1880.] On the Critical Point of Mixed Vapours. 



543 



tion. The pressure at the point of liquefaction was, as in the former 

 cases, lower than either of the gases liquefied by themselves. Thus : — 



o 



At 13 *5 C, the pressure was 25 "23 atmospheres. 

 „ 21 -0 „ 26 -8 



26 '8 

 31 -9 

 39 

 41 



34 1 

 40 -26 

 55 -3 

 75 -32 



The critical point was, on the other hand, heightened, being 41° C. ; 

 that of carbonic acid being 31° C, and of acetylene, 37° C. 



Carbonic Acid and Hydrochloric Acid Gases. 



A mixture of equal volumes of these gases was filled into a tube, 

 the liquefied gases mixed completely together at all temperatures 

 below the critical point, which was 36° C, forming a perfectly homo- 

 geneous fluid ; in fact, it was impossible to tell that two different gases 

 were present, as even at the point of liquefaction no difference was 

 discernible. 



The following are the pressures at which the mixture liquefied : — 



At 0*0 C 36 '0 atmospheres. 



„ 5-0 „ 39'0 



„ 8-0 „ 43-8 



„ 10-1 „ 48-2 



„ 18-5 „ 59-0 



„ 34-0 „ 83'0 



„ 35-5 „ 90-0 



Carbonic Acid and Bromine. 



A tube filled with a mixture of carbonic acid and bromine 

 vapour by passing dry carbonic acid through a tube containing dry 

 bromine before entering the liquefying tube. A little strong sul- 

 phuric acid was also introduced, to protect the mercury. On com- 

 pressing this mixture at 11°'5 C. the sulphuric acid appeared in sight 

 with a layer of liquid at 50 atmospheres, the liquid having a decidedly 

 red colour. 



On increasing the pressure the liquid became more highly coloured, 

 while a little pure bromine liquid fell through the liquid carbonic acid, 

 remaining a short time on the surface of the sulphuric acid, through 

 which a globule also sank. 



As this tube was spoiled through the amount of bromine which fell 

 through the sulphuric acid, another was put up in the same way, and 

 heated at once to about 40° C, before compressing the mixture. 



