AFFINITIES OF COMPRESSED GA.SJE5. gQQ 



It had long ago occurred to me, that the various affinities His fufpidon 

 which take place among the gafes under the common preffure |j^ Jf* h * ffi ]J~ 

 of the atmofphere, would undergo confiderable alteration by would be 

 the influence of condenfation ; and the fuccefs attending the changed by 

 violent method adopted by the French chemifts, which vio- 

 lence did not appear to me requifile, afforded additional en- 

 couragement to my undertaking fome experiments upon the 

 fubject. 



I communicated this to the late chemical operator in the 

 Royal Inflitution, a gentleman eminently converfant in the 

 fcience, and with whom I was then engaged in a feries of 

 experiments : he not only approved of my defign, but feemeo! 

 to think it not improbable that an extenfive field might thus 

 be opened to future dilcoveries.. Whether thefe opinions are 

 juftly founded, is now left for you, Sir, and the public to 

 judge. 



In entering upon a field entirely new, obflacles were of Difficulties of 

 courfe to be expected ; nor without reafon ; for though I had the undertaking 

 applied to one of the mofi eminent philofophical inftrument-^ ei ° s> 

 makers in London, Mr. Cuthbertfon, yet I began to fear, 

 even at the outfet, that his fkill would be fet at defiance. 

 The rirft infiruments which he made for the prefent purpofe Condenfing- 

 were, a brafs condenfing-pump, with a lateral fpring forp um P* 

 the admiftion of the gas by means of flop-cock and bladder; 

 two pear-fhaped receivers, one of metal of the capacity of Receivers. 

 feven cubic inches, and another of glafs of about three and a 

 half: thefe were connected by a brafs flop-cock, having a 

 fcrew at each end. The metallic receiver was foon found to Various objec- 

 be of little or no utility, as well on account of its liability to tlons « 

 be acted upon by the generated acids ; its being too capacious, 

 apd thus confuming too large a quantity of gas : as becaufe, 

 though the refult of an experiment might thus be known, yet 

 the changes which the fubjects might undergo would necef? 

 farlly elcape obfervation. The glafs receiver obviated all * " 



thefe difficulties, and one or two imperfect experiments were 

 performed with it; but the ftop-cock fpeedily failed in its 

 effect. For thepower of the compreffed gafes was fo great, 

 partly from their elafticity, and partly (where affinities had 

 operated) from their corrofive quality, as absolutely to wear a 

 channel in the metal of which the plug was made, and thus 

 r Vol. XII. — Supplement. Bb to 



