Starch color

Peroxide Value Accurately weigh about 10 g of sample, add 30 mL of a 3 2 mixture of glacial acetic acid chloroform, and mix. Add 1 mL of a saturated solution of potassium iodide, and mix for 1 min. Add 100 mL of water, begin titrating with 0.05 N sodium thiosulfate, adding starch TS as the endpoint is approached, and continue the titration until the blue starch color has just disappeared. Perform a blank determination (see General Provisions), and make any necessary correction. Calculate the peroxide value, as milliequiva-lents of peroxide per kilogram of sample, by the formula... 

Starch color is greatly affected by the effectiveness of the wet-milling process, especially in yellow maize rich in carotenoids. 

Molisch s Test. Dissolve about 01 g. of the carbohydrate in z ml. of water (for starch use 2 ml. of starch solution ), add 2-3 drops of a 1 % alcoholic solution of i-naphthol (ignoring traces of the latter precipitated by the water) and then carefully pour 2 ml. of cone. H2SO4 down the side of the test-tube so that it forms a heavy layer at the bottom. A deep violet coloration is produced where the liquids meet. This coloration is due apparently to the formation of an unstable condensation product of i-naphthol with furfural (an aldehyde produced by the dehydration of the carbohydrate). 

Action of sodium hydroxide. Boil about 0 2 g. of glucose with 5 of 10% NaOH solution the mixture turns yellow, then brown, and emits the odour of caramel. Fructose, maltose, lactose and soluble starch behave similarly sucrose and ordinary starch do not give colorations. 

Starch Iodide coloration. To a small volume of starch solution ... 

Hydrolysis by acids. Place 15 ml. of starch solution in a boiling-tube, add I ml. of cone. HCl, mix well and place in a boiling water-bath for 20 minutes. Cool and add 2 drops of iodine solution to i ml. of the solution no blue coloration is produced. On the remainder, perform tests for glucose in particular show that glucosazone can be formed. Neutralise the excess of acid before carrying out these tests. (Note that a more concentrated acid is required to hydrolyse starch than to hydrolyse the disaccharides, such as sucrose.)... 

Recovery of the wopropyl alcohol. It is not usually economical to recover the isopropyl alcohol because of its lo v cost. However, if the alcohol is to be recovered, great care must be exercised particularly if it has been allowed to stand for several days peroxides are readily formed in the impure acetone - isopropyl alcohol mixtures. Test first for peroxides by adding 0-6 ml. of the isopropyl alcohol to 1 ml. of 10 per cent, potassium iodide solution acidified with 0-6 ml. of dilute (1 5) hydrochloric acid and mixed with a few drops of starch solution if a blue (or blue-black) coloration appears in one minute, the test is positive. One convenient method of removing the peroxides is to reflux each one litre of recovered isopropyl alcohol with 10-15 g. of solid stannous chloride for half an hour. Test for peroxides with a portion of the cooled solution if iodine is liberated, add further 5 g. portions of stannous chloride followed by refluxing for half-hour periods until the test is negative. Then add about 200 g. of quicklime, reflux for 4 hours, and distil (Fig. II, 47, 2) discard the first portion of the distillate until the test for acetone is negative (Crotyl Alcohol, Note 1). Peroxides generally redevelop in tliis purified isopropyl alcohol in several days. 

Iodine compounds are important in organic chemistry and very useful in medicine. Iodides, and thyroxine which contains iodine, are used internally in medicine, and as a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. The deep blue color with starch solution is characteristic of the free element. 

Suspend 5 g of soluble starch in 50 mL of saturated NaCl solution, and stir slowly into 500 mL of boiling saturated NaCl solution. Cool and bottle. Free iodine produces a blue-black color. 

Titrate liberated iodine with thiosulfate Ee/1 = 55.847 Ee203/2 = 79.845 I2 + 2 820 = 2 D + 8401 [titrate solution (pH ° 7.0) with thiosulfate until color is pale yellow. Add K1 and starch and continue titration to disappearance of blue color. I2/2 =... 

A few substances indicate the presence of a specific oxidized or reduced species. Starch, for example, forms a dark blue complex with 13 and can be used to signal the presence of excess 13 (color change colorless to blue), or the completion of a reaction in which 13 is consumed (color change blue to colorless). Another example of a specific indicator is thiocyanate, which forms a soluble red-colored complex, Fe(SCN) +, with Fe +. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Starch pyrodextrins and British gums have the abiUty, in aqueous dispersion, to form films capable of bonding like or unlike materials. Thus, they have uses as adhesives for envelopes, postage stamps, and other products. These dextrins are used in glass-fiber siting to protect the extmded fiber from abrasion, and as binders for metal core castings, water color paints, briquettes, and many other composite materials (qv). 

Acid-modified starches are used in the manufacture of gum candies because they form hot concentrated pastes that form strong gels on cooling. ThermaUzed starches are used in foods to bind and carry flavors and colors. Sweetening agents (com symp, HFCS) are made from starch by enzymatic or acid treatment as previously noted. 

Low DS hydroxyethyl starches are used as paper coatings and sizes to improve sheet strength and stiffness. They are also employed as paper-coating color adhesives, and to increase fiber bonding in paper products. Hydroxyethylstarches are also used as textile warp sizes. 

The determination of tin in metals containing over 75 wt % tin (eg, ingot tin) requites a special procedure (17). A 5-g sample is dissolved in hydrochloric acid, reduced with nickel, and cooled in CO2. A calculated weight of pure potassium iodate (dried at 100°C) and an excess of potassium iodide (1 3) are dissolved in water and added to the reduced solution to oxidize 96—98 wt % of the stannous chloride present. The reaction is completed by titration with 0.1 Af KIO —KI solution to a blue color using starch as the indicator. 

Cellulose. Cellulose or starch xanthate cross-linked by titanates can adsorb uranium from seawater (536). CarboxymethylceUulose cross-linked with TYZOR ISTT is the bonding agent for clay, talc, wax, and pigments to make colored pencil leads of unusual strength (537). 

PuUy hydroly2ed poly(vinyl alcohol) and iodine form a complex that exhibits a characteristic blue color similar to that formed by iodine and starch (171—173). The color of the complex can be enhanced by the addition of boric acid to the solution consisting of iodine and potassium iodide. This affords a good calorimetric method for the deterrnination of poly(vinyl alcohol). Color intensity of the complex is effected by molecular weight, degree of... 

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