Volume Changes attending Mixture. 511 



tion into the tube. This, also, is not quite exact. Neither of 

 these errors has been taken into account in the following 

 Table ; for they are both of them negligible in comparison with 

 the numerical data sought. 



Table LXIY. 



Vapour-tensions of Mixtures of Chloroform and Ether. 



T = 19°-02. 



Chloroform, per cent, 

 by weight. 



Ether, 

 per cent, 

 by weight. 



Mercurial 

 depression. 



Liquid 



above 



mercury. 



"Vapour-ten- 

 sion in millim 

 of mercury at 

 19°02. 



100 







2000 



84-0 



190-7 



90 



10 



205-2 



87-2 



196-0 



80 



20 



222-3 



106-5 



211-7 



70 



30 



236-2 



104-0 



226-4 



63 



37 



240-2 



79-2 



233-1 



(O 4 H 10 O, CHCL) 61-76 



38-24 



243-9 



85-0 



236-4 



60 



40 



248-5 



81-2 



241-4 



50 



50 



285-0 



83-3 



278-2 



40 



60 



318-7 



85-2 



312-2 



30 



70 



349-8 



77-5^ 



344-8 



20 



80 



383-2 



81-8 



377-9 



10 



90 



4138 



83-9 



408-8 







100 



442-6 



90-0 



437-8 



§ 273. The increase of vapour-tension as the proportion of 

 ether increases is therefore continuous, but by no means 

 regular. There is in the neighbourhood of the monomolecular 

 ratio a diminution in the rate of increase ; but immediately 

 this region is past, the curve becomes rectilinear. As the 

 barometer-tubes stand side by side in a row, they present a very 

 interesting appearance, as the mercurial levels form a curve 

 closely similar to that in fig. 6, A (p. 515) turned upside down. 

 Guided by heat-development and shrinkage, we have there- 

 fore detected the existence of C 4 H 10 O, CHC1 3 , and showed that 

 the vapour-tension confirmed the existence of this body. Are 

 we, then, to assume that in every case in Table LXl. where 

 there is heat-development and shrinkage, there is also true 

 chemical union ? Reluctant as some may be to admit to the 

 title of chemical compounds a class of bodies which probably 

 numbers many thousands, there seems no help for it. There 

 can be but little doubt, for instance, that ether unites with 

 alcohol and benzol, that chloroform unites with alcohol and with 

 amylene, and so on. The experiments necessary for the proof 

 of this assertion will be laborious, and will require such care 

 and concentration that I must again invite other workers into 

 this fertile field. There is, however, one point which may be 

 here noted. Two elements may unite to complete saturation 

 in respect of one another, yet the molecules so formed may 



