A letter to Dr. David Boswell Reid, ... in answer to his pamphlet intitled "An exposure of the misrepresentations in the Philosophical Magazine and Annals," / by Richard Phillips.

Date:: 1831

Credit: A letter to Dr. David Boswell Reid, ... in answer to his pamphlet intitled "An exposure of the misrepresentations in the Philosophical Magazine and Annals," / by Richard Phillips. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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$It had become, by means of this process and the evaporatfora together, exceedingly weak.” Now can any experiment more distinctly prove my assertion, that acid ot no one degree of strength is capable of exhibiting all the colours? The experiment which yo\i next quote is from Dav-y. Ibis I shall not give at length; tor I confess I do not place any de- pendance upon the result; it was made with only 93 grains of nitric acid, which, it is stated, became of a dark orange colour by absorbing nitric oxide, and yet diminished in sp. gr. from 1.5 to 1.48. I come now to the experiment by which you intend to prove,, that in strong nitric acid all the appearances described may be produced in the course of a single minute, by operating “ on a small quantity of acid with a brisk current ot gJis.” I have performed this experiment, and will readily admit, that by passing a strong current of nitric oxide through a lluidrachm of nitric acid, of sp. gr. 1.497, I obtained nearly the tints you mention; biit the acid, as in Dr. Priestley’s experiment, had become “ exceedingly weak,” by the evaporation of nitrous acid, into which the nitric acid had been converted by combining with nitric oxide. Nitric acid, of 1.497, decomposes about 72.8 per cent, of carbonate of lime; but the blue-green acid remaining after the passage of the nitric oxide through it, decomposed only 52.5 per cent. I consider it as completely proved, by Dr. Priestley’s and my own experiments, that “strong nitric acid never becomes at all olive, green, or blue, by absorbing nitric oxide.” I proceed, therefore, to consider what you have advanced, in opposition to my statement, that nitric acid, of any one degree of strength, is incapable of exhibiting all the colours which you have enumerated. “ I have made the experiment,” say you, “frequently, with pale acid of various specilic gravities; with acid of the very speeific gravity to u'hich he alludes [I.4G]; and with acid both stronger and weaker than this. I have seen each of these kinds of acid become not only yellow and red, but also olive and green, and almost blue, as 1 have described, or, to use Sir H. Davy’s expression, blue-green.” 1 shall meet this statement, both with quotations and experiments; and, first, with the former. M. Laugier (Cours de Chimie generale, Le9on x.) makes the following observations—“ On prepare de I’acide nitreux en faisant passer un courant de deutoxide d’azote a travxrs de I’acide nitrique, qui prend des couleurs diverses, suivant qu’il a plus on moins de densite. Si on le refoit succes- sivement dans quatre (lacons nontenant des acides a 1.15, a 1.3*2, k 1.41, de density et enfin de I’acide le plus concentre, il se developpera dans le premier flacon une couleur bleuatre, verte dans le second, jaune foncee dans le troisieme et brune fonc6e dans le qufitri^nie. Ainsi la nuance est d’autant moins prononcee$