Chemistry Reference
In-Depth Information
2.91.7
High performance liquid chromatography
Silicate has been determined by high performance liquid chromatography [654].
2.91.8
Preconcentration
The application of preconcentration techniques in the determination of silicate is
discussed in section 15.1.10.
2.92
Succinate
2.92.1
Ion chromatography
The application of this technique is discussed under multianion analysis in section 12.2.4.
2.93
Sulphate
2.93.1
Titration methods
Various titration procedures have been described for the estimation of sulphate. These
include reaction with excess barium ions and back titration of excess barium, direct
titration of sulphate with barium ions, and direct titration of sulphate with lead ions.
2.93.1.1
Reaction with excess barium ions and back titration of unconsumed
barium
In one method [703] for the determination of sulphate in non saline waters, the sample is
passed through a strongly acidic cation-exchange resin (H
+
form), aerated to remove
carbon dioxide, then titrated with 0.1N sodium hydroxide to the methyl orange end-point
to obtain the sum of sulphate, chloride and nitrate.
The titrated solution is acidified with 0.2N nitric acid and excess of 0.05N barium
nitrate and then ethanol is added to precipitate barium sulphate. The solution is
neutralised with 0.1N sodium hydroxide, made alkaline with aqueous ammonia, and a
solution of metalphthalein and naphthol green (CI Acid Green 1) added. Unconsumed
barium ions are titrated with 0.05N EDTA to a green colour to obtain the content of
sulphate. The solution acid is made with 0.2N nitric acid, a small amount of aluminium
sulphate added then naphthol green solution and ethanolic diphenylcarbazone added.
Titrate with 0.05N mercuric nitrate until the solution is violet. The amount of chloride
and the amount of nitrate are obtained by difference. Correction factors are determined by
analogously treating water (but omitting the addition of barium nitrate and aluminium
sulphate).
Duvivier [704] has described a potentiometric method which can be used for the
continuous determination of sulphate ions in non saline waters. It is based on the
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