Molybdic anhydride

Chemical Designations - Synonyms Molybdenum trioxide Molybdic anhydride Chemical Formula M0O3... 

Synonyms molybdenum trioxide molybdic acid anhydride molybdic anhydride molybdic oxide... 

Preparation of Potassium Hexachloromolybdate(III). Perform the experiment in a fume cupboard ) Dissolve 50 g of molybdic anhydride in 250 ml of concentrated hydrochloric acid. Spill the molyb-denum(Vl) oxide into the beaker in small portions as it dissolves during 6 hours. If the solution is turbid, filter it through a glass filter (prepare the solution beforehand). 

Phosphoric Add. Quantitative Determination, As de tailed under (Add) Molybdic Anhydride, below. 

Alkalies. — On heating 1 gm. of molybdic anhydride in a test tube, the particles adhering to the heated portion begin to fuse at a red heat, while at the upper, cooler portion of the tube a crystalline formation of sublimed anhydride may be observed. If the molybdic anhydride is contaminated with salts of the alkalies, the whole melts to a dark-colored mass. In such case the melting-point is low. 

Ammonium Salts. — On boiling 1 gm. of molybdic anhydride with sodium hydroxide solution, there must be no liberation of ammonia (to be ascertained by means of moistened litmus paper). 

Solubility in Ammonia Water Heavy Metals. — 2 gm. of molybdic anhydride, when gently heated with a mixture of 10 cc. of water and 5 cc. of ammonia water (sp. gr. 0.91), should entirely dissolve, yielding a clear solution. The solution acquires a slight yellow color on adding hydrogen sulphide water. This color must not change within ten minutes nor should a precipitate form. 

Nitric Acid. — Shake 1 gm. of molybdic anhydride with 10 cc. of water, and add a small crystal of sodium chloride, followed by one drop of a 1 1000 solution of indigo the blue color of the solution must not disappear on adding 10 cc. of concentrated sulphuric acid. 

Large, colorless, or slightly greenish crystals, soluble in water, which, when heated, liberate ammonia and water, leaving molybdic anhydride. 

Quantitative Determination. — The content of molybdic anhydride may be approximately determined by gently igniting about 1 gm. of the salt until the ammoniacal odor has disappeared, and then weighing the residue of inolybdic anhydride it should amount to about 81 per cent. The accurate determination is carried out in the manner described under Acid Molybdic Anhydride, on page 19. 

Urea (27 g), tetramethylurea (TMU, 0.8 g), copper powder (2.13 g), 19.95 g phthalic anhydride, 0.105 g molybdic anhydride, and trichlorobenzene (mixture of isomers, 72 g) were introduced in the above order into the reactor. The reaction mixture was heated from 20 to 170°C in 90 min with stirring and then kept at 170°C for 5 hr. The volatile portion was distilled off (at... 

SYNS MOLYBDENUM(VI) OXIDE MOLYBDIC ANHYDRIDE MOLYBDIC TRIOXIDE... 

Chlormolybdic" Acids.—The compound MoOCl2(OH)2, molybdenum hydroxychloride or dichlormolybdic add, is readily obtained by passing hydrogen chloride over any heated oxygenated compound of molybdenum. Fine white unstable needles are obtained, the aqueous solution of which deposits on evaporation amorphous molybdic anhydride. The substance is also soluble in ether, with which it forms a crystalline compound. An alternative method of preparation of dichlormolybdic acid consists in cooling a solution of molybdic acid saturated with hydrochloric acid. ... 

From wulfenite, molybdenum trioxide is prepared by digesting the mineral (previously washed with dilute hydrochloric acid) with concentrated hydrochloric acid lead still remaining in solution after cooling and filtration is removed by the addition of sulphuric acid, and the filtrate is evaporated to dryness with the addition of a small quantity of nitric acid. The ammonia extract of this mass is then subjected to the method of purification previously described. Another method consists in decomposing the finely powdered mineral by means of concentrated sulphuric acid, diluting to precipitate lead sulphate, and evaporating the filtrate until precipitation of molybdic anhydride occurs. ... 

Molybdic anhydride is a white powder which, on heating, becomes yellow. It melts at 795° C. without decomposition, yielding a reddish-brown liquid, which solidifies on cooling to a yellowish-white fibrous crystalline mass, of density 4-696 at 26° C. It sublimes fairly readily in air, rhombic crystals, colourless and transparent, though small, being obtained. Like the dioxide, it is more strongly magnetic than the metal. 

Molybdic anhydride, if unfused, is soluble in acids mth the production of a number of complex acids if i3re dously fused it is, however, insoluble in acids though still soluble in alkalies, yielding the corresponding molybdates. 

If a solution of a molybdate be treated in acid solution with hydrogen peroxide, oxidation to permolybdic acid takes place, the solution becoming yellowA The colour remains on warming,- and cannot be extracted by ether. Moreover, when molybdic anhydride, M0O3, is dissolved in hydrogen peroxide, a yellow insoluble compound is deposited from the stable, dark yellow solution. ... 

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