Relations between Viscosity and Chemical Nature of Liquids. 153 



the relation between viscosity in absolute measure and temperature 

 are calculated for each liquid. The general results of the observa- 

 tions are then discussed in the same manner as in the previous 

 memoir. With regard to the two hydrocarbons, it is found that the 

 isopentane from fusel oil gives slightly different values from that 

 originally observed, which was obtained from American petroleum, 

 and which, although of an approximately constant boiling point, was 

 undoubtedly a mixture. The new sample of ethylbenzene, however, 

 gave results which were in very good agreement with those pre- 

 viously obtained. 



The conclusions relating to the graphical representation of the 

 results may be thus summarised. Both ethers and esters give no 

 evidence of molecular aggregation, and conform to the rules that : 



(1) In homologous series, the viscosity is greater the greater 



the molecular weight. 



(2) An iso-compound has a smaller viscosity than a normal 



isomer. 



(3) The more symmetrical the molecule of an isomeric compound 



the lower is the viscosity. 



As regards the esters themselves, it is noteworthy, where the com- 

 parison is possible, that : 



(4) Of isomeric esters, the formate has the larger viscosity. 



As regards the algebraical representation of the results, it is shown 

 that in the expression / = C/(l+/3'-f 7^), derived from Slotte's 

 formula : 



(1) In any homologous series, /3 and 7 increase as the molecular 



weight increases. 



(2) Of isomeric compounds, the iso-compound has the smallest 



coefficient. 



(3) Ethyl ether, the symmetrical isomer, has smaller coefficients 



than methyl propyl ether. 



(4) As regards normal isomeric esters, the formate has the 



largest, and the propionate the smallest coefficients, and 

 the values of the acetate are larger than of the butyrate. 



The authors then deal with the relationships existing between the 

 various viscosity magnitudes the viscosity coefficient, the molecular 

 viscosity, and the molecular viscosity work (1) at the boiling point, 

 and (2) at temperatures of equal slope, the slope adopted being that 

 employed in their previous paper, namely, 0'0 4 323, and values for the 

 oxygen in three different conditions are given for each system of com- 

 parison in the same manner as in their first communication. 



The two main results supported by all the methods of comparison, 

 both at the boiling point and at temperatures of equal slope, are : 



