1864.] 



Prof. Guthrie on Drops. 



481 



mixture o/Y and Z through X, is greatest when the ratio between Y and 

 Z is unity. 



From Tables XVII. and XVIII. we may gather an interesting fact, 

 which illustrates other branches of physics. The drop-numbers of tur- 

 pentol and benzol through water being relatively 286 and 102, and the 

 drop-numbers of water through benzol and turpentol being relatively 256 

 and 86*2, we may construct the following Table, in which the theoretical 

 numbers are compared vi'ith the experimental ones. The theoretical num- 

 bers are got as follows. Ex. : — 



3^^1037 + 2x287^ 



BT: 



1037 + 287 



Mixture of benzol and tur 

 pentol through water. . 1 



T. 



287 



L287 



Water through mixtures J 256 

 of benzol and turpentol ] 



1^256 



BT,. 

 225-9 



2517 



199-4 



219 



&c. 



Theoretical. 

 BT. 

 195-3 



Experimental. 



230 

 Tlieoretical. 



171-1 



Experimental. 

 177-5 163 



B,T. 

 164-8 



205-7 

 142-8 



B. 

 103-7 



103-7 



86-2 



86-2 



In all cases, then, the theoretical drop-number is less than the experi- 

 mental one ; or the theoretical drop-size is greater than the experimental 

 one. Mixture impairs cohesion. Generally, when two solids are mixed, 

 the melting-point of the two is lower than the mean of the melting-points 

 of its components ; sometimes lower than that of either. When two hquids 

 are mixed, the boiling-point of the mixture (the initial boihng-point) is 

 lower than that of either. The drop- size, which is also a function of the 

 cohesion, we find here in no case to be less than the drop-size of either of 

 the constituents, but in all cases to be less than the theoretical mean. 

 Mixture impairs cohesion. 



Further, comparing the drop-sizes of Table XVII. with one another, 

 or all with B^^ we get 



Table XX. 

 Bw^ 287 

 Tw 103-7 

 Bw 251-7 



= 2-767. 



BT2 " 



Bw 

 BTw" 



Bw . 



103-7 

 230 

 + 03-7' 

 205-7 



2-427. 



: 2-227. 



BgTw 

 Bw 



103-7 

 103-7 



Bw 1037 



= 1-983. 



= 1-000. 



