Acid

a. and sb. [a. mod. Fr. acide (Cotgr., 1611) or ad. L. acid-us adj. of state, f. acē-re to be sour (root ac- sharp).]

  A.  adj.

  1.  Sour, tart, sharp to the taste; of the taste of vinegar.

1626.  Bacon, Sylva, VII. § 672. It [sorrel] is a cold and acid herb.

1676.  in Phil. Trans., XI. 614. These crystals are pure vitriol, acid-austere.

a. 1704.  Locke, Cond. Underst., § 40. The acid oil of vitriol is found to be good in such a case.

1855.  Bain, Senses & Intell., II. ii. § 13. 162 (1864). The sour or acid taste is much more uniform in its nature than either the saline or the alkaline.

1866.  J. T. Syme, in Treas. of Bot., 830. This plant has a pleasant acid taste.

  2.  fig.

1775.  Boswell, Johnson, II. 370 (1826). Beauclerk … said in his acid manner, ‘He would cut a throat to fill his pockets, if it were not for the fear of being hanged.’

1826.  Disraeli, Viv. Grey, VI. vi. 346. A hale old woman, with rather an acid expression of countenance.

1851.  Ruskin, Stones of Venice, I. xxiii. 264 (1874). The mere dogtooth is an acid moulding, and can only be used in certain mingling with others, to give them piquancy; never alone.

  3.  Chem. Having the essential properties of an ACID. See B. (Not separable in early use from 1.)

a. 1727.  Newton, quoted in Chambers’ Cycl., s.v. Acid, In decompounding sulphur we get an Acid salt.

1747.  Berkeley, Siris, 124. The mild native acids are observed more kindly to work upon and more thoroughly to dissolve metallic bodies than the strongest acid spirits produced by a vehement fire.

1812.  Sir H. Davy, Chem. Philos., 48. The analysis of mineral bodies … by the application of acid and alkaline menstrua.

1873.  Williamson, Chem., § 58. The solution has a slightly acid reaction to litmus-paper.

  b.  Acid Salt: A salt that retains part of the replaceable hydrogen of a bibasic acid.

1869.  Roscoe, Elem. Chem., 132. Thus [from dibasic acids] two classes of salts are derived; the so-called acid salts, where only one atom of hydrogen has been replaced, and the neutral salts, where both atoms have been replaced by a metal. Hydrogen potassium sulphite HKSO₃ in an acid salt.

1873.  Fownes, Chem., I. 339. The acid sulphite is very soluble in water, and has an acid reaction.

  4.  Min. = ACIDIC 2.

1874.  Lyell, Elem. Geol., xxviii. 497. Rocks containing an excess of silica from 60 to 80 per cent. are termed by many petrologists ‘acid’ rocks.

  B.  sb.

  Popularly, A sour substance. Chem. A substance belonging to a class of which the commonest and most typical members are sour, and have the property of neutralizing alkalis, and of changing vegetable blues to red; all of which are compounds of hydrogen with another element or elements (oxygen being generally the third element), and in the decomposition of a compound substance are relatively electro-negative, and borne to the positive pole.

1696.  Phillips [not in ed. 1678], Acid in Chymistry, that sharp Salt, or that potential and dissolving Fire which is in all mix’d Bodies, and gives ’em being. Of Acids, Vitriol is the chiefest, Sea-salt next to that.

1712.  trans. Pomet’s Hist. Drugs, I. 57. The Edges or Points of the Acid penetrate the gustatory Nerve.

a. 1727.  Newton, quoted in Chambers’ Cycl. (1751), s.v. Acid, The particles of Acids are of a size grosser than those of water.

1747.  Berkeley, Siris, 159. What the chemists say, of pure acids being never found alone, might as well be said of pure fire.

1791.  Hamilton, Berthollet, Art of Dyeing, Pref. 7. The improvement depends principally on the use of the acids.

1814.  Sir H. Davy, Agric. Chem., 106. The acids found in the Vegetable kingdom are numerous.

1837.  Whewell, Hist. Induct. Sc., XIV. x. The whole fabric of chemistry rests, even at the present day, upon the opposition of acids and bases; an acid was certainly at first known by its sensible qualities, and how otherwise, even now, do we perceive its quality?

1871.  Tyndall, Frag. of Sc., I. v. 161 (ed. 6). Neither acids nor alkalies had the power of rapid destruction.

1879.  McCarthy, Hist. own Times, I. 42. Lord John Russell … was especially effective in a cold irritating sarcasm, which penetrated the weakness of an opponent’s argument like some dissolving acid.