Hydranal® Standardization of Titre:
Determining the titre of reagents is a necessary task as the titre of standard solutions can change,
for example by the penetration of atmospheric moisture. The frequency of the titre control depends
mainly on the choice of the titrating agent employed and the degree of hermeticity of the equipment used.
The same working conditions, i.e. the same solvent(s), the same volumes, the same temperature,
are used as for the subsequent investigation of the sample. The plastic tubes on the machines are not
absolutely impervious to moisture, and so the titre of the KF reagent decreases slightly overnight.
The tubes should therefore be flushed through several times, prior to determining the titre.
The determined titre should always be compared with the value from the previous day to ensure it
does not vary beyond normal limits.
Use of Water
Pure water can also be used as a standard calibration substance.
While this would appear to be a simple method, the problems encountered in administering exactly 20-200
mg amounts of water should not be underestimated.
Differential weighing of a micro-syringe proves to be the most suitable method.
HYDRANAL®-Standard Sodium Tartrate 2-Hydrate
Sodium tartrate dihydrate is the primary titre standard for KF titrations.
It has a guaranteed water content of 15.66 ± 0.05%. It dissolves relatively quickly in methanol,
and the titration can be started within 3 minutes. In HYDRANAL®-Solvent it dissolves so rapidly
that the titration can be started immediately. Depending on the titre to be determined,
0.03-0.2 g (equivalent to 5-30 mg H2O) are used.
The amount of titrating reagent to be standardized should be about 5 mL.
HYDRANAL®-Water Standards
Standards in liquid form are easy to handle and are therefore preferred for routine analyses.
HYDRANAL®-Water Standard 10.0 is a certified liquid standard. It is delivered in 8 mL glass ampoules.
One package contains 10 ampoules and a "Certificate of Analysis" giving the exact water content of the batch.
To determine the titre, an ampoule is opened and portions of about 2g (exactly weighed)
are administered into the titration vessel using a syringe.
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