Encyclopaedia Britannica Volume 2, Slice 2 Part 14

GROUP C.

Family 9. CYATHOPHYLLIDAE.--Solitary and colonial aporose corals.

Tabulae and vesicular endotheca present. Septa numerous, generally radial, seldom pinnate. Typical genera--_Cyathophyllum_, Goldfuss (Devonian and Carboniferous). _Moseleya_, Quelch (recent).

Family 10. ASTRAEIDAE.--Aporpse, mainly colonial corals, ma.s.sive, branching, or maeandroid. Septa radial; dissepiments present; an epitheca surrounds the base of ma.s.sive or maeandroid forms, but only surrounds individual corallites in simple or branching forms. Typical genera--_Goniastraea_, M. Edw. and H. _Heliastraea_, M. Edw. and H.

_Maeandrina_, Lam. _Coeloria_, M. Edw. and H. _Favia_, Oken.

Family 11. FUNGIDAE.--Solitary and colonial corals, with numerous radial septa united by synapticulae. Typical genera--_Lophoseris_, M.

Edw. and H. _Thamnastraea_, Le Sauvage. _Leptophyllia_, Reuss (Jura.s.sic and Cretaceous). _Fungia_, Dana. _Siderastraea_, Blainv.

GROUP D.

Family 12. EUPSAMMIDAE.--Solitary or colonial perforate corals, branching, ma.s.sive, or encrusting. Septa radial; the primary septa usually compact, the remainder perforate. Theca perforate. Synapticula present in some genera. Typical genera--_Stephanophyllia_, Michelin.

_Eupsammia_, M. Edw. and H. _Astroides_, Blainv. _Rhodopsammia_, M.

Edw. and H. _Dendrophyllia_, M. Edw. and H.

GROUP E.

Family 13. CYSTIPHYLLIDAE.--Solitary corals with rudimentary septa, and the calicle filled with vesicular endotheca.

Genera--_Cystiphyllum_, Lonsdale (Silurian and Devonian).

_Goniophyllum_, M. Edw. and H. (In this Silurian genus the calyx is provided with a movable operculum, consisting of four paired triangular pieces, the bases of each being attached to the sides of the calyx, and their apices meeting in the middle when the operculum is closed). _Calcecla_, Lam. (In this Devonian genus there is a single semicircular operculum furnished with a stout median septum and numerous feebly developed secondary septa. The calyx is triangular in section, pointed below, and the operculum is attached to it by hinge-like teeth.)

AUTHORITIES.--The following list contains only the names of the more important and more general works on the structure and cla.s.sification of corals and on coral reefs. For a fuller bibliography the works marked with an asterisk should be consulted: * A. Andres, _Fauna und Flora des Golfes von Neapel_, ix. (1884); H.M. Bernard, "Catalogue of Madreporarian Corals" in Brit. Museum, ii. (1896), iii. (1897); * G.C.

Bourne, "Anthozoa," in E. Ray Lankester's _Treatise on Zoology_, vol.

ii. (London, 1900); G. Brook, "_Challenger_ Reports," _Zoology_, x.x.xii. (1899) (_Antipatharia_); "Cat. Madrep. Corals," Brit. Museum, i. (1893); D.C. Danielssen, "Report Norwegian North Atlantic Exploring Expedition," _Zoology_, xix. (1890); J.E. Duerden, "Some Results on the Morphology and Development of Recent and Fossil Corals," _Rep.

Brit. a.s.sociation_, 1903, pp. 684-685; "The Morphology of the Madreporaria," _Biol. Bullet_, vii. pp. 79-104; P.M. Duncan, _Journ.

Linnean Soc._ xviii. (1885); P.H. Gosse, _Actinologia britannica_ (London, 1860); O. and R. Hertwig, _Die Actinien_ (Jena, 1879); R.

Hertwig, "_Challenger_ Reports," _Zoology_, vi. (1882) and xxvi.

(1888); * C.B. Klunzinger, _Die Korallthiere des Rothen Meeres_ (Berlin, 1877); * G. von Koch, _Fauna und Flora des Golfes van Neapel_, xv. (1887); _Mitth. Zool. Stat. Neapel_, ii. (1882) and xii.

(1897); _Palaeontographica_, xxix. (1883); (also many papers in the _Morphol. Jahrbuch_ from 1878 to 1898); F. Koby, "Polypiers jura.s.siques de la Suisse," _Mem. Soc. Palaeont. Suisse_, vii.-xvi.

(1880-1889); A. von Kolliker, "Die Pennatuliden," _Abh. d. Senck.

Naturf. Gesell_. vii.; * "_Challenger_ Reports," _Zoology_, i.

_Pennatulidae_ (1880); Koren and Danielssen, _Norske Nordhaus Exped., Alcyonida_ (1887); H. de Lacaze-Duthiers, _Hist. nat. du corail_ (Paris, 1864); H. Milne-Edwards and J. Haime, _Hist. nat. des coralliaires_ (Paris, 1857); H.N. Moseley, "_Challenger_ Reports,"

_Zoology_, ii. (1881); H.A. Nicholson, _Palaeozoic Tabulate Corals_ (Edinburgh, 1879); M.M. Ogilvie, _Phil. Transactions_, clx.x.xvii.

(1896); E. Pratz, _Palaeontographica_, xxix. (1882); J.J. Quelch, "_Challenger_ Reports," _Zoology_, xvi. (1886); * P.S. Wright and Th.

Studer, "_Challenger_ Reports," _Zoology_, x.x.xi. (1889).

(G. C. B.)

ANTHRACENE (from the Greek [Greek: anthrax], coal), C14H10, a hydrocarbon obtained from the fraction of the coal-tar distillate boiling between 270 and 400 C. This high boiling fraction is allowed to stand for some days, when it partially solidifies. It is then separated in a centrifugal machine, the low melting-point impurities are removed by means of hot water, and the residue is finally hot-pressed.

The crude anthracene cake is purified by treatment with the higher pyridine bases, the operation being carried out in large steam-jacketed boilers. The whole ma.s.s dissolves on heating, and the anthracene crystallizes out on cooling. The crystallized anthracene is then removed by a centrifugal separator and the process of solution in the pyridine bases is repeated. Finally the anthracene is purified by sublimation.

Many synthetical processes for the preparation of anthracene and its derivatives are known. It is formed by the condensation of acetylene tetrabromide with benzene in the presence of aluminium chloride:--

BrCHBr /CH C6H6 + + C6H6 = 4HBr + C6H4<>C6H4, BrCHBr CH/

and similarly from methylene dibromide and benzene, and also when benzyl chloride is heated with aluminium chloride to 200 C. By condensing ortho-brombenzyl bromide with sodium, C.L. Jackson and J.F. White (_Ber_., 1879, 12, p. 1965) obtained dihydro-anthracene

/CH2Br Br /CH2 C6H4< +="" 4na="" +="">C6H4 = 4NaBr + C6H4<>C6H4.

Br BrCH2/ CH2/

Anthracene has also been obtained by heating ortho-tolylphenyl ketone with zinc dust

/CH8 /CH C6H4< =="" h2o="" +=""><>C6H4.

COC6H5 CH /

Anthracene crystallizes in colourless monoclinic tables which show a fine blue fluorescence. It melts at 213 C. and boils at 351 C. It is insoluble in water, sparingly soluble in alcohol and ether, but readily soluble in hot benzene. It unites with picric acid to form a picrate, C14H10C6H2(NO2)3OH, which crystallizes in needles, melting at 138 C.

On exposure to sunlight a solution of anthracene in benzene or xylene deposits para-anthracene (C14H10)2, which melts at 244 C. and pa.s.ses back into the ordinary form. Chlorine and bromine form both addition and subst.i.tution products with anthracene; the addition product, anthracene dichloride, C14H10Cl2, being formed when chlorine is pa.s.sed into a cold solution of anthracene in carbon bisulphide. On treatment with potash, it forms the subst.i.tution product, monochlor-anthracene, C14H9Cl.

Nitro-anthracenes are not as yet known. The mono-oxyanthracenes (anthrols), C14H9OH or

/CH C6H4<>C6H3OH CH/

([alpha]) and ([beta]) resemble the phenols, whilst

/C(OH) C6H4<>C6H4 CH /

([gamma]) (anthranol) is a reduction product of anthraquinone.

[beta]-anthrol and anthranol give the corresponding amino compounds (anthramines) when heated with ammonia.

Numerous sulphonic acids of anthracene are known, a monosulphonic acid being obtained with dilute sulphuric acid, whilst concentrated sulphuric acid produces mixtures of the anthracene disulphonic acids. By the action of sodium amalgam on an alcoholic solution of anthracene, an anthracene dihydride, C14H12, is obtained, whilst by the use of stronger reducing agents, such as hydriodic acid and amorphous phosphorus, hydrides of composition C14H16 and C14H24 are produced.

Methyl and phenyl anthracenes are known; phenyl anthranol (phthalidin) being somewhat closely related to the phenolphthaleins (q.v.). Oxidizing agents convert anthracene into anthraquinone (q.v.); the production of this substance by oxidizing anthracene in glacial acetic acid solution, with chromic acid, is the usual method employed for the estimation of anthracene.

ANTHRACITE (Gr. [Greek: anthrax], coal), a term applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition; or, in other words, which burn with a smokeless and nearly non-luminous flame. Other terms having the same meaning are, "stone coal" (not to be confounded with the German _Steinkohle_) or "blind coal" in Scotland, and "Kilkenny coal" in Ireland. The imperfect anthracite of north Devon, which however is only used as a pigment, is known as _culm_, the same term being used in geological cla.s.sification to distinguish the strata in which it is found, and similar strata in the Rhenish hill countries which are known as the Culm Measures. In America, culm is used as an equivalent for waste or slack in anthracite mining.

Physically, anthracite differs from ordinary bituminous coal by its greater hardness, higher density, 1.3-1.4, and l.u.s.tre, the latter being often semi-metallic with a somewhat brownish reflection. It is also free from included soft or fibrous notches and does not soil the fingers when rubbed. Structurally it shows some alteration by the development of secondary divisional planes and fissures so that the original stratification lines are not always easily seen. The thermal conductivity is also higher, a lump of anthracite feeling perceptibly colder when held in the warm hand than a similar lump of bituminous coal at the same temperature. The chemical composition of some typical anthracites is given in the article COAL.

Anthracite may be considered to be a transition stage between ordinary bituminous coal and graphite, produced by the more or less complete elimination of the volatile const.i.tuents of the former; and it is found most abundantly in areas that have been subjected to considerable earth-movements, such as the flanks of great mountain ranges. The largest and most important anthracite region, that of the north-eastern portion of the Pennsylvania coal-field, is a good example of this; the highly contorted strata of the Appalachian region produce anthracite exclusively, while in the western portion of the same basin on the Ohio and its tributaries, where the strata are undisturbed, free-burning and c.o.king coals, rich in volatile matter, prevail. In the same way the anthracite region of South Wales is confined to the contorted portion west of Swansea and Llanelly, the central and eastern portions producing steam, c.o.king and house coals.

Anthracites of newer, tertiary or cretaceous age, are found in the Crow's Nest part of the Rocky Mountains in Canada, and at various points in the Andes in Peru.

The princ.i.p.al use of anthracite is as a smokeless fuel. In the eastern United States, it is largely employed as domestic fuel, usually in close stoves or furnaces, as well as for steam purposes, since, unlike that from South Wales, it does not decrepitate when heated, or at least not to the same extent. For proper use, however, it is necessary that the fuel should be supplied in pieces as nearly uniform in size as possible, a condition that has led to the development of the breaker which is so characteristic a feature in American anthracite mining (see COAL). The large coal as raised from the mine is pa.s.sed through breakers with toothed rolls to reduce the lumps to smaller pieces, which are separated into different sizes by a system of graduated sieves, placed in descending order. Each size can be perfectly well burnt alone on an appropriate grate, if kept free from larger or smaller admixtures. The common American cla.s.sification is as follows:--

Lump, steamboat, egg and stove coals, the latter in two or three sizes, all three being above 1 in. size on round-hole screens.

Chestnut below 1 inch above 7/8 inch.

Pea " 7/8 " " 9/16 "

Buckwheat " 9/16 " " 3/8 "

Rice " 3/8 " " 3/16 "

Barley " 3/16 " " 3/32 "

From the pea size downwards the princ.i.p.al use is for steam purposes. In South Wales a less elaborate cla.s.sification is adopted; but great care is exercised in hand-picking and cleaning the coal from included particles of pyrites in the higher qualities known as best malting coals, which are used for kiln-drying malt and hops.