Thomsoii's Sj/stem of Chemist ri/. lo£> 



irrite la membrane pituitaire, et determine le larmoiement ; sa 

 densite determinee par le calcul est de 2.111 ; il rougit le tour- 

 nesol, n'est point inflammable, ^"c.*" 



M. Gay-Lussac, indeed, proved that it was not naturally 

 gaseous, by placing the liquid, before applying heat to it, in a 

 jar, inverted over mercury, under the receiver of an air-pump ; 

 and exhausting the air, till the vapour had expelled the liquid. 

 On re-admitting the atmospheric pressure, the whole vapour 

 condensed again. Now Dr. Thomson mistakes this expe- 

 riment of probation, for the process of production, and omits 

 the latter entirely. " In my experiments," says M. Gay-Lussac 

 " it was mixed with carbonic acid gas. It would have been more 

 advantageous, if instead of this gas, an insoluble gas had been 

 present ; but after finishing my analysis of the mixture of chloro- 

 cyanic acid and carbonic acid, I did not think that I should add 

 to its accuracy, by repeating it with another mixture : .... It is 

 colourless, its smell is very strong. A very small quantity of 

 it irritates the pituitary membrane, and occasions tears. It 

 reddens litmus, is not inflammable, and does not detonate when 

 mixed with twice its bulk of oxygen or hydrogen. Its density, 

 determined by calculation, is 2.1 1 1 , i^'C.f" 



Let us see how our Doctor travesties the French philosopher. 

 " Chloro-cyanic acid, thus obtained, possesses the following 

 properties. It is a colourless liquid, having a very strong and 

 peculiar odour, so that a very small quantity of it irritates the 

 pituitary membrane, and occasions tears. It reddens infusion 

 of litmus, is not inflammable, and does not detonate when mixed 

 with twice its weight of oxygen, or with hydrogen^." The acid 

 which M. Gay-Lussac examined was not liquid, it was rendered 

 gaseous by admixture with carbonic acid, and thereby separated 

 from muriatic acid ; which must exist abundantly in the Doc- 

 tor's acid, in consequence of the union of chlorine with the 

 hydrogen of the hydro-cyanic acid. " This liquid mixture 

 does not detonate when mixed with twice its weight of hydro- 

 gen." Who would expect that it should? Its density is un- 

 doubtedly much greater than that of water ; but twice its weight 

 of hydrogen will be eleven thousand eight hundred times its 

 bulk, supposing its density equal only to water. " It reddens 

 litmus." Who can doubt it ? It consists of an atom of muriatic 

 acid, mixed with an atom of the chloro-cyanic acid, dissolved 

 in water. It would be much wiser for the Doctor to stick to 

 literal transcription. He never alters the language of the ori- 

 ginal author, without impairing its force, or changing its mean- 



* TiaiU. Tome II, 540. 



t Annates de C'hvnie, Tom. 95. The above is Dr. Thomson's transla- 

 tion, in his Annuts for July jalC, p. 48 ; which renders the mistake in his 

 system more ridiculous. 



t System, II. 290. 



