310 PROCEEDINGS OF THE AMERICAN ACADEMY, 



Introduction. 



This paper is in the nature of a supplement to a former paper on 

 the properties of water in the liquid and the solid forms. -^ The solid 

 forms were studied over a range of 20,000 kgm./cm.^, and from —80° 

 to +76°, but the study of the liquid reached only from the lowest 

 temperature of its existence to about +20°. Above 0°, measurements 

 were made on the liquid at only 20°, The two measurements, at 0° 

 and 20° were sufficient to give the mean dilatation between 0° and 20°, 

 but not the variation of dilatation with temperature. It w^as assumed 

 in the earlier paper that the variation of dilatation with temperature 

 became negligible at high pressures, since this seemed to be the most 

 plausible assumption in view of all the data then available. 



In this present paper the study of the liquid has been continued 

 from 20° to 80°, and to 12000 kgm. The pressure range is greater 

 than that of the preceding paper by about 2,500 kgm. The range is 

 not great enough to entirely cover the region of stability of the liquid, 

 but it is as great as it was convenient to cover with the method used 

 here, which is different from that of the former work. It has the 

 advantage of very much greater rapidity of operation, but since it 

 depends on the complete elastic integrity of the steel pressure cylinders 

 it is not possible to reach so high pressures with it as with the former 

 method. [The former limit of 9500 kgm. was set by the freezing of 

 the liquid and was not due to any limitation of the method.] Never- 

 theless, it may be hoped that the present temperature and pressure 

 ranges are both wide enough to give a fairly complete idea of the nature 

 of the effects to be expected at high pressures with varying tempera- 

 ture. 



Measurements of the dilatation have been made at four tempera- 

 tures, so that it has been possible to find the variation of dilatation 

 with temperature at any pressure. Perhaps the most unlooked for 

 feature disclosed by the measurements is the fact, contrary to the 

 assumption of the first paper, that the variation of dilatation with 

 temperature does not become vanishingly small at high pressures, but 

 reverses in sign. This means that while at low pressures the volume 

 increases more and more rapidly with rising temperature, at high 

 pressures the expansion becomes more slow at high temperatures. 

 i%The data of this paper are sufficient to completely map out the 

 p-v-t surface over the domain in question: Both the first and second 



1 Bridgman, These Proceedings, 47, 439-558 (1912). 



