Page:Text-book of Electrochemistry.djvu/173

 ��DEGREE OF DISSOCIATION.

��CHAP.

��Of the substances mentioned hydrochloric acid is the most highly dissociated.

The other monovalent strong acids, like nitric, hydro- bromic, hydriodic, chloric acids, etc., have about the same degree of dissociation ; the strong bases, such as potassium, sodium, lithium, and thaUiom hy(hroxides, and the ammonium bases, etc., are also dissociated to about the same extent. The salts formed from monovalent acids and monovalent bases have a slightly lower degree of dissociation, as seen from the numbers given for potassium chloride and potassium acetate. The degree of dissociation is much smaller for salts formed from divalent acids with monovalent bases and for those formed from monovalent acids and divalent bases ; the degrees for these two classes of salts are very similar (compare potassium sulphate and barium chloride in the table). Salts produced from a divalent acid and a divalent base (zinc sulphate) have a still lower degree of dissociation.

We know the mobilities, l^, of almost all ions and the degree of dissociation for various salts (from the investiga- tions of Kohbrausch (1), Ostwald, and Bredig), and with the aid of these we can calculate the conductivity of any salt solution. We cannot, however, make the calculation for solutions of weak bases and acids. These compounds are much less dissociated than the salts. From the table on p. 135 we find the following degrees of dissociation, a, for acetic acid and ammonia : —

��Acetic ACid.

� �▲mm< I

�rata. r •

� �100a.

�lOOa.

o-ooi

��We shall return later to these weak electrolytes, which appeared at first to show the least agreement, but which later exhibited more regularities than the strong electrolytes.

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