92 Mr. Faraday on the [Feb. 



[Note on the Condensation of Muriatic Acid Gas into the liquid 

 Form. By Sir H. Davy, Bart. Pres. RS. 



In desiring Mr. Faraday to expose the hydrate of chlorine to 

 heat in a closed glass tube, it occurred to me, that one of three 

 things would happen ; that it would become fluid as a hydrate ; 

 or that a decomposition of water would occur, and euchlorine and 

 muriatic acid be formed ; or that the chlorine would separate in 

 a condensed state. This last result having been obtained, it 

 evidently led to other researches of the same kind. I shall hope, 

 on a future occasion, to detail some general views on the subject 

 of these researches. I shall now merely mention, that by seal- 

 ing muriate of ammonia and sulphuric acid in a strong glass tube, 

 and causing them to act upon each other, I have procured liquid 

 muriatic acid: and by substituting carbonate for muriate of 

 ammonia, I have no doubt that carbonic acid may be obtained, 

 though in the only trial I have made the tube burst. I have 

 requested Mr. Faraday to pursue these experiments, and to 

 extend them to all the gases which are of considerable density, 

 or to any extent soluble in water ; and I hope soon to be able to 

 lay an account of his results, with some applications of them that 

 I propose to make, before the Society. 



I cannot conclude this note without observing, that the gene- 

 ration of elastic substances in close vessels, either with or with- 

 out heat, offers much more powerful means of approximating 

 their molecules than those dependent upon the application of 

 cold, whether natural or artificial : for, as gases diminish only 

 about 1-480 in volume for every — degree of Fahrenheit's scale, 

 beginning at ordinary temperatures, a very slight condensation 

 only can be produced by the most powerful freezing mixtures, 

 not half as much as would result from the application of a strong 

 flame to one part of a glass tube, the other part being of ordi- 

 nary temperature : and when attempts are made to condense 

 gases into fluids by sudden mechanical compression, the heat, 

 instantly generated, presents a formidable obstacle to the success 

 of the experiment ; whereas, in the compression resulting from 

 their slow generation in close vessels, if the process be conducted 

 with common precautions, there is no source of difficulty or dan- 

 ger ; and it may be easily assisted by artificial cold in cases 

 when gases approach near to that point of compression and tem- 

 perature at which they become vapours.] 



The refractive power of liquid muriatic acid is greater than 

 that of nitrous oxide, but less than that of water; it is nearly 

 equal to that of carbonic acid. The pressure of its vapour at the 

 temperature of 50° is equal to about 40 atmospheres. 



