218 



Mr. V. H. Veley. The Conditions of the [June 6, 



It will be seen from the above table that the amount dissolved off 

 per unit area in the first experiment is less than that in the succeeding 

 experiments, when the products of the change were present in the 

 acid. 



In another series of experiments the nitric acid used in the first 

 operation was rejected, and another portion of the same sample was 

 taken for the second operation ; but for those succeeding this latter 

 was used again. It was observed that in the first two experiments 

 the evolution of gas did not commence immediately after the intro- 

 duction of the sphere into the acid, whereas in all the succeeding 

 experiments this was the case. 



Table II. 



Sp. gr. of Acid at 19° = 1-1643. Percentage of Free Nitric Acid = 

 27-02. Temperature 20° C. 



Weight at com- 

 mencement. 



Weight at 

 conclusion. 



Loss. 



Mean area. 



Value of — . 



A 



4-762 



4-6519 



0-1102 



313-16 



3-52 



46519 



4-5451 



-1068 



307 -29 



3-48 



4 -5451 



4-3823 



0-1628 



300-41 



5-42 



4-3823 



4-2303 



1520 



293 23 



5 20 



4 -2303 



4-0838 



1475 



286 -77 



5-29 



4 -0838 



3 9456 



0-1383 



280 -15 



5-05 



It will be manifest from the above table that the values for the 

 amount dissolved off: per unit area on the first two experiments are 

 concordant among themselves, as also are those of the succeeding 

 experiments, but that those of the former are lower than those of the 

 latter. 



When copper is dissolved in nitric acid, the substance more imme- 

 diately evident to the senses is cupric or cuprous nitrate or nitrite, or 

 possibly a mixture of some of them ; at first I was inclined to the 

 belief that the copper salt was the third substance which induced the 

 reaction between the metal and the nitric acid to start at once. 

 Indeed, at a meeting of the Chemical Society I expressed this opinion 

 in the course of a debate. 



It was found subsequently that the dilute nitric acid used in the 

 above experiments contained a small trace of nitrous acid. Accord- 

 ingly a sample of nitric acid of sp. gr. 1*41 was freed from nitrous 

 acid by passing a rapid stream of air through it at a temperature not 

 exceeding 35° C. ; during the process the acid was protected from 

 direct sunlight. If the temperature rose to 40° 0., or the acid was 



