OF THE ALLOYS OF COPPER AND ZINC. 
Discussion of Results. 
When the results of Table YIII. are plotted in the same manner as those of 
Table IV., the two series of experiments strikingly confirm each other. 
The small divergences from actual coincidence are not surprising, when it is 
remembered that each result is obtained as the difference between two large and 
nearly equal numbers. 
It is evident at a glance that a clearly-defined maximum heat of formation is to be 
found in the case of the alloy containing about 32 per cent, of coj^per. From this 
point the curve drops until the alloy containing some 40 per cent, of copper is 
reached, whence it becomes nearly horizontal until the 50 per cent, ordinate is 
crossed. 
Beyond this the curve drops at once, and proceeds with consideralfie regidarity to 
the axis of percentages. 
The significance of the foregoing lies in the coincidence of the maximum heat of 
formation with the j^ercentage comj^osition which represents an alloy of the atomic 
constitution CuZn^. 
The existence of this comjDound is now pretty generally accepted owing to the 
work of Laurie, Ciiarpy, and Herschkowitsch,"^ and tlie author’s results appear to 
confirm this conclusion. 
It is also worthy of note that the upward trend of the curve, as traced from the 
copper end, ceases temporarily when the alloy containing about 51 per cent, of copper 
is reached. 
This alloy corresponds very nearly witli one possessing the atomic formula, CuZn. 
The author does not wish to lay too much stress upon this circumstance, as con¬ 
siderable irregularity appears to characterise the observations in the region lying 
between the 40 and 50 per cent, ordinates. 
It was, however, the occurrence of this apparent sub-maximum, near the alloy 
containing 50 jier cent, of copper, which led the author to test so many alloys In this 
region. 
Taking the mean of the results afforded by Tables IV. and VIII. we may conclude 
that the heat of formation of 1 gramme of the comjoound CuZng is about 52‘5 
calories. 
* See page 529. 
