Potassium Salts in Sea-Water

Abstract

A CORRESPONDENT in NATURE of January 1 (p. 199), in asking why it is that the water of the ocean contains such a large proportion of sodium and so little, comparatively, of potassium salts, raises one of the most instructive inquiries in the whole range of mineral physiology. The waters which flow into the sea convey the soluble salts derived from the land, and these often include a considerable proportion of potassium. The sources of these salts are two-fold: (1) the sub-aërial decay of crystalline rocks, which give up their alkalies as carbonates; (2) saline solutions and solid salts which have come from evaporated seas or lake basins, and have thus been withheld or abstracted from the ocean's waters. In the latter case they are fossil sea-waters, as in many saline springs from the older sediments. These waters show that the proportion of potassium salts was then not greater but less than at present. Of the alkaline salts of the St. Lawrence River estimated as chlorides, the potassium equalled, by my analysis, 16 per cent., and the Ottawa 32 per cent., the remainder being, of course, sodium chloride. In the numerous saline and alkaline springs which rise from the Palæozoic strata throughout the great valley drained by these rivers the proportion of potassium chloride is seldom over 2 or 3 per cent, of the alkaline salts, and often less, while in the waters of the modern ocean it is found to be not far from 3 per cent.