110 COMPRESSIBILITY OF GASES. 



FROM BOYLE TO MENDELEEF, OIST THE COMPRESSI- 

 BILITY OF GASES. 



BY LEROY C. COOLEY, PH.D. 



What is the law which governs the compressibility of 

 gases and what are its* limitations? Experimental inves- 

 tigations to answer these questions have been going on 

 at intervals during the last two hundred years. The 

 literature of the subject is quite extensive and consider- 

 ably scattered. It is my purpose in this paper to bring 

 together, into a single story, these experimental investi- 

 gations as far as I have been able to find them, and to 

 embody in it all that has been learned about this subject 

 by experiment down to the present time. 



ROBERT BOYLE — 1661. 



The relation between the volume of air and the press- 

 ure it sustains was first experimentally sought by Robert 

 Boyle in 1661 1 . Taking a long glass tube he bent it near 

 one end until the branches were parallel. The end of 

 the shorter branch was closed ; that of the other was left 

 open. He fixed this bent tube in a vertical position and 

 alongside of its branches he placed scales to measure 

 their lengths. Pouring a little mercury into the instru- 

 ment he rilled the bend up to the zeros of these scales. 

 By so doing he enclosed in the short branch a portion of 

 air which could neither be augmented nor diminished in 

 quantity during the experiments. The next thing was 

 to bring this mass of air under the influence of various 

 degrees of pressure, and he did this by pouring mercury 

 into the longer branch. 



Now Robert Boyle measured the volume and the cor- 

 responding pressure, represented by the mercury column, 



1 Defensio Doctrinae de Aire Contra Linus. 

 Encyclopaedia Brittanica, 8th Ed.— Pneumatics. 



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