Page:Outlines of Physical Chemistry - 1899.djvu/254

 ��OUTLINES OF PHYSICAL CHEMISTRY

��volumes mixed, but that an expansion or a contraction of a certain number of cubic centimetres has taken place.

The difference between the volume changes which accompany the neutralisation of the same acid by two different bases is practically constant whatever be the acid. The expansion caused by neutralisation with caustic potash is on the average 0*21 c.c. greater than that caused with caustic soda, and 25*97 c.c. greater than that when ammonia is used (in this last case the effect is negative, that is, a contraction takes place).

The following table gives some results for the expan- sion by neutralisation :

Expansion in cubic centimetres produced by neutralisation with

��Acids

�KOH

�NaOH

�NH,

�HNO,

�HC1.

�CC1..C02H. .

�CHClyCOaH.

�CKfil.COJB. .

�CHs-CO^jH

�Butyric acid

�Ieobutyric acid.

�Average differen

��The following table shows by how much the expansion which accompanies neutralisation of different acids is greater than that of isobutyric acid (the smallest expan- sion yet found). We see that the differences are almost independent of the nature of the base used.

�� �By KOH

�By NaOH

�ByNH s

�Mean

�HNO,.

�HC1.

�CCl3.CO.5H.

�CHCl^CO^

�CKfilCOja.

�CH3.CO2H •

�Butyric acid

�� �