ORBECO SP600, Instruction Manual, Page: 211 / 334

209
SP600 Spectrophotometer 01/2008
1.1 Methods
Notes:
1. When testing chlorinated water the residual chlorine contents can influence the colour
reaction of the liquid reagent. This can be avoided (without interfering the pH
measurement) by adding a small crystal of Sodiumthiosulfate (Na
2
S
2
O
3
x 5 H
2
O) to
the sample before adding the PHENOL RED solution. PHENOL RED tablets already
contain Thiosulfate.
2. Due to differing drop size results can show a discrepancy in accuracy by comparison
with tablets. This can be minimised by using a pipette (0.18 ml PHENOL RED solution
is equivalent to 6 drops).
3. After use replace the bottle cap securely.
4.
Store the reagent in a cool, dry place ideally at between 6°C and 10°C.