chloranilines and elimination of nitrogen, whilst on boiling with sulphuric acid it is converted into aminophenols.
Aliphatic Diazo Compounds.—The esters of the aliphatic amino acids may be diazotized in a manner similar to the primary aromatic amines, a fact discovered by T. Curtius (Ber., 1833, 16, p. 2230). The first aliphatic diazo compound to be isolated was diazoacetic ester, CH·N2·CO2C2H5, which is prepared by the action of potassium nitrite on the ethyl ester of glycocoll hydrochloride, HCl·NH2·CH2·CO2C2H5 + KNO2 = CHN2·CO2C2H5 + KCl + 2H2O. It is a yellowish oil which melts at −24° C.; it boils at 143-144° C., but cannot be distilled safely as it decomposes violently, giving nitrogen and ethyl fumarate. It explodes in contact with concentrated sulphuric acid. On reduction it yields ammonia and glycocoll (aminoacetic acid). When heated with water it forms ethyl hydroxy-acetate; with alcohol it yields ethyl ethoxyacetate. Halogen acids convert it into monohalogen fatty acids, and the halogens themselves convert it into dihalogen fatty acids. It unites with aldehydes to form esters of ketonic acids, and with aniline yields anilido-acetic acid. It forms an addition product with acrylic ester, which on heating loses nitrogen and leaves trimethylene dicarboxylic ester. Concentrated ammonia converts it into diazoacetamide, CHN2·CONH2, which crystallizes in golden yellow plates which melt at 114° C. For other reactions see Hydrazine. The constitution of the diazo fatty esters is inferred from the fact that the two nitrogen atoms, when split off, are replaced by two monovalent elements or groups, thus leading to the formula 
for diazoacetic ester.
Diazosuccinic ester, N2·C(CO2C2H5)2, is similarly prepared by the action of nitrous acid on the hydrochloride of aspartic ester. It is decomposed by boiling water and yields fumaric ester.
Diazomethane, CH2N2, was first obtained in 1894 by H. v. Pechmann (Ber., 1894, 27, p. 1888; 1895, 28, p. 855). It is prepared by the action of aqueous or alcoholic solutions of the caustic alkalis on the nitroso-acidyl derivatives of methylamine (such, for example, as nitrosomethyl urethane, NO·N(CH3)·CO2C2H5, which is formed on passing nitrous fumes into an ethereal solution of methyl urethane). E. Bamberger (Ber., 1895, 28, p. 1682) regards it as the anhydride of iso-diazomethane, CH3·N:N·OH, and has prepared it by a method similar to that used for the preparation of iso-diazobenzene. By the action of bleaching powder on methylamine hydrochloride, there is obtained a volatile liquid (methyldichloramine, CH3·N·Cl2), boiling at 58-60° C., which explodes violently when heated with water, yielding hydrocyanic acid (CH3NCl2 = HCN + 2HCl). Well-dried hydroxylamine hydrochloride is dissolved in methyl alcohol and mixed with sodium methylate; a solution of methyldichloramine in absolute ether is then added and an ethereal solution of diazomethane distils over. Diazomethane is a yellow inodorous gas, very poisonous and corrosive. It may be condensed to a liquid, which boils at about 0° C. It is a powerful methylating agent, reacting with water to form methyl alcohol, and converting acetic acid into methylacetate, hydrochloric acid into methyl chloride, hydrocyanic acid into acetonitrile, and phenol into anisol, nitrogen being eliminated in each case. It is reduced by sodium amalgam (in alcoholic solution) to methylhydrazine, CH3·NH·NH2. It unites directly with acetylene to form pyrazole (H. v. Pechmann, Ber., 1898, 31, p. 2950) and with fumaric methyl ester it forms pyrazolin dicarboxylic ester. (F. G. P.*)See G. T. Morgan, B.A. Rep., 1902; J. Cain, Diazo Compounds, 1908.
DIAZOMATA (Gr. διάζωμα, a girdle), in architecture, the landing places and passages which were carried round the semicircle and separated the upper and lower tiers in a Greek theatre.
DIBDIN, CHARLES (1745–1814), British musician, dramatist, novelist, actor and song-writer, the son of a parish clerk, was born at Southampton on or before the 4th of March 1745, and was the youngest of a family of eighteen. His parents designing him for the church, he was sent to Winchester; but his love of music early diverted his thoughts from the clerical profession. After receiving some instruction from the organist of Winchester cathedral, where he was a chorister from 1756 to 1759, he went to London at the age of fifteen. Here he was placed in a music warehouse in Cheapside, but he soon abandoned this employment to become a singing actor at Covent Garden. On the 21st of May 1762 his first work, an operetta entitled The Shepherd’s Artifice, with words and music by himself, was produced at this theatre. Other works followed, his reputation being firmly established by the music to the play of The Padlock, produced at Drury Lane under Garrick’s management in 1768, the composer himself taking the part of Mungo with conspicuous success. He continued for some years to be connected with Drury Lane, both as composer and as actor, and produced during this period two of his best known works, The Waterman (1774) and The Quaker (1775). A quarrel with Garrick led to the termination of his engagement. In The Comic Mirror he ridiculed prominent contemporary figures through the medium of a puppet show. In 1782 he became joint manager of the Royal circus, afterwards known as the Surrey theatre. In three years he lost this position owing to a quarrel with his partner. His opera Liberty Hall, containing the successful songs “Jock Ratlin,” “The Highmettled Racer,” and “The Bells of Aberdovey,” was produced at Drury Lane theatre on the 8th of February 1785. In 1788 he sailed for the East Indies, but the vessel having put in to Torbay in stress of weather, he changed his mind and returned to London. In a musical variety entertainment called The Oddities, he succeeded in winning marked popularity with a number of songs that included “’Twas in the good ship ‘Rover’,” “Saturday Night at Sea,” “I sailed from the Downs in the ‘Nancy,’” and the immortal “Tom Bowling,” written on the death of his eldest brother, Captain Thomas Dibdin, at whose invitation he had planned his visit to India. A series of monodramatic entertainments which he gave at his theatre, Sans Souci, in Leicester Square, brought his songs, music and recitations more prominently into notice, and permanently established his fame as a lyric poet. It was at these entertainments that he first introduced many of those sea-songs which so powerfully influenced the national spirit. The words breathe the simple loyalty and dauntless courage that are the cardinal virtues of the British sailor, and the music was appropriate and naturally melodious. Their effect in stimulating and ennobling the spirit of the navy during the war with France was so marked as to call for special acknowledgment. In 1803 Dibdin was rewarded by government with a pension of £200 a year, of which he was only for a time deprived under the administration of Lord Grenville. During this period he opened a music shop in the Strand, but the venture was a failure. Dibdin died of paralysis in London on the 25th of July 1814. Besides his Musical Tour through England (1788), his Professional Life, an autobiography published in 1803, a History of the Stage (1795), and several smaller works, he wrote upwards of 1400 songs and about thirty dramatic pieces. He also wrote the following novels:—The Devil (1785); Hannah Hewitt (1792); The Younger Brother (1793). An edition of his songs by G. Hogarth (1843) contains a memoir of his life. His two sons, Charles and Thomas John Dibdin (q.v.), whose works are often confused with those of their father, were also popular dramatists in their day.
DIBDIN, THOMAS FROGNALL (1776–1847), English bibliographer, born at Calcutta in 1776, was the son of Thomas Dibdin, the sailor brother of Charles Dibdin. His father and mother both died on the way home to England in 1780, and Thomas was brought up by a maternal uncle. He was educated at St John’s College, Oxford, and studied for a time at Lincoln’s Inn. After an unsuccessful attempt to obtain practice as a provincial counsel at Worcester, he was ordained a clergyman at the close of 1804, being appointed to a curacy at Kensington. It was not until 1823 that he received the living of Exning in Sussex. Soon afterwards he was appointed by Lord Liverpool to the rectory of St Mary’s, Bryanston Square, which he held until his death on the 18th of November 1847. The first of his numerous bibliographical works was his Introduction to the Knowledge of Editions of the Classics (1802), which brought him under the notice of the third Earl Spencer, to whom he owed much important aid in his bibliographical pursuits. The rich library at Althorp was thrown open to him; he spent much of his time in it, and in 1814–1815 published his Bibliotheca Spenceriana. As the library was not open to the general public, the information given in the Bibliotheca was found very useful, but since its author was unable even to read the characters in which the books he described were written, the work was marred by the errors which more or less characterize all his productions. This fault of inaccuracy however was less obtrusive in his series of playful, discursive works in the form of dialogues on his favourite subject, the first of which, Bibliomania (1809), was republished with large additions in 1811, and was very popular, passing through numerous editions. To the same class belonged the Bibliographical Decameron, a larger work, which appeared in 1817. In 1810 he began the publication of a new and much extended edition of Ames’s Typographical Antiquities. The first volume was a great success, but the publication was checked by the failure of the fourth volume, and was
