| 释义 |
depressant, a. and n. Med.|dɪˈprɛsənt|
[f. depress v.: see -ant1.]
A. adj.
a. Having the quality of lowering the activity of the vital functions; sedative.
1887Athenæum 13 Aug. 217/1 The depressant and narcotic action. 1892N. Moore in Dict. Nat. Biog. XXIX. 221/1 The depressant treatment of fever.
b. In ore and froth flotation: having the property of a depressant (sense c).
1945A. F. Taggart Handbk. Mineral Dressing xii. 32 Lime..present in excess in sulphide flotation..has a definite depressant effect on the copper sulphides other than chalcopyrite. 1959Chambers's Encycl. X. 235/2 Alkalis are generally depressant in action on all sulphide flotations, preventing the collectors from working.
B. n.
a. A medicine or agent having this quality; a sedative.
1876Gross Dis. Bladder 267 The heart's action is reduced with aconite and other depressants. 1890Standard 19 Nov. 3/6 Malaria and heat are remarkable depressants.
b. Also depressent. A depressing influence.
1894Stevenson & Osbourne Ebb-Tide i. v. 87 So strong a tonic to the merely weak, and so deadly a depressent to the merely cowardly. 1923Kipling Irish Guards in Gt. War I. 121 There are times when Extreme Unction can be a depressant. 1961Times 22 Mar. 18/3 To the ambitious athlete there is really no reason why standards should not be an incentive rather than a depressant.
c. In ore and froth flotation, an agent that causes certain of the solids to sink while not affecting the others.
1934Webster, Depressant..Ore Dressing, a reagent that depresses. 1939A. M. Gaudin Princ. Mineral Dressing xv. 393 Practical depressants for sulphide flotation include alkali hydroxides. 1951Engineering 19 Oct. 492/1 Agents, known as depressants, are..used to promote wetting of..constituents, such as pyrites, which would otherwise float with the coal. 1962Gloss. Terms Coal Preparation (B.S.I.) 24 Depressant, a substance which when added to a pulp prevents a particular mineral or minerals from floating. |