Manganese.

This is a brittle, greyish white, brilliant metal, somewhat resembling iron in its external aspect, of a granular texture, and not possessing ductility or malleability. It has not been discovered native in its metallic state1, but its ores are found in most of the countries of Europe, both in primitive and transition mountains. It has neither odour nor taste; is softer than cast iron, and is not magnetic. Its specific gravity is 8.013.2 It rapidly attracts oxygen from the air, loses its lustre, and progressively becomes violet, brown, and ultimately black. It rapidly decomposes water. It is very abundantly found in the state of the grey oxide. Manganese in-the ore, both in primitive and transition mountains, is found

Of these species the first only has been introduced into the list of materia medica.

Officinal. Manganesii Binoxydum, Lond. Manganesii oxy-dum3, Dub. Manganese, or more properly, Binoxide of Manganese.

Syn. Manganese (F.), Braunstein ( G.), Manganese (I. S.).

Under the name of black or binoxide of manganese are implied all the varieties of the first species. It was discovered in England by Boyle, in the beginning of the 17th century, but was regarded as a modification of iron ore, till the separate experiments of Scheele and Bergman, published in 1774, proved it to be an oxide of a peculiar metal; which Gahn afterwards succeeded in obtaining in its metallic state, and to which he gave the name of Manganesium. It is found in Great Britain, Germany, Switzerland, the north of Italy, and France.

1 La Perouse suspected that he had found manganese in a metallic state; but his opinion was not confirmed.

2 John, vide Gehlen's Journ. iii. p. 460.

3 This term is improperly used by the Dublin College : for although the black oxide was originally named oxide of manganese, and is still so named in commerce; yet, in a professedly scientific work, more accuracy of nomenclature is required. It ought to be Binoxydum.

The greater part of the binoxide of manganese used in England is obtained near Exeter in Devonshire, in Cornwall, and at Howth, near Dublin. The best is furnished by Upton mine, near Exeter. Good binoxide of manganese has lately been procured in Scotland. It occurs crystallized and amorphous; and is generally in combination with small portions of oxide of iron, carbonate of lime, silex, and barytes.

Qualities.-Binoxide of manganese differs in its external characters. It is seldom pure, being mixed with oxide of iron, carbonate of lime, and siliceous and aluminous earths. Its usual colour varies from iron-grey to black; when crystallized it is shining, but when amorphous devoid of lustre. It generally occurs massive; but sometimes its texture is radiated, or foliated, or in minute prisms grouped together. None of the varieties are very hard; all of them are brittle, and several of them soil the fingers. Their specific gravity varies from 3.5 to 4.7. One hundred parts of the binoxide consists of 71.23 of metallic manganese, and 28.67 of oxygen. Exposed to the heat of ignition, all the varieties afford oxygen gas; and, when mixed in powder with sulphuric acid, they afford it at a boiling temperature. It converts hydrochloric acid into chlorine1; the hydrogen of the hydrochloric acid is attracted by the oxygen of the binoxide of manganese, forming water, whilst the chlorine of the acid is evolved.

It consists of 1 proportion of manganese = 27.7 + 2 proportions of oxygen = 16, making the equivalent = 43.7-Mn. + 20.

Medical properties and uses.-This oxide is only used for procuring oxygen and chlorine gas; and for fumigation in cases of infection. To procure oxygen gas, a portion of the oxide, broken into small pieces, is put into an iron retort (a), fitted with a long curved tube (b), the extremity of which being placed under an inverted jar filled with water in a pneumatic trough, the retort is put into a common fire, and exposed to a full red heat. The caloric at this high temperature weakens the affinity between the manganese and the oxygen, with which it is united, and causing it to assume a gaseous state, the oxygen gas is transmitted through

1 The greatest consumption of Binoxide of manganese is for the formation of chlorine, as employed in the art of bleaching.

11 2 the water, and collected in the jar, leaving oxide of manganese in the retort. From the necessity of oxygen for carrying on the process of animal respiration, much benefit was expected from the breathing oxygen gas in disease; but experience has not confirmed the high expectations which were formed of its powers. It certainly increases the force and velocity of the pulse; and has been exhibited with seeming advantage in asthma, chlorosis, scrofula, typhoid fevers, and other diseases of debility. Diluted with from ten to twenty parts of atmospheric air, one or two quarts of it may be breathed at intervals in the course of the day.

But a more certain benefit is obtained from the use of this oxide of manganese in fumigations. Medicine is indebted to Morveau for the discovery of this mode of destroying infection; and the numerous instances in which it has proved beneficial have fully established its use. For a fumigation the following ingredients are required: dried common salt 50 parts, or ivss., oxide of manganese in powder 44 parts, or iij., sulphuric acid xij., and water vj.: the water and acid must be previously mixed together, and then, after the mixture is cold, poured over the other ingredients in a China or porcelain basin. The doors and windows of the room which is to be fumigated must be closely shut for two hours after the charged basin has been placed in it; then thrown open, and a current of air allowed to pass through the room. Chlorine is extricated by this process, and neutralizes the infectious and contagious matter floating in the atmosphere and attached to the walls and floors of the infected rooms. All metallic furniture should be previously removed. Chlorine, largely diluted, is now also employed in phthisis and asthma, inhaled into the lungs.

Officinal preparation.-Aqua Chlorini, D.