226 



Mr. William Sutherland on the 



'dp/'dT being independent of temperature in the case of the 

 alcohols ; if it is variable then the values of our functions are 

 affected with error. In any case we have seen that above the 

 critical region the alcohols behave differently from our two 

 typical compounds, ethyl oxide and carbonic dioxide ; in 

 section 14 it will be seen that in the liquid region, on the other 

 hand, the alcohols approach the regular compounds in many 

 respects, but are still exceptional in others. There remains 

 now only ethylene to consider as to its gaseous behaviour. 



Table XIII.— Ethylene. 



V. 



■Rvf(v). 



v*${v). 



v. 



nv/(v). 



v*<p(v). 



Perfect gas. 



2-22 





461 



4-15 



4500 



2075 



271 



5800 



4-15 



4-45 



4500 



1614 



2-78 



5320 



3 69 



4-81 



4400 ! 



11-53 



3-07 



5500 



322 



571 



4700 



9-23 



3-24 



5300 



2-77 



641 



4400 



6-92 



358 



5100 



265 



6-63 



4200 



5 76 



383 



4900 



254 



7-87 



5000 



According to Cailletet and Mathias (Compt. Rend, cii.), 

 the critical volume of ethylene is about 4*5 ; so that again in 

 the above table we see llvf{v) near the critical volume attaining 

 double its initial value and increasing rapidly thereafter. Once 

 more, too, we see v 2 <f>(v) attaining near the critical volume a 

 value which it retains constant below ; but ethylene is excep- 

 tional in that this value is not half the limit at high volumes. 

 The facts in the above table may be summarized in the state- 

 ments that Hvf(v) maybe represented by the form R(l + &/y), 

 and v 2 (p(v) by the form vl/(v + a) ; so that the characteristic 

 equation for ethylene is 



F \ v) v + a' 



with & = 4'15, a=l-64, and Z = 6270. 



The form for ethylene is intermediate in simplicity between 

 that for the simple gases and that for compounds, except that 

 it has an extra constant, 

 forms 



k // k 



2 



It is also worth noting that the 



(v — <A k/vj and 2&/(u + &) 

 are special cases of a general form 



nk/{v + (n — !)&}, 



with n = J, 1, and 2. 





