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.—KCl. 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.—KCl. 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. 
