Volume Changes attending Mixture. 503 



be perfectly mixed. When brought again to 17°' 6, the height # 

 was observed. The volume of the capillary from / to g is got 

 by measuring the length, and weighing a column of mercury 

 which has a length (exactly measured) of about the length /-#. 



Actual weight of bisulphide . . 1*8180 gram. 



„ „ alcohol . . . 1-9856 „ 



Eeduced expansion (at 17°*6) . 0*02912 cub. cent. 



This gives an expansion of 0"007405 of the original joint 

 volume. The method is seen to be one capable of extreme 

 accuracy, and is, I think, though more laborious, preferable 

 to a specific-gravity method, because the temperature is better 

 under control. This individual result has, however, no 

 special numerical significance, because the two liquids are 

 not in any simple relationship by weight or volume, and 

 because, as we should expect and as we shall see is the case 

 (§ 271), the ratio of change of volume depends upon the ratio 

 of the constituents. 



It is important to note that the increase in volume here 

 observed is accompanied by a fall in temperature, which at 

 first, and until the temperature is recovered, tends to reduce 

 the volume. This, the natural corollary of expansion, will be 

 examined later. 



§ 265. Alcohol and bisulphide of carbon mix with one 

 another in all proportions at all temperatures between 0° and 

 100° C. This fact does not seem to be generally known, 

 the reason perhaps being that a very small quantity of water 

 prevents the perfect mixture taking place between some pro- 

 portions of the nominal constituents. The examination of the 

 simultaneous reciprocal solubilities of the three bodies alcohol, 

 bisulphide, and water would be a fascinating inquiry, but a 

 very onerous one; for many thousand experiments would 

 have to be performed in order to trace the effect of even a 

 few variations in temperature and in the threefold ratio. 

 Moreover, the complication would be much further increased 

 by the chemical attitude between alcohol and water. 



§ 266. I made nine mixtures of alcohol and bisulphide con- 

 taining the two liquids in different ratios. The liquids were 

 weighed in tubes closed at one end, and having capillary necks, 

 which were then sealed off. These solutions, when used, 

 were transferred to open tubes, which were then cooled in an 

 ordinary ice-salt cryogen with the following results. 



