1238 
7. These results are corroborated by the observations made at 
96°.0 ©. (Table I); there occurs a change in the direction of motion 
of the meniscus at a constant temperature. 
8. I hope to report shortly on the limits of stability of the 
different modifications. 
Utrecht, March 1915. vAN “tT Horr-Laboratory. 
Chemistry. — “The Metastability of the Metals in consequence of 
Allotropy and its Significance for Chemistry, Physics, and 
Technics.” IV. By Prof. Ernst Conen and Mr. W. D. Her.DERMAN. 
(Communicated in the meeting of March 27, 1915). 
On the necessity of redetermining the data of 
Thermochemistry. 1. 
1. Since our investigations as well as those of our collaborators 
have proved that the metals are metastable systems in consequence 
of the fact that different allotropie modifications of these substances 
may be simultaneously present, we wish to consider here some 
conclusions which may have an important bearing on thermochemistry. 
a. Heats of Reaction. 
2. The heat developed when a definite quantity of a metal reacts 
with any other substance, will be a function of the previous thermal 
treatment of the metal, as the relative quantities of the a-, B-, y-,.... 
modifications present in the metal are dependent on that treatment. 
For instance, a definite quantity of cadmium (chemically pure) 
formed from the molten metal and which we shall indicate by the 
~ symbol M,, will develop a different quantity of heat when it combines 
with any other substance than the same quantity of cadmium (M,) 
will do which has been formed at ordinary temperatures by electro- 
lysis of the solution of a cadmium salt. 
While M, contains unknown quantities of a-, 8-, y-cadmium, M, 
consists of pure y-cadmium; moreover we know to-day that the 
heat of transformation (per gram atom) of y-cadmium — «-cadmium 
is 739 gram calories at 18° C.’). 
If, for instance, equal quantities of M, and M, are dissolved at 
18° C. in equal quantities of HCl. 200H,O, the evolution of heat 
which accompanies this reaction will be in maximo 739 gram calories 
1) Proc. 17, 1050 (1915). 
