Preparation of calcium alginate from sodium alginate Ĭalcium alginate can be produced from a sodium alginate solution by the addition of a calcium salt such as calcium chloride. This frothy mix of air and residue is removed from the top and the solution is withdrawn from the bottom and pumped to the filter. The diluted extract is left standing for several hours while the air rises to the top, taking the residue particles with it. Fine air bubbles attach themselves to the particles of residue. To reduce the quantity of filter aid needed, some processors force air into the extract as it is being diluted with water (the extract and diluting water are mixed in an in-line mixer into which air is forced). However, filter aid is expensive and can make a significant contribution to costs. Therefore, before filtration is started, a filter aid, such as diatomaceous earth, must be added this holds most of the fine particles away from the surface of the filter cloth and facilitates filtration. However, the pieces of undissolved residue are very fine and can quickly clog the filter cloth. After dilution, the solution is forced through a filter cloth in a filter press. The solution is too thick (viscous) to be filtered and must be diluted with a very large quantity of water. This insoluble residue must be removed from the solution. This slurry also contains the part of the seaweed that does not dissolve, mainly cellulose. Over a period of about two hours, the alginate dissolves as sodium alginate to give a very thick slurry. To extract the alginate, the seaweed is broken into pieces and stirred with a hot solution of an alkali, usually sodium carbonate. Alginate is present in the cell walls of brown algae, as the calcium, magnesium and sodium salts of alginic acid. "Alginate" is usually the salts of alginic acid, but it can also refer to derivatives of alginic acid and alginic acid itself in some publications the term "algin" is used instead of alginate. Calcium alginate is also used for entrapment of enzymes and forming artificial seeds in plant tissue culture. Please help improve this article by introducing citations to additional sources.Ĭalcium alginate is a water-insoluble, gelatinous, cream-coloured substance that can be created through the addition of aqueous calcium chloride to aqueous sodium alginate. Relevant discussion may be found on the talk page. This article relies largely or entirely on a single source.
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