Color calculations

Annatto extract is sold ia several physical forms, including dry powders, propylene glycol/monoglyceride emulsions, oil solutions and suspensions, and alkaline aqueous solutions containing anywhere from 0.1—30% active colorant calculated as bixia, norhixin, as appropriate. It... 

Useful Equations for Monomeric Anthocyanin and Polymeric Color Calculation... 

Reducing Substances Transfer about 1 g of sample, accurately weighed, into a 250-mL Erlenmeyer flask, dissolve it in 10 mL of water, add 25 mL of alkaline cupric citrate TS, and cover the flask with a small beaker. Boil gently for exactly 5 min, and cool rapidly to room temperature. Add 25 mL of a 1 10 solution of acetic acid, 10.0 mL of 0.1 N iodine, 10 mL of 2.7 N hydrochloric acid, and 3 mL of starch TS, and titrate with 0.1 N sodium thiosulfate to the disappearance of the blue color. Calculate the weight, in milligrams, of reducing substances (as D-glucose) by the formula... 

Determination of Sodium Carbonate Add 2 drops of methyl orange TS to the solution retained from Determination of Alkalinity (above), and continue the titration with 1 A hydrochloric acid to a permanent pink color. Calculate the percentage of Na2C03 by the formula... 

Pipet 10.0 mL of the dissolved colorant into a 250-mL Erlenmeyer flask containing 90 mL of 0.04 N ammonium acetate, and mix well. Determine the net absorbance of the solution relative to water at the wavelength maximum given for each color. Calculate the percentage of colorant present using the following equation, which presumes a 1-cm pathlength cell ... 

Transfer the quantity of acetylated oil specified in the monograph, and accurately weighed, into a tared 125-mL Erlen-meyer flask, and add 10 mL of neutral alcohol, 10 drops of phenolphthalein TS, and 0.1 N alcoholic potassium hydroxide, dropwise, until a pink endpoint is obtained. If more than 0.20 mL is needed, reject the sample, and wash and test the remaining acetylated oil until its acid content is below this level. Prepare a blank for residual titration (see General Provisions), using the same volume of alcohol and indicator, and add 1 drop of 0.1 /V alkali to produce a pink endpoint. Transfer 25.0 mL of 0.5 N alcoholic potassium hydroxide into each of the flasks, reflux them simultaneously for 1 h, cool, and titrate the contents of each flask with 0.5 N hydrochloric acid to the disappearance of the pink color. Calculate the percentage of Total Alcohols (A) by the equation... 

Ammonium Thiocyanate, 0.1 N (7.612 g NH4SCN per 1000 mL) Dissolve about 8 g of ammonium thiocyanate (NH4SCN) in 1000 mL of water, and standardize by titrating the solution against 0.1 N Silver Nitrate as follows Transfer about 30 mL of 0.1 N Silver Nitrate, accurately measured, into a glass-stoppered flask. Dilute with 50 mL of water, then add 2 mL of Ferric Ammonium Sulfate TS and 2 mL of nitric acid, and titrate with the ammonium thiocyanate solution to the first appearance of a red-brown color. Calculate the normality, and, if desired, adjust the solution to exactly 0.1 A. If desired, 0.1 N Ammonium Thiocyanate may be replaced by 0.1 A potassium thiocyanate where the former is directed in various tests and assays. 

Mercuric Nitrate, 0.1 M [32.46 g Hg(N03)2 per 1000 mL] Dissolve about 35 g of mercuric nitrate [Hg(N03)2-H20] in a mixture of 5 mL of nitric acid and 500 mL of water, and dilute with water to 1000 mL. Standardize the solution as follows Transfer an accurately measured volume of about 20 mL of the solution into an Erlenmeyer flask, and add 2 mL of nitric acid and 2 mL of Ferric Ammonium Sulfate TS. Cool to below 20°, and titrate with 0.1 N Ammonium Thiocyanate to the first appearance of a permanent brown color. Calculate the molarity. 

Sodium Hydroxide, 1N (40.00 g NaOH per 1000 mL) Dissolve about 40 g of sodium hydroxide (NaOH) in about 1000 mL of carbon dioxide-free water. Shake the mixture thoroughly, and allow it to stand overnight in a stoppered bottle. Standardize the clear liquid as follows Transfer about 5 g of primary standard potassium biphthalate [ KHCgH4(COO )2], previously dried at 105° for 2 h and accurately weighed, to a flask, and dissolve it in 75 mL of carbon dioxide-free water. If the potassium biphthalate is in the form of large crystals, cmsh it before drying. To the flask add 2 drops of Phenolphthalein TS, and titrate with the sodium hydroxide solution to a permanent pink color. Calculate the normality. Each 204.2 mg of potassium biphthalate is equivalent to 1 mL of 1 N Sodium Hydroxide. 

Compound Melting Point (°C) Color Calculated (%) C H Found (%) H NMR Chemical Shifts (5) ... 

It is possible to use a unique simulation of FSCL to obtain the dominant colors. However, this method is dependent of the goodness of the unit initialization. So, in order to smooth this noisy initialization in the results of the analysis, we use an ensemble of 50 FSCLs for each number of dominant colors (except for the case of one dominant color, calculated as the mean of the image colors). After generating the 50 networks of each ensemble, their prototypes are used to... 

The minimum of the graph of this index versus log (c/cref) gives the optimum indicator concentration Cref is the reference experimental value of the indicator concentration, c is the indicator concentration and AE is the total difference between two colors, calculated by using the CIELAB or CIELUV systems. The results obtained for the series of indicators studied are summarized in Tables 1 and 3. 

Usually, we assume daylight illumination on or through an object when we discuss its color. A correlated color temperature of 6500 K closely approximates average overcast daylight color at the earth s surface (29). However, this temperature is too hot to physically produce as a standard in laboratories so the mathematical equivalent is factored in by computer when making daylight color calculations (Fig. 1). 

The tables incorporated into color calculating routines by spectrophotometer manufacturers can be found in the ASTM publication Standard Test Method for Computing the Color of Objects by Using the CIE System (90). This ASTM standard is a compilation of calculated product tables for various illuminants with the two standard observers for color matching. Both standard observers are used in various industries to specify color. The operator must choose which observer is to be incorporated into the color calculations for the measured specimens. The overall difference in the color of an object observed by the 10° CIE 1964 Supplementary Observer or the 2° CIE 1931 Observer is usually small but noticeable. This is due to an uneven distribution of cone receptors in the retina of the standard eye. At a solid acceptance (cone) angle of 2°, light from the object activates the cones around the fovea, which are relatively close together and allow maximum... 

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