of the fixed Alkalis. 1 i 



a small globule is used, it is completely dissipated with explo- 

 sion accompanied by a most vivid flame, into alkaline fumes. 



It is an excellent conductor of heat. 



Resembling the metals in all these sensible properties, it 

 is however remarkably different from any of them in specific 

 gravity ; I found that it rose to the surface of naphtha di- 

 stilled from petroleum, and of which the specific gravity was 

 •861, and it did not sink in double distilled naphtha, the 

 specific gravity of which was about *77o, that of water being 

 considered as one. The small quantities in which it is pro- 

 duced by the highest electrical powers, rendered it very 

 difficult to determine this quality with minute' precision. I 

 endeavoured to gain approximations on the subject by com- 

 paring the weights of perfectly equal globules of the basis 

 of potash and mercury. I used the very delicate balance of 

 the Royal Institution, which when loaded with the quan- 

 tities I employed, and of which the mercury never exceeded 

 ten grains, is sensible at least to the ■'aoWfo °f a grain. 

 Taking the mean of four experiments, conducted with great 

 care, its specific gravity at 62° Fahrenheit, is to that of 

 mercury as ten to 223, which gives a proportion to that of 

 water nearly as six to ten ; so that it is the lightest fluid- 

 body known. In its solid form it is a little heavier, but even/ 

 in this state when cooled to 40° Fahrenheit, it swims in the 

 double distilled naphtha. 



The chemical relations of tlv; basis of potash are still more 

 extraordinary than its physical ones. 



I have already mentioned its alkali zation and combustion 

 in oxygen gas. — It combines with oxygen slowly and with- 

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

 its vaporization. — Eut at this temperature combustion takes- 

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

 intense. When heated slowly in a quantity of oxygen gas 

 not sufficient for its complete conversion into potash, and' 

 at a temperature inadequate to its inflammation^ 400° Fah- 

 renheit, for instance, its tint changes to that of a red brown, 

 and when the heat is withdrawn, ail the oxygen is found to 

 be absorbed, and a solid is formed of a grayish colour, whlch- 

 partly consists of potash and partly of the basis of potash in 



a lower 



