IN MIXTURES OF ACETONE AND WATER. 103 



for the molecular conductivity of the N/50 solution was that given by 

 Ostwald, namely, 129.7 reciprocal Siemens units at 25. Three resist- 

 ances were used in the measurement of each solution. 



It should be pointed out that the fact that w is measured in ohms is 

 not incongruous with the use of reciprocal Siemens units in the result, 

 the factor 1/1.063 being included in the cell constants obtained. To 

 convert the results given in the tables into reciprocal ohms, it is only 

 necessary to multiply by 1.063. 



The calculation of data was facilitated by the use of tables of values 



of -r X . By use of notation by powers of 10, twenty values of were 



sufficient for the preparation of these tables, which were readily com- 

 puted with a calculating machine. Not only does the use of such tables 

 save considerable time in computation, but in their preparation the 

 chances of mistakes are eliminated by methods which do not obtain 

 when the values c.re independently computed. The tables used in 

 this work gave all Wheatstone-bridge ratios from 400/600 to 600/400 

 to millimeters with interpolations to tenths of millimeters. 



The greatest error in the measurements of the components K, v, a, b, 

 of the molecular conductivity /j. v occurs in the determination of the cell 

 constants of the plate cells. This is subject to considerable variation, 

 and it was necessary to make frequent determinations of these values. 

 Under average conditions the precision of /* is from 0.5 to 1.0 per cent. 



Temperature Coefficients. The temperature coefficient in conduc- 

 tivity units is the increase in conductivity for each degree rise in temp- 

 erature; that is, 



Temp, coeff. = ^F^ 

 t 2 ti 



the temperatures compared always differing from each other by 10. 

 The temperature coefficients in per cent is the above quantity divided 

 by the conductivity at the lower temperature and multiplied by 100, 

 e. g., 



. M35 M25 100 



Percentage coefficient = 



M25 



71 St 



Viscosity measurements were calculated from the formula = -7 



??o SQ^O 

 in which rj is the viscosity coefficient for the liquid in question, r) the 



absolute viscosity of water, s the specific gravity of the liquid at the 

 given temperature, t the time of flow of the same, s and t the density 

 and time of flow of water at the same temperature. 



Fluidity was calculated from the formula <f> = -'- where </> represents 

 the fluidity. 



