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delicate balance, can only be considered as a near approximation to 

 the truth. By an average of four such trials of its specific gravity, 

 its weight when compared to that of an equal globule of mercury, 

 was as 10 to 223, which gives its proportion to that of water nearly 

 as 6 to 10, so that it is the lightest fluid body yet known to chemists. 



In consequence of the great affinity of this body for oxygen, it 

 decomposes water instantly, with great heat, accompanied with ex- 

 plosion and a brilliant flame. By its union with oxygen, potash is 

 formed and is found dissolved in the water ; while hydrogen, in its 

 nascent state, uniting to another portion, becomes spontaneously in- 

 flammable at the time of its formation. 



The heat during combustion is such, that when a globule of the 

 base of potash was placed upon ice, it burned instantly with a bright 

 flame, and a deep hole was made in the ice, which contained a strong 

 solution of potash. 



Such is the attraction of this substance for oxygen, and so great 

 the energy of its action upon water, that it discovers and decomposes 

 the small quantities of water contained in alcohol and ether, even 

 when they are most carefully purified. 



The properties of the base of soda are in all respects so analogous 

 to those of the base of potash, that in this abstract it will be suffi- 

 cient to notice only those circumstances in which they principally 

 differ. 



The specific gravity of the base of soda exceeds that of the base of 

 potash ; but it is inferior to that of water in the proportion of 9 to 10. 

 Its point of fusion is also so much higher, that at all common 

 temperatures of the atmosphere it appears as a soft and extremely 

 malleable metal ; and it does not fuse till exposed to a heat exceed- 

 ing 150 Fahrenheit, and does not become volatile in a heat sufficient 

 to melt plate -glass. 



In proportion to the less fusibility of this body, its oxidation is less 

 rapid, and its combustion when heated less vivid than the former. 

 In the decomposition of water also, which it effects immediately, there 

 is no luminous appearance, although it is accompanied with violent 

 effervescence and a loud hissing noise. 



In endeavouring to determine the proportion in which each of 

 these bases unites with oxygen to form potash or soda, Mr. Davy is 

 again necessarily limited in accuracy by want of sufficient quantity of 

 materials for experiment ; but by a comparison of different methods, in 

 each of which the results of several trials were taken, he had reason 

 to be convinced, from their coincidence, that there could be no consi- 

 derable error. 



In his attempt to ascertain this point by direct union, he had va- 

 rious difficulties to overcome from the action of the simple base or 

 of the compound product on the vessel employed, and from the affi- 

 nity of the alkali for water, which would affect the apparent result. 

 By an average, however, of six experiments, selected as the most 

 carefully made, and under the most favourable circumstances, he in- 

 ferred that 100 parts of potash consist of 86 base and 14 oxygen ; 



