Alkali
3 of the 6 encyclopedias on this shelf carry an entry for Alkali. All 3 are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
al'ka-li, a compound resulting from the decomposition of water by any one of the alkali metals, as potassium, sodium, or lithium. Ammonia has the characteristics of an alkali, and is known as the volatile alkali. The alkalies are all very soluble in water, forming soapy, caustic solutions. They unite with oils and fats to form soaps, neutralize acids forming alkaline salts, change some of the vegetable yellows to brown, and reddened litmus to blue. Common lye, obtained by leaching wood ashes, is an alkaline solution consisting largely of potassium salts. It is used in a number of factories and by the housewife in making soft soap, and for hulling corn. The alkali waters of the Western States contain considerable quantities of alkali salts, chiefly in the form of carbonates or sulphates of potassium and sodium. Large areas of soil, both in the Old World and in the New, are so impregnated with alkali salts as to be practically barren; but recent experiments in irrigation have demonstrated that water and drainage will leach out the salts and convert deserts into fertile plains. Among the useful plants which subsist on certain proportions of alkali salts in the soil are barley, rice, millet, beets, rape, sunflower, celery, asparagus, spinach, onion, alfalfa, clover, and grape. To this list may be added the date palm of the Old World. Plants require variable small amounts of alkali salts. Water, however, containing ten per cent of alkali material is destructive to vegetation. So called spent lye is the liquid which remains after the combination of the alkali and grease in the manufacture of soap. It is of great value for plants. Before its application to the land it is mixed sometimes with peat or turf, or diluted with water. Besides containing potash or soda, this lye contains a large quantity of nitrogenous material.--JULIUS HORTVET.
Collier's New Encyclopedia (1921)
a strong base, capable of neutralizing acids, so that the salts formed are either completely neutral, or, if the acid is weak, give alkaline reactions. It was formerly restricted to the hydrates of potassium, sodium, lithium, and ammonium, but now includes the hydrates of alkaline earths (baryta, strontia, and lime) and many organic substances. The term alkali usually means, in commerce, caustic soda or potash, impure, NaHO or KHO; both are used in the arts for the manufacture of glass and soap, and for many other purposes. Caustic potash is used in surgery as a cautery.
The Encyclopedia of Founding (1892)
Alkalies in their pure state possess the following general properties; to the taste they are caustic and acrid; they dissolve animal matter, and form a saponaceous compound with oils or fat; they combine with acids in definite proportions, but the respective properties of each are destroyed, and a neutral salt is the result. It is on this account that most metals are precipitated from their acid solutions by the introduction of an alkali. The most important alkalies are potash, ammonia, and soda--ammonia being soluble, while potash and soda are termed fixed alkalies. See PRECIPITATION.
What Has Changed in the Last Century
The chemistry described here is still sound: alkalies still neutralize acids, saponify fats and turn reddened litmus blue. What has changed is how the strength of an alkali is stated. The Encyclopedia of Founding in 1892 could only offer the taste test — "caustic and acrid" — while Sørensen's pH scale of 1909 and the Brønsted–Lowry definition of a base as a proton acceptor (1923) put a number and a mechanism behind the word; Collier's in 1921 was writing just before that redefinition arrived. Aiton's optimism that irrigation "will leach out the salts and convert deserts into fertile plains" proved only half true: leaching works, but a century of irrigating the American West has shown that without drainage the salts simply move, and salinization has since taken large tracts of the San Joaquin Valley and similar districts out of production. Collier's note that caustic potash "is used in surgery as a cautery" describes a practice long abandoned; the same substance now reaches most households as drain cleaner and oven cleaner.
Written for this edition, 2026.