740 Portable Suspended Solids
21 Preparation of Formazin Turbidity Standard
21.1 Health & Safety Precautions
The chemicals used when following this procedure are harmful, therefore the correct
safety precautions must be carried out. During handling, avoid inhalation and contact
with the eyes or skin. Wash hands thoroughly after use. Refer to the data sheets for
further details of the chemicals used.
21.2 Method of Preparation
he preparation of a Formazin Turbidity Standard should be carried out with great care.
Absolute cleanliness should be observed at all times to avoid any contamination of the
solution.
All water used should be freshly distilled or de-mineralised. During preparation and use,
keep the solution covered to prevent contamination.
Dissolve the Hydrazinium Sulphate 10g into 1 litre of water. Stir the solution
thoroughly.
Dissolve the Hexamine 100g into 1 litre of water. Stir the solution thoroughly.
Pour the above solutions into a 2.5 litre Winchester or similar type amber
glass bottle and mix thoroughly. Allow the mixture to stand undisturbed for 24
hours at 25
C. The resultant solution will have a turbidity of 4000 FTU.
Prior to use the standard should be mixed thoroughly. i.e. before pouring out
the standard, shake the bottle well.
21.3 Preparation of Dilution's
The 4000 FTU standard can be used to prepare solutions of lower values by diluting
with water. The formula below can be used to calculate the ratio of water to 4000 FTU
standard to produce a solution of the required value.
W
A
4000
1
W = parts water to 1 part 4000 FTU standard
A = Required FTU value
172430IM-Iss07.odt 172430IM-Iss07 Issue Date 23/10/2014
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