CHAPTER XII. 



CONCLUSION. 



The work reported upon in the preceding chapters is only a fraction 

 of the task which the author hopes to accomplish, or to see accomplished 

 by others. The investigation — already 15 years old — was undertaken, 

 in the first instance, with a view to developing a practicable and fairty 

 precise method for the direct measurement of the osmotic pressure of 

 aqueous solutions. The need of such a method for the investigation 

 of solutions seemed to the author very great and very urgent. The 

 freezing- and boiling-point methods were of great value, but of limited 

 applicability, in that they could give no certain information as to the 

 conditions within a solution, except at two widely separated and rather 

 exceptional temperatures. There appeared to be a need of more com- 

 prehensive methods — of methods which could be effectively applied 

 to the investigation of solutions at all temperatures between the freezing 

 and boiling points. Two such methods naturally suggested themselves . 

 One of these was a method for the direct determination of the osmotic 

 pressure, and the other was a method for the measurement of the 

 depression of the vapor tension of solutions. Neither had been per- 

 fected to a point where it could be made to yield convincing results. 

 The method selected by the author for development was that for the 

 measurement of osmotic pressure. Nearly eight years were devoted 

 to one or another phase of this part of the enterprise. The difficulties 

 which were encountered during the evolution of the method were great, 

 and often they were baffling and for long periods seemingly insurmount- 

 able. Fortunately for the undertaking, it was adopted by the Carnegie 

 Institution of Washington as soon as it became apparent that the 

 problems involved would require many years and large means for their 

 effective solution. It was also fortunate for the enterprise that the 

 author has had associated with him during the greater part of the time 

 two such able and tireless coadjutors as Dr. J. C. W. Frazer and Dr. W. 

 W. Holland, whose resourcefulness has contributed much to whatever 

 success has been attained. The development of the method, which is 

 described in the earlier chapters of this report, is now regarded as 

 reasonably complete — inasmuch as, in the hands of experienced persons, 

 it can be made to yield results which compare favorably with those of 

 other and simpler quantitative operations. 



Having perfected the method, it was to be applied to the measure- 

 ment of osmotic pressure in accordance with a systematic plan. It 

 was determined to measure with all possible care the pressures of four 

 substances over a wide range of concentration and temperature. The 



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