Reid's " Elements of Practical Chemistry" 4>55 



acid which, we believe, never occurred to any chemist before. 

 Mr. Reid surely does not mean to state that an admixture of sul- 

 phuric or muriatic acid would prevent the action of the nitric acid 

 so contaminated ; on the contrary, he must know that there is a 

 " lovely experiment;" — we mean the accension of oil of turpentine 

 by nitric acid, in which it is common to add sulphuric acid to it, 

 to accelerate the combustion. We really suspect that the word 

 pure has crept in here by mistake ; and yet something is wanting 

 to account for the introduction of the remainder of the paragraph, 

 for we have been before told of the mutual action of nitric acid, 

 metals, and combustibles. 



Continuing the quotation, we learn that pure nitric acid, "when 

 present in small quantitj', however, is not so easily recognised, 

 a there are no substances with which it forms characteristic 

 and insoluble precipitates. The only test indeed which can be 

 relied on, is that proposed by Dr. Liebig [Ann. de Chimie, xxxv. 

 p. 80.) : he recommends the liquid under examination to be mixed 

 with a solution of indigo in sulphuric acid till it requires [acquires] 

 a perceptible blue colour : a few drops of sulphuric acid are then 

 added to the solution, and the whole is boiled for a short time. If 

 the liquid contain any nitric acid it will be completely deprived of 

 colour, or rendered yellow if the proportion of acid is extremely 

 small." 



We presume that Mr. Reid will not insist that the acid must be 

 pure in order that its presence may be detected, though such is the 

 legitimate inference deducible from his statement. We may also ob- 

 serve that Liebig's process is not intended for the detection of un- 

 combined nitric acid, as Mr. Reid supposes, but of a nitrate ; and 

 the use of the sulphuric acid is to separate the nitric acid from its 

 base, that it may act upon the indigo. Our author then informs us 

 that another very delicate test consists in subjecting a solution, 

 suspected to contain a nitrate, to the action of sulphuric and muri- 

 atic acid and gold-leaf; adding, " this test, however, cannot be re- 

 lied on in all cases, as chloric acid produces the same effect when 

 treated in this manner." Now we would simply inquire whether 

 the acid of a chlorate would not by suffering decomposition also 

 discharge the colour of indigo? Mr. Reid must admit this, for 

 chlorine is notoriously employed for this purpose ; there can there- 

 fore be no difference in the accuracy of the two modes, as far as 

 the action of chloric acid is likely to interfere. 



We have now arrived at the concluding paragraph of the chap- 

 ter on Nitric .Acid; it is as follows : •' Oxygenated nitric acid may 

 be prepared much in the same manner as oxygenated water, the 

 deutoxide of barium being dissolved in diluted nitric acid, the 

 bastes removed by sulphuric acid, and the liquid that remains 

 strengthened by evaporation in the exhausted receiver of the air- 

 pump. It presents the same general phsenomena with many of the 

 metals and metallic oxides, &c. as oxygenated water, but has not 

 hitherto been applied to any use." In the yearl818 (Annals of Phi- 

 losophy, vol. xv. p. 378), M. Thenard announced to the Academy 



of 



