FROM VARIOUS LIQUIDS. Hi I 



fame eircumftances is .5117; the differences are .0852 anci 

 .0534. which fliould meafare the effedive force of mercurial 

 vapour of 212'', nearly. This is in all probability too 

 much ; as it is next to impollible to free any liquid en- 

 tirely from air ; and if any air enter the vacuum, it unites 

 its force to that of the mercurial vapour. 



That the force of vapour from fulphurlc acid, in low tem- 

 peratures, is exceedingly fmall, will appear from the en* 

 fuing fedion. 



SECTION n. 



On Vapour in Air. 



The experiments under this head were made with manome- Effei^ of the 

 ters, or ftraight tubes of different lengths, hermetically fealed ^''P^"'^?" "f 



1 r . • 1 • II- , , . . . vapour in air« 



at one end, or ^ mch mternal diameter, and their capacities The experi- 

 divided into equal portions. A drop or two of the liquid, the mentsmadeby 



r 1 • n r- ■ 1 11 /-i.^ «r"^" tube, 



lubject or experiment, was conveyed to the bottom or lealed flopped by a 

 end of the tube; the internal furface was then dried by a wire "^^^^^ble plug 

 and thread, and atmofpheric, (or any other air) was admitted ° "^"^ "'^^* 

 into the tube, upon which a column of mercury was fufpended 

 of r^ of an inch, or of 30 inches, lefs or more, according to 

 the nature of the experiment. By immerling ihe end of the 

 manometer, containing the air thus circuraftanced, into a tall 

 giafs veflel containing water of any temperature, the effedt of 

 Ihe vapour in expanding the air could be perceived. It was 

 firft indeed neceffary to determine the incrcafeair unaffected by 

 any liquid (except mercury) would obtain by increafe of tem- 

 perature: that was done, as will be particularly fliewn in the 

 next effay.* The expanlion of all elaftic fluids, it feems pro- 

 bable, is alike or nearly fo, in like circumftances; 1000 parts 

 of any elaftic fluid expands nearly in a uniiorm manner into 

 1370 or 1380 parts by 180° of heat. 



It will be unneceffary to repeat in detail the numerous ex- General law of 

 periments made on the various liquids in all temperatures from "J y"p"u°to*y 

 32° to 212°; as the refults of all agree in one general rule or gether. 

 principle, which is this: let 1 reprefent the fpace occupied by Jhe fpace at any 

 r V ' • , c r •/! temperature ic 



any kind of air of a given temperature and free from moilture ; direajy as the 



p= the given preffure upon it, in inches of mercury ; /= the PJ^^'j:^ ^^^^^j^^ 



. , -,,• o preffure lefs the 



Philofophlcal Journal, Vol. III. page 130. force of tlie 



force vapour. 



