YOKOGAWA TB830D, User Manual, Page: 56 / 85

< 7. Calibration >
7-5
IM 12E01B30-02EN 1st Edition : Mar. 08, 2023-00
(2) Cleaning with detergent
Touch the surface with your hands. If your hands still get dirty, or if the stain does not come
off even after cleaning (1), clean it with the neutral detergent.
Take the following steps below for cleaning.
a. Dissolve an appropriate amount of detergent in tap water and soak the check tool.
b. Shake the check tool in the detergent solution to clean the surface.
c. If the stain is tough and does not come off by just shaking it, rub gently the surface in the
detergent solution.
d. After the stain comes off, rinse off the cleaning solution with the tap water and drain the
water droplets on the surface.
e. Wipe off the residual solution on the surface with tissue paper, but do not rub hard the
surface.
CAUTION
• Avoid rubbing hardly regardless of the material of the cloth.
• Do not use agents other than mild detergent for wash; avoid ethanol, acetone, and other
solvents.
• Do not use fingers to wash off the stain on the surface.
• Handle with care. Scratches on the surface may interfere with accurate measurement.
7.3 Formazin Standard Solution
A turbidity standard calibration solution should be prepared by diluting a 400 NTU formazin
standard stock solution. This section describes the procedures for preparing a standard stock
solution and a diluted solution for calibration.
7.3.1 Preparing a 4000 NTU Formazin Standard Stock
Solution
(1) Reagents Required
• Hydrazine sulfate, (NH
2
)
2
·H
2
SO
4
• Hexamethylene tetramine, (CH
2
)
6
·N
4
(2) Equipment Required
• Measuring flask, 1 x 2000 mL
• Beaker, 2 x 1000 mL
(3) Precautions
• Use clean, high quality laboratory glassware and measure the volume needed accurately.
• To dilute the formazin standard stock solution, use deionized water or water filtered through
a 1.0 μm zero turbidity filter.
(4) Procedure
a. Weigh out 10.00 g ±0.01 g of hydrazine sulfate with a balance, place it in a 1000-mL beaker,
and add deionized water 700 mL (solution A).
b. Weigh out 100.00 g ±0.01 g of hexamethylene tetramine with a balance, place it in another
1000-mL beaker, and add deionized water 700 mL (solution B).