CHAPTER V. 



CONDUCTIVITY AND VISCOSITY OF SOLUTIONS OF RUBIDIUM SALTS 

 IN MIXTURES OF ACETONE AND WATER. 



BY P. B. DAVIS AND H. HUGHES. 



The work done in the Chemical Laboratory of the Johns Hopkins 

 University during the past dozen years, on the relations between the 

 viscosities of solvents and solutions of certain salts in these solvents, was 

 referred to at the beginning of the last chapter. That which is closely 

 related to the contents of this chapter is the work of Jones and Veazey, 

 Jones and Schmidt, Jones and Guy, and especially that of Jones and 

 Davis. 1 The last named extended the work in glycerol as a solvent, 

 studying especially the conductivities and viscosities of glycerol solu- 

 tions of ammonium and rubidium salts, as has already been pointed out. 



All previous work in the laboratory with acetone as a solvent shows 

 that it has exceptional properties. Measurements of both conduc- 

 tivity and fluidity have usually given results that are abnormal in 

 terms of other solvents: for this reason it was chosen as a solvent in 

 this investigation, in the hope that the property possessed by rubidium 

 salts of forming solutions having a lower viscosity than that of the 

 solvent might throw some additional light upon the phenomena pre- 

 sented by solution. Only mixtures of acetone and water have been 

 used, because in pure acetone the rubidium salts studied are not suf- 

 ficiently soluble to affect the fluidity to a measurable extent. 



EXPERIMENTAL. 

 CONDUCTIVITY APPARATUS. 



Bridge. The conductivity measurements were made by means of a 

 slide-wire bridge about 5 meters long, the balance being detected by a 

 telephone receiver. The bridge and rheostat were made and stand- 

 ardized by Leeds and Northrup Co., of Philadelphia, Pennsylvania; 

 and the rheostat was compared with one recently standardized by the 

 United States Bureau of Standards. 



A double system of wiring was used between the rheostat, slide wire, 

 and cells, so that by means of a double-arm double-throw switch the 

 arms of the bridge could be interchanged. In this way the resistance 

 a of the first portion of the slide wire was read and then b = 1000 a 

 for comparison. The circuit was opened and closed by an ordinary 

 telegraph key, whose resistance was made of negligible value by con- 

 necting the frame to the lever by a short spring of large copper wire. 



The wire used throughout was number 12 gage, and the cells con- 

 taining the solutions were connected with the rest of the bridge by a 

 large flexible cable of copper having a negligible resistance. All con- 

 nections were soldered, and the various portions of the apparatus were 



Carnegie Inst. Wash. Pubs. Nos. 80 and 180. 

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