Zinc chloride

• Zinc ( II) chloride
• Zinkchlorür
• Zinc chloride
• Acid zinc salt

White granular powder of hexagonal- rhombohedral Papers

Fixed

2.91 g · cm -3 ( 25 ° C)

318 ° C

732 ° C

• Very well in water ( 4300 g · l-1 at 20 ° C)
• Soluble in ethanol, diethyl ether, acetone, glycerin, and pyridine

Risk

350 mg · kg -1 ( LD50, rat, oral)

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Zinc chloride ( ZnCl2 ) is a white, granular powder, which is obtained by heating zinc chloride or zinc sulfate, calcium chloride, and in the reaction of zinc oxide, zinc oxide or zinc blende with hydrochloric acid.

History

Zinc chloride was shown in 1648 by Johann Rudolph Glauber from calamine and 1741 by Johann Heinrich Pott of zinc.

Production and representation

For the preparation of pure zinc chloride is given to zinc in hydrochloric acid in order, wherein the metal has to be present in excess, last, the solution is treated with chlorine to convert impurities of iron in iron ( III) chloride (FeCl3 ), the iron hydroxide precipitated by digesting with zinc oxide, filtered and evaporated until a drop solidified to a cold porcelain plate.

In stronger evaporation escapes hydrochloric acid, and the preparation is then due to the formation of basic zinc a cloudy solution. Is evaporated to dryness, to give intensive heating a sublimate of anhydrous zinc chloride.

On a large scale zinc chloride, reaction zinkischer furnace breaks ( zinc oxide) with hydrochloric acid, by treatment of sphalerite with hydrochloric acid, the escaping hydrogen sulfide gas (H2S) is utilized for the manufacture of sulfuric acid, and also by leaching roasted blende containing pyrite.

Properties

Anhydrous zinc chloride is whitish, translucent (zinc butter), melts at about 318 ° C, distilled at red heat, is very hygroscopic and very soluble in ethanol. The solution is syrupy during evaporation and supplies, mixed with a little hydrochloric acid, colorless, very deliquescent crystals with one molecule of water.

Zinc chloride tastes burning, highly corrosive, dissolves plant fibers, removes many organic substances - in the way of concentrated sulfuric acid - water, charred wood, for example, results in the conversion of alcohol into ether (ether ), paper parchment paper, etc.

Use

To use zinc chloride for impregnating of wood, for the preservation of animal substances, during the refining of oils, in the production of paper, parchment, vulcanized fiber, ether, stearic acid; with chloride of lime to bleach the paper, in dyeing as a mordant for aniline blue, to display some of the coal-tar dyes and Garancins, for pickling and dyeing of brass, for the sizing of paper pulp, to disinfect, in chemical works as a dehydrating agent, in medicine as an etchant a concentrated solution for uniform heating of vessels to a certain higher temperature.

A solution of syrupy zinc chloride, mixed with zinc oxide, solidifies and is a composed of basic zinc chloride white, very hard mass that can be used as dental and Metal kit, especially if you added some glass powder. Even paintings in which forms Zinkoxidchlorid, have been recommended.

Mix example 4 l acid-free zinc chloride solution of 58 ° Be ( corresponding to a density of 1.74 g/cm3) with 10 l of a solution containing 2% sodium carbonate, and zinc oxide is added to the corresponding consistency. This odorless and cheap mixture must be used immediately. The paint is permanent, but does not tolerate coloring additives. A solution of zinc chloride on the specific gravity 1.7, boiled with excess zinc oxide dissolves silk.

For mixed, very concentrated solutions of zinc chloride and ammonium chloride or a solution of oxide or zinc hydroxide in ammonium chloride crystallized ammonium zinc chloride (NH 4 ) 2 [ ZnCl4 ] ( Lötsalz ). A solution of zinc in concentrated hydrochloric acid, which as much as zinc ammonium chloride contains ( soldering fluid ), eliminates the oxides of one piece of metal (copper, iron) before it is soldered or tinned.

You can also use an acidified with a little hydrochloric acid about 30 % solution of zinc chloride in water with the addition of a little ammonium chloride as soldering fluid but alternatively. It is used in the art as wetting and surface activating agent to tin is about 300 ° C. The zinc chloride is able, especially in the heat on the surfaces eg steel is located ligand oxides ( Fe2O3) dissolve by complex formation to transfer from the steel surface and to allow after tinning direct contact between steel and tin: it arises a strong bond between steel and tin.

In fog or smoke sets zinc chloride is in a finely divided form generated by the combustion of a mixture of zinc oxide, hexachloroethane and powdered aluminum. In addition to zinc chloride smoke thus generated also contains hydrochloric acid and other chlorinated organic compounds.

Proof

Sodium hydroxide (NaOH ) results with zinc chloride a gelatinous precipitate of zinc hydroxide Zn ( OH) 2, which is in excess of the precipitant to form the tetrahedral complex Tetrahydroxidozinkats (II ) [ Zn ( OH) 4] 2 - loose again. With ammonia solution instead of sodium hydroxide, the hydroxide initially formed solves the tetraammine.

When silver nitrate was added to a solution of zinc chloride as a white precipitate of silver chloride forms:

From a hydrochloric acid, acetate-buffered solution, the zinc coincides with Kaliumhexacyanidoferrat (II ) as a sparingly soluble, off-white precipitate of:

Zinc may also be detected as Rinmans green.