Phenomena of some Substances and Mixtures. 181 



who finds 37-9 at 15° C, and 42*8 at 20°-2. Ansdell's * 

 values are a good deal different, his pressures being 32'77 at 

 13°'5, 39-76 at 20°-15, 48'99 at 27°-55, 56'20 at 31°-6. For 

 the critical point he found 68*0 atmospheres and 36°'9 C. 

 As to Pictet's t values, they show no resemblance whatever 

 with the others. His pressures were : 29'0 at 14°*1, 33*5 at 

 19°- 5, 58-5 at 27°-6, and 480 at 36°- 5 (critical point). 



Mixture of Carbonic Acid and Acetylene. 



15. The mixture was made in a mercury gasometer con- 

 sisting of two parallel wide glass tubes of 300 c.c. each, 

 provided at the bottom with a tap, an indiarubber tube, and a 

 funnel with mercury sufficient to fill up the whole of the 

 tubes. At the top the tubes ended in threeway stopcocks 

 communicating together, the whole, as described before, con- 

 nected on one side with the pump, and at the other side with 

 the rest of the apparatus. The mixture contained ^C 2 H 2 and 

 *C0 2 . 



16. The results obtained are the following : — 



Table VI. 

 Mixture 0*5 C„H 2 



0-5 CO,. 



t. 



Pb- 



Pe- 



735 



35-98 



36-90 



14-95 



43-46 



4462 



2015 



4954 





2475 



55-18 



56-10 



26 15 



5710 



57-95 



31-55 



64-79 



65-17 



3255 



66 



52 C 



The differences between pj, and p e (fig. 1) , the pressures at 

 the beginning of the condensation and at the end, are some- 

 what larger than for acetylene, as might be expected. It 

 would be possible to make an allowance for the impurity of 

 the component gases, and in that manner obtain approximate 

 corrected values for the pressures. This would, however, be 

 a rather uncertain calculation, and in drawing the border- 

 curve for this mixture I have preferred to use the direct 

 experimental values. Obviously, though the slight impurities 

 of the C0 2 , and specially of the C 2 H 2 , also affect the values 

 for the mixture, the divergence from the true values can only 

 be of the same order of magnitude as for the components. 



* Proc. R. S. of London, xxix. p. 211 (1879). 



t Zeitsvhrift Compr. undjlussige Gase, i. p. 32 (1897). 



