Mercuric oxide decomposition

Red mercuric oxide generally is prepared in one of two ways by the heat-induced decomposition of mercuric nitrate or by hot precipitation. Both methods require careful control of reaction conditions. In the calcination method, mercury and an equivalent of hot, concentrated nitric acid react to form... 

Although red mercuric oxide usually vigorously decomposes hydrogen peroxide, the presence of traces of nitric acid inhibits decomposition and promotes formation of red mercury(II) peroxide. This explodes on impact or friction, even when wet, if the mercury oxide was finely divided. 

The photosensitized decomposition of C02 at 1849 A produces CO and a solid containing mercuric oxide and oxalates of mercury68. Oxalate formation is believed to result from dimerization on the vessel walls of a complex formed between C02 and Hg 6(1P1) atoms. 

The unconventional 3-diazoindoles were prepared by oxidative conversion of hydrazones and oximes. Thus, l-methyl-3-diazo-2-oxindole (21d) was prepared by mercuric oxide oxidation of l-methylisatin-3-hydrazone 297 (X = NNH2) in benzene at room temperature (1891JPR551) (Scheme 91). It can also be prepared by decomposition of l-methylisatin-3-tosyl-hydrazone 297 (X = NNHTs) with aqueous sodium hydroxide in a two-... 

The modern science of chemistry began during the eighteenth century, when several brilliant natural philosophers classified the products of decomposition into a small number of fundamental substances. For example, in 1774, the Englishman Joseph Priestley discovered that when the red powder mercuric oxide was heated, it decomposed to liquid metal mercury and to a colorless gas capable of supporting combustion. (This gas... 

To a vigorously stirred suspension of 40 gm (0.138 mole) of mercuric oxide in 100 ml of water is added slowly 15 gm (0.134 mole) of A-ethyl-A -isobutyl-hydrazine. After the addition has been completed, stirring is continued for an additional hr at room temperature. The mercury and mercury oxides are then removed by filtration. The precipitate is washed with ether and the aqueous phase is extracted with ether. The ether solutions are combined and dried with anhydrous magnesium sulfate. Then the ether is distilled off. The residue is distilled at 105°-107°C (741 mm Hg) yield 5.8 gm (40%). On redistillation, an appreciable quantity of a high-boiling residue is left behind, possibly because of thermal decomposition. 

A. J. Balard,9 in 1821, also prepared hypobromous acid in a similar manner, namely, by the gradual addition of mercuric oxide of bromine water, and thoroughly shaking the mixture after each addition. Further, quantities of bromine and mercuric oxide can be added until the yellow fluid contains between 6 and 7 parts of HOBr per 100 c.c. The mercuric oxide can be replaced by silver oxide, silver or mercuric nitrate, mercuric acetate, etc. The soln. with 6-7 parts of HOBr per 100 c.c. decomposes at 30°, but more dil. soln. when distilled under ordinary atm. press, give a distillate of bromine followed by a straw-yellow fraction which is a dil. aq. soln. of hypobromous acid. The decomposition is not so pronounced if it be conducted at 40° under a press, of, say, 50 mm. of mercury. 

Hydrogen trisulphide is much more easily combustible than the crude parent hydrogen polysulphide. Exposure to light tends to accelerate its decomposition. It slowly reduces concentrated sulphuric acid to sulphur dioxide, whilst on contact with dry silver oxide, cupric oxide, lead dioxide or mercuric oxide, it bursts into explosive combustion,2 a residue of the metallic sulphide being obtained. Many other metallic oxides and most salts bring about a less vigorous decomposition metals in the massive condition only react with it slowly. With potassium permanganate or dichromate the reaction is violent. 

The earliest methods for preparing cyclic a-diazo ketones involved the oxidation of the monohydrazones prepared from a-diketones, generally using mercuric oxide.7,8 Recent modifications of this procedure include the use of calcium hypochlorite in aqueous sodium hydroxide or activated manganese dioxide as oxidants.1 The latter reagent, especially, hoc ms preferable to mercuric oxide. The base-catalyzed decomposition of tile monotosylhydrazoneH of a-diketones has been... 

In static systems hydrogen and mercuric oxide were found as decomposition products (59,73). Hydrogen peroxide formation was not investigated. The quantum yield for a water vapor pressure of 8.5 mm. varied from 0.02 at 45°C. to 0.04 at 580°C. (59). In flow systems about 27% oxygen was found in the gaseous products, but no hydrogen peroxide was found (9). The flow system results have been substantiated in a more recent study (7) in which the quantum yields were found to be comparable to those obtained in static systems (59). 

The former is deposited in yellow crystals, mixed with sulphur when acetoxime is treated with phosphorus pentasulphide in carbon bisulphide soln. the insoluble product extracted with alcohol and the alcoholic soln. heated to boiling the compound separates from cold water in large, transparent, seemingly monoclinic prisms, melts at 146° 150° with decomposition, and is readily soluble in water, but only sparingly in alcohol, and insoluble in ether and carbon bisulphide. It decomposes carbonates, gives a colourless precipitate with lead acetate, and is decomposed by hot dilute nitric acid with separation of sulphur and formation of phosphoric acid it is also decomposed by mercuric oxide, the filtrate from the precipitated mercury sulphide giving all the reactions of phosphoric acid. 

Typical exposure to mercury in the General Chemistry laboratory occurs during (A) Boyle s Law experiments, (B) thermal decomposition of mercuric oxide, (C) displacement of mercury from its dissolved salts, and (D) cleaning up spills from broken thermometers. 

Thermal decomposition of mercuric oxide (B) 1s a classic experiment that is very much worthwhile in the freshman laboratory. It is an excellent example of how different a compound can be from its component elements. It is also the historical reaction that Joseph Priestley carried out when he discovered oxygen. However, it need not be done individually by every student. If the instructor demonstrates this experiment, the students exposure to mercury is greatly reduced. (Note that this experiment generates hot mercury vapor, which is more hazardous than the same amount of cool liquid mercury.) This reaction could also be shown to students by means of a film strip or video tape. 

Pure (6) can be prepared via the oxidative decomposition of the bishydrazone (7) with mercuric oxide 6) or thermal decomposition of the selenadiazole (8)7). 

The decomposition of mercuric oxide by heat has already been mentioned as the method by which Priestley was led to the discovery of oxygen. The oxide, which is yellow or brick red m colour, first becomes black—a reversible, physical effect. Oxygen is then evolved and a sublimate of mercury collects on the cooler parts of the containing vessel. The reaction is reversible, thus ... 

Mercury(II) oxide, or mercuric oxide, is a bright red powder. It decomposes on heating. What are the products of the decomposition of HgO ... 

Consider the equation corresponding to the decomposition of mercuric oxide. 

Many other reactions are known in which ferric oxide acts as a catalyser. Thus, it assists the decomposition of mercuric oxide at temperatures between 360° and 480° C.,2 and the oxidation of carbon monoxide with steam, the reaction proceeding very slowly at 250° C. but rapidly at 400° C.3... 

ACGIH TLV TWA 0.6 ppm SAFETY PROFILE A poison by ingestion. Moderately toxic by inhalation, skin contact, and subcutaneous routes. Mutation data reported. Used as an antiseptic, disinfectant on superficial wounds, and in female reproductive tract. 1 1 mixtures with hexamethylenetetramine explode at 178°C. Incompatible with mercuric oxide, calomel, silver nitrate, tannin, balsam Peru directiy mixed, Li, acetone. When heated to decomposition it emits toxic fumes of T. 

The chloride is prepared by the action of dilute hydrochloric acid upon the iiitrate, or by using potassium chloride and carbon dioxide. When treated with moist silver oxide it yields an aqueous solution of the hydi oxide, the latter also being formed when freshly precipitated mercuric oxide, allyl alcohol, and water are shaken together. Reduction of the chloride by zinc and hydrochloric acid gives an odour of allyl alcohol, whilst oxidation with permanganate causes the immediate decomposition of the compound mth the formation of oxalic acid. 

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