NATURE AND DECOMPOSITION OF THE FIXED ALKALIS. ^nft 



ten grains, is sensible at least to the ^Vt ^jf a grain. Taking 

 the mean of 4 experiments, conducted with great care, its 

 specitic gravity at 62° Fahrenheit is to that of mercury as 

 1,0 to 2-23, which gives a proportion to that of water nearly about -g TT"hen 

 as-6 to 10; so that it is the lightest fluid body known. In fhan'z'^ ^^""' 

 its solid form it is a little heavier, but even in this state, solid. ^ ^ 

 when cooled to 40° Fahreaheit, it swims in the double dis- 

 tilled naphtha. 



The chemical relations of the basts of potash are still ^'^ cnemica! . 

 more extraordmary than its physical ones. extraoSma^! 



I have already mentioned its alkalization and combustion Tooxigea. 

 in oxigen gas. — It combines with oxigen slowly, and with- 

 out flame, at all temperatures that I have tried below that 

 of its vaporization. — But at this temperature combustioa 

 takes place, and the light is of a brilliant whiteness and the 

 heat intense* When heated slowly in a quantity of oxio-ea 

 gas not sufficient for its complete conversion into potash, 

 and at a temperature inadequate to its inflammation, 400^ 

 Fahrenheit, for instance, its tint changes to that of a red 

 brown, and when the heat is withdrawn, all the oxigen is 

 found to be absorbed, and a solid is formed of a grayish co- 

 Jour, which partly consists of potash and partly of the basis 

 of potash in a lower degree of oxigenation, — and which be- 

 comes potash by being exposed to water, or by being again 

 heated in fresh quantities of air. 



The substance consisting of the basis of potash combined 

 with an under proportion of oxigen may likewise be formed 

 by fusing dry potash and its basis together under proper 

 circumstances.— -The basis rapidly loses its metallic splen- 

 dour; the two substatncea unite into a compound of a red 

 brov/n colour when fluid, and of a dark gray hue when so- 

 lid ; and this compound somi absorbs its full proportion of 

 oxigen v/hen exposed to air, and js wholly converted into 

 potash. 



' And the same body is often formed in the analytical ex- 

 periments when the action of the electricity is intense, and 

 the potash rfiuch heated. 



The basis of potash when introduced into oxsmuriatic Bums in oxi- 

 acid gas burns spontaneously with a bright red light; and a mufiatic acid. 

 white salt, proving to be jnuriate of potash, is formed. 



When 



