Viscosity of Solutions. 

 Table XVII.— Water. 



229 





Time. 



Pressure. 



pxt 



Viscosity. 



Temperature. 



Seconds (t). 



Om. of water 



at 20° 0). 



1000 



Water at 2U° = 1. 



21-4 



687 



32-62 



2242 



•966 



30-3 



568-5 



3261 



1854 



•799 



40-7 



467-5 



32-58 



1524 



•656 



533 



3845 



32-58 



1253 



•540 



601 



353-5 



3262 



11-53 



•497 



73-6 



304 



3262 



9-92 



•427 



78-3 



290 



3262 



9-46 



•408 



Arrhenius has recently (Phil. Mag. July 1889) made some 

 remarks on Graham's paper above referred to. He appears 

 to think the explanations given by Graham to be quite anti- 

 quated. [Graham's work is not forty years old yet, by the 

 way, since it was published in 1861.] He cites, in particular, 

 the example of alcohol, and inaccurately states that the vis- 

 cosity is a maximum for a solution having the composition 

 C 2 H 5 OH . 5H 2 instead of C 2 H 5 OH . 3H 2 ; the proportions, 

 in fact, for which, as Mendelejeff has shown, the greatest con- 

 traction occurs on mixing. He states that the fact that a 

 maximum of viscosity occurs on dilution cannot be used as 

 evidence of a combination of the liquids. ^Now the strange 

 thing is, if this be so, that in a series of experiments such as 

 Graham's these maxima should occur in every case when the 

 number of molecules of water and the number of molecules 

 of the other liquid are in some simple ratio ; that in the case 

 of sulphuric acid the hydrate can be obtained in the solid 

 state ; that in other cases the solution of maximum viscosity 

 is that for which the greatest contraction occurs. 



Again, Arrhenius states that the reason the hydrate expla- 

 nation has been " abandoned " is because it was found that 

 the maximum varies with the temperature. The solutions 

 used in the acetic-acid experiments, above described, were 

 specially chosen to test this ; no such change occurs within 

 the limits of experimental accuracy in the case of this acid 

 below 7 60° at any rate. 



In cases where the maximum does vary, I do not think the 

 hydrate theory need be abandoned; since, if such a solution 

 be considered as a dissociating system, the mixture containing 

 the largest percentage of hydrate at any temperature need not 

 necessarily be that in which the components are mixed in the 

 proportions in which they combine, but there will be for each 

 acid &c. at any particular temperature a certain mixture (the 

 case being analogous to that of a gas mixture) which will 



