Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/505

Rh M A N M A N 481 From the purple liquid crystals of permanganate are easily obtained by evaporation. The crystals (long prisms) are isomorphous with perchlorate of potash, KC1O 4. They are soluble in. 16 parts of cold and far less of hot water. They are almost black, and endowed with a peculiar greenish or bluish metallic lustre. Their powder is red. Their aqueous solution is most intensely purple, one milligramme of the salt giving a perceptible colour to a whole litre and more of water. On addition of acid the solution, through libera tion of Mn 2 O 7, becomes pink. Of all wet-way reagents, manganates and permanganates are the most powerful oxidizing agents, especially when they are employed in conjunction with free alkali, or (the permanganates) along with free mineral acid. By one or the other of the two combinations most oxidizable inorganic and almost all organic substances are promptly oxidized. Hence both manganates and permanganates are extensively employed as disinfectants, and, in chemical laboratories, as oxidizing agents. For the former purpose impure forms of the soda salts are generally used, while pure per manganate of potash, nowadays, is exclusively employed for scientific or analytical laboratory work. The ultimate fate of the reagent depends on whether alkali or acid was used as an auxiliary agent. In the former case the salt passes successively into (green) manganate and (insoluble brown) hydrated binoxide of manganese, three-sevenths of the oxygen in the Mn 2 7 being utilized. In the presence of free acid (sulphuric works best) the Mn 2 7 loses five-sevenths of its oxygen with formation of a colourless solution of manganous (MnO) salt. Hence, supposing such a change to take place promptly, and the reagent to be added gradually, the exact point of completed oxidation is reached when the liquid, by the addition of another drop of the permanganate, assumes a permanent pink colour. This is the principle of a num ber of processes for the determination of certain reducing agents by means of a standard solution of permanganate. Analysis. A manganiferous substance when fused up with car bonate of soda on platinum in the presence of air yields a green mass (manganate), the colour being more distinct after cooling. Manganese oxides, when fused up with a borax bead in the oxidizing flame, impart to it an intense amethyst colour, which disappears in the reducing flame. To detect manganese in a solution of mineral salts, we first eliminate what can be precipitated by sulphuretted hydrogen in the presence of mineral acid. In the filtrate the iron (if present) is oxidized by boiling with a grannie of chlorate of potash, and the ferric oxide precipitated along with the alumina by addition of sal-ammoniac and excess of ammonia, and boiling off the free volatile alkali. From the filtrate the manganese is pre cipitated by sulphide of ammonium, as a sulphide which, when pure, exhibits a delicate flesh-red colour but is readily discoloured, by oxidation, when in contact with air. Cobalt, nickel, and zinc, if present, go down with the manganese, but can be eliminated by treatment of the washed sulphides with acetic acid, which dissolves the manganese only. (W. D.) MANGEL WUEZEL. See AGRICULTURE, vol. i. p. 368. MANGO. The mango-tree (Mangifera indica, L., natural order Anacardiacese, or Terebinthacese) is a native of tropical Asia, but during the last hundred years has been exten sively cultivated in the tropical and subtropical regions of the New as well as the Old World. It grows rapidly to a height of 30 to 40 feet, and its dense, spreading, and glossy foliage would secure its cultivation for the sake of its shade and beauty alone. Its fruit, a drupe, though in the wild variety (not to be confused with that of Spondias mangifera, Pers., belonging to the same order, also called wild mango in India) stringy and sour from its containing much gallic acid, and with a disagreeable flavour of turpentine, has become sweet and luscious through culture and selection, to which we owe many varieties, differing not only in flavour but also in size, from that of a plum to that of an apple. When unripe, they are used to make pickles, tarts, and preserves ; ripe, they form a wholesome and very agreeable dessert. In times of scarcity, the kernels also are eaten. Not only the flesh and kernel of the fruit, but also the bark and resin are of some medicinal value; and the timber, although soft and liable to decay, serves for common purposes, and, mixed with sandal wood, is employed in cremation by the Hindus. It is usually propagated by grafts, or by layering or inarching, rather than by seed. See Drury s Useful Plants of India. MANGOSTEEN, Garcinia Mangostana, L., is a tree belonging to the gamboge order (Clusiacex or Guttiferee), It is a native of the Molucca Islands, but has been intro duced into the other islands of the eastern archipelago, Ceylon, and southern Asia, and even the Antilles, though not without difficulty. It grows about 20 feet high, and is somewhat fir-like in general form, but the leaves are large, oval, entire, coriaceous, and glistening. Its fruit, the much-valued mangosteen, is about the size and shape of an orange, and is somewhat similarly partitioned, but is of a reddish-brown to chestnut colour. Its thick rind yields a very astringent juice, rich in tannin, and containing a gamboge-like resin. The soft and juicy pulp is snow-white or rose-coloured, and of exceedingly delicious and subtle flavour and perfume. Being perfectly wholesome, it may be eaten freely, and administered in fever. G. purpurea is known in India as mate mangosteen, and Embryopteris glutinifera, an ebenaceous tree, as wild mangosteen. See Drury s Useful Plants of India. MANGROVE. The remarkable &quot;mangrove forests&quot; which fringe tidal estuaries, overrun salt marshes, and line muddy coasts in the tropics of both Old and New Worlds, are composed of trees and shrubs belonging to the Ithizo- phoracese, a small order of calycifloral exogens, mixed, however, with the &quot; white mangrove,&quot; Avicennia, a ver- benaceous plant. Their trunks and branches constantly emit adventitious roots, which, descending in arched fashion, strike at some distance from the parent stem, and send up new trunks, the forest thus spreading like a banyan grove. The roots and stems .afford lodgment and shelter to innumer able bivalves, crabs, and other marine animals, while the branches are inhabited by aquatic birds. A further advantage in dispersal, very characteristic of the order, is afforded by the seeds, which have a striking peculiarity of germination. While the fruit is still attached to the parent branch, the long radicle emerges from the seed and descends rapidly towards the mud, where it may even establish itself before falling off. Owing to its clubbed shape, this is always in the right position, the plumule then making its appearance. The wood of some species is hard and durable, and the astringent bark is employed in tanning. The fruit of the common mangrove, Rhizophora Mangle, L., is sweet and wholesome, and yields a light wine. See Treasury of Botany, and Lindley s Vegetable Kingdom. MANICHJEISM. At the close of the 3d century three great religious systems stood opposed to one another in western Asia and the south of Europe ; these were Neo- Platonism, Catholicism, and Manichaeism. All three may be described as the final results reached, after a history of more than a thousand years, by the religious development of the civilized nations stretching from Persia to Italy. Each had put off the national and particular character of the ancient religions, and had become a world-religion, with universalizing tendencies, and with demands which in their effect transformed the whole of human life, both public and private. The place of national worship was taken by a system which not only aimed at being a philosophy of God, the world, and history, but at the same time embraced a definite code of ethics and a religious ritual. In point of form, then, the three religions were like each other, as they also were in this, that each had appropriated elements of older and widely different religions. Their mutual resem blance becomes still further apparent when we observe that in all three the ideas of revelation, redemption, ascetic virtue, and immortality come into the foreground. Neo- Platonism, however, was the spiritualized religion of nature, XV. 6 1