546 ON THE THERMO-CHEMISTEY OF THE ALLOYS OF COPPER AND ZINC. 
Summary. 
1. The production of an alloy of copper and zinc is always accompanied by evolu¬ 
tion of heat. 
2. The maximum heat of formation belongs to the alloy whose composition corre¬ 
sponds to the atomic formula CuZii.^, and amounts to 52’5 calories per gramme 
of alloy formed. 
This coincidence confirms the existence of a definite chemical compound, 
CuZiio, whose heat of formation would therefore be 10,143 calories per 
gramme-molecule. 
3. There is some indication of the possible existence of another definite comj^ound, 
CuZn, having a heat of formation per gramme of alloy of about 45 calories, 
but the evidence is not decisive. 
4. If Lord Kelvin’s calculation of the molecular dimensions of copper and zinc is 
accepted, the results of this paper agree with his estimate of 10~® centim. 
and 10“^ centim. as limits. 
5. The energy liberated in the union of copper with zinc must be taken into 
account in a complete theory of the electro-dejiosition of brass. 
