310 NATURE AND DECOMPOSITION OF THE FIXED ALKALIS. 



being accurately weighed or compared with a jjlobule of 

 mercury equal in size*, was plaied: the lube was ^n)aiL at 

 one end, curved, and bvouj^ht to a tine point, but suffered 

 to remain open ; and the other end was titted to a lube 

 Comnnunicating with a gasometer, from which the oxi^ien 

 gas was introdueed, ior neither water nor mercury touid 

 be used for filling the appara us. The oxigeii gas was car- 

 ried through the tube, till it was found that the whole of 

 the comuioa air was expelled. The degree ol" its purity 

 was ascertained by sudering a small quantity to })ass iuto 

 the mercurial apparatus. Tiie lower ciilict- was then her- 

 metically sealed by a spirit lai^p, and the upper part diawli 

 out and finally closed, when the aperture was so small, as 

 to render the temperature emp oyed incapable of mate- 

 terially influencing the volume of the gas; and when the 

 •whole arrangement was made, the combination was efiected 

 by applying heat to the glass in contact with the metallic 

 tray. 

 Difficulties. In performing these experiments many difficulties occur- 



red. When the Havne of the lamp was immediately brought 

 to play upon the glass, the combustion was very vivid, so 

 as sometimes to break the tube ; and the alkali generated 

 partly rose in white fumes, which were deposited upon the 

 glass. 



When the temperature was slowly raised, the bases of the 

 alkalis acted upon the metallic tray and formed alleys, and 

 in this state it was very difficult to combine them with thejr 

 full propo tion of oxigen ; glass alone could not be em- 

 ployed on account of its decomposition by the alkahne ' 

 bases; and porcelain is so bad a conductor of heat, that it 

 was not possible to raise it to the point required for the prQ< 

 cess, without softening the glass. 



In all cases the globides of the alkaline bases were care- 

 fully freed from naphtha before ihey were introduced ; of 

 course a slight crust of alkali was formed before the com- 



* Whea the g1ot)iiles were very small, the comparison wi'h mercury, 

 which m;iv be quickly made by means of a nii^ronioter, w«> ge.ierally 

 employed as the nieuiis of ascertaining the weight ; for in this cise the 

 globule could be immediately introduced into the tube, and the weigiit 

 of ruercury ascertained at leisure, 



bustion, 



