Mercury oxide, thermal decomposition

Oxygen can also be prepared by the thermal decomposition of certain solid compounds containing it. These include oxides of the more noble metals, for example of mercury or silver ... 

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. 

The use of ethyl nitrate as a component of rocket fuel involves the problem of thermal decomposition. Levy [16] has studied the decomposition of ethyl nitrate in the gaseous phase, in the temperature range 161 and 201°C under a pressure of a few centimeters of mercury. He found that ethyl nitrite is the main decomposition product. By-products include methyl nitrite, nitromethane, nitrogen dioxide and nitrous oxide. 

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. 

The French scientist Antoine Lavoisier (1743-1794) was one of the first to use an analytical balance like the one shown in Figure 3-10 to monitor chemical reactions. He studied the thermal decomposition of mercury(II) oxide, known then as calx of mercury. Mercury(II) oxide is a powdery red solid. When it is heated, the red solid reacts to form silvery liquid mercury and colorless oxygen gas as shown in Figure 3-11 on the next page. The color change and production of a gas are indicators of a... 

Small amounts of oxygen can be prepared by the thermal decomposition of certain oxygen-containing compounds. Some metal oxides, such as mercury(II) oxide, HgO, decompose on heating to produce oxygen ... 

Oxygen was discovered in 1774 by an English minister and scientist, Joseph Priestley (1733-1804). He observed the thermal decomposition of mercury(II) oxide, a red powder ... 

The reverse of combination is decomposition, AB->A+B. The thermal decomposition of mercury oxide,... 

Mercury(II) oxide exists in yellow (formed by heating Hg in O2 or by thermal decomposition of Hg(N03)2) and red (prepared by precipitation from alkaline solutions of Hg ) forms both have infinite chain structures (22.85) with linear Hg(II). The thermal decomposition of HgO (equation 22.161) led to the discovery of O2 by Priestley in 1774. 

MERCURY CYANIDE or MERCURY(II) CYANIDE (592-04-1) Hg(CN)2 Slowly decomposes in light. A moderate impact- and heat-sensitive explosive. Violent reaction with metal chlorates, fluorine, hydrogen cyanide, magnesium, nitrates, nitrites, metal perchlorates, sodium nitrite. Contact with strong acids evolves flammable and poisonous hydrogen cyanide gas, which can be detonated by this material. Thermal decomposition releases toxic nitrogen oxides, mercury, and hydrogen cyanide. On... 

EXPLOSION and FIRE CONCERNS combustible solid flammable moderate fire risk NFPArating (not rated) volatile in steam contact with strong oxidizing agents may cause fires and explosions violent reaction with ammonium perchlorate incompatible with tetrani-tromethane and mercury (II) nitrate thermal decomposition may generate carbon monoxide and carbon dioxide use alcohol foam, water spray, dry chemical powder, or carbon dioxide for fire fighting purposes. 

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