the Action of Copper-Zinc Alloys on Nitric Acid. 237 



regular progression between copper and the above alloy, 

 following closely the theoretical line. We see a fair ap- 

 proximation to this in the diagram, but there is a gradual 

 divergence from the line, indicating a deficit of heat. The 

 specimen containing 38'38 per cent, of copper, which is not 

 far from the predominant alloy CuZn 2 , shows a loss of 

 32 calories. Baker's experiments show almost exactly the 

 same amount of loss of heat, though at a somewhat different 

 place in the series. 



The only way in which, as far as I can see, this residual deficit 

 can be explained on chemical grounds, is by supposing that the 

 action of this alloy upon nitric acid produces a larger amount 

 of nitric oxide than in the case of pure copper. Table I. 

 gives some indication that this may be the case, because the 

 amount of nitrous acid produced is rather smaller in the 

 alloys than with the metal itself, indicating that there must 

 be more of some other product, presumably nitric oxide. 

 But, allowing full force to this argument, it cannot account 

 for as much as 10 calories of the deficit. There is in any 

 case a residual deficit as yet unaccounted for on chemical 

 grounds, and which may be regarded as the amount of heat 

 evolved in the formation of the alloy. 



The action of zinc, or of the alloys rich in zinc, upon 

 nitric acid is very different. There is less nitrous acid formed, 

 while ammonia and nitrous oxide are produced in consider- 

 able quantities. The substitution of ammonia for nitrous 

 acid will not make much thermal difference ; but as the 

 calories obtained by the formation of nitrous oxide are at 

 least 175 more than with nitric oxide, and 83 more than with 

 uitrous acid, there does not seem any difficulty in accounting 

 for the excess shown between the observed and calculated 

 values for pure zinc, or for the alloys containing more than 

 70 per cent, of this metal. 



The work both of Dr. Gait and Mr. Baker has evidently 

 been carried out with the greatest care; but, considering the 

 uncertainty of the thermo-chemical data and the great 

 physical interest attaching to the research, it would seem 

 highly desirable that further experiments on the copper-zinc 

 alloys should be made with solvents which give a chemical 

 action far more simple than that produced by nitric acid. 



In concluding, I desire to acknowledge the great assistance 

 Mr. Hibbert has rendered me in this inquiry. 



