappear, or nearly 

 so, indicating that in very dilute solutions the double salt 

 entirely decomposes into its constituents. 



