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XL Complete Freezing-Point Curves of Binomy Alloys containing Silver or Copper 
together with another Metal. 
By 0. T. Heycock, F.R.S., and F. H. Neville. 
{From the Laboratory of Sidney Sussex College, Cambridge.) 
Received 6tli .June,—Read .Juue 18, 1896. 
>Sectton I. 
This paper contains some results of a study of the freezing points of binary alloys, 
the freezing points being traced for all proportions of the two metals, so that the 
results when plotted give a complete freezing-point curve. 
The freezing point, properly speaking, is the temperature at which a liquid and 
some solid that can be formed from it are in equilibidum. In practice, at all events 
when working with alloys, it is necessary to take as the freezing point the tempera¬ 
ture at which solid matter begins to separate from a liquid that is being slowly 
cooled. The first indication of this formation of solid is generally afforded by a 
thermometer immersed in the liquid, the heat given out when solid matter separates 
arresting the fall in temperature and causing the thermometer to register a constant 
temperature for a shorter or longer time. It is evident that, except when we are 
dealing with a pure substance, the freezing point obtained in this way must be below 
the true freezing point. This cause of error can be diminished by using a sensitive 
thermometer, by using a large mass of substance, and by causing the rate of fall to 
be very slow.* Surfusion also, where it occurs, must be prevented by the usual 
method of dropping in nuclei. When the freezing point changes a good deal for a 
small change in the concentration, this method is liable to give values of the freezing 
point considerably below the true value. 
The general theory of the equilibrium between a liquid mixture of two bodies and 
the various solids that can be formed from such a mixture, has been developed by 
Le Oh atelier, Van't Hoff, Bakhuis Boozeboom, Kuster, and other writers, and 
it will be convenient to give here a brief outline of that part of their conclusions 
which we shall afterwards need. 
The solid which separates wdien a homogeneous liquid mixture of two bodies is 
cooled may consist of either of the two substances, or it may be a compound formed 
* See note. Section IV. 
MDCCCXCVII.—A. 
E 
1.6.97 
