422 Mr. R. Phillips's Letter io Dr. 1). Boswell Reid. 



upon that of I'iS it has no effect; but when a larger quantity 

 is used the action is similar, being in both cases immediate 

 and strong. With acid of r44-l the action of antimony is 

 identical with that of 1-48, whether the quantity of metal be 

 small or large. 



In page 1 1 of the Continuation, you refer to the production 

 of nitrous acid by the action of metals upon nitric acid; and 

 you mention that some metals, and especially mercury, when 

 decomposing nitric acid, evolve nitrous acid by direct action; 

 while I am of opinion that whenever it is formed, it results 

 from the intermediate action of the nitric oxide evolved, upon 

 the nitric acid undecomposed. 



You have correctly stated in p. 48 of the Elcvients, that 64 

 of copper, by combining with 16 of oxygen, derived from the 

 decomposition of nitric acid, evolve 20 of nitric oxide gas; and 

 I presume you will therefore admit, that 200 of mercury, in 

 becoming peroxide, unite also with 16 of oxygen, and give out 

 either nitric oxide or nitrous acid gas, during solution in nitric 

 acid. 



To determine what occurs in this operation, I put into a 

 weighed two-ounce vial, to which a tube was fitted, 441*7 

 grains of nitric acid of sp. gr. 1*504, and 1200 grains of mer- 

 cury. When the metal was dissolved, I weighed the vial and 

 its contents, and found the loss of weight to be four grains ; 

 this experiment was several times repeated with very slight 

 variations in the results. It is then evident, that supposing 

 nitric oxide to have been generated, only one fifth of it was 

 evolved ; and let us now examine what the loss of weight would 

 have been if nitrous acid gas, as you assert, had been formed 

 by the direct action of the metal. One atom of mercury = 

 200, acts upon two atoms of nitric acid = 108, and taking an 

 atom of oxygen from each, is converted into an atom of per- 

 oxide = 216; there then remain 8 atoms of oxygen = 64 

 to combine with two atoms of azote = 28, and these form 2 

 atoms of nitrous acid = 92. 



It is therefore evident that the 200 grains of mercury, if 

 they had occasioned the formation of nitrous acid, would have 

 induced a loss of 92 grains in weight instead of only 4; and I 

 contend that the 16 grains of nitric oxide not evolved, com- 

 bined with the undecomposed nitric acid, and, as was evident 

 by its colour, converted a portion of it into nitrous acid, almost 

 the whole of which remained in solution. I contend also that 

 this is the cause of the existence of a small portion of orange- 

 coloured vapour, in the experiment detailed by you in p. 18 

 of the Exposure. 



We proceed now to consider a subject mentioned in p. 13 



of 



