Magnesium oxide

“ These three metals give, like magnesium, oxides RO, which form feebly energetic bases, and like magnesium they are volatile. The volatility increases with the atomic weight. Magnesium can be distilled at a white heat, zinc at a temperature of about 930°, cadmium about 770°, and mercury about 351°. Their oxides, RO, are more easily reducible than magnesia, and mercuric oxide is the most easily reducible. The properties of their salts RX2 are very similar to the properties of MgX2. ”

“ Whether it is desirable that it should heat through readily or slowly (coefficient of thermal conductivity) depends on whether it is wanted as a crucible or as a furnace lining. Lime (calcium oxide) fuses only at the highest heat of the electric furnace, but it breaks down into dust. Magnesia (magnesium oxide) is better and is most extensively employed. For every ton of steel produced five pounds of magnesite is needed. Formerly we imported 90 per cent. of our supply from Austria, but now we get it from California and Washington. In 1913 the American production of magnesite was only 9600 tons. ”

“ The stronger the solution administered, the greater is the quantity of water that passes into the bowel, a fact to be borne in mind when the salt is administered for the purpose of draining superfluous fluid from the system, as in dropsy. The oxide and carbonate of magnesium are also invaluable as antidotes, since they form insoluble compounds with oxalic acid and salts of mercury, arsenic, and copper. ”

“ Asbestos—a magnesium silicate—gives as chief product magnesium silicide; the other substances formed being silicon, silicon dioxide and a little magnesium oxide.
Such are the astounding changes wrought by simple heat upon those substances which we are accustomed to regard as infusible. It must be remembered that the range of temperature which chemists employ in ordinary laboratory work is not very great and that the conditions of work in the laboratory and of nature’s work on the earth’s surface at the present day favor the formation of two classes of compounds—the oxides and their hydrates. ”

“ The effect of the heat on single substances is very interesting. Refractory metals, such as iron, manganese, uranium, platinum, melt rapidly and then become gaseous; the most refractory non-metallic elements, silicon, boron, carbon, are also changed into the gaseous form. Very refractory compounds are broken down into simpler ones. Magnesium pyrophosphate yields phosphorus, magnesium oxide and oxygen. ”

“ Magnesium is now produced in great abundance, and is very inexpensive. It is a metal endowed with a great affinity for oxygen, and it is only necessary to thrust it into the flame of a candle to produce combustion; it burns with a brightness that the eye can scarcely tolerate, and is transformed [Pg 321] into a white powder—oxide of magnesium, or magnesia. Combustion is still more active in oxygen, and powder of magnesium placed in a jar filled with this gas produces a perfect shower of fire of very beautiful effect. ”

“ In colour and lustre it resembles silver, but in chemical properties is more like zinc; its sp. gr. is only 1·743; it is malleable; fusible at a red heat, and can be distilled like zinc; unaffected by dry air and by cold water; burns with brilliancy when heated to dull redness in air or oxygen gas, yielding oxide of magnesium; inflames spontaneously in chlorine, yielding chloride of magnesium; it dissolves in the acids with the evolution of hydrogen gas, and pure salts of magnesium result. ”

“ Silver chloride and iodide approach the condition of equality, and are not decomposed by heat. The most stable oxides under the action of heat are those of magnesium, calcium, silicon, and aluminium, since they also approach the condition of equality. For the same reason hydriodic acid decomposes with greater facility than hydrochloric acid. Chlorine does not act on magnesia or alumina, but it acts on lime and silver oxide, &c. ”

“ At first lead-lined tanks were used, but later it was found that tanks [Pg 141] made of iron could be substituted. In order to take care of the small amount of hydrobromic acid, which is slowly formed, a small amount of magnesium oxide was added to the material. The amount of the oxide used was approximately in the proportion of 1 part to 1000 parts of ketone. When the magnesium oxide was used, it was found that the bromoketone kept without appreciable decomposition for about 2 months. The yield of the product from 580 kg. of acetone (10 kg.-mol. wts.) was 1,100 kg. The yield from 720 kg. ”

“ Magnesium, although it does form such a compound, does so with great difficulty.
[3] For the solution of one part of the oxide 55,400 parts of water are required. Nevertheless, even in such a weak solution, zinc oxide (hydroxide, ZnH2O2) changes the colour of red litmus paper. ”

“ It is now made by electrolysis, but instead of using as the electrolyte the melted anhydrous chloride, which is difficult to obtain, the natural mineral carnallite is used. This is melted in an iron pot which also serves as the cathode in the electrolysis. A rod of carbon dipping into the melted salt serves as the anode. The apparatus is very similar to the one employed in the preparation of sodium.
Properties. Magnesium is a rather tough silvery-white metal of small density. Air does not act rapidly upon it, but a thin film of oxide forms upon its surface, dimming its bright luster. ”

“ Magnesium is a very light metal, its specific gravity being only 1·743; that is, it is only one and three-quarter times heavier than water. When heated in the air it takes fire, and is rapidly converted into the oxide, magnesia. In the form of wire or of narrow ribbon, it burns easily in the air, producing a light of dazzling brilliancy, which among artificial modes of illumination is rivalled only by the electric light. ”

“ Reduction of the oxide with magnesium is never complete, and the carbon method gives only a mixture of carbide and metal. Electrolytic methods give no better results, since the metal liberated at the cathode always encloses oxide and other impurities. Moissan and Hönigschmid in 1906, by heating the carefully purified [254] anhydrous chloride with sodium in a sealed glass tube from which air and moisture had been removed, claim to have obtained a product containing only 3 per cent. ”

“ Among the oxygen compounds the saline oxides which are capable of forming salts either through the function of a base or through the function of an acid anhydride attract the greatest interest in every respect. Certain elements, like calcium and magnesium, only give one saline oxide—for example, MgO, corresponding with the type MgX2. ”

“ The hydroxide is thrown down from solutions by addition of alkali, alkali carbonate, alkali cyanide, or ammonium sulphide, as a black precipitate. It cannot be transformed to the corresponding oxide by drying, since it attacks the water with evolution of hydrogen, forming the dioxide. The monoxide, TiO, has probably never been obtained in the pure state; it is formed by reduction of the dioxide with zinc or magnesium. ”

“ In these metals and in the succeeding groups there is a pronounced tendency towards a diminution of resistance by the action of electric radiation. Magnesium being easily oxidisable, there is a thin coating of oxide on the surface. When this is scraped, the metal makes a very highly sensitive receiver. The adjustment is not difficult, the metal allowing a considerable latitude of pressure and E. M. F. It has already been stated that the metals which are slightly tarnished can be more easily adjusted. ”

“ Dissolve the precipitate off the filter with dilute ammonia, and run the solution into the original beaker. Run in from a burette, slowly and with stirring, "magnesia mixture," using about 15 c.c. for each 0.1 gram of phosphoric oxide. Allow to stand for one hour. The white crystalline precipitate contains the phosphorus as ammonium-magnesium phosphate.
Phosphate of lead is decomposed by sulphuric acid; the lead is converted into the insoluble lead sulphate, and the phosphoric acid is dissolved. Phosphate of copper and phosphate of iron may be treated with sulphuretted hydrogen ”

“ However, the hydroxides RH2O2 of calcium and magnesium are in no respect so energetic as the hydroxides of the true metals of the alkalis; thus when heated they lose water, are not so soluble, develop less heat with acids, and form various salts, which are less stable and more easily decomposed by heat than the corresponding salts of sodium and potassium. Thus calcium and magnesium carbonates easily part with carbonic anhydride when ignited; the nitrates are also very easily decomposed by heat, calcium and magnesium oxides, CaO and MgO, being left behind. ”

“ Five grams of the substance are taken, and the baryta they contain converted into carbonate (if necessary) . The carbonate is dissolved in dilute hydrochloric acid. Ten grams of sodium acetate are added, and the solution, diluted to 500 c.c., is boiled, and titrated in the manner described. [Pg 328]
Lead salts must be absent in the titration, and so must strontia and lime. Ferrous salts should be peroxidised by means of permanganate or chlorate of potash. Other salts do not interfere.
MAGNESIA.
Magnesia, the oxide of magnesium (MgO) occurs in nature in the rare mineral periclase (MgO) ”

“ The other method by which nitrogen may be absorbed on a considerable scale is by the aid of magnesium. The metal in the form of thin turnings is charged into hard glass or iron tubes heated to a full red in a combustion furnace. Into this air, previously deprived of oxygen by red-hot copper and thoroughly dried, is led in a continuous stream. At this temperature the nitrogen combines with the magnesium, and thus the argon is concentrated. A still more potent absorption is afforded by calcium prepared in situ by heating a mixture of magnesium dust with thoroughly dehydrated quick-lime. ”

“ In a 0.1 molar solution of magnesium sulphate, which is ionized to the extent of 37.3%, the concentration of magnesium-ion is 0.0373, and it would require a concentration greater than 2E−5 of hydroxide-ion to precipitate any magnesium hydroxide.349 Now, the concentration of the hydroxide-ion, in an ammoniacal solution, can easily be reduced far below this value by the addition of ammonium chloride, nitrate, sulphate or other readily ionizable ammonium salt to the solution, and then magnesium hydroxide will not be precipitated. ”

“ Commercial sources of magnesium raw material are widespread throughout the world and are so large that a tenfold increase in world demand would have little long run effect on avail ability or price.
About 90 percent of the magnesium consumed in the United States is in the nonmetallic form, mostly in high temperature refractories, pharmaceuticals, and in oxychloride and oxysulfate cements. Principal uses for the metal include the production of aluminum alloys and ductile iron, as a reducing agent for titanium and other metals, and for cathodic protection devices. ”

“ Such a solution, however, has an alkaline reaction, and gives, with a salt of phosphoric acid, a precipitate of magnesium phosphate, which is still more insoluble. Magnesia is not only dissolved by acids, forming salts, but it also displaces certain other bases—for example, ammonia from ammonium salts when boiled; and the hydroxide also absorbs carbonic anhydride from the air. The magnesium salts, like those of calcium, potassium, and sodium, are colourless if they are formed from colourless acids. Those which are soluble have a bitter taste, whence magnesia has been termed bitter-earth. ”

“ The carbon anode passes through the cover of a porcelain cylinder, open at the bottom, and provided with a side-tube at the top to remove the chlorine formed during electrolysis. The operation is conducted at a dull red heat (about 760° C. or 1400° F.) , the current density being about 0.64 amperes per sq. in. of cathode surface, and the pressure about 7 volts. The fusing-point of the metal is about 730° C. (1350° F.) , and the magnesium is therefore reduced in the form of melted globules which gradually accumulate. ”

“ The magnesium is coated with hot wax or paraffin, which not only acts as a binder for the mixture when it is pressed into its container but also serves to prevent oxidation of the magnesium when the shells are stored. The barium and potassium nitrates supply the oxygen to the magnesium, which burns with a brilliant white flame. The potassium nitrate takes fire more readily than the barium nitrate, but it is more expensive than the latter. ”

“ 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. ”

“ The second method for the separation of argon is based on the fact that red-hot magnesium unites with nitrogen, forming a nonvolatile compound. Air from which moisture and carbon dioxide have been removed is freed from oxygen by passing it over heated copper, and then from nitrogen by means of magnesium turnings at a red heat. The removal of the last portions of nitrogen is a tedious operation, requiring some two days. The residual gas is pure argon. ”