Silica
© Hach Company, 2003. All rights reserved. Printed in the U.S.A. 3/04 1ed
Page 4 of 4 Silica_PP_Low_HTB_Eng_Ody.fm
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Telephone: (970) 669-3050
FAX: (970) 669-2932
FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING:
Call 800-227-4224
Contact the HACH office or distributor serving you.
www.hach.com techhelp@hach.com
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On the Worldwide Web – ; E-mail –
toll-free
2. To adjust the calibration curve using the reading obtained with the
1.00 mg/L Standard Solution, touch
Options on the current program menu.
Touch
Standard Adjust.
3. Touch
On. Touch Adjust to accept the displayed concentration. If an alternate
concentration is used, touch the number in the box to enter the actual
concentration, then touch
OK. Touch Adjust.
See Section 3.2.4 Adjusting the Standard Curve on page 40 for more information.
Method Performance
Precision
Standard: 1.00 mg/L SiO
2
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Silica and phosphate in the sample react with molybdate ion under acidic
conditions to form yellow silicomolybdic acid complexes and phosphomolybdic
acid complexes. Addition of citric acid destroys the phosphate complexes. An
Amino Acid is then added to reduce the yellow silicomolybdic acid to an intense
blue color, which is proportional to the silica concentration. Test results are
measured at 815 nm.
Required Reagents
Quantity Required
Description per test Unit Cat. No.
Low Range Silica Reagent Set (100 tests) .....................................................................................................24593-00
Includes:
(1) Amino Acid F Reagent Powder Pillows (for 10-mL sample).1 pillow........... 100/pkg.............22540-69
(2) Citric Acid Powder Pillows ........................................................2 pillows......... 100/pkg.............21062-69
(2) Molybdate 3 Reagent Solution ...................................................1 mL ................ 50 mL...................1995-26
Required Apparatus
Sample Cells, 10-mL, w/cap...................................................................2 ....................... 6/pkg.................24276-06
Required Standards
Deionized Water ................................................................................................................. 4 L ..........................272-56
Silica Standard Solution, 1-mg/L SiO
2
............................................................................ 500 mL.................1106-49
Silica Standard Solution, 25-mg/L as SiO
2
..................................................................... 236 mL...............21225-31
Program 95% Confidence Limits of Distribution
651 0.95–1.05 mg/L SiO
2
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.013 mg/L SiO
2
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