Lovibond MD 110 - Page 46

pH value L / M331
ENMethod Reference Book1.0 47
EN
Chemical Method
Phenol Red
Appendix
Interferences
Removeable Interferences
1. Salt error Correction of test results (average values) for samples with salt contents
of:
2.
Salt content of the sample Correction
30 g/l (seawater)
-0.15
1)
60 g/l
-0.21
2)
120 g/l
-0.26
2)
180 g/l
-0.29
2)
1)
according to Kolthoff (1922)
2)
according to Parson and Douglas
(1926)
3. When testing chlorinated water the residual chlorine contents can influence the
colour reaction of the liquid reagent. This can be avoided by adding a small crystal
of Sodiumthiosulphate (Na
2
S
2
O
3
⋅5 H
2
O) to the sample solution before adding the
PHENOL RED solution.
Bibliography
Colorimetric Chemical Analytical Methods, 9th Edition, London