Page:The American Cyclopædia (1879) Volume XI.djvu/745

 MOLYBDENUM MOMMSEN 727 terminated in favor of the Portuguese. A sys- tem of violence and oppression was maintained for 60 years, when the Dutch with the assis- tance of the natives expelled the Portuguese. The Dutch East India company early in the 17th century obtained supremacy over many of the native princes, and allowed them to re- tain their authority by tribute to the company. To secure the exclusive trade in nutmegs and cloves, the Dutch nearly extirpated the spice trees on all the islands except Amboyna and Banda, which two they reduced entirely under their authority. To keep up prices in foreign markets, they frequently burned whole cargoes of spices. The English were allowed at one time to have a mercantile establishment at Am- boyna, when held by the Dutch ; but the latter in 1622, after forcing some Chinese and Java- nese soldiers by torture to make confession of a plot on the part of the English, seized on the leaders and put them to death with horrible cruelty. In common with the other Dutch East Indian possessions, the Moluccas were held by the British from 1796 to 1802, and from 1810 to 1814. In 1824 some of the more oppres- sive laws were repealed, and the free cultiva- tion of the islands was allowed. The Dutch possessions are divided, in point of administra- tion, into the three residencies of Amboyna, Ternate, and Banda. The seat of the Dutch governor general is at Amboyna. MOLYBDENUM, a metal usually obtained from the native bisulphide (molybdenite). It is also found as a molybdate of lead. , Its symbol is Mo ; atomic weight, 96 ; specific gravity, 8'6. The resemblance of the bisulphide ore to graph- ite gave the metal its name (Gr. poMpdaiva, a piece of lead). It was first distinguished from graphite by Scheele in 1778, but was first ob- tained in the metallic form by Hjelm in 1782. The most complete investigations of its prop- erties and combinations were made by Berze- lius. The metal may be obtained by roasting the native sulphide in a free current of air, by which impure molybdic acid is produced in the form of a gray powder. This is digested in ammonia, the solution filtered and evaporated to dryness, the residue dissolved in nitric acid and again evaporated to dryness, pure molyb- dic acid being left. This being made into a paste with oil and charcoal and heated to white- ness, the oxygen is abstracted and the metal remains. It may also be obtained by passing hydrogen over molybdic acid at a red heat in a porcelain tube. It is a white metal, brittle, and difficult to melt. When heated to white- ness in the air or in oxygen, it forms a crystal- line sublimate of molybdic acid. It is easily oxidized by nitric acid, with evolution of ni- trous acid fumes, and if ignited in a stream of aqueous vapor hydrogen is evolved. Molyb- denum forms alloys with tin, lead, iron, cop- per, silver, gold, and platinum, rendering them less fusible, more brittle, and, except the sil- ver, whiter. It forms three oxides: protox- ide, MoO (or according to Rammelsberg, who doubts the existence of MoO, sesquioxide, Mo 2 3 ) ; the dioxide, Mo0 2 ; and a third, molyb- dic anhydride, MoO 3. The first two possess basic characters, while the last is an active acid. The protoxide (or sesquioxide) is obtained by dissolving molybdic acid in hydrochloric acid, and placing in the solution zinc or one of the metals capable of decomposing water, and afterward treating with excess of ammonia. The dioxide is obtained by heating a mixture of sal ammoniac and molybdate of soda and digesting the residue in caustic potassa. Mo- lybdenum forms with bromine dibromide, tri- bromide, and tetrabromide, and with chlorine and sulphur corresponding salts; and there may also be formed chloro-bromides. The iodine compounds are molybdous and molyb- dic iodides. Molybdic anhydride forms salts with various bases, called molybdates. The molybdate of ammonium is used as a delicate test for phosphoric acid. The solution sus- pected to contain the phosphate is acidulated with nitric acid, and the molybdate is added. If phosphoric acid is present, either free or uncombined, a yellow crystalline precipitate is formed, consisting of molybdic and phosphoric acids in combination with ammonia. Arsenic acid forms a similar compound with ammonic molybdate when the solutions are boiled. A mixture of sulphuric and molybdic acids yields a beautiful purple with pure morphia or its salts. The oxygen salts of molybdenum are not well enough known or of enough impor- tance to require notice here. MOMBAS, Mombaz, or Mombasali, a town on a small island of the same name, in a bay on the coast of Zanzibar, in lat. 4 6' S., Ion. 39 43' E. ; pop. of the island, about 6,000. The isl- and is about 3 m. long and 2 m. wide; the coasts consist of steep cliffs, and the town is defended by an old Portuguese fort. The town is in a ruinous condition, and is inhabited by Arabs and people of mixed race. The bay in which the island is situated is about 5 m. long and 3 m. broad, and forms an excellent harbor. There is very little trade, and the people are exceedingly poor. The Portuguese destroyed the native town in 1505, and again in 1529 ; from which time they held the place till they were driven out by the sultan of Muscat in 1720. In his turn he was expelled by the na- tives, and from 1824 to 1826 the town was un- der British protection ; but they abandoning it, Mombas fell again under the power of Muscat. MOMMSEX, Christian Matthias Theodor, a German historian, born at Garding, Schleswig, Nov. 30, 1817. He studied at Altona and Kiel, was aided by the Berlin academy in his archaeological ex- plorations in France and Italy (1844-'7), and in 1848 was attached to the staff of the ScJiles- wig-Holsteiri'sche Zeitung. For participation in the movements of 1848-'9 he was removed from the chair of jurisprudence at Leipsic, which he had filled for two years. From 1852 to 1854 he was professor at Zurich, from 1854 to 1858 at Breslau, and from that time till