TO THEIR STATE OF IONIZATION MACGREGOR. 225 



at 18 for the D line. He seems to regard his observations as 

 possibly in error by 1 in the fourth decimal place. 



The tables on page 224 contain the results of the calculations 

 of the values of the physical properties mentioned, with both 

 the observed values on which the determination of the con- 

 stants was based, and a few additional observed values for 

 stronger solutions. 



The following comments may be made on these tables : 



Density. NaCl. The first four observations were used in 

 determining the constants ; and up to a concentration of 1'5 

 the differences are within the limits of experimental error, and 

 show a satisfactory alternation of sign. KC1. The first five 

 observations were used. The differences are large, but the 

 alternation of sign show r s that the expression is applicable. On 

 plotting Bender's values they are readily seen not to lie on a 

 smooth curve. 



Thermal Expansion. NaCl. The first four observations 

 were used. The differences up to a concentration of 2 '5 are 

 probably within the limits of experimental error, and their 

 alternation of sign is satisfactory. KC1. The first five obser- 

 vations were used. The differences are not so satisfactory as in 

 the case of the sodium salt either as to magnitude or sign ; but 

 on plotting the observations the third is seen to be somewhat 

 out ; and it is obviously to this observation that the defective 

 agreement is due. 



Viscosity. NaCl. The first five observations were used. 

 The differences are within the limits of error, but the signs are 

 not satisfactory. The fourth observation, however, appears to 

 be defective. Miitzel*, in applying a formula for viscosity in 

 terms of density and concentratiou to these observations, found 

 also that this observation was out. It is worth noting, also, 

 that Miitzel found his formula, which expressed the increase of 

 viscosity due to the salt in solution on the assumption that the 

 only action occurring was between salt and water, was applicable 



*Wied. Ann. xliii. (1891) p. 35. 



