Manganese dioxide

“ The new still-liquor formed in this manner is treated as above, so that the manganese does its work over and over again. There is only a slight mechanical loss, which is reduced in the best managed works to about 2 parts of manganese dioxide to 100 of bleaching-powder. There are also other advantages of this process which explain its wide extension, in spite of the fact that only from 30 to 35 parts of the hydrochloric acid employed is converted into chlorine, the remainder ultimately leaving the factory in the shape of a harmless but useless solution of calcium chloride. ”

“ Solution of manganese in hydrochloric acid, rendered alkaline with ammonia, yields a clear solution, [79] which rapidly takes up oxygen from the air, forming a brown precipitate of the oxide (Mn2O3) . The addition of [Pg 299] bromine or chlorine to such a solution determines the precipitation of a still higher oxide (approximately MnO2) . On treating a compound containing manganese with nitric acid and dioxide of lead (PbO2) , the oxidation is carried still further, a purple-coloured solution of permanganic acid (HMnO4 or H2O.Mn2O7) being formed. ”

“ The possibility of a reaction analogous to that between potassium permanganate and lead dioxide in the presence of strong nitric acid seems to be excluded by the fact that the higher oxides of manganese may be prepared in the presence of concentrated nitric acid. ”

“ The higher grades of oxidation containing Mn2O7 and MnO3 are quite unknown in nature, and even MnO2 is not so widely spread in nature as the ores composed of manganous compounds which are met with nearly everywhere. The most important ore of manganese is its dioxide, or so-called peroxide, MnO2, which is known in mineralogy as pyrolusite. Manganese also occurs as an oxide corresponding with magnetic iron ore, MnO,Mn2O3 = Mn3O4, forming the mineral known as hausmannite. The oxide Mn2O3 also occurs in nature as the anhydrous mineral braunite, and in a hydrated form, Mn2O3,H2O, called manganite. ”

“ Oxygen may be prepared by heating mercuric oxide; by strongly heating manganese dioxide and many other peroxides; by heating the oxides of precious metals; and by heating many oxy-acids and oxy-salts to high temperatures, for example, nitric acid, sulphuric acid, nitre, lead nitrate, zinc sulphate, potassium chlorate, &c. Potassium chlorate is generally used and the reaction is accelerated and carried out at a lower temperature by previously mixing the salt with about one-third of its weight of manganese dioxide, which acts as a catalytic agent. ”

“ Acid neutralized = 38.10 percent.
XI. The flask contained black oxide 150 m.g. potassium permanganate 20 c.c. = 177.71 m.g., N/10 nitric acid 22.39 c.c. (= 2 molecules for each molecule of KMnO4) and was heated four and one half hours in the water bath.
Acid neutralized = 100.00 percent.
No definite conclusions can be drawn from these neutralization experiments since it is well known that manganese oxides prepared as were those used in these experiments always contain some, though probably not a constant quantity of alkali. ”

“ It liberates halogens from the halogen acids, and oxidises manganese salts to permanganates, but does not completely oxidise ferrous or stannous salts, losing instead a part of its oxygen in the gaseous form. The dioxide cannot be obtained in the wet way. ”

“ Whatever doubt there may be as to the action of lead salts, there can be none whatever as to that of manganese compounds. In the first place, manganous oxide is a powerful base, which readily dissolves in oil; manganic oxide is also readily soluble, yielding fatty acid salts of manganese, and causing oxidation of glycerine. Manganese borate and manganese oxalate are both soluble in oil, the former much more readily than the latter, but they are both salts of little stability at high temperatures in contact with oils. They both dissolve by the aid of heat, forming fatty acid salts of manganese. ”

“ The metal may be obtained by the reduction of its sesquioxide by carbon at an extreme heat.
Manganese forms no less than six different oxides--viz., protoxide, sesquioxide the red oxide, the binoxide or peroxide, manganic acid, and permanganic acid. The protoxide occurs as olive-green powder, and is obtained by igniting carbonate of manganese in a current of hydrogen. Its salts are colorless, or of a pale rose color, and have a strong tendency to form double salts with the salts of ammonia. The carbonate forms the mineral known as manganese spar. ”

“ This property has obtained for it the appellation of the soap of glass.
It is from manganese that all the oxygen gas (21) used by chemists is obtained. By the application of a red heat this is yielded in such abundance that an ounce of the oxide of this metal will yield about two quarts of gas. The consumption of manganese has, of late years, become very considerable by the discovery of the oxygenated muriatic acid, which is now extensively used in the bleaching of linen and cotton; that liquor being made by the distillation of the oxide of manganese with spirit of salt (muriatic acid, 29) . ”

“ It should be kept in closely stoppered bottles, under naphtha, like potassium, because with contact of air it speedily gets oxidized, and falls into powder. It decomposes water slowly at common temperatures, and rapidly at a red heat. Pure oxide of manganese can be reduced to the metallic state only in small quantities, by mixing it with lamp black and oil into a dough, and exposing the mixture to the intense heat of a smith’s forge, in a luted crucible; which must be shaken occasionally to favour the agglomeration of the particles into a button. ”

“ This decomposition also proceeds at the common temperature, though much more slowly, and we may therefore say that manganese when dissolved in hydrochloric acid always tends to descend to its lowest, and, considered as a base, strongest degree of oxidation, which is not raised to a higher degree even by chameleon solution. In slightly acid, neutral, or alkaline solutions on the other hand, protoxide of manganese absorbs oxygen with great avidity and forms with it different compounds, according to the means of oxidation employed. ”

“ If, on dissolving the ignited mass, the solution should appear greenish from the formation of alkaline manganates, add a few drops of alcohol to reduce the manganese to insoluble dioxid. The residue of barium, magnesium, and manganese compounds is treated on the filter with hydrochloric acid, and the platinum dish is washed with warm nitric acid (not hydrochloric, for the platinum dish may be attacked by chlorin from the manganese oxid) dissolving any small traces of precipitate that may have been left behind. ”

“ It is the only oxide of manganese that is directly employed in the arts. It is a very plentiful mineral production, and is found in great abundance in some parts of the West of England. The manganese of the shop is prepared by washing, to remove the earthy matter, and grinding in mills. The blackest samples are esteemed the best. It is chiefly used to supply oxygen gas, and in the manufacture of glass and chlorine; in dyeing and to form the salts of manganese. It has been occasionally employed in medicine, chiefly externally in itch and porrigo, made into an ointment with lard. ”

“ Manganous oxide in oxidising gives the red oxide of manganese, Mn5O4. This is the most stable of all the oxides of manganese; it is not only stable at the ordinary but also at a high temperature—that is, it does not absorb or disengage oxygen spontaneously. When ignited, all the higher oxides of manganese pass into it by losing oxygen, and manganous oxide by absorbing oxygen. This oxide does not give any distinct salts, but it dissolves in sulphuric acid, forming a dark red solution, which contains both manganous and manganic (of the oxide, Mn2O3) sulphates. ”

“ Manganese is prepared by mixing one of its oxides in a finely-divided state with oil and soot; the resultant mass is then first ignited in order to decompose the organic matter, and afterwards strongly heated in a charcoal crucible. The manganese thus obtained, however, contains, as a rule, a considerable amount of silicon and other impurities. Its specific gravity varies between 7·2 and 8·0. It has a light grey colour, a feebly metallic lustre, and although it is very hard it can be scratched by a file. It rapidly oxidises in air, being converted into a black oxide ”

“ Such a substance is provided in the use of the black oxide of manganese, which is placed either in a small flask or in a tube provided with two bulbs, and when heated with the lamp it separates the hydrogen from the hydrochloric gas, and forms water, which partly condenses in the second bulb. And now the gas that escapes is no longer acid and fuming with a white smoke on contact with the air; but is green, has a strong odour, bleaches, and is so powerful in its action on all living tissues, that it must be carefully avoided and not inhaled ”

“ But such a solution has a blue or red color. The color is here more brown than red, the reason being that the very finest portions of the manganese, which do not sink so easily, swim in the red solution; for without these fine particles the solution is red, and red mixed with black is brown. The manganese has here attached itself so loosely to acidum salis that the water can precipitate it, and this precipitate behaves like ordinary manganese. When, now, the mixture of manganese and spiritus salis was set to digest, there arose an effervescence and smell of aqua regis. ”

“ Manganous Carbonate, MnCO3, found native as manganese spar, may be prepared as an amorphous powder by heating manganese chloride with sodium carbonate in a sealed tube to 150° C., or in the hydrated form as a white flocculent precipitate by adding sodium carbonate to a manganous salt. In the moist condition it rapidly turns brown on exposure to air. ”

“ Nature, however, is prodigal in her creation, and hence we have but to pursue our search diligently to find a substance or mineral containing an abundance of oxygen, and part of which it will relinquish by what used to be called by the "old alchemists" the torture of heat. Such a mineral is the black oxide of manganese, or more correctly the binoxide of manganese, which consists of one combining proportion of the metal manganese—viz., 27.6, and two of oxygen—viz., 8 × 2 = 16. ”

“ As a general rule the manganese acts best when applied as a top dressing rather than when added together with the manure. Further the stimulating action differs greatly with the nature and reaction of the manurial mixture. Uchiyama concludes that 20–50 kgm. per hectare of crystallised manganese sulphate is a good general amount to apply.
Takeuchi (1909) corroborates the statements of the various writers that plants differ in their response to the manganese manuring. ”

“ If we dissolve black oxide of manganese, permanganate of potash, or any other compound of manganese of a higher degree of oxidation than the protoxide in hydrochloric acid, we obtain, as is well known, a dark colored solution of perchloride of manganese, which, when heated to boiling loses color pretty rapidly, chlorine being given off, until finally only protochloride remains. ”

“ Theoretically the action is very attractive, as the oxygen liberated by their decomposition oxidizes some of the organic matter of the water, thereby purifying it in part, while the manganese is precipitated as a flocculent precipitate having all of the advantages pertaining to a precipitate of hydrate of alumina, and without the disadvantage of adding acid to the water, as is the case with the compounds of alumina and iron. ”

“ It is a hard black solid which readily loses oxygen when strongly heated, leaving a residue of Mn3O4. When heated with concentrated hydrochloric acid it yields chlorine, and with concentrated sulphuric acid it yields oxygen. It is reduced to the monoxide when heated in a current of hydrogen. It is a strong oxidizing agent. ”

“ If you have an iron bottle, the first mode is by far the cheapest, as the heat of a bright fire is sufficient for the operation, and a large quantity of gas is obtained in a short time from a very inexpensive material. The most rapid and convenient process of all is to heat a mixture of two parts chlorate of potash, and one of powdered black oxide of manganese, in a common clean oil flask, to which a cork and bent tube has been adapted. Care must be taken not to mistake sulphide of antimony for black oxide of manganese, as very serious accidents have arisen from this cause. ”

“ The precipitate of manganese is dissolved either in water to which 0.5 per cent. of hydrochloric acid has been added, or in boiling nitric acid. When manganese occurs along with iron, which in general is the case, we must take care that the iron in the solution is in the state of peroxide, which is precipitated on the addition of the bicarbonate of soda, and is allowed to remain as a precipitate, because it does not affect the titration injuriously. ”

“ Richard Phillips has made some observations in the Philosophical Magazine and Annals of Philosophy for April last, to which I am desirous of briefly adverting. He says, “Mr. M’Mullen having observed, when sulphuric acid is added to peroxide of manganese, that chlorine is evolved, he conceived it might be derived from an admixture of muriate of manganese, iron, or copper; but having washed some of the peroxide of manganese with water, he did not find that any chloride of silver was precipitable from it; he, therefore, concluded that the peroxide in question contained no muriatic salt.” ”