Ferric chloride (III) in the form of a brown solution can be prepared in the laboratory or at home. It will require heat-resistant non-metallic dishes and clean hot water (boiled or distilled). After dissolution and settling, a dark brown liquid is obtained. There are a number of features for preparing a solution of ferric chloride, which you should know about before you start working with it.
Anhydrous ferric chloride, produced by the chemical industry - FeCl 3 , - crystals of dark brown color with shades of red, purple, dark green. The molar mass is 162.21 g / mol. The substance melts at a temperature of 307.5 ° C, at 500 ° C begins to decompose. 100 g of water dissolves the weight of the anhydrous salt:
- 74.4 g (0 ° C);
- 99 g (25 ° C);
- 315 g (50 ° C);
- 536 g (100 ° C).
Anhydrous iron (III) chloride is a very hygroscopic substance, quickly attracts moisture from the environment. In air, it interacts with water, turning into yellow crystals of FeCl 3 + 6H 2 O hexahydrate. The mass fraction of anhydrous ferric chloride in the substance purchased in the trade network reaches 95%. There is a small amount of ferric chloride FeCl 2 and insoluble impurities. The trade name is "Chlorine iron". The substance is fire and explosion-proof, but its solution has a corrosive effect on metal objects.
Ferric chloride hexahydrate
- NaOH (a brown precipitate of Fe (OH) 3 appears);
- K 4 [Fe (CN) 6 ] (a precipitate of KFe [Fe (CN) 6 ] appears in blue);
- KCNS, NaCNS (iron thiocyanate Fe (CNS) 3 is formed in red color).
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The use of ferric chloride in industry and municipal services. Household use
Iron salts are used in many areas. Trivalent metal chloride is used to treat water, metals and fixing paints. The substance is used in industrial organic synthesis (catalyst, oxidizer). Especially appreciated are the coagulating properties of the Fe 3+ ion in the purification of communal and industrial effluents. Under the action of iron chloride, small insoluble particles of impurities coalesce and precipitate. Also, some of the soluble contaminants that are removed at the treatment facilities are bound. Crystalline hydrate and anhydrous salt of FeCl 3 are used in the etching of metal plates. Add the substance to the concrete to strengthen its strength.
Chemical phenomena in etching boards. Security measures
A popular chemical substance for etching printed circuit boards is chlorine iron. A solution for these purposes is prepared from 0.150 kg of salt and 0.200 liters of warm water. It contains ions Fe 3+ , Cl - , and during hydrolysis a brown compound is formed - ferric hydroxide. The process proceeds according to the scheme: FeCl 3 + 3HOH↔ Fe (OH) 3 + 3Cl - + 3H + . The disadvantage of the method is contamination of the board by reaction by-products, which hinders further etching. The salt itself is a non-volatile substance, but in the process of interaction with water it releases corrosive fumes. Work should be carried out outdoors or in a well-ventilated room. The solution on the skin and mucous membranes leads to irritation and can cause dermatitis. Personal protective equipment (glasses, gloves) should be used. When contact with a caustic solution, it is necessary to wash the skin with plenty of water.