| 释义 |
‖ potassa Chem.|pəʊˈtæsə|
[mod.L.: see potash.]
The name appropriated by Davy to potassium monoxide, K2O, also called anhydrous potash; sometimes also applied to the hydrate or hydroxide, KHO (= K2H2O2), also called potassa fusa and caustic potash.
Formerly used in names of chemical compounds in which current nomenclature uses potassium, as carbonate of potassa = potassium carbonate, K2CO3 (regarded as K2O.CO2).
liquor potassæ, an aqueous solution of potassium hydrate, containing about 5·84 per cent of the hydrate.
1812Sir H. Davy Chem. Philos. 324 This substance is pure potash or potassa, which was unknown in its uncombined state till I discovered potassium, but which has long been familiar to chemists combined with water in the substance which has been called pure potash; but which ought to be called the hydrat of potassa. 1813― Agric. Chem. ii. (1814) 52 Potassa or the pure caustic vegetable alkali consists of one proportion of potassium and one of oxygene. 1836–41Brande Chem. (ed. 5) 611 The Liquor Potassæ of the Pharmacopœia is directed to be prepared as follows:—‘Take of carbonate of potassa 15 ounces, lime 8 ounces, boiling distilled water a gallon [etc.].’ 1842Brande Dict. Sc., etc. s.v. Potassium, What is called caustic potash, which is a compound of 48 potassa + 9 water. 1858Mayne Expos. Lex., Potassa Fusa, fused potash; the hydrate of potash; also called Lapis infernalis. 1877Roberts Handbk. Med. (ed. 3) I. 66 Liquor potassæ seems to be of use in some cases. |