APHA color scale

Color can be removed effectively and economically with either alum or ferric sulfate at pH values of 5—6 and 3—4, respectively. The reaction is stoichiometric and is a specific reaction of the coagulant with the color to form an insoluble compound (17). The dosage required may be as high as 100—150 mg/L (380—570 mg/gal). Raw-water colors may be as high as 450—500 units on the APHA color scale. The secondary MCL (maximum contaminant level) for color in the finished water is 15 units, although most municipal treatment plants produce water that seldom exceeds 5 units. 

APHA color scale n. Abbreviation for American Public Health Asscoation color scale developed for visually evaluating slight yellowness of solutions. It is based on dilutions of a platinum-cobalt standard solution of 500 APHA. This single-number color scale was originally developed by Hazen, and may also be referred to as the Hazen color scale. 

Hazen color scale n. See apha color scale. 

Hazen Color Scale n See Apha Color Scale. 

Color. Standards Stock standard. Dissolve 1.245g of potassium chloroplatinate (K2PtCl6) and l.OOOg of cobaltous chloride (C0CI26H2O) in water. Add 100ml of coned HQ, and dilute the soln to 1000.0ml with water. (This soln has a color of 500 on the APHA and ASTM platinum-cobalt scales)... 

During the appropriate tests phthalic anhydride was smoothly esterified with 2-ethylhexanol in the mole ratio 1 4. The reaction temperature rose to 200°C. after about 15 minutes, then rose slowly up to 210°C. till the end of the esterification. Table I shows the esterification time in hours after 99.9% conversion, while continuously removing the reaction water, according to the acid number relative to monooctyl phthalic acid. Furthermore, it indicates the ester colors according to the iodine scale in milligrams iodine/100 ml., whereby 1 mg. iodine/100 ml. can be more or less compared with a dye number of 120 APHA. Since, the values are obtained with the same starting materials, it is possible to compare the color numbers. They show that with the same times, the amphoteric catalysis achieves better colors than in the reaction course containing catalytically effective acids. 

Color, Pt-Co scale (APHA, American Public Health Association)... 

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