36 



NEW METHOD FOR DETERMINING COMPRESSIBILITY 



readily, this tube was closed with a slightly lubricated stopper contain- 

 ing a single fine orifice. This tube thus filled was attached to a small 

 hook on the inside of the glass jacket, a profitable precaution which 

 prevented the inner tube from rising by its great buoyancy and cutting 

 off the electrical connection, as well as facilitated the filling of the 

 jacket with mercury. 



After adding successive amounts of mercury to the jacket thus filled, 

 applying the corresponding pressures, and thus determining the pres- 

 sure-volume relations of this complex system, the phosphorus was 

 removed, and its place was filled by precisely the same volume of 

 mercury, everything else remaining unchanged. The compression ex- 

 periments were then repeated, and the difference between the two 

 series obviously gave at once the difference of compression between 

 the given volume of phosphorus and mercury. 



Two entirely independent sets of experiments were made, every de- 

 tail of the operation being repeated. Their very satisfactory agree- 

 ment not only shows that no trivial errors of recording were made, but 

 also affords excellent evidence of the accuracy of the method. The 

 values marked with asterisks were obtained by removing" small 

 amounts of mercury after the maxima had been reached. Their ex- 

 act coincidence with the appropriate curves drawn through the other 

 points showed that no permanent " set " had been caused by the appli- 

 cation of the high pressures. 



The results of the two complete sets are given below. The weight of 

 the phosphorus in the first case was 8.304 grams, and in the second 

 case 8.283 g ram s- 



Upon plotting these values, regular curves are obtained which, when 



Data for Compressibility of Phosphorus 20 C. (cor.). 



Series 17 with Phosphorus. 



Series 18 with Mercury. 



