Molecular Constitution, of Water. 469 



Temp, of 1 198° 100° 90° 50° 0° 



Temp, of ethyl oxide 71 -1 -8 -37 



Compr. of ethyl oxide Xl0 5 ... 28 13 105 8 



Compr. ofl X10 G ... 82 38 31 23"5 16 



In equation (15) we can use Amagat's values of the com- 

 pressibility of water to give dv/df, as in the next table ; from 

 the last table wo derive dv u 'df, and from Table I. p±, and thus 

 get the values of p 2 dv 2 /df+ (v 2 — v x ) dp 2 /df given in the last 

 line of the next table. 



Table III. 



Temp. G 0° 50° 100° 198° 



Wdvfvdf for Water 492 425 468 800 



Wdv/df for water 492 430 488 928 



Wp^vjdf 93 165 301 769 



10 7 {p 2 dv 2 /df+(v 2 -v 1 )dp.Jdf\... 399 265 187 159 



It should be noticed that the compressibility we have 

 calculated for 1 at 198° is nearly the same as that found by 

 Amagat for water at 198°, at which temperature it ought to 

 be nearly all 1 ; this, therefore, confirms our calculated com- 

 pressibilities for 1. The numbers of the last row are made 

 up of two parts, p 2 dv 2 /df and {v 2 —vi)dp s /df. Now p 2 has a 

 vjilue, '375 at 0°, which falls to '217 at 100°, so that these 

 numbers may be said to include on the average about ^ of 

 dv 2 /df for 2. But for a substance so near its solidifying- 

 point as 2 is at these temperatures, '00001 would be a reason- 

 able allowance for dv 2 /df at C , and as dvjdf increases while 

 p 2 diminishes with rising temperature, '000003 may be used 

 as an approximate value of p 2 dv 2 /df, at all temperatures up 

 to 100°. As we now can calculate v 2 and v x at all tempera- 

 tures, we have v 2 — v^ as given in the next table, and therefore 

 dp 2 jdf given in the last row. 



Table IV. 



0° 50° 100° 



-W(v 2 -Vj)d P Jdf 369 235 157 



lO^v-Wi) 2185 1869 1509 



-Wdp.Jdf 170 126 104 



We have thus obtained estimates of the rate at which a 

 gramme of 2 (trihydrol) is dissociated by pressure at different 

 temperatures, namely, '00017 gramme per atmo at 0° and 

 '0001 gramme per atmo at 100°. 



