dispersion
(dɪˈspɜːʃən)
Also 5 -cioune, 6 -tion.
[a. F. dispersion (disparcion 13th c. in Hatz.-Darm.), or ad. L. dispersiōn-em scattering, n. of action f. dispergĕre: see disperse v.]
1. The action of dispersing or scattering abroad; the condition or state of being dispersed; scattering, distribution, circulation.
Early applied to the scattering of the Jews among the Gentiles after the Babylonian Captivity; whence sense 5.
| c 1450 Mirour Saluacioun 3635 The Jewes y{supt} tyme hadde bene thorgh the werlde in dispersionne. 1555 Eden Decades 266 In the fyrst dispertion of nations. 1656 Manasseh ben Israel Vind. Judæorum in Phenix (1708) II. 423, I conceiv'd that our universal Dispersion was a necessary Circumstance to be fulfil'd. 1786 Burke W. Hastings Wks. 1842 II. 180 The dispersion and exile of the reigning family. 1793 Trial Fyshe Palmer 22 The alleged dispersion of a seditious writing. 1882 Vines Sachs' Bot. 929 The specialities of organisation which effect the dispersion of their seeds. |
| fig. c 1450 tr. De Imitatione i. xx, What comeþ þerof but grucching of conscience & dispersion of herte? |
2. The action of diffusing or spreading; diffusion.
| 1664 Power Exp. Philos. i. 29 That all Vegetables have a constant perspiration, the continual dispersion of their odour makes out. 1794 Sullivan View Nat. II. 36 When the natural dispersion of heat is disturbed..then a sensible heat is produced. 1874 Hartwig Aerial W. ii. 21 By this means is also gradually effected the dispersion of all gases. |
3. Med. ‘The removal of inflammation, suppuration, or other morbid processes, from a part, and restoration to health’ (
Syd. Soc. Lex.); dissipation.
| 1753 Chambers Cycl. Supp. s.v., This is commonly term'd in surgery the resolution or dispersion of tumors. Ibid., Remedies for the dispersion of inflammations. 1789 W. Buchan Dom. Med. (1790) 573 An inflammation..must terminate either by dispersion, suppuration, or gangrene. |
4. Optics. The divergence or spreading of the different-coloured rays of a beam of composite light when refracted by a prism or lens, or when diffracted, so as to produce a spectrum:
esp. in reference to the amount of this divergence.
| 1727–51 Chambers Cycl., Point of Dispersion, is a point from which refracted rays begin to diverge. 1794 G. Adams Nat. & Exp. Philos. II. xxii. 447 This diffusion or dispersion of the rays is greater. 1833 N. Arnott Physics (ed. 5) II. 199 The quality of..bending a beam, or of refraction, and that of dividing it into coloured beams, or of dispersion, are distinct. 1871 tr. Schellen's Spectr. Anal. §18. 63 The decomposition of white light into its colored rays is called dispersion. 1881 N. Lockyer in Nature No. 617. 399 [The lines] are..visible when considerable dispersion is employed. |
5. the Dispersion: The Jews dispersed among the Gentiles after the Babylonian Captivity; the scattered communities of Jews in general, or the communities in some single country, as
the Egyptian Dispersion;
= diaspora.
| 1382 Wyclif 1 Pet. i. 1 To the chosen gestis of dispersioun [gloss, or scateringe abroad]. c 1450 St. Cuthbert (Surtees) 3781 Of ysrael þe dispercioune he gadird samen fra strete and toune. 1582 N. T. (Rhem.) John vii. 35 Wil he goe into the dispersion of the Gentiles, and teach the Gentiles? 1641 Evelyn Mem. (1857) I. 30 Transported..to all the desolate ports and havens throughout the world, wherever the dispersion was, to convey their brethren and tribes to the Holy City. 1880 J. E. Carpenter tr. Ewald's Hist. Israel V. 4 The ‘Coasts of the Sea’..are now (as in the eighth century) mentioned as a residence of the Dispersion. 1893 Smith & Fuller Dict. Bible s.v., The African Dispersion..preserved their veneration for the ‘holy city’. |
6. law of dispersion: The ‘Law of Error’ as regards distance from the mark without reference to the direction of error. So
dispersion = the degree of scatter of values in a set of observations.
| 1876 Catal. Sci. App. S. Kens. Mus. §48 Testing how far the relative numbers in the several classes accord with the results of the Law of Error or Dispersion. Ibid. §49 The well-known bell-shaped curve, by which the law of error or of dispersion is mathematically expressed. 1897 Jrnl. R. Statist. Soc. LX. 865 Notice that no term measuring the dispersion of weights enters in the formula; but that the approximation was made on the assumption that the weights were equal. 1930 Engineering 13 June 756/1 The observations were characterised by a large dispersion, which was attributed to the numerous factors involved. 1963 B. Fozard Instrum. Nucl. Reactors vii. 70 A commonly used measure of the dispersion or scatter of a number of observed values about the central values is the standard deviation σ. |
7. Physical Chem. A type of intimate mixture in which one substance is present in a large number of separate small regions distributed throughout another, continuous, substance; examples are emulsions (one liquid in another) and aerosols (a solid or a liquid in a gas); also, the state of being so distributed. Also
attrib., as
dispersion medium; a substance that may contain another substance ‘dispersed’ in it.
| 1915 [see dispersed ppl. a. c]. 1919 E. Hendrick Chem. Everyday Life 74 Soap is a colloid, and when we get a little of it in a great deal of water we have it in dispersion. 1924 A. Findlay Physical Chem. 173 A colloidal sol..consists of finely divided particles (the dispersed phase) distributed throughout a dispersion medium. 1927 Crocker & Matthews Theoret. & Exper. Physical Chem. 274 Dispersion medium, the continuous phase in a colloidal solution, corresponding to the solvent in true solution. 1944 Petroleum Refiner Dec. 504/2 The property of maintaining insoluble matter (sludges and contaminants) in dispersion in the oil so that they will not settle out. 1957 Encycl. Brit. VI. 25/2 A foam is a gaseous dispersion (usually of air) in a liquid continuum. Ibid., Pastes are concentrated dispersions of fine solid particles in a liquid continuum. 1958 Times Rev. Industry May 69/1 The main dispersion mill..will turn out 500 gallons of emulsion paint in an hour. |
8. attrib. dispersion hardening Metall., a process of ageing produced by heating at high temperatures.
| 1891 Times 28 Sept. 13/6 By an appropriate choice of dispersion lenses. 1932 Metallurgist VIII. 110/1 The hardening depends on the degree of dispersion of the particles, and it is accordingly sometimes known as dispersion hardening. 1934 H. O'Neill Hardness of Metals vi. 195 ‘Dispersion hardening’ and ‘precipitation hardening’ are good labels to employ for the phenomenon in general. |