CHAPTER V. 



A STUDY OF THE DISSOCIATING POWERS OF FREE AND OF COMBINED 



WATER. 



BY G. FRED. ORDEMAN. 



INTRODUCTION. 



The work of Uhler, 1 Anderson, 2 Strong, 3 Guy and Shaeffer, 4 and 

 Paulus 5 on the absorption spectra of solutions in their relation to the 

 phenomenon of solvation has been reviewed in a preliminary paper on 

 this subject. 6 These investigators having found a marked physical 

 difference between free water and combined or water of hydration in 

 their behavior towards light, it was believed that a determination of the 

 dissociation power of this combined water might lead to the establish- 

 ment of further differences between it and free water. A few prelim- 

 inary measurements showed the probability of such a difference in 

 dissociating power. The present investigation is a continuation of 

 this work along somewhat broader lines. For the sake of completeness, 

 certain details of the method, although described in the preliminary 

 paper, are repeated here. The object has been to ascertain the differ- 

 ence, if any, between the dissociating power of combined water or 

 water of hydration and the dissociating power of uncombined or free 

 water. 



EXPERIMENTAL. 

 APPARATUS. 



Conductivity Apparatus. The improved slide-wire bridge used for 

 the conductivity measurements was manufactured by The Leeds and 

 Northrup Company, of Philadelphia. In this instrument the resist- 

 ance wire, 5 meters in length, is wrapped around a porcelain drum. 

 Readings were made corresponding in most cases to at least 0.25 mm. 

 The resistance box had been standardized by the Bureau of Standards, 

 Washington. An alternating current was supplied by an induction 

 coil specially constructed for such work. The coil was actuated by a 

 single lead accumulator and the strength of the current was regulated 

 by adjusting the length of a thin manganin wire inserted between 

 battery and coil. A telephone receiver was employed to determine the 

 point of equilibrium. A double system of wiring was used between the 



'Carnegie Inst. Wash. Pub. No. 60, 160(1907). 3 Ibid., 130 (1910). 6 Ibid, 210, 9 (1915). 

 ., 110 (1909). *Ibid., 190 (1913). *Ibid t 230, 161 (1915). 



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