Properties of Aqueous Solutions to their State of Ionization. 51 



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 50 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 the above 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 shows 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 ob- 

 servations 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 concentration to these observations, 

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

 also, that Miitzel found his formula, which expressed the in- 

 crease of viscosity due to the salt in solution on the assump- 

 tion that the only action occurring was between salt and 

 water, was applicable to only the first five of the above ob- 

 servations. To represent the viscosity of stronger solutions 

 he had to introduce a term expressing the effect due to the 

 mutual action of the molecules of salt. — KC1. All six obser- 

 vations were used. The agreement in this case is quite 

 satisfactory. 



Surf ace-Tension. — NaCl. Only two observations on suf- 

 ficiently dilute solutions were available, and the applicability 

 of the formula cannot therefore be tested. The constants 

 were found, for use in the calculation of the surface-tension 

 of mixtures. — KG. The first four observations were used, 



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

 E 2 



