302 Affinity and Heat. 
for instance, as a spider's web; and suppose, further, that 
the vessel is athermanous, and can neither be heated nor 
cooled—in other words, that its specific heat is zero. 
The level of the upper of the two liquids being at A, 
they are mixed in an infinitely short time, and in a 
complete manner. Heat at once manifests itself, and 
assumes a maximum value, which is indicated by a ther- 
mometer (whose weight can be neglected) placed in the 
interior of the liquid; this temperature will be the degrees. 
At the same moment, the temperature being supposed 
to be equal and invariable, the liquid will sink in the narrow 
neck to the level B. Finally, cooling the acid to its 
original temperature of OY, its volume will again diminish 
until the surface is level with the point C. The volume of 
the cylindrical space AC, divided by the original volume 
of the elements (water and acid), which I shall call V, 
will represent the contraction. Calling v the volume of 
the acid after mixture we shall have for this contraction 
the value— 
I~. 
What I call heat of contraction is the quantity of heat 
necessary to restore the volume of the mixture wv to the 
volume V. Knowing the co-efficient of expansion & of 
the liquid from O2 to a temperature a little higher than @, 
the specific heat ¢ of the liquid being supposed constant 
between the same temperatures and 7 its weight, we shall 
have for the heat of contraction lig the value— 
The temperature 6, at which the mixture resumes its 
volume, being — 
y Dime 
I have determined, by methods which I cannot describe 
here, the heats of contraction of a great number of liquids 
resulting from the combination or the solution of two 
elements, also liquid, such as sulphuric acid and water in 
very variable atomic proportions, sulphuric acid and soda 
of various degrees of dilution, water and alcohol, water and 
acetic-acid, water and formic ‘acid, varying the proportions, 
which are always atomic, in a greatinumber of modes. 
The following is the result of my experiments :— 
1. When two. liquids combine or dissolve, and give. aris 
