Calcium hypochlorite, manufacture

Dichlorine monoxide is an intermediate in the manufacture of calcium hypochlorite. It has been used in sterilization for space appHcations (70) (see Sterilization techniques). Its use in the preparation of chlorinated solvents (71) and chloroisocyanurates has been described. Chlorine monoxide has been shown to be effective in bleaching of pulp (qv) and textiles (72—74). 

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]. 

Calcium Hypochlorite. High assay calcium hypochlorite [7778-54-3] was first commercialized in the United States in 1928 by Mathieson Alkali Works, Inc. (now Olin Corp.) under the trade name HTH. It is now produced by two additional manufacturers in North America (Table 5). Historically, it usually contained about 1% water and 70—74% av CI2, so-called anhydrous product, but in 1970, a hydrated product was introduced (234). It is similar in composition to anhydrous Ca(OCl)2 except for its higher water content of about 6—12% and a slightly lower available chlorine content. This product has improved resistance to accidental initiation of self-sustained decomposition by a Ht match, a Ht cigarette, or a small amount of organic contamination. U.S. production in the 1990s consists primarily of partially hydrated Ca(OCl)2, which is sold as a 65% av CI2 product mainly for swimming pool use. Calcium hypochlorite is also sold as a 50% av CI2 product as a sanitizer used by dairy and food industries and in the home, and as a 32% product for mildew control. 

Manufacture. A high purity, completely hydrated lime of high reactivity is employed in the manufacture of calcium hypochlorite. It should contain low levels of impurities such as siUca, MgO, CaC03, CaSO, AI2O3, Fe203, and trace metals such as Co, Ni, Cu, and Mn, since some of these can cause process difficulties and can also affect the quaUty and stabiUty of the final product. 

Manufacture. Hemibasic calcium hypochlorite is manufactured by chlorination of lime slurry followed by filtration and dryiag of the filter cake. 

Pennwalt Formerly called Pennsalt. A process for making calcium hypochlorite by passing chlorine into an aqueous suspension of calcium hypochlorite and calcium hydroxide. Developed by the Pennsylvania Salt Manufacturing Corporation in 1948. 

Table 6.2 shows the important applications of sodium hydroxide. Direct applications can be further broken down into pulp and paper (24%), soaps and detergents (10%), alumina (6%), petroleum (7%), textiles (5%), water treatment (5%), and miscellaneous (43%). Organic chemicals manufactured with sodium hydroxide are propylene oxide (23%), polycarbonate (5%), ethyleneamines (3%), epoxy resins (3%), and miscellaneous (66%). Inorganic chemicals manufactured are sodium and calcium hypochlorite (24%), sodium cyanide (10%), sulfur compounds (14%), and miscellaneous (52%). As you can see from the number of applications listed, and still the high percentages of miscellaneous uses, sodium hydroxide has a very diverse use profile. It is the chief industrial alkali. 

Calcium hypochlorite is manufactured by chlorination of calcium hydroxide [CaOH)2] followed by the separation of the calcium hypochlorite [Ca(OCl)2] through salting out from solution with sodium chloride. 

Calcium hypochlorite is also manufactured by the formation under refrigeration of the complex salt Ca(OCl)2 Na0ClNaC112H20, which is prepared by the chlorination of a mixture of sodium hydroxide and calcium hydroxide. The salt is reacted with a chlorinated lime slurry, filtered to remove salt, and dried, resulting finally in a stable product containing 65 to 70% calcium hypochlorite. 

Efforts to produce a bleaching powder in a more concentrated and stable form resulted in the manufacture of calcium hypochlorite Ca(0 Cl)2. In pure form it contains 99.2 per cent active chlorine. It is manufactured in various ways and sold commercially under different names, e. g. Perchloron produced by I. G. Far ben, H. T. H. by Mathieson Alkali Works, Pittchlor by Pittsburg Plate Glass Co., Columbia. Chemical Division. 

Calcium hypochlorite There are a number of processes for the manufacture of calcium hypochlorite ( high percentage bleaching powder ). The oldest is the Griesheim Elektron process ( Perchloron process ) in which a calcium hydroxide suspension is chlorinated to such an extent that the calcium chloride formed mostly dis.solves, but not the calcium hypochlorite. 

United States goes to this application. Sodium hydroxide is also an important raw material in the manufacture of soap. The method by which soap is made has not changed very much for thousands of years. A fat or oil is added to a boiling solution of sodium hydroxide in water. The fat or oil hydrolyzes into its component parts, glycerol and fatty acids. The sodium hydroxide then reacts with the fatty acids, forming sodium salts. The sodium salt of a fatty acid is a soap. Sodium hydroxide is also an important raw material in the manufacture of inorganic compounds, especially sodium and calcium hypochlorite, sodium cyanide, and a number of sulfur-containing compounds. Some other important uses of sodium hydroxide include ... 

Sufficient amounts of nickel and copper to decrease stability and release oxygen to deform or rupture storage containers is usually acquired from water, sodium hydroxide solutions, or contact with metal during hypochlorite manufacture. Metals such as calcium and iron may precipitate after packaging to make the product cloudy or form undesirable residues. Iron or manganese may also turn the solution red, pink, or purple. ... 

This is often done to recycle filtrates and other solutions produced during the manufacture of calcium hypochlorite. 

Manufacturing processes will continue to evolve with incremental improvements, with an emphasis on the continuous production of sodium and calcium hypochlorites. Improvements will also be made to improve purity and control by-products such as chlorate and bromate. Partly, this will involve changes to raw materials such as the eventual elimination of mercury cell caustic and the use of brine with minimal bromide. Improvements in equipment that combine the generation of chlorine and the preparation of sodium hypochlorite will also continue. 

Chlorine is manufactured in Canada by the electrolysis of brine, which produces chlorine and caustic soda in about a 1 1.1 ratio, as well as some hydrogen. There are about 14 chloralkall plants in Canada, with a total nameplate capacity of about 1,293 kt per year. The ICI plant in Cornwall, Ontario produces caustic potash as well as chlorine, while the PGG s plant at Beauharnois, Quebec, also produces sodium hypochlorite. Saskatoon Chemicals in Saskatchewan produces chloralkall and calcium hypochlorite. 

Between 1870 and 1910, scientific progress allowed production of sodium hypochlorite solutions at concentrations up to 3% and the sale of them for consumer use. More importantly, between 1910 and 1940, the progress of the electrolytic industry enabled producers to manufacture sodium hypochlorite solutions of greater than 10% concentration. Further technology advances allowed the preparation of solutions of sodium hypochlorite up to a concentration of 25%. The latest breakthrough which enabled production of hy-pochlorous acid salts at even higher concentrations has been described in a U.S. patent [3], wherein a method to produce an aqueous slurry of calcium hypochlorite at concentrations of up to about 50% is disclosed. 

Bleaching. Crude wood cellulose is bleached by means of calcium or sodium hypochlorite in large tanks, bleachers , equipped with stirrers. Bleaching cellulose is of great importance for nitrocellulose manufacture, particularly in the case of nitrocellulose intended for the production of smokeless powder. It is essential that the powder should be pale in colour, as a change in the colour of the powder often indicates decomposition. Similarly, cellulose destined for manufacturing collodion cotton, for varnishes, celluloid and film, should be carefully stripped of colour so that the final products are colourless. 

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