Calcium hypochlorite bleaching powder

A solution of bleaching powder contains calcium hypochlorite [Ca(0Cl)2.4H20], calcium chloride [CaCl, Ca(OH),.Hp], lime hypochlorous acid formed by the 

Bleaching powder is partially soluble in water. A smooth paste with water is first prepared and then diluted with water. This is then allowed to stand until whole of the suspended matter has settled to bottom. The clear supematent liquid is then drained-off for use which is about 12 Tw and contains about 3.9% available chlorine. This is then diluted to the required strength. 

Calcium hypochlorite undergoes rapid exothermic decomposition on heating above 175°C. Bleaching powder solution reacts with acids with the evoluation of chlorine. 

Certain metals or their oxides bring about catalytic decomposition of bleaching powder. Similar reaction can also occur with other metals such as iron or copper. Ca(OCl), + 4CoO = 2C0O3 + CaClj 2C0O3 = 4CoO + Oj 

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Sodium hypochlorite is commercially available as an alkaline solution, normally containing the equivalent of 12-14% available chlorine. However, this is so unstable that analytical testing of its strength is always necessary before use. Calcium hypochlorite (bleaching powder), stabilised by adding lime, has been used in the past but this product is no longer used in textile bleaching. 

Summary Chloroform is prepared by reacting acetone with calcium hypochlorite (bleaching powder), and then extracting the mixture with benzene, toluene, or xylene. After extraction, the solvent/chloroform mixture is then distilled to collect the chloroform, which is then re-distilled. After collecting the chloroform after re-distillation, it is mixed with a small amount of 95% ethanol to act as a stabilizing agent. 

Chlorine gas. This gas is available commercially in steel cylinders and should be taken from these. Alternatively, it can be produced in a Kipp apparatus (with glass joints only) from calcium hypochlorite (bleaching powder) and 1 1 hydrochloric acid. It is advisable to mix the bleaching powder with some gypsum powder, making the mixture wet, to produce lumps of the reagent. After drying these lumps can be placed into the Kipp apparatus. 

As reagent, a saturated aqueous solution of calcium hypochlorite [bleaching powder, Ca(OCl)2] or a dilute aqueous solution of sodium hypochlorite (NaOCl) is employed. Some commercial bleaching fluids, containing active chlorine, can be used as substitutes.TheCa(OCl)2andNaOClsolutions must be prepared daily, since they decompose within 24-48 hours. In sunlight, they are stable for less than 1 hour. The stock chemicals are best stored in a cool dry place. Light, heat, humidity, and carbon dioxide hasten their decomposition. 

Sodium hypochlorite is one of the best disinfectants known, capable of killing bacteria, yeasts, fungus, spores, and even viruses. Because it is an excellent disinfectant as well as a bleaching agent, it is used in many household cleaners. Sodium hypochlorite is also used to disinfect water supplies and swimming pools (although calcium hypochlorite in powder or pellet form is often used as a substitute, due to the convenience of its solid form). 

Othei hypochlorites include calcium hypochlorite, bleach liquor, bleaching powder and tropical bleach, dibasic magnesium hypochlorite, lithium hypochlorite, chlorinated tnsodium phosphate, and hypochlorous acid. 

The Principal Compounds of Calcium are the hydroxide, oxide, carbonate, chloride, sulphate, fluoride, and hypochlorite (bleaching powder). 

Dichloranrine-T (p-toluenesulphondichloramide). Prepare about 200 ml. of a saturated solution of calcium hjrpochlorite by grinding a fresh sample of bleaching powder with water and filtering with shght suction. Dissolve 5 g. of p-toluenesulphonamide in as small a volume of the calcium hypochlorite solution as possible (about 150 ml.) and filter the solution if necessary. Cool in ice, and add about 50 ml. of a mixture of equal volumes of glacial acetic acid and water slowly and with stirring until precipitation is complete. The dichloramine T separates out first as a fine emulsion, which rapidly forms colourless crystals. Filter the latter... 

After World War I, other chlohne-based bleaches were developed. In 1921 the use of chlorine dioxide for bleaching fibers was reported followed by the development of the commercial process for large-scale production of sodium chlorite. In 1928 the first dry calcium hypochlorite containing 70% available chlorine was produced in the United States. This material largely replaced bleaching powder as a commercial bleaching agent. 

Historically, bleaching powder and tropical bleach were significant sources of available chlorine but very Httle are used today. This is because of the greater availabiUty of sodium hypochlorite solutions and the development of calcium hypochlorite. They are stiU used to sanitize fields, drainage ditches, and reservoirs where its insoluble portion is not important. And, they are important sources of available chlorine within some less developed tropical countries. 

Calcium hypochlorite is the principal commercial soHd hypochlorite it is produced on a large scale and marketed as a 65—70% product containing sodium chloride and water as the main diluents. A product with a significantly higher available chlorine, av CI2, (75—80%) has been introduced by Olin. Calcium hypochlorite is also manufactured to a smaller extent as a hemibasic compound (- 60% av Cl ) and to a lesser extent in the form of bleaching powder (- 35% av CI2). Lithium hypochlorite is produced on a small scale and is sold as a 35% assay product for specialty appHcations. Small amounts of NaOCl ate employed in the manufacture of crystalline chlorinated ttisodium phosphate [56802-99-4]. 

Because of the simplicity of the manufactuting process it is cheaper than neutral calcium hypochlorite, and because of its higher av CI2 and better stabiHty, it is a superior alternative to bleaching powder [64175-94-6J. 

Applications. Because of its high lime content, the use of hemibasic calcium hypochlorite ia geaeral sanitatioa is limited. It is used primarily ia Japan and lesser developed countries as an alternative to bleaching powder. 

Bleaching Powder. This material, known siace 1798, is made by chlorination of slightly moist hydrated lime, calcium hydroxide [1305-62-0] Ca(OH)2- It has the empirical formula Ca(OCl)2 CaCl2 Ca(OH)2 2H20. Its compositioa, loag a subject of coatroversy, was estabHshed by phase studies, microscopy, and x-ray diffraction techniques (241). The initial chlorination products are monobasic calcium chloride [14031-38-4] and dibasic calcium hypochlorite [12394-14-8] ... 

Discussion. Most hypochlorites are normally obtained only in solution, but calcium hypochlorite exists in the solid form in commercial bleaching powder which consists essentially of a mixture of calcium hypochlorite Ca(OCl)2 and the basic chloride CaCl2,Ca(0H)2,H20 some free slaked lime is usually present. The active constituent is the hypochlorite, which is responsible for the bleaching action. Upon treating bleaching powder with hydrochloric acid, chlorine is liberated ... 

The oxygen either bubbles out of the solution or attacks oxidizable material. Calcium hypochlorite is the main component of bleach powders and is used for purifying the water in home swimming pools. It is used for swimming pools in preference to sodium hypochlorite because the Ca2+ ions form insoluble calcium carbonate, which is removed by filtration sodium would remain in solution and make the water too salty. 

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