LaMotte DC1600 Colorimeter - Manual (Page 27)

CHROMIUM
HEXAVALENT, TRIVALENT & TOTAL
DIPHENYLCARBOHYDRAZIDE METHOD CODE 3698
QUANTITY CONTENTS CODE
60 mL *Sulfuric Acid, 5N *7681-H
10 g *Chromium Reagent Powder *V-6276-D
15 mL *Sodium Azide, 5% *7683-E
30 mL Potassium Permanganate, 0.5% 7682-G
60 mL Deionized Water 5115PT-H
1 Pipet, plain, glass, w/cap 0341
1 Pipet, 1.0mL, plastic 0354
1 Pipet, plain, plastic 0352
1 Spoon, 0.1 g, plastic 0699
1 Graduated Cylinder, 50 mL, glass 0418
1 Flask, Erlenmeyer, 125 mL, glass 0431
1 Test tube holder 1113
1 Filter Paper 0465
1 Funnel, plastic 0459
*WARNING: Reagents marked with a * are considered hazardous substances. Material Safety Data Sheets (MSDS) are supplied for
these reagents. For your safety, read label and accompanying MSDS before using.
A toxic chemical, chromium is found in two forms in the water; trivalent chromium (Cr+3) and hexavalent chromium
(Cr+6). Chromium enters the water from industrial waste, including large air conditioning units where it may be used to
control corrosion, or metal finishing plants. Trivalent chromium is more toxic than hexavalent chromium. Levels greater
than 0.5 ppm indicate improperly treated industrial waste. It is important to maintain chromium levels at or below 0.5 ppm,
because clams and other shellfish will store chromium in their systems, accumulating levels which may be dangerous to the
consumer, whether human or animal.
APPLICATION: Drinking, surface, & saline water; domestic and industrial waste
RANGE: 0 – 1.0 ppm
METHOD: The trivalent chromium is converted to hexavalent chromium by permanganate under acidic
conditions. Hexavalent chromium reacts with 1,5 diphenylcarbohydrazide under acidic
conditions to form a red-purple color in proportion to the amount of chromium present.
SAMPLE HANDLING
& PRESERVATION: Analysis for chromium should be made as quickly as possible after sample collection since
storage in glass or plastic containers may result in low chromate values.
INTERFERENCES: High concentrations of mercurous and mercuric ions may interfere.
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