336 COMPOSITION- or suLrnumc ether. 



Specific gravity' A knowledge of thd ypcclfic gravity of vapours may far- 

 fords^ useful ^ ' "'sh considerable resources in chemical analyses. By the 

 data. help of this datum, and detonating a few cubic inches of 



the vapour of ether with oxigen gas, I was able to deter- 

 mine with more precision the proportions of oxigen, hidro- 

 gen, and carbon in ether, than by burning two ounces of 

 this liquor in a red hot tube. I obtained results nearly as 

 accurate with the vapour of alcohol. 

 Vapour of ether 'f jj^ yapour of ethcr may be employed with as little cx^ 



employed to as- '■ . . . . 



ceriain its affi- pense for determining the affinities of this fluid to diflferent 



nities to pitch, gyjjg^jjj^(,gg_^ I introduced over mercury 12 grains of 

 pounded pitch into 20 measures of atmospheric air dilated hy 

 the vapour of ether, Avhich consisted of 10 measures of air 

 previous to its dilatation. The 20 measures occupied a co- 

 lumn 6 inches high, and 6 lines in diameter; and were re- 

 duced to eleven measures by the presence of the dry pitch, 

 which became semifluid in thus condensing almost the whole 

 of the ethercous vapour. 



^"^*» I obtained a somewhat less condensation with 12 grains 



of suet, 20 measures being reduced only to 13. The suet 

 was softened. 



India rubber. Twelve grains of caoutchouc, very minutely divided, re- 



duced 20 measures to 15. 



camphor. Twelve grains of camphor reduced 20 measures to 16. 



The camphor was moistened. 



wax. Twelve grains of yellow wax reduced 20 measures to 16f. 



fee. The vapour had very little action on gum lac, 12 grains 



of this only reducing 20 measures to 19. 



and tragacanth. A similar quantity of gum tragacanth produced a con- 

 densation too small to be measured. 



.Specific gravity The knowledge of the specific gravities of the vapour of 



the^irect^^ratio '^'''^^6r, of alcohol, and of ethcr, may give us an idea of 



of the volatility the law, which the gravities of vapours follow in proportion 



ces producing'^" *^ ^^^^ volatility of the liquids from which they arise. Water 



tlieiTi. at a given temperature is less evaporable than alcohol, and 



alcohol than ether. The elastic vapour of water is lighter 



than that of alcohol ; and the vapour of alcohol is lighter 



than that of ethcr. The specific gravity of elastic vapours 



then. 



