Humphry Davy (1778-1829)

Of the Analogies between the Undecompounded Substances: Ideas Respecting their Nature

excerpt from Elements of Chemical Philosophy (London, 1812) vol. 1, part 1, pp. 478-9 [from Maurice Crosland, ed., The Science of Matter: a Historical Survey (Harmondsworth, UK: Penguin, 1971)]

The undecompounded substances most analogous to each other, are certainly to be found amongst the metals; some of these are so similar that it requires refined observation, and sometimes experiment to distinguish them. There is likewise a chain of gradations of resemblance which may be traced throughout the whole series of metallic bodies, at the same time that certain similar and characteristic properties are found to belong to metals in other respects most unlike each other.

Silver and palladium, antimony and tellurium, agree in a great number of qualities. Potassium and platinum, if we except their lustre, colour and power of conducting electricity, are bodies extremely dissimilar; yet, by arranging the metals in the order of parts of their natural resemblances, these two substances may be made parts of one chain of natural bodies: potassium, sodium and barium are very like each other; barium approaches to manganese, zinc, iron, tin and antimony. Platinum is analogous to gold, silver and palladium; and palladium is connected by distinct analogies with tin, zinc, iron and manganese. Arsenic and chromium, though amongst the most dissimilar of the metals in other respects, agree in the property of forming acid matter by combination with oxygen.

Amongst the inflammable bodies not metallic there are analogies, but not a similar series. Sulphur and phosphorus agree in many respects; carbon and boron are likewise analogous, and are connected with distinct relations to the metallic substances. Azote, whilst it agrees with the other combustible bodies that have been named in forming an acid by saturation with oxygen, is analogous to carbon in its incapacity of uniting to chlorine.

Chlorine and oxygen are separated from the inflammable bodies by a number of marked distinctions; yet sulphur agrees with chlorine in forming an acid by combining with hydrogen; and has a weak attraction for chlorine and a strong attraction for metallic substances.

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