Page:Proceedings of the Royal Society of London Vol 1.djvu/301

Rh 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 aﬂinity 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 aheat suﬁicient 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 eﬂ‘ervescence 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 various difficulties to overcome from the action of the simple base or of the compound product on the vessel employed, and from the affinity 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 inferred that 100 parts of potash consist of 86 base and 14 oxygen;