564 SCIENCE PROGRESS 



These measurements required the construction of a new series 

 of thermostats and were very costly in other ways on account of 

 the extreme brittleness of the heated glass. Thus whilst the 

 measurements at 30 were begun with an equipment of sixteen 

 manometers, the preparation of which had cost more than a 

 year's labour, not less than twelve of these were put out of 

 commission, half of them permanently, during the course of the 

 work between 6o° and 8o°. 



The results, however, are both striking and important. As 

 soon as 25 is passed the ratio of osmotic pressure to gas 

 pressure begins to drop (in the case of the more dilute solutions 

 with perplexing rapidity), the result being that, in the case of 

 each of the ten concentrations examined, this ratio falls to unity 

 at some temperature below 8o° C. In the case of the decinormal 

 solution this equality is maintained over the range from 30 to 

 6o°; in the case of the more concentrated solutions, experiments 

 now in progress will show whether the ratio remains constant 

 at unity or whether it diminishes to some smaller figure. 



E. Lord Berkeley's Experiments 



The experiments of the Earl of Berkeley and Mr. E. G. J. 

 Hartley " On the Osmotic Pressures of some Concentrated 

 Aqueous Solutions " are published in the Philosophical Tran- 

 sactions for 1906 (A. 206, 481-507). Two additional papers " On 

 the Osmotic Pressures of Aqueous Solutions of Calcium Ferro- 

 cyanide " are published in the 1908 and 1909 volumes {Phil. 

 Trans., 1908, A. 209, 177-203; 1909, A. 209, 319-36). Of these 

 three papers the first two dealt with osmotic pressures from 13 

 to 133 atmospheres, the third covered the region from 15 

 atmospheres downwards. It will be seen that the work on 

 concentrated solutions takes up and extends to regions of much 

 higher pressure the type of observation that was being made 

 by Morse and Fraser in America. In this region of high 

 pressures a considerable range of substances was examined, 

 including a number of metallic ferrocyanides. Most of the 

 measurements were made at one temperature, o° C, the object 

 of the experiments being to determine the absolute values of the 

 osmotic pressures and not the temperature coefficients. 



The Osmotic Apparatus. — This was of a different type from 

 that used by Pfeffer and by Morse. The chief novelty consisted 



