PROM WATER AND OTHER LiaUIDS, QQ"] 



lime, folution of potafh, &c. and It appears that the force 

 of vapour from each in a vacuum is proportionate to its eva- 

 porability. M. Betancourt maintains that the force of vapour 

 from fpirit of wine is in a conftant ratio to that from water 

 at all temperatures; namely, as 7 to 3 nearly. My firft 

 experiments with fpirits of wine led me to adopt this con- 

 clulion, and naturally fuggefted that the force of vapour 

 from any other liquid would bear a conftant ratio to that of 

 water. The principle, however, is not true, either with 

 regard to fpirit of wine or any other liquid. Experiments 

 iiiade upon fix different liquids agree in eflablifhing this as a 

 general law ; namely, that the variation of the force of vapour The law enun^ 

 from all liquids is the fame for the fame variation oj tempera^ dated. 

 ture, reckoning from vapour of avy given force : thus alfuming 

 a force equal to thirty inches of mercury as the ftandard, it 

 being the force of vapour frou) any liquid boiling in the 

 open air, we find aqueous vapour lofes half its force by a 

 diminution of 30° degrees cf temperature ; fo does the 

 vapour of any other liquid lofe half its force by diminifhing 

 its temperature thirty degrees below that in which it boils ; 

 and the like for any other increment or decrement of heat. 

 This being the cafe, it becomes unneceffary to give diftin^l 

 tables of the force of vapour from different liquids, as one 

 and the fame table is fufficient for all. But it will be proper 

 to relate the experiments on which this conclufion refis. 



Experiment on Sulphuric Ether. 

 The ether I ufed boiled in the open air at 102 . — I filled Experiments 

 a barometer tube with mercury, moiftened by agitation in J^g barometer'" 

 ether. After a few minutes a portioiw^of ether rofe to the 

 top of the mercurial column, and the height of the column below ebullition. 

 became fiationary. When the whole had acquired the tem- 

 perature of the air in the room, 62°, the mercury flood at 

 17.00 inches, the barometer at the fame time being 29.75. 

 Hence the force of vapour from ether at 62 is equal to 

 12.75 inches of mercury, which accords with the force of 

 aqueous vapour at 172°, temperatures which are 40** from 

 the refpedive boiling points of the liquids. By fubfequent 

 obfervations I found the forces of the vapour from ether in 

 all the different temperatures from 33** to 102° exaflly cor- 

 refponded with the forces of aqueous vapour of the like 



range 



