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of sodium, in absolute ether solution (A. Wurtz, Ann. chim. phys., 1855 (3), 44. p. 275), 2RI+2Na＝R·R+2NaI. They may also be obtained by the reduction of the higher fatty acids with hydriodic acid (F. Krafft, Ber., 1882, 15, pp. 1687, 1711), C_𝑛H_2𝑛O₂+6HI＝C_𝑛H_2𝑛+2+2H₂O+3I₂; by the conversion of ketones into ketone chlorides by the action of phosphorus pentachloride, these being then reduced by hydriodic acid,

C_𝑛H_2𝑛+12CO→C_𝑛H_2𝑛+1CCl₂→C_𝑛H_2𝑛+12CH₂;

by the reduction of unsaturated hydrocarbons with hydrogen in the presence of a “contact” substance, such, for example, as reduced nickel, copper, iron or cobalt (P. Sabatier and J. B. Senderens, Ann. chim. phys., 1905 [8], 4, pp. 319, 433); by the elimination of carbon dioxide from the fatty acids on heating their salts with soda-lime or baryta, CH₃CO₂Na + NaOH＝CH₄+Na2CO₃, or by heating their barium salts with sodium methylate in vacuo (I. Mai, Ber., 1889, 22, p. 2133); by the electrolysis of the fatty acids (H. Kolbe, Ann., 1849, 69, p. 257), 2C₂H₄O₂＝C₂H₆+2CO₂+H₂O; and by the action of the zinc alkyls on the ketone chlorides, (CH₃)₂CCl₂ + Zn(CH₃)₂＝C₅H₁₂+ZnCl₂.

The principal members of the series are shown in the following table:—

Name.	Formula.	Melting-  point.	Boiling- point.
Methane	CH4	−184°	−164° (760 mm.)
Ethane	C2H6	−172·1°	−84·1° (749 „ )
Propane	C3H8	−45°	−44·5°
Normal Butane	C4H10	—	+1°
Isobutane	„	—	−17°
Normal Pentane	C5H12	—	+36·3°
Secondary Pentane	„	—	+30·4°
Tertiary Pentane	„	—	+9°
Hexane	C6H14	—	+69°
Heptane	C7H16	—	98–99°
Octane	C8H18	—	125–126°
Nonane	C9H20	−51°	150°
Decane	C10H22	−31°	173–4°
Undecane	C11H24	−26·5°	196°
Dodecane	C12H26	−12°	214–216°
Tridecane	C13H28	−6·2°	234°
Tetradecane	C14H30	+4°	252°
Pentadecane	C15H32	+10°	270°
Hexadecane	C16H34	+18°	287°
Heptadecane	C17H36	+22°	170° (15 mm.)
Octadecane	C18H38	+28°	317°
Nonadecane	C19H40	+32°	330°
Eicosane	C20H42	+37	205 (15 mm.)
Heneicosane	C21H44	+40°	215° ( „ „ )
Docosane	C22H46	+44°	224° ( „ „ )
Tricosane	C23H48	+48°	234° ( „ „ )
Tetracosane	C24H50	+51°	243° ( „ „ )
Hexacosane	C26H52	+58°	—
Hentriacontane	C31H64	+68°	302° (15 mm.)
Dotriacontane	C32H66	+70·5°	331° ( „ „ )
Pentatriacontane	C35H72	+75°	331° ( „ „ )
Dimyricyl	C60H122	+102°	—

The lowest members of the series are gases at ordinary temperature; those of carbon content C₅ to C₁₅ are colourless liquids, and the higher members from C₁₅ onwards are crystalline solids. The highest members only volatilize without decomposition when distilled under diminished pressure. They are not soluble in water, although the lower and middle members of the series are readily soluble in alcohol and ether, the solubility, however, decreasing with increase of molecular weight, so that the highest members of the series are almost insoluble in these solvents. The specific gravity increases with the molecular weight but always remains below that of water. The paraffins are characterized by their great inertness towards most chemical reagents. Fuming sulphuric acid converts the middle and higher members of the series into sulphonic acids and dissolves the lower members (R. A. Worstall, Amer. Chem. Journ., 1898, 20, p. 664). Dilute nitric acid, when heated with the paraffins in a tube, converts them into secondary and tertiary nitro-derivatives (M. Konowalow, Ber., 1895, 28, p. 1852), whilst long boiling with strong nitric acid or nitro-sulphuric acid converts the middle and higher members of the series partly into primary mono- and di-nitro compounds and partly oxidizes them to carbonic, acetic, oxalic and succinic acids (Worstall, ibid., 20, p. 202; 21, p. 211). Fuming nitric acid only reacts slowly with the normal paraffins at ordinary temperature, but with those containing a tertiary carbon atom the reaction is very energetic, oxidation products (fatty acids and dibasic acids) and a small quantity of polynitro compounds are obtained (W. Markownikow, Centralblatt, 1899, 1, p. 1064; Ber., 1899, 32, p. 1441). Chlorine reacts with the paraffins, readily substituting hydrogen. Isomeric hydrocarbons in this series first appear with butane, the number increasing rapidly as the complexity of the molecule increases. For a means of determining the number of isomers see E. Cayley, Ber., 1875, 8, p. 1056; F. Hermann, Ber., 1898, 31, p. 91.

For Methane see Marsh Gas. Ethane, C₂H₆, occurs in crude petroleum. It may be prepared by the general methods given above; by heating mercury ethyl with concentrated sulphuric acid (C. Schorlemmer, Ann., 1864, 132, p. 234); or by heating acetic anhydride with barium peroxide (P. Schützenberger, Zeit. für Chemie, 1865, p. 703), 2(CH₃CO)2O+BaO₂＝C₂H₆ + Ba(C₂H₃O₂)₂+2CO₂. It is a colourless gas which can be liquefied at 4° C. by a pressure of 46 atmospheres. By slow combustion it yields first water and acetaldehyde, which then oxidizes to oxides of carbon and water (W. A. Bone; see Flame), whilst in ozonized air at 100° it gives ethyl alcohol, together with acetaldehyde and traces of formaldehyde (Bone, Proc. Chem. Soc, 1904, 29, p. 127).

Dimyricyl (hexacontane), C₆₀H₁₂₂, is prepared by fusing myricyl iodide with sodium (C. Hell and C. Hägele, Ber., 1889, 22, p. 502). It is only very slightly soluble in alcohol and ether.

PARAGON, a term for that which is a model of excellence or pattern of perfection, hence some person or thing which has no equal. The word was adopted from the O. Fr. paragon, Mod. parangon, Ital. paragone and Span. paragon. The Spanish has usually been taken as the source, and the word explained as from the prepositional phrase para con, in comparison with. But the word first appears in Italian, meaning a “touchstone.” The Italian word may be connected with the Gr. παρακονᾶν, to sharpen by the use of a whetstone (ἀκονή). The term has been used in several technical applications, e.g. in printing, of a large style of type between “great primer” and “double pica,” now usually called “two-line long primer”; of a diamond weighing more than 100 carats; and formerly of a fabric used for hangings in the 17th and 18th centuries.

PARAGRAPH, a term for a section or division of written or printed matter, which, as beginning a new subject, marking a break in the subject, &c., is signified by beginning the section on a new line set back or indented; also by the symbol, now ¶, a reversed P, formerly ( or ), to mark such a division. The Gr. παραγραφός (παρὰ and γράφειν, to write alongside or beside) was used of the short horizontal line or stroke which marked a line in a MS. where such a division occurs; and παραγραφή of a marginal note, also the division so marked. The word “paragraph,” besides these technical typographical meanings, is also applied to the separate numbered sections in an affidavit or other legal document, or in a statute, &c., and in journalism to a short item of news or brief notice of events.

PARAGUAY, an inland republic of South America, between 20° 16′ 14" and 26° 31′ S. and 54° 37′ and 62° W. It is bounded on the N.W. by Bolivia, N. and E. by Brazil, S.E., S. and W. by Argentina. Pop. (1905 estimate), 631,347, including 50,000 Iguassú Indians; area, about 97,700 sq. m.

By the treaty of 1872 the Brazilian frontier was drawn up the Paraná from the mouth of the Iguassú or Y-Guazú (25° 30′ S.) to the Salto Grande or Great Cataract of La Guayra (24° 7′), thence west along the watershed of the Sierra de Maracayú, north along the Sierra de Ambaya to the sources of the Apá, and down that stream to its junction with the Paraguay. The Buenos Aires treaty of the 3rd of February 1876 fixed the frontier between Argentina and Paraguay, and assigned to Paraguay the portion of the Gran Chaco between Rio Verde and Bahia Negra; the appropriation of the portion between Rio Verde and the Pilcomayo was submitted to the arbitration of the president of the United States, who in 1878 assigned it to Paraguay. The frontier line towards Bolivia has long been in dispute.

Physical Features.—The river Paraguay, running from north to south, divides the republic into two sections, the eastern section, or Paraguay Oriental, being the most important. The