454? Notices respecting New Books. 



were visible; they were, however, instantaneously succeeded by 

 red fumes, in which it required powers of vision superior to those 

 of second sight to detect any blending of white vapour. 



We suppose that Mr. Reid takes the .white vapour for volatilized 

 nitrate of ammonia : but he must surely be aware that this salt is 

 decomposed at a low temperature and not vaporized ; and in proof 

 that it is neither decomposed nor volatilized in the present instance, 

 it is well known that when lime is added to the oxide of tin, the 

 nitrate of ammonia diffused through it is decomposed and the al- 

 kali evolved. 



Mr. Reid next notices the action of nitric oxide upon nitric acid, 

 and the changes of colour which result from it. " If a current of 

 nitric oxide gas be transmitted through colourless nitric acid, a 

 large quantity of this gas is absorbed, and the acid speedily ac- 

 quires a light-straw colour, which deepens to a reddish brown, and 

 passes through various shades of olive and green, till it at last be- 

 comes almost blue." From this statement, it would appear that the 

 only circumstance which determines the colour of the acid, is the 

 quantity of nitric oxide which it absorbs. We have been already 

 instructed to consider, that by nitric acid we are to understand that 

 which is concentrated, and such we presume is that to be employed 

 in this experiment; and if this be the case, the effects produced are 

 described with extreme and most culpable inaccuracy. In the first 

 place, strong nitric acid never becomes at all either olive, green, or 

 blue by absorbing nitric oxide : and what proves that Mr. Reid 

 never made the experiment is, that when the colours are produced 

 they do not occur in the order stated by him ; nor is acid of any 

 one degree of strength capable of exhibiting them all, whatever 

 may be the quantity of nitric oxide passed into it. If, for example, 

 pale acid of sp. gr. 1-46 be used, the nitric oxide renders it for a 

 moment yellowish, and then it becomes red, but never olive, green, 

 nor blue at all : dilute a portion of this acid with an equal bulk of 

 water, the nitric oxide then renders it green, but it assumes no 

 other colour ; mix three measures of the acid with four of water, and 

 the mixture may be rendered blue, but neither yellow, olive, red, 

 nor green. The mistakes committed by Mr. Reid in this part of 

 the subject are the more remarkable, because in the very next page 

 to that in which they occur, he shows that the production of the 

 different colours does not depend upon the quantity of nitric oxide 

 absorbed by strong acid, but upon that retained after various de- 

 grees of dilution ; for he says, if small quantities of water be added 

 to the strong fuming acid, " it gradually loses its deep orange red 

 colour and passes through various shades of olive, green and blue ; 

 and if a sufficient quantity of water be added, it becomes quite 

 colourless." 



" Pure nitric acid," according to our author, " is easily recog- 

 nised by the facility with which it is decomposed by inflammable 

 substances and the metals, especially zinc, tin, mercury and cop- 

 per, and the large quantity of deep ruddy fumes which are disen- 

 gaged." Now this is a method of ascertaining the purity of nitric 



acid 



