■■qyi^ Mr. Cavendishes Experiwenis on Au\ 



air {hould be of, in order to be dlminifhed moft readily, and to- 

 t-he greatefl: degree; and 1 found, that, when good dephlogiOi*- 

 cated air was iiltd, the diminution waj but fmall ; when per- 

 fedly phlogifticated air was, ufed, no fenfible diminution took- 

 place; but when iivc parts of pure dephlogirticated air were 

 mixed wirli^ three parts of common- air, almoft the wJiole of 

 the air was made to di (appear. 



It muft be confidered, that common air confifFs of one part^ 

 of dephlogiflicated air, mixed with four of phlogifticated ; To- 

 that a trixture of (ive parts of pure dephlogifticated air, and- 

 three of common air, is the fame tiling as- a- mixture ©f feven- 

 parts of dephlogifticated air with threeof phlogifticated. 



Having made thefe previous trials, I introduced in&o the tube^; 

 a~ little foap-lees,. and- then let- up fome dephlogifticated and 

 common air, mixed in the above-mentioned^proportions, which 

 rikng to the top of the tube M, divided the -loap-lees into its- 

 two legs. As fafi-^ as the air was dimini(hed by the electric 

 fpark, I contihued adding mors of the fame k-ind, till no fur- 

 ther diminution took place: aftervvhich a little pure dephlo- 

 gifticnted air, and afrer that^ a little cammon air, were added^ 

 in m-der to fee whether the ceiiation of diminution was not 

 owing to ion^ imperfe(2:i(5n in the proportion of the two kinds - 

 of air to each other^; but without effe6l % The f»ap-iees being - 

 then poured out of the tube, and feparated from the quick— 



■i-, 



* Frogi whnt follaws it appears,,, that thft reafonvvh'y the air ceafed to diminish. . 

 vns, that as the foap-Iee<S' were then l/ecomc neutmlized, noalkaiiTemainedto ab* 

 foFb the acid fsrm«i i>y the ope<ration^ and in coHlcquence fcaree any aii-vvns turned • 

 into acid. The fpjirk, however, was not continued long enough after the appa-. 

 rspt cefiation .of diminution, to determine with certainty, whether it was only, 

 that the diminution went on remarkably flower than before, or that it was ahuoft 

 cuiTie to a fland, and could not have been .carried 'nyjch' further, though I lad 

 y«;riiiled"«in pr.HJng the fparks, 



fiJvsr, , 



