BRIDGMAN. — WATER UNDER PRESSURE. 473 



A v(p,t) = V, (p,t) - r, 0,0 = A F (0,0) + dj^ [_(j^)- (|,) 



--[(tx-c^);j- 



This holds for any values of dp and dt. On the equilibrium curve, 



and we have 



dr = -r- dp, 

 dp 



dAV dAV dr f^^'A , (djA^^ 



dp ~ dr dp~ \dpjr' \dp J ' dp[_ \dT Jp \ Q^- A J 

 Everything in this equation is known except ( "^-^ ) • 

 We have f ?^M = O.O452 kgm./cm.'^ (Amagat), 





— , = + O.O3I52 (Vincent),8 

 dr Jj, 



dr 



-—- = — 0.00722 [already computed ; see p. 468]. 



—J— = — 0.00200 [from these experiments]. 

 Substituting these values in the above expression, we find 



\dpj. 



O.O436. 



The compressibility of ice, with the larger volume, is therefore about 

 1/3 less than the compressibility of the liquid. There seem to be no 

 published experimental data with which to compare this value. 



The Curve I-III. 



The existence of this new variety of ice, III, was discovered by Tam- 

 mann, who obtained it by increasing the pressure on ordinary ice to 

 about 2500 kgm. at temperatures between —22° and — G0°. The nota- 



8 Vincent, Phil. Trans. A, 198, 463-481 (1902). 



