Oxide mercuric

Acid amides have weakly amphoteric properties, and thus give salts such as CjHsCONHj.HCl with strong acids, and salts of the type C HsCONHNa with strong bases. These compounds have to be prepared at low temperatures to avoid hydrolysis, and are difficult to isolate. The mercury derivatives can, however, usually be readily prepared, because mercuric oxide is too feebly basic to cause hydrolysis of the amide, and the heavy mercuric derivatives crystallise well. 

Add I g. of finely powdered mercuric oxide and o-8 g. of benzamide to 10 ml. of ethanol, and boil the mixture under a reflux water condenser for 30 minutes. Now filter the hot solution through a fluted filter-... 

Phenylbenzoyldiazomethane may be prepared by the oxidation of benzil-monohydrazone with mercuric oxide in the presence of dry etber as a solvent Tbe addition of a little alcoholic potassium hydroxide serves to catalyse the reaction ... 

Difluoroethanol is prepared by the mercuric oxide cataly2ed hydrolysis of 2-bromo-l,l-difluoroethane with carboxyHc acid esters and alkaH metal hydroxides ia water (27). Its chemical reactions are similar to those of most alcohols. It can be oxidi2ed to difluoroacetic acid [381-73-7] (28) it forms alkoxides with alkaH and alkaline-earth metals (29) with alkoxides of other alcohols it forms mixed ethers such as 2,2-difluoroethyl methyl ether [461-57-4], bp 47°C, or 2,2-difluoroethyl ethyl ether [82907-09-3], bp 66°C (29). 2,2-Difluoroethyl difluoromethyl ether [32778-16-8], made from the alcohol and chlorodifluoromethane ia aqueous base, has been iavestigated as an inhalation anesthetic (30,31) as have several ethers made by addition of the alcohol to various fluoroalkenes (32,33). Methacrylate esters of the alcohol are useful as a sheathing material for polymers ia optical appHcations (34). The alcohol has also been reported to be useful as a working fluid ia heat pumps (35). The alcohol is available ia research quantities for ca 6/g (1992). 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

Batteries. Many batteries intended for household use contain mercury or mercury compounds. In the form of red mercuric oxide [21908-53-2] mercury is the cathode material in the mercury—cadmium, mercury—indium—bismuth, and mercury—zinc batteries. In all other mercury batteries, the mercury is amalgamated with the zinc [7440-66-6] anode to deter corrosion and inhibit hydrogen build-up that can cause cell mpture and fire. Discarded batteries represent a primary source of mercury for release into the environment. This industry has been under intense pressure to reduce the amounts of mercury in batteries. Although battery sales have increased greatly, the battery industry has aimounced that reduction in mercury content of batteries has been made and further reductions are expected (3). In fact, by 1992, the battery industry had lowered the mercury content of batteries to 0.025 wt % (3). Use of mercury in film pack batteries for instant cameras was reportedly discontinued in 1988 (3). 

Pharmaceuticals. A variety of mercury compounds have had pharmaceutical appHcations over the years, eg, mercury-containing diuretics and antiseptics. Whereas some mercury compounds remain available for use as antiseptics such as merbromin [129-16-8] mercuric oxide, and ammoniated mercury [10124-48-8] or as preservatives such as thimerosal [54-64-8] in dmgs and cosmetics, most have been supplanted by more effective substances. A detailed discussion of mercury-containing antiseptics is available (37). Many hospitals use mercury metal to serve as weight for keeping nasogastric tubes in place within the stomach. 

Mercuric Acetate. Mercuric acetate/7ti(9(9-27-7/, Hg(C2H202)2, is a white, water-soluble, crystalline powder, soluble in water and many organic solvents. It is prepared by dissolving mercuric oxide in warm 20% acetic acid. A slight excess of acetic acid is helpful in reducing hydrolysis. 

Mercuric Carbonate. Basic mercuric carbonate/7ti5 ti7-7< -7/, HgCO 3HgO, maybe prepared by the addition of sodium carbonate to a solution of mercuric chloride. The brown precipitate, which lacks usefulness, is generally not isolated rather, the slurry is refluxed, whereupon the carbonate decomposes to red mercuric oxide. 

Mercuric Cyanides. Mercuric cyanide7, Hg(CN)2, is a white tetragonal crystalline compound, Httle used except to a small degree as an antiseptic. It is prepared by reaction of an aqueous slurry of yellow mercuric oxide (the red is less reactive) with excess hydrogen cyanide. The mixture is heated to 95°C, filtered, crystallized, isolated, and dried. Its solubihty in water is 10% at 25°C. 

Mercuric o s.ycy2inide[1335-31 -5] or basic mercuric cyanide, Hg(CN)2 HgO, is prepared in the same manner as the normal cyanide, except that the mercuric oxide is present in excess. The oxycyanide is white and crystalline but only one-tenth as soluble in water as the normal cyanide. Because this compound is explosive, it normally is suppHed as a 1 2 mixture of oxycyanide to cyanide. 

The mercury contained in the mother Hquid and washings of either method is recovered by treatment with sodium hydroxide solution. Yellow mercuric oxide is precipitated and filtered. The filtrate is treated further to remove the last traces of mercury before it is discarded. 

Mercuric chloride is widely used for the preparation of red and yellow mercuric oxide, ammoniated mercury/7(9/USP, mercuric iodide, and as an intermediate in organic synthesis. It has been used as a component of agricultural fungicides. It is used in conjunction with sodium chloride in photography (qv) and in batteries (qv), and has some medicinal uses as an antiseptic. 

Mercuric Oxide. Mercuric oxide[21908-53-2] HgO, is a red or yellow water-insoluble powder, rhombic in shape when viewed microscopically. The color and shade depend on particle size. The finer particles (< 5 -lm) appear yellow the coarser particles (> 8 -lm) appear redder. The product is soluble in most acids, organic and inorganic, but the yellow form, which has greater surface area, is more reactive and dissolves more readily. Mercuric oxide decomposes at 332°C and has a high (11.1) specific gravity. 

Yellow mercuric oxide may be obtained by precipitation from solutions of practically any water-soluble mercuric salt through the addition of alkah. The most economical are mercuric chloride or nitrate. Although yellow HgO has some medicinal value in ointments and other such preparations, the primary use is as a raw material for other mercury compounds, eg, Millon s ha.se[12529-66-7], Hg2NOH, which is formed by the reaction of aqueous ammonia and yellow mercuric oxide. 

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... 

Red mercuric oxide, identical chemically to the yellow form, is somewhat less reactive and more expensive to produce. An important use is ia the Ruben-MaHory dry cell, where it is mixed with graphite to act as a depolarizer (see Batteries). The overall cell reaction is as follows ... 

Yellow mercuric oxide is considered less suitable because it is less dense and would not permit adequate packing ia the cell casiag. 

Mercuric Sulfate. Mercuric s Af2iX.e.[7783-35-9] HgSO, is a colorless compound soluble ia acidic solutions, but decomposed by water to form the yellow water-iasoluble basic sulfate, HgSO 2HgO. Mercuric sulfate is prepared by reaction of a freshly prepared and washed wet filter cake of yellow mercuric oxide with sulfuric acid ia glass or glass-lined vessels. The product is used as a catalyst and with sodium chloride as an extractant of gold and silver from roasted pyrites. 

Antisyphilitics. Mercuric sahcyiate/T77(9-72-/] (6) and mercuric succinimide [584 3-0] (7) are simple salts prepared by the reaction ia water of mercuric oxide and sahcyhc acid or succinimide, respectively. Use as antisyphilitics has been substantially eliminated by virtue of the discovery of more potent and effective nonmetaUic biocides. 

Galen, a physician whose views outUved him by about a thousand years, died about 200 AD. He beUeved that mercurials were toxic, and did not use any mercury compound therapeutically. However, as a result of Arabian influence, the therapeutic uses of mercury were slowly recognized by Western Europe. In the thirteenth century mercury ointments were prescribed for treating chronic diseases of the skin. Mercury and its compounds, such as mercurous chloride, mercuric oxide, mercuric chloride, and mercuric sulfide, were used widely from the fifteenth to the nineteenth centuries, and to some extent in the twentieth century. During the first half of the twentieth century, the primary therapeutic uses of mercury included bactericidal preparations, such as mercuric chloride, mercuric oxycyanide, and mercuric oxide and diuretics, such as aryl HgX (Novasural) and mercurated ahyl derivatives (14). 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

Miniature zinc—mercuric oxide batteries have a zinc anode and a cathode containing mercuric oxide... 

Eig. 11. Typical discharge curve comparison for zinc—mercuric oxide batteries (-) model 325, HgO, and (-... 

Miniature zinc—mercuric oxide batteries may be made with either KOH or NaOH as the electrolyte. Cells having KOH operate more efficiently than those having NaOH at high current drains (Eig. 12) because of the higher conductivity of KOH. On the other hand, batteries with KOH are more difficult to seal, cells with NaOH are more resistant to leakage. 

Eig. 12. Comparison of battery efficiency for miniature zinc—mercuric oxide cells containing KOH or NaOH electrolyte (21). 

Fig. 13. Effect of temperature on discharge efficiency (a) at 270 mA-h of miniature 2inc—mercuric oxide batteries type EP675E, and (b) at 175 mA-h of...

Eig. 14. Retention of discharge capacity of miniature 2inc—mercuric oxide batteries after storage at temperatures of A, 40°C B, 20°C and C, 0°C (21). 

Although the 2inc—mercuric oxide battery has many excellent qualities, increasing environmental concerns has led to a de-emphasis in the use of this... 

Fig. 15. Relative discharge curves for (-) 2inc—silver oxide, and (—) 2inc—mercuric oxide batteries. Cells are of equal volume (21).

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