258 ACTIONS OF NITRIC AND OXALIC ACIDS. 



the presence of oxalic acid alone would not cause the evolu- 

 tion of hydrogen gas. Experiment, however, showed that this 

 manner of testing the question was fallacious, and no other 

 method suggesting itself it was impossible to decide the ques- 

 tion positively. Sufficient was ascertained to show that if the 

 sulphate was decomposed it was only to a very minute extent. 



In connection with this last experiment it is proved that 

 zinc decomposes water readily in presence of oxalic acid, hy- 

 drogen gas being evolved. The action ceases in a short time 

 from the formation of insoluble oxalate of zinc. With iron the 

 action is very feeble even when the solution is heated. 



The decomposing action of oxalic acid on the nitrates and 

 chlorides of alkalies appears to be due simply to the fact of a 

 more stable acid being able to replace a more volatile one, and 

 in no way measures the relative strengths of the acids; it 

 being a well-established fact that the physical as well as chem- 

 ical properties of acids have much to do with their capability 

 of replacing each other, a mere change of circumstances often 

 reversing their relative action. 



