Yellow oxide

L. Holmia, for Stockholm). The special absorption bands of holmium were noticed in 1878 by the Swiss chemists Delafontaine and Soret, who announced the existence of an "Element X." Cleve, of Sweden, later independently discovered the element while working on erbia earth. The element is named after cleve s native city. Holmia, the yellow oxide, was prepared by Homberg in 1911. Holmium occurs in gadolinite, monazite, and in other rare-earth minerals. It is commercially obtained from monazite, occurring in that mineral to the extent of about 0.05%. It has been isolated by the reduction of its anhydrous chloride or fluoride with calcium metal. 

Bromates represent a potential fire and explosion hazard if heated, subjected to shock, or acidified. They should not be allowed to contact reactive organic matter, including paper and wood. Industrial quantities are packed in fiber dmms with polyethylene liners or in metal dmms. Laboratory quantities are supphed in glass bottles. For shipment, a yellow oxidizer label is required under DOT regulations. 

The yellow oxides are prepared by precipitating hydrated ferric oxide from a ferrous salt usiag an alkaU, followed by oxidation. The shades obtained range from light lemon yellow to orange, depending on the conditions used for the precipitation and oxidation. Yellow oxides contain about 85% Fe202 and 15% water of hydration. 

Red iron oxides are usually prepared by calcining the yellow oxides to form Fe202- The shade of the ted oxide depends on the characteristics of the original yellow pigment, and the conditions of calciaation and ranges from light to dark red. The product is 96—98.5% Fe202-... 

Inorganic yellow oxide combinations may contain lead, antimony, tin, nickel, or chromium. They are classed as yellows rather than brown, but they are dull compared with the cadmium yellows. 

Mixtures of the red or yellow oxides with sodium-potassium alloy explode violently on impact, the yellow (more finely particulate) oxide giving the more sensitive mixture [1], Mixtures with magnesium or potassium may explode on heating [2],... 

C. Diphenyldiazomethane. In a pressure bottle are placed 19.6 g. (0.1 mole) of benzophenone hydrazone, 22 g. (0.1 mole) of yellow oxide of mercury, and 100 ml. of petroleum ether (b.p. 30-60°). The bottle is closed, wrapped in a wet towel, and shaken mechanically at room temperature for 6 hours. The mixture is then filtered to remove mercury and any benzophenone azine (Note 5), and the filtrate is evaporated to dryness under reduced pressure at room temperature. The crystalline residue of diphenyldiazomethane melts when its temperature reaches that of the room (Note 6), but it is difficult to purify and this product is pure enough for all practical purposes. The material weighs 17.3-18.6 g. (89-96%). The product should be used immediately (Note 7). 

Experiment.—A small quantity of acetamide is dissolved in water, mixed with a little yellow oxide of mercury, and warmed. The oxide goes into solution and the compound formulated above is formed. 

Experiment.—Phenyl isothiocyanate (0-5 c.c.) is heated for some time in a test tube with an equal volume of yellow mercuric oxide. Heating is continued until the isothiocyanate boils. The yellow oxide is converted into black mercuric sulphide and at the same time the extremely pungent odour of jphenyl cyanate is observed its vapour has a powerful lachrymatory effect. 

When heated in air, bismuth burns with a blue flame, giving off clouds of its yellow oxide. Bismuths melting point is 271.40°C, its boiling point is 1,564°C, and its density is 9.807 g/cm. ... 

Samarium is somewhat resistant to oxidation in air but will form a yellow oxide over time. It ignites at the rather low temperature of 150°C. It is an excellent reducing agent, releases hydrogen when immersed in water, and has the capacity to absorb neutrons in nuclear reactors. 

Mercury(ll) oxide exists in two modifications, red and yellow, differing in particle size— finer particles under 5pm appear red, while particle size greater than 8pm appear reddish. The yellow form converts to red oxide on heating, which reverts hack to yellow oxide on cooling. At 400°C, the red oxide becomes black which changes back to red again on cooling. The oxide decomposes at 500°C. 

The yellow oxide reacts with aqueous ammonia to yield a bright yellow crystalline powder, dihydroxymercury(ll)—ammonium hydroxide, known as Millon s base, [(HO-Hg)2NH2]OH [12529-66-7], a photosensitive unstable product. 

The element was discovered in 1843 by Carl Gustav Mosander. He determined that the oxide, known as yttria, was actually a mixture of at least three rare earths which he named as yttria—a colorless oxide, erbia— a yellow oxide, and terbia— a rose-colored earth. Mosander separated these three oxides by fractional precipitation with ammonium hydroxide. Pure terbia was prepared by Urbain in 1905. The element was named terbium for its oxide, terbia, which was named after the Swedish town, Ytterby. 

When Klaproth dissolved some pitchblende in nitric acid and neutralized the acid with potash, he obtained a yellow precipitate which dissolved in excess potash. Klaproth concluded correctly that the mineral must contain a new element, which he named in honor of the new planet, Uranus, which Herschelhad recently discovered (12). He then attempted to obtain metallic uranium just as Hjelm had prepared metallic molybdenum. By strongly heating an oil paste of the yellow oxide in a charcoal crucible, he obtained a black powder with a metallic luster, and thought he had succeeded in isolating metallic uranium (29). For over fifty years the elementary nature of his product was accepted by chemists, but in 1841 Peligot showed that this supposed uranium metal was really an oxide. 

Since the properties of erythronium closely resembled those which Fourcroy had ascribed to the recently discovered metal chromium, del Rio lost confidence in the importance of his discovery and concluded that his supposed new element was, after all, nothing but chromium (11). In a note to his translation of Kars ten s Mineralogical Tables he wrote (7, 9,12) .. . but, knowing that chromium also gives by evaporation red or yellow salts, I believe that the brown lead is a yellow oxide of chromium, combined with excess lead also in the form of the yellow oxide. ... 

Both polonium derivatives are chemically very stable, requiring hot fuming nitric acid for their decomposition. However, they char rapidly under the intense alpha bombardment and attempted analyses with acetyl-acetone labeled with carbon-14 in the 1 and 3 positions were unsuccessful. It is interesting that the corresponding yellow oxide, prepared by treating (VI) with aqueous hydrogen peroxide, reverts to (VI) on treatment with aqueous alkali (12). 

Tha orude solution of prussiate of potassa, and even the prussiate purified by a single crystallization, still contain, as has been stated, more or less carbonate of potassa, so that, besides the prussian blue, there is precipitated at the same time yellow oxide of iron, which deteriorates its tint. To obviate tills inconvenience, the carbonate of potassa is neutralized by sulphuric acid, which may he added cither to the solution of prussiate of potassa or to that of the protosnlphate of iron. In the manufacture of the common Berlin blues, the carbonate of potassa is neutralized by alum thoro results a precipitate of alumina, which mixes intimately with the prussian blue, and greatly augjnente... 

Figure 9. CIELAB color differences between two yellow oxide pigments...

In addition to the tungsten(II) bonde mentioned above, the element forms at least two other borides, W2B and WB2 it forms a similar series of phosphides, W2P, WP, and WP2 as well as W02 (brown oxide), W4On (blue oxide), and WO3 (yellow oxide), and two sulfides, WS2 and WS3. The tungsleu(IV) oxide and sulfide are representative uf the simple Lelravalent compounds, which also include a tetrabromide, WBr4, and tetraiodide, WI4. Like lire drhalides, these tetiahalides undergo hydrolysis quite readily. 

Flavin coenzymes exist in three spectrally distinguishable oxidation states that account in part for their catalytic functions the yellow oxidized form, the red or blue one-electron reduced form, and the colorless two electron re-... 

In the Journal de physique for 1779 the apothecary, Bayen, described a fulminating mercurial preparation of another kind. Thirty parts of precipitated, yellow oxide of mercury, washed and dried, was mixed with 4 or 5 parts of sulfur the mixture exploded with violence when struck with a heavy hammer or when heated on an iron plate. Other mixtures which react explosively when initiated by percussion have been studied more recently,2 metallic sodium or potassium in contact with the oxide or the chloride of silver or of mercury or in contact with chloroform or carbon tetrachloride. 

The functional end of the flavin coenzymes FMN and FAD is the tricyclic isoalloxazine system, with the numbering system shown in structure I, the air-stable, yellow, oxidized form. The other two functionally important redox states are the one-electron-reduced semiquinone, II (pKa = 8.4 for dissociation at N(5)), and the two-electron-reduced, colorless dihydroflavin, III. In the dihydro form N(5), C(4a), C(la), andN(l) form a diaminoethylene system and it was anticipated that nitrogen at the 5 and 1 positions would be key to coenzymatic function. 

It is also possible to monitor in the gas phase such components as ammonia (concentration range of 30-400 mg/m3, color of sample is yellow), oxide sulfur (concentration range of 360-1400 mg/m3, color is blue), hydrogen sulfide (concentration range of20-140 mg/m3, color is violet).3 9... 

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