How to prepare mercuric chloride?

There are many compounds in mercury, but only sulfides, oxides and chlorides of mercury are of industrial significance:

(1) Mercury sulfide Among all mercury compounds, mercury sulfide is the most important one. Almost all mercury mines mined from mines and sent to smelting exist in this form and are the main mineral raw materials for smelting mercury. Natural mercury sulfide is also called cinnabar or cinnabar. There are many isomers of HgS, the most important of which are α-HgS and σ-HgS. σ-HgS is a red powder, usually called cinnabar. When hydrogen sulfide or various alkali metal sulfides are added to the acidic solution containing mercury, the precipitated HgS is often black powder, that is, α-HgS. Cinnabar is a precious traditional Chinese medicine, which can also be used as industrial raw materials and other special uses. Cinnabar is one of the traditional products in China's mercury industry, and there are three production methods. One is an ore with high HgS grade and obvious cinnabar crystals mined from mercury mine, which is made by crushing cinnabar, separating gangue by gravity separation, removing iron filings by high-intensity magnetic separation, and then dispersing with water (i.e. spraying water on cinnabar) and drying. The paste yield of cinnabar is generally 30% ~ 35%. Most mercury mines in China use this method to produce cinnabar. The other two methods can also be used to prepare cinnabar by synthetic method and wet method (that is, chemical precipitation method), but the former has serious mercury pollution and the latter has not been widely used in industrial production.

(2) Mercury Oxide Mercury oxide is often bright red or orange-yellow powder, and there are also red and yellow mercury oxides in industrial production. Red mercuric oxide is widely used as battery depolarizer in various standard mercury batteries, and yellow (red) mercuric oxide is also used in analytical reagents, anticorrosion, mildew prevention and pharmaceutical industry. There are three main methods to produce mercury oxide in industry. One is the production of mercury oxide by suspension electrolysis of mercury sulfide concentrate, that is, the mercury sulfide concentrate is suspended in brine solution for electrolysis to obtain Na2HgCl4 solution, and after purification, sodium hydroxide solution is added to obtain red or yellow mercury oxide. Secondly, metallic mercury is dissolved in hydrochloric acid to make mercuric chloride, and then reacts with alkaline solution, or mercuric chloride is directly dissolved in water and reacts with sodium hydroxide to obtain red or yellow mercuric oxide. Thirdly, metallic mercury is dissolved in nitric acid to generate Hg(NO3)2, and then it is decomposed by heating to generate red mercury oxide or added with sodium hydroxide solution to generate yellow mercury oxide.

Both Guizhou Mercury Mine and China Tongren Mercury Mine have established workshops for producing mercury oxide by the above method.

(3) production of mercuric chloride and its extended products: mercuric chloride (HgCl2), also known as mercuric chloride, is a white rhombic needle-like crystal or white crystalline powder, with a lethal dose of 0.2 ~ 0.4g ... the contents of analytically pure and chemically pure mercuric chloride are not less than 99.5% and 99% respectively, and the contents of residue on ignition are 0.02% and 0.04% respectively. Mercury chloride is mainly used as chemical catalyst, zinc-manganese battery, medicine, analytical reagent, preservative and preparation of other mercury salts. In industrial production, the gas phase synthesis method is adopted, that is, the metal is heated above the boiling point (360℃), and the excess preheated chlorine gas is synthesized in a timely reactor. Guizhou mercury mine, Tongren mercury mine and Xinhuang mercury mine have all established corresponding production workshops. Mercury chloride is widely used in plastic industry. In the form of mercury chloride catalyst, it is used as a catalyst in the synthesis of vinyl chloride when producing polyvinyl chloride by acetylene method.