4G Mr. W. Sutherland on Weak Electrolytes and 



dihydrol only 0*0030. This is rather an unexpected result 

 that the less dense form of a substance should have the 

 larger viscosity, but it is due to the fact that the normal 

 physical melting-point of trihydrol, if ascertainable, would 

 be found to be above the melting-point of ice, and that of 

 dihydrol to be below it. This being so, it might seem that 

 the effect of adding alcohol to water, if it changes trihydrol 

 into dihydrol, would be to lower the viscosity below, or raise 

 the fluidity above, that given by the simple mixture formula, 

 to give a minimum of viscosity and not a maximum. Here 

 then we encounter another difficulty which may prove 

 instructive. We must remember that viscosity in a liquid 

 is determined largely by the conditions ruling in the inter- 

 space between neighbour molecules. Thus alcohol, though it 

 changes trihydrol into the less viscous dihydrol, may at the 

 same time have its molecules brought nearer to the other 

 molecules of the mixture in such a way as to increase the 

 viscosity due to their mutual relations. If this- increase 

 exceeds the decrease due to change of trihydrol, the viscosity 

 may rise to a maximum. Here then is a case where (6) is 

 useful, because in x 1 and x 2 it provides measures of the 

 changes brought about by the changed relations of molecules 

 of 1 and 2 as neighbours. In that equation we put u = 1/t] 

 and study 



{ I/7; -pjvi —P2/V2 — (pjvi +Pi/V2)P A \/Pi*>2p - Xi/Pi + Xa/Pi- (34) 



The data in the next table for ethyl alcohol and water are 

 those of Dnnst.au (Journ. Chem. Soc. Ixxxv. p. 817, 1904), 

 from which the left-hand member of (34) is calculated to 

 enable us to study the right-hand. 



Table IV. 



Viscosity of Ethyl Alcohol and Wafer at 25° C. 



100^ 00 3-6 5-09 1250 16-00 24-66 129-63 



IOS7 891 959-6 1013 1356 1552 1851 2129 



~tfi/Pa-*a/i°i ••• ••• 215 268 346 350 3U 312 



100^ 32-40 37-39 38-26 41-21 46-17 47-72 50-20 



IOS7 2162 2290 2301 2327 2368 2354 2337 



-xjp. 2 r-xjp x ... 286 291 289 283 278 275 272 



lOOjp! 55-58 5583 57-51 60-15 6017 60-49 61*06 



10 5 /7 2273 2273 2247 2243 2240 2226 2212 



-xJ P% -xJ Pl ... 268 268 267 271 270 270 269 



100^ 65-36 65-85 70-54 73 90 80-20 100 



10 5 r7 2104 2112 1995 1957 1744 1113 



-xJPi-xJP! .- 268 271 275 287 294 



