Starch, complexes salt solutions

As discussed next, barium salts form insoluble complexes with starch. Similar behavior is exhibited by the complex of Ca(OH)2 with starch. This property is utilized for the precipitation of starch from aqueous solution, a process that is rather slow.475,476 In his subsequent paper, Rakowski477 studied the effect of salts on the adsorption of metal hydroxides it was observed that increases in salt increased the adsorption of hydroxides. This effect is absent in the case of the adsorption of NH4OH. More extensive studies478 demonstrated the following order of adsorption capacities Ca(OH)2 = Ba(OH)2 > KOH > NaOH > LiOH > Me3(PhCH2) NOH > Me4NOH. Rakowski,466,468 Lloyd,463 and Leach etal.47S accordingly... 

Although, for obvious reasons, fractional precipitation from salt solutions is by far the most economical of the methods discus.sed for the industrial fractionation of starch, such processes as that of Cantor and WimmeH might possibly become of interest for the production of reactive intermediates of each starch fraction. Several types of chemical derivatives of both starch components can be synthesized by way of the calcium hydroxide complexes. 

Like the simple formazans, the formazans of oxidized polysaccharides form complexes with heavy metal salts with ease. On warming the formazans of oxidized cellulose, starch, dextrin, dextran, or inulin with copper, cobalt, nickel, or uranium salt solutions, their characteristically-colored metal complexes are obtained. The presence of carboxyl groups in the polysaccharide formazans frequently facilitates complex formation. ... 

Spectrophotometric Measurements. Spectrophotometric measurements were made with a Cary Model 14 recording spectrophotometer. Absorption spectra of solutions were obtained in silica cells. Absorption spectra of the crystalline salts were obtained using mixtures of the materials with petrolatum between glass or silica plates using the Cary Model 1417200 source. Blanks for the solid spectra were CaCOa mulls in petrolatum plus aqueous starch solution if necessary to produce a flat base line. The reference was adjusted so the base line was flat in the 520 to 600 m/x region where the U(VI) acetate complexes do not absorb. Slit widths for spectra of solids were typically <0.1 mm. 

Although the Tilden-Hudson test is very useful it has certain drawbacks in precise work, (a) The exact time at which needles appear is difficult to determine, (b) Enzyme activity is slowed but not stopped by the addition of iodine solution in fact, it is possible to add starch to a mixture of enzyme and iodine solution and observe the gradual formation of the crystalline dextrin-iodine complexes, (c) The apparent activity depends very much on the presence of such foreign materials as salts, n-glucose, maltose, etc., which may be present in the enzyme solution. In some enzyme preparations which seem to have fair activity, the needles are never observed. 

Antimony(ni) is titrated to antimony(V) in neutral or slightly alkaline solution with iodine to a blue starch end point. The iodine is standardized against primary standard arsenic(in) oxide. Tartaric acid is added to complex the antimony and prevent its hydrolysis to form insoluble basic salts such as SbOCl and Sb02Cl (which form in slightly acid and neutral solution). 

The starch-iodine complex does not have a well-defined stoichiometry. The ratio [I ]/([l2]+[IJ]) must be greater than zero in aqueous solution. The actual stoichiometry depends on the polymer chain length, the iodide and salt... 

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