LIB* ART 



NEW YORK 



BOTANKAL 



(i A V URN 



THE EFFECT OF PRESSURE UPON OPTICAL ABSORPTION. 



By Frances G. Wick. 



Presented by P. W. Bridgman. Received March 22, 1923. 



The effect of pressure upon vai-ious optical properties of matter has 

 been the subject of considerable research, a very good account of which 

 is given in a paper by Wahl. 1 Experimental difficulties have greatly 

 limited the results obtained in high pressure optical work since the 

 pursuit of problems along this line involves the construction of ap- 

 paratus having transparent windows which will stand high pressure 

 without fracture and which are mounted in such a way as to prevent 

 leaks. Little work has been done at pressures above 1000 atmospheres 

 although Wahl occasionally succeeded in reaching a limit of 4000 

 atmospheres. 



The work described in this paper was undertaken at the suggestion 

 of P. W. Bridgman and it was done with pressure apparatus designed 

 by him and manipulated under his supervision in the Jefferson Physi- 

 cal Laboratory, through the courtesy of Harvard University. Experi- 

 ments were made upon the absorption of light in solutions and in 

 solids up to pressures of 3500 atmospheres. The difficulties encoun- 

 tered were many and the results are principally qualitative but they 

 appear to be of sufficient interest to warrant publication at this time 

 since this is a field which has been left practically unexplored. 



Apparatus. 



The part of the apparatus used for this work which has to do with 

 the production, transmission, and measurement of pressure is similar 

 to that commonly used by Bridgman 2 in different kinds of pressure 

 experiments. The only parts of the outfit peculiar to this particular 

 work were the observation chamber, in which the specimen under 

 consideration was subjected to pressure, and the optical system used 

 for the study of the absorption of light. The general arrangement of 

 the apparatus is shown in Figure 1. The specimen, S, was mounted 

 at the bottom of an observation chamber, O, made by drilling a hole 

 tf of an inch in diameter and 7 inches deep along the axis of a steel 



1 Wahl, Phil. Trans. Royal Soc. London, Vol. 212A, p. 117. 



2 Bridgman, Proc. Am. Acad., 47, p. 321, 1911-12; 49, p. 627, 1913-14. 



