Lovibond MD 100, Manual Of Methods, Page: 42 / 369

pH-value T / M330
EN Method Reference Book 1.0 43
EN
Chemical Method
Phenol Red
Appendix
Interferences
Persistant Interferences
1. Water samples with little Carbonate hardness* can lead to false pH values.
*K
S4.3
< 0.7 mmol/l ≙ total alkalinity < 35 mg/l CaCO
3
.
Removeable Interferences
1. pH values below 6.5 and above 8.4 can produce results inside the measuring range.
A plausibility test (pH-meter) is recommended.
2. Salt error
For salt concentrations below 2 g/l, no significant error, is expected due to the salt
concentration of the reagent tablet. For higher salt concentrations the measurement
values
have to be adjusted as follows:
Salt
content per
sample in
g/l
30
(seawater)
60 120 180
Correction
-0.15
1)
-0.21
2)
-0.26
2)
-0.29
2)
1)
according to Kolthoff (1922)
2)
according to Parson and Douglas (1926)
Bibliography
Colorimetric Chemical Analytical Methods, 9th Edition, London