56 
MESSRS. C. T. HEYCOCK AND F. H. NEVILLE ON 
erroron the other hand, as the solution becomes more concentrated, the atomic 
fall changes from a number of causes that are but imperfectly understood. It is 
therefore somewhat difficult to decide how to take the average of a number of 
atomic falls. Moreover, for the strict application of equation (1) to the purpose of 
obtaining we need the atomic fall at infi^iite dilution. We have attempted to get 
this for copper in fig. 5, by plotting the atomic percentage of dissolved metal 
Fig. .5. 
Atomic fails in Copper. 
Each line corresponds to the fall in the freezing point of coijper caused by the metal whose 
name is written above the line. The concentration is written in atoms from left to 
i-ight. The atomic fall is reckoned for each metal from a different zero, but the 
numbers below the lines give the atomic falls in degrees Centigrade. 
horizontally from left to right, and tlie atomic fall fi-om column (4) of the tables 
vertically. A line drawn through the points thus obtained and produced to cut the 
zero ordinate should then give the atomic fall at infinite dilution. Unfortunately, 
there is a good deal of uncertainty about the exact direction of the lines corresponding 
to each metal. 
It will be seen that bismuth gives 11'6, lead 11'7, and tin 10‘7 for this limiting 
value of the atomic fall. As bismuth and lead do not appear to combine wdth the 
copper, and tin evidently does so, it will be wisest to take the higher value 11'7°. 
Using this value in equation (1) we find that the latent heat of an atomic weight 
of copper, is 3138 calories, the melting point being taken as 1082° C. Hence the 
latent heat of fusion of one gram of copper is 49'6 calories. 
If instead of attempting to get the atomic falls at infinite dilution, we mean the 
atomic falls for concentration greater than ’5 atom and less than 2 atoms, we get, 
* We have not hitherto seen a way of applying to our results a correction similar to that suggested 
by Neknst and Abegg, but a modification of our method of experiment has been suggested to us that 
will probably enable us to do so. 
