1821.] Mr. Phillips's Reply to Dr. Hope. 27 



whole of the acid maybe obtained, if we employ enough of sul- 

 phuric acid to convert the residuum into bisulphate of potash. 

 In this case each portion of potash, from which dry nitric acid is 

 separated, will displace the water from the two equivalent quan- 

 tities of sulphuric acid, and each portion of nitric acid weighing 

 67*54 will be found combined with 22*64 of water. Hence 

 90*18 of liquid nitric acid so obtained should dissolve the equi- 

 valent 63 of carbonate of lime ; " and the author then goes on 

 to show from some experiments which I had made, that this is 

 as nearly as possible actually the case, and that the specific 

 gravity of the acid was 1*50. 



I conceive it impossible to cite a more direct application of 

 the scale to the purpose for which I had ventured to employ it. 

 We have not only the quantity of the " decomposing material " 

 assigned, but its composition stated, and aiso that of the sub- 

 stance to be decomposed, and of the product and residuum. 

 With respect to the strength of the product, it is quite as great 

 whether we use only 12 parts of acid or 24, instead of 16 as yo* 

 direct. I do not speak from theory, but from examining the 

 nature of the nitric acid produced with all three proportions of 

 sulphuric acid. As to its being so free from sulphuric acid as 

 not to require the second distillation enjoined by the London Col- 

 lege, I beg to state that the redistillation ordered by the London 

 College is useless ; for I never found the product to contain any 

 sulphuric acid. 



Acid it m Nitriann. — Witli regard to this article, voir at once 

 state that my criticism of it appears to you " to be incorrect in 

 every point." And you assert, " that though, for many purposes, 

 the nitric and nitrous acids may be used indiscriminately, yet 

 there are some where they cannot with propriety." I wish you 

 had pointed out one of those cases. I will not deny that such 

 exist, but I know of no one. Allow me to inquire whether there 

 is any case in which the nitrous acid is not either previously to, 

 or during its use, converted into nitric acid ? But allowing this for 

 a moment not to be the fact, is there any instance in which it is 

 preferable to use nitrous than nitric acid? I shall presently show, 

 that unless pressure be used so as to condence that part of the 

 nitric acid, which is liberated in the state of gas when only one 

 atom of sulphuric acid is used to decompose nitre ; that it is 

 more advantageous in every respect to use equal weights of sul- 

 phuric acid and nitre than two parts of one and three of the 

 other, as ordered in your Pharmacopoeia. 



You tell me that 1 " have assigned as a reason for preferring 

 the process of the London College, should a pale acid be wanted, 

 that it affords it by one operation ; while that of the Edinburgh 

 requires two, but I had forgotten you state that the London 

 Pharmacopoeia directs a second distillation of a fresh quantity 

 of nitre, and after all docs not procure a colourless acid." You 

 have, I am sure, unintentionally misrepresented me on this occa- 



