Page:Text-book of Electrochemistry.djvu/184

 CHAP. XI. SPECIFIC GRAVITY OF SOLUTIONS.

��Specific Gravity of Electrolytic Solutions. — ^When we dissolve a substance, e.g. cane sugar, in water, the specific gravity of the solution deviates more and more from 1 as the concentration increases. In the case of most electrolytes the specific gravity increases. When we examine the depend- ence of the specific gravity on the normality n, we find that it can be represented by a function of the form —

S =^ Sq + an + ai«*.

Thus, for sugar solutions at 17*5^ we find, if the density of water at 17*5° be taken as unit —

S^ = 1 4- 0-1328?i - 0-002?i^

The first part of the following table shows how exactly the specific gravity may be obtained from a formula of this type—

��^ Cane migAr.

�Normality.

�Specific gravity (obaerred).

�Ppedfic gravity (calculated).

�

�

��The numbers in the lower part of the table have been calculated from the simpler formula — -

8^1 + 0-1313/1,

which gives the specific gravities up to normal concentration (30 per cent.) sufficiently accurately for most purposes.

�� �