Page:Outlines of Physical Chemistry - 1899.djvu/269

 CHEMICAL DYNAMICS

��The columns II., IV., and V. certainly do not absolutely agree, but the constants which they attribute to each acid are of the same order of magnitude and in many cases are tolerably close — which is all the more remarkable since these constants are derived by very diverse operations.

The constants e have been determined by yet another means, namely, by the rapidity with which acids decom- pose acetamide in aqueous solution.

The reaction

CH 3 CONH 2 + HA + H 2 = CH 3 C0 2 H + NH 4 A

gives rise to the formation of an ammonium salt, and the amount of this present at any moment can be determined by means of alkaline hypobromite.

As far as bases are concerned, very little work has been done. However, Ostwald has given us a series of numbers which expresses the relative speeds with which different bases bring about the saponification of ethyl acetate in an aqueous medium. As the metallic acetate formed in the reaction exerts a retarding influence, greater or smaller according to the nature of the base, Ostwald has eliminated this source of irregularity by calculating for each case the initial coefficient of speed.

The following are his results :

��Sodium hydrate

�Amylamine.

�Potassium ,,

�Allylamine.

�Lithium ,,

�Dimethylamine.

�Thallium „

�Diethylamine

�Ammonia

�Triethylamine

�Methylamine.

�Piperidine.

�Ethylamine.

�Tetraethylammoniui

�n

�Propylamine.

�hydrate

�Isobutylamine

� � ��For the alkaline-earth bases (lime, strontia, and baryta) the constant seems to be slightly lower than that for soda

�� �