DILATATION OF THE GASES. 20P 



advice, and that of Cit. Laplace. Thefe great authorities 

 will add to the confidence to which my work may be en- 

 titled. 



The experiments which I have undertaken on the law ot TW experi- 



ments r 



-l.te 



the dilatation of gafes and vapors, and the march of the ther- ofl , t0 tj, ecom .- 

 mometer not being yet completed, the only object of this me- parative expan- 

 moir will be to examine the dilatation of gafes and vapors at a fio " of <| lfferen * 



, g a * es anc * vapors 



determined elevation of temperature, and to (hew that it is at a given tem-n 

 the fame in all thefe fluids. But before I relate my experi- P^ature. 

 ments, I think it proper to give a fliort account of what has 

 been done on this fubject ; and as I JhaH make obfervations 

 on each of the methods that have been employed, I (hall pre- 

 fix this amount to the examination of one of the principal 

 caufes of uncertainty to which this fpecies of experiments is 

 liable. Although it is very important, and feems to nave re- 

 mained unknown to the generality of philofophers who have 

 examined the dilatations of gafes, its influence will be fully 

 admitted when (imply pointed out. What I (hall fay of at- 

 mofriheric air will apply to the other gafes. 



This caufe of uncertainty is owing to the prefence of water Water in tho 

 in the apparatus. If a few drops of this fluid be left in a re- ^J™^ 8 * * 

 ceiver full of air, and its temperature then raifed to that of uncertainty, 

 boiling water; this water when converted into vapor, will 

 occupy a volume about 1800 times greater than its primitive 

 bulk, and will drive off' by this means a very confiderable por- 

 tion of the air contained in the receiver. It neceflarily hap- Explanation of 

 pens then, that when thefe vapors are condenfed, and come thiSeffe<2 "' 

 to occupy a volume 1800 times lefs, a dilatation much too 

 great will be attributed to the air remaining in the receiver ; 

 becaufe it will be fuppofed that it was this air which at the 

 temperature of boiling water occupied all the capacity of the 

 receiver. If the temperature be not raifed to this degree, the 

 fame caufe of uncertainty will not the lefs exift, and its inten- 

 sity will be relative to the height of temperature : for in this 

 cafe the water will not entirely evaporate, but the air will 

 diflblve more of it in proportion as its temperature is raifed, 

 and it will confequently receive a greater or lefs augmenta- 

 tion of volume, independent of that occafioned by heat ; io 

 that as it paflfes to a lower temperature, the volume of air 

 which occupied the whole receiver will diminifti for two rea- 



Vot. III.— November, 1802. < ? fon«, 



