DILATATION OF THE GASES. 215 



Their apparatus was compofed of a body with a bended Their experi- 

 tube, by which means, the air expelled by heat from the body, The gas was ex- 

 was received in a jar on the pneumato mercurial apparatus, truded from a 

 The body filled with the gas on which the experiment was to ^ y b ^ 1 ^ ea 

 be made, was plunged into a bath at the temperature of melt- this excefsre- 

 ing ice, and was kept down by an iron cover. The bath was ceived our mcrr 

 fucceffively heated to the degrees 20, 40, 60, and 80, and they 

 collected in feparate jars the produces of the dilations for each 

 of thefe degrees. They then determined the volumes of air 

 expelled from the body by meafuring them in their refpeclive 

 jars after having reduced them to the temperature of melting 

 ice, and they determined the volume of that remaining in the 

 body.* But letting afide that their apparatus obliged to af- Objection* 

 certain many data which mult have been an objection to the 

 exa&nefs of their refults, I remark that after the immerfion The mercury in 

 of the bended tube in the mercury, as they did not introduce the tubs di flu i-b» 

 new air into the receiver to difplace the mercury which had 

 entered the tube by reafon of the preflure of the mercury in 

 the trough feveral degrees of heat mull be required before any 

 bubble of air can come out ; fo. that had they reckoned from 

 divifions more nearly together, as from 5 ° to 5° they would 

 have concluded that from zero ; the firft degrees of heat do not 

 caufe the different gafes to undergo any dilatation. Hence 

 they found for the lirft twenty degrees a dilatation much too 

 Tveak for the gafes in general. 



: This caufe of error, thd' great, would not have made the Their retort or 

 refults of Citizens Guyton and Duvernois fo far from the truth bod y does not 

 had there not been a fti 11 greater. I fufpeci then that their re- been dry enough, 

 ceiver was not fufficiently dry, and that a little water might 

 have been introduced with the gas. In facl, a decigramme of 

 water would have been fufficient to have influenced their re- v 



fults very conflderably, particularly in the higher degrees ; for, 

 as it changed into elaftic fluid, it would have expelled a great 

 quantity of the air from the receivers. 



The inereafing progreffion which they obtained in all the And from this 

 gafes is this way explained, whilft they ought to have obtained cau ^ e tne expan- 

 a decreafe of volume in the produces of each dilatation were greateft^the 

 reduced to the temperature of melting ice. I fhall obferve that higher temper- 

 pit. Guyton expreffes himfelf thus relative to the dilatation of atures * 



* Annates de £himie, Vol. I. 



hidfogen 



