Hach DR/850, Procedures Manual, Page: 339 / 460

339
Standard Adjust
To adjust the calibration curve using the reading obtained with the
7.0 buffer solution, press the
SETUP
key and scroll (using the
arrow keys) to the STD setup option. Press
ENTER
to activate the
standard adjust option. Then enter
7.0
to edit the standard
concentration to match that of the standard used. See Section 1 ,
Standard Curve Adjustmen t for more information. Press
ENTER
to
complete the curve adjustment.
Interferences
Chlorine does not interfere at levels of 6 mg/L or lower.
Salt water (sea water) will interfere and cannot be analyzed using
this method.
Summary of Method
This method uses a sulfonphthalein indicator (Phenol Red) to
determine pH colorimetrically. Phenol Red has a working range
of pH 6.8 (yellow) to 8.2 (red).
REQUIRED REAGENTS & APPARATUS
Quantity Required
Description Per Test Units Cat. No.
Dropper, 0.5 & 1.0 mL marks ............................................ 1.............. 20/pkg..............21247-20
Phenol Red Indicator Solution, spec grade ...............1.0 mL...............50 mL..............26575-12
Sample Cells, 10-20-25 mL, w/ cap ................................... 2................ 6/pkg..............24019-06
OPTIONAL REAGENTS
pH 7.0 Buffer Solution .......................................................................500 mL..............12222-49
OPTIONAL APPARATUS
Description Units Cat. No.
Thermometer, -20 to 110 °C, Non-Mercury............................................ each..............26357-02
For Technical Assistance, Price and Ordering
In the U.S.A. call 800-227-4224
Outside the U.S.A.—Contact the Hach office or distributor serving you.
pH,
continued