Silica Test Kit

Method Determination with color-disk comparator In sulfuric solution silicate ions react with molybdate ions to form a yellow heteropoly acid. This is reduced to silicomolybdenum blue. The silicate concentration is measured semiquantitatively by visual comparison of the color of the measurement solution with the color fields of a color disk.

2. Measuring range and number of determinations Measuring range / color-scale Number of graduation 1) determinations 0.3 - 0.6 - 1.0 - 1.5 - 2 - 3 - 5 - 7 - 10 mg/l Si 150 0.64 - 1.3 - 2.1 - 3.2 - 4.3 - 6.4 - 11 - 15 - 21 mg/l SiO2 1) for conversion factors see section 8

3. Applications Sample material: Groundwater, surface water, and seawater Drinking water and mineral water Industrial and process water Boiler water and boiler feed water Wastewater and percolating water

4. Influence of foreign substances This was checked individually in solutions containing 5 and 0 mg/l Si. The determination is not yet interfered with up to the concentrations of foreign substances given in the table. Cumulative effects were not checked; such effects can, however, not be excluded. Concentrations of foreign substances in mg/l or % AsO43- 1 Mg2+ 1000 Surfactants 1) 100 Ca2+ 1000 Mn2+ 10 Na-acetate 10 % Cd2 + 1000 NH4+ 1000 NaCl 5 % Cr3 + 100 Ni2+ 1000 NaNO3 10 % Cr2O72- 100 NO2- 1000 Na2SO4 5 % Cu2+ 10 Pb2+ 10 Fe3+ 10 PO43- 50 Hg2+ 100 Zn2+ 100 1) tested with nonionic, cationic, and anionic surfactants

5. Reagents and auxiliaries Please note the warnings on the packaging materials! The test reagents are stable up to the date stated on the pack when stored closed at +15 to +25 °C. Package contents: 1 bottle of reagent Si-1 1 bottle of reagent Si-2 3 bottles of reagent Si-3 1 graduated 6-ml plastic syringe 2 test tubes with screw caps 1 color-disk comparator Other reagents and accessories: MQuant® Universal indicator strips pH 0 - 14, Cat. No. 1.09535 Sodium hydroxide solution 1 mol/l Titripur® (approx. 4 %), Cat. No. 1.09137 Sulfuric acid 0.5 mol/l Titripur®, Cat. No. 1.09072 MQuant® pH-indicator strips pH 0 - 6.0, Cat. No. 1.09531 Silicon standard solution Certipur®, 1000 mg/l Si, Cat. No. 1.70236 MQuant® Flat-bottomed tubes with screw caps for MQuant® tests with color disk comparator (12 pcs), Cat. No. 1.17988 Refill pack: Cat. No. 1.18323 Silicate (Silicic Acid) Test Refill pack for 1.14792 and 1.14410 (Reagents without technical accessories for the number of determinations stated in section 2)

6. Preparation • Analyze immediately after sampling. • The pH must be within the range 2 - 8. Adjust, if necessary, with sodium hydroxide solution or sulfuric acid. • Filter strongly turbid samples.

7. Procedure Measurement Blank sample right-hand tube (A) left-hand tube (B) behind the color behind the color disk disk Pretreated 6 ml 6 ml Inject into the test sample tube with the (20 - 40 °C) syringe. Reagent Si-1 3 drops 1) - Add, close the tube, and mix. The pH must be within the range 1.2 - 1.6. Check with MQuant® pH-indi- cator strips. Adjust the pH, if necessary, with reagent Si-1. Leave to stand for 3 min (reaction time 1). Reagent Si-2 3 drops 1) - Add, close the tube, and mix. Reagent Si-3 10 drops 1) - Add, close the tube, and mix. Leave to stand for 2 min (reaction time 2). Hold the comparator to the light, keeping it upright, and rotate the disk until the closest possible color match is achieved between the two large windows. Read off the result in mg/l Si shown in the small window. 1) Hold the bottle vertically while adding the reagent! Notes on the measurement: • The color of the measurement solution remains stable for at least 60 min after the end of the reaction time 2 stated above. • Turbidity in the measurement solution makes the color comparison more difficult. • If the color of the measurement solution is equal to or more intense than the darkest color on the scale, repeat the measurement using fresh, diluted samples until a value of less than 10 mg/l Si is obtained. Concerning the result of the a