Page:Text-book of Electrochemistry.djvu/188

 XI.

��REFRACTIVE INDEX OF SOLUTIONS.

��ordinary temperature, and it will be seen that the differences for each column are constant. Water and ammonia, which are not very much dissociated, form exceptions, and ought, therefore, not to be included. The compressibility of water is set = 1000, and the numbers refer to this standard.

��I. .

NO,. Br. CI. OH.

��H.

�^.

�NB4.

�A.

�Li.

�A.

�K.

�(8)

�(97)

��^.

��Na.

��The capillarity and internal friction of solutions are also additive properties. In proof of this we subjoin some results obtained by Eeyher (J) for the internal friction of normal salt solutions referred to that of water at 25° as unity.

�� �Cl.

�Br.

�ClOa.

�NOg.

�CIO4.

�C2HSO2.

�Na. . . . H. . ..

�Diiference.

��The difTerence Na — H is on the average about 0*030, except in the case of phosphate and acetate, and this is due to the fact that the corresponding free adds have only a low degree of dissociation, and therefore do not fit properly into the scheme.

Refractive Index of Solutions. — According to the formula —

n = iV, + (a + b)x

we can calculate the refractive index n o{ a salt solution if the normality (x) be known ; JV, is the refractive index of another salt solution (taken as standard) of the same con- centration, and a and h are the moduli, M, of the refractive index.

�� �