656 Professor T. E. Thorpe [March 4, 



Constants in Slotte's Formula tj = C/(l + 6 ty — continued. 



Methyl acetate 

 Etliyl acetate .. 

 Propyl acetate . . 

 Methyl propionate .. 

 Ethyl propionate 

 Methyl butyrate 

 Methyl isobutyrate .. 



Diethyl ether .. 

 Methyl propyl ether 

 Ethyl propyl ether . . 

 Diproj)yl etlier 

 Methyl isobutyl ether 

 Ethyl isobutN 1 ether 



•004781 



• 005783 



• 007706 

 •005816 

 •006928 

 •007587 

 •006720 



•002864 

 •003077 

 •003969 

 •005401 

 •003813 

 •004826 



6. 



006472 

 007:584 

 007983 

 006820 

 007468 

 008081 

 007144 



007332 

 006809 

 005454 

 006740 

 005737 

 0C6549 



8636 

 8268 

 8972 

 8972 

 8914 

 8375 

 9405 



1-4644 

 l-f863 

 2-1454 

 1-9734 

 2 0109 

 1-9733 



Slotto's formula gives the best results in the case of observed 

 viscosity curves in which tlie slope varies but little with the tempera- 

 ture. As regards the relation between the chemical nature of the 

 substances and the magnitude of their temperature coefficients, it is 

 evident that — 



(a) From the mode in which the constants n and h are derived, 

 their individual values cannot be expected to be simply related to 

 chemical nature. 



(b) For the majority of the liquids the formula — 



V = C/(l+ lit + yr-) 



obtained from Slotto's formula by neglecting terms in the denominator 

 involving higher powers of t than <^, closely expresses the eflfect of 

 temperature on viscosity, and in the formula the magnitudes of the 

 coefficients f3 and r) are found to be definitely related to the molecular 

 weight and constitution of the substances, except in the case of liquids 

 which, like water and the alcohols, contain molecular aggregate. 



In order to obtain quantitative relationships between viscosity 

 and chemical nature, and to compare one group of substances with 

 another, it is necessary to fix upon particular temperatures, and to 

 obtain and compare the values corresponding with those tempera- 

 tures. The first point to decide was at what temperatures viscosities 

 should be compared. Inasmuch as the viscosity curves, even in the 

 same family of substances, cross one another, it is obvious that quanti- 

 tative relationships obtained at any single temperature of comparison, 

 as has usually been done, can have no pretensions to generality. 

 Following the method of Kopp, temperature of the boiling point may 

 be considered as a comparable temperature, or we may adopt the 



