“Taking the mean of 4 experiments, conducted with great care, its specific gravity at 62° Fahrenheit, is to that of mercury as 10 to 223, which gives a proportion to that of water nearly as 6 to 10; so that it is the lightest fluid body known. In its solid form it is a little heavier.”
Although no great stress can be laid on numbers so obtained, they serve to indicate that Davy had not yet obtained the pure metal. The real ratio of the specific gravities of potassium and mercury is as 10 to 154.
An account is then given of the behaviour of potassium towards oxygen, oxymuriatic acid gas [chlorine], hydrogen, water, alcohol, ether, the various mineral acids, phosphorus, sulphur, mercury, a number of metallic oxides, and the various forms of glass.
The “basis” of soda is described as a white opaque substance of the lustre and general appearance of silver. It is soft and malleable, and is a good conductor of heat and electricity. Its specific gravity was found by flotation in a mixture of oil of sassafras and naphtha to be 0·9348 (the true specific gravity of sodium is 0·974). It was found to fuse at about 180° F. (the real melting-point of sodium is 197·5°). Its action on a number of substances—oxygen, hydrogen, water, etc.—is then described, and its general behaviour contrasted with that of the “basis” of potash.
Davy then attempted, by synthetical experiments, to determine the amount of the “metallic bases” in potash and soda respectively, and, considering the extremely small quantities he had to operate upon, the results are fairly accurate.
He then enters upon some general observations on the relations of the “bases” of potash and soda to other bodies.
“Should the bases of potash and soda be called metals? The greater number of philosophical persons to whom this question has been put, have answered in the affirmative. They agree with metals in opacity, lustre, malleability, conducting powers as to heat and electricity, and in their qualities of chemical combination.
“Their low specific gravity does not appear a sufficient reason for making them a new class; for amongst the metals themselves there are remarkable differences in this respect, ... and in the philosophical division of the classes of bodies, the analogy between the greater number of properties must always be the foundation of arrangement.
“On this idea, in naming the bases of potash and soda, it will be proper to adopt the termination which, by common consent, has been applied to other newly discovered metals, and which, though originally Latin, is now naturalized in our language.
“Potasium [sic] and sodium are the names by which I have ventured to call the new substances; and whatever changes of theory, with regard to the composition of bodies, may hereafter take place, these terms can scarcely express an error; for they may be considered as implying simply the metals produced from potash and soda. I have consulted with many of the most eminent scientific persons in this country, upon the methods of derivation, and the one I have adopted has been the one most generally approved. It is perhaps more significant than elegant. But it was not possible to found names upon specific properties not common to both; and though a name for the basis of soda might have been borrowed from the Greek, yet an analogous one could not have been applied to that of potash, for the ancients do not seem to have distinguished between the two alkalies.”
He thinks there is the greater necessity for avoiding any theoretical views in terms because the time is yet far distant for a complete generalisation of chemical facts, and although the antiphlogistic explanation of the phenomena has been uniformly adopted, the motive for employing it has been rather a sense of its beauty and precision than a conviction of its permanency and truth.
“The discovery of the agencies of the gases destroyed the hypothesis of Stahl. The knowledge of the powers and effects of the etherial substances may at a future time possibly act a similar part with regard to the more refined and ingenious hypothesis of Lavoisier; but in the present state of our knowledge, it appears the best approximation that has been made to a perfect logic of chemistry.”
Led by analogy, Davy soon convinced himself that the volatile alkali—ammonia—also contained oxygen, and in amount not less than 7 or 8 per cent. It is not necessary to go into detail concerning the experiments on which this erroneous conclusion was founded. Davy was subsequently made aware of his error; but at the time he seemed anxious to overturn—as, indeed, he did in the end, but on other grounds—the Lavoisierian doctrine that oxygen was the principle of acidity, by showing that it was equally the principle of alkalescence.