BRIDGMAN. — MERCURY UNDER PRESSURE. 



395 



may be mentioned here, because they throw some light on certain 

 properties of mercury under pressure, even if these are not the thermo- 

 dynamic properties which are the particular subject of this paper. 



The electrical resistance of the liquid mercury was usually measured 

 over the entire range up to the freezing pressure. The matter of the 



o 



Ul 80 



60 



20 



CO 



CL 



PRESSURE, KGW/CM*XIO"^ 



Figure 16. Departure of the melting curve of mercury from linearity. 

 The initial slope is 196.5 kgm. for a rise of temperature of 1° C. 



electrical resistance of mercury under pressure has already been treated 

 in a paper in which the pressure range was only 6800 kgm./cm.^ The 

 results obtained during the present work were pretty irregular, dis- 

 crepancies of 1 or 2 per cent not being rare; but within the limits of 

 error, the empirical formula given in the previous paper may be used 

 by extrapolation up to the freezing pressure, at least within the present 

 temperature range from — 1.5° to + 20°. The irregularities observed 

 in the present work were without doubt due to the strains set up in 

 the glass by the passage of the mercury from one state to the other. To 

 reach the accuracy of which the measurements are susceptible it would 

 be necessary to repeat the above resistance measurements, taking care 

 never to push the pressure beyond the freezing value. 



The electrical resista,nce of the solid mercury was also usually meas- 

 ured. These results cannot be expected to much more than indicate 

 the order of the effect, for in addition to the comparatively small irregu- 

 larities mentioned above, as due to elastic after-effects and hysteresis, 

 comparatively large temporary alterations in the glass capillary are 

 probably produced by the freezing of the mercury. The results are 



