100 REPORT— 1891. 



to affect the general character of the curve, or the nature of the 

 lesson to be learned from it. 



The specific solution-volumes of the aniline, calculated in 

 this manner, were found to be as follovr : — 



Temperature. 



8° ... 



16° ... 



25° 



89° ... 



55° ... 



68° ... 



77° 



137° ... 



142° ... ... — ... 7-696 



156° ... ... — ... 5-248 



157-5° ... ... 1-498 ... — 



164-5° ... ... — .. 3-412 



These specific solution-volumes are represented as abscissae 

 in Fig. 2, with the temperatures as ordinates. For the sake of 

 comparison I have placed side by side with it a specific volume 

 and temperature-curve (Fig. 3, PI. IV.) for pure alcohol and 

 its saturated vapour, plotted from the experimental data of 

 Eamsay and Young (Phil. Trans., 1886). The reason that 

 alcohol was chosen is simply that the data were convenient to 

 my hand. 



The two curves are strikingly similar in form and significance. 

 In Fig. 3 we see the specific volume of liquid alcohol increasing 

 slowly with rise of temperature, while that of the saturated 

 vapour rather rapidly decreases. In Fig. 2 we see the specific 

 solution-volume of the aniline in the aniline layer slowdy in- 

 creasing, while that of the aniline in the water layer decreases- 

 more rapidly, with rise of temperature. In Fig. 3 we see that 

 above the critical point the existence of liquid alcohol in 

 presence of its vapour is impossible. In Fig. 2 we see that 

 above the critical solution-point the existence of an aniline 

 layer in presence of a water layer is impossible. In Fig. 3 we 

 see an enclosed area which represents those temperatures and 

 specific volumes which are mutually incompatible. In Fig. 2 

 we see an enclosed area which represents those temperatures 

 and specific solution- volumes wliich are mutually incompatible. 

 In Fig. 3 we see that any tw^o points on the curve which cor- 

 respond to equal temperature also correspond to equal vapour- 

 pressure. In Fig. 2 we see that any two points on the curve 

 which correspond to equal temperature must also, from the 

 nature of the case, correspond to equal osmotic pressure. In 

 Fig. 3 some of the pressures are indicated, as this can be done 



