Question 1

What is the optimal substance weight for titer determination?

Accepted Answer

	Sample size for 5 mL buret
Type of standard	Titrant 1	Titrant 2	Titrant 5
Water standard 10 mg/g	0.05–0.45 g	0.1–0.9 g	0.25–2.25 g
Na tartrate 156.6 mg/g		0.006–0.057 g	0.03–0.27 g
Water 1000 mg/g	–	–	~ 0.02 g
Water	–	–	~ 20 µL

	Sample size for 10 mL buret
Type of standard	Titrant 1	Titrant 2	Titrant 5
Water standard 10 mg/g	0.1–0.9 g	0.2–1.8 g	0.5–4.5 g
Na tartrate 156.6 mg/g	0.02–0.057 g	0.013–0.115 g	0.03–0.287 g
Water 1000 mg/g	–	~ 0.015 g	~ 0.025 g
Water	–	~ 15 µL	~ 25 µL

	Sample size for 20 mL buret
Type of standard	Titrant 1	Titrant 2	Titrant 5
Water standard 10 mg/g	0.2–1.8 g	0.4–3.6 g	1–9 g
Na tartrate 156.6 mg/g	0.02–0.175 g	0.026–0.23 g	0.065–0.58 g
Water 1000 mg/g	–	0.02–0.035 g	0.02–0.09 g
Water	–	15–35 µL	15–90 µL

Question 2

Poor reproducibility of the titer determination with water

Accepted Answer

It is also possible to determine the titer with water. It should be noted in this connection that very small volumes have to be used. The handling takes a bit of getting used to in the beginning and requires a great deal of practice.

The detailed procedural method can be seen in the videos here.

Question 3

How often should the titer be determined?

Accepted Answer

It is difficult to make a general statement. The frequency of titer determination depends on a variety of different factors:

leak-tightness of the titration system
selection of the titrant
humidity in the laboratory
changes in room temperature
requirements regarding exactness of the result

In principle, we recommend that titer determination should be carried out daily in the presence of high requirements concerning exactness. If no relevant changes are found, then the frequency can be reset to weekly. It should be noted that in general the titer of one-component reagents drops faster than that of two-component reagents.

Question 4

Rise in the values during titer determination with disodium tartrate dihydrate

Accepted Answer

The disodium tartrate dihydrate dissolves incompletely when several determinations are carried out in the same working medium because of the limited capacity of methanol to dissolve disodium tartrate dihydrate.

We recommend that you replace the working medium at shorter intervals.

Question 5

Poor reproducibility of the titer determination with disodium tartrate dihydrate

Accepted Answer

The disodium tartrate dihydrate has probably not dissolved completely. The extraction time should be increased in order to prevent this.

In addition, care should be taken to ensure that the sample does not remain on the side of the vessel or on the electrode.

An increasing titer may be traced back to the limited capacity of the methanol to dissolve disodium tartrate dihydrate. We recommend that you replace the working medium at shorter intervals.

Another reason may be that the sample size selected was not optimal.

Question 6

How to carry out the titer determination?

Accepted Answer

Leading reagent manufacturers offer certified water standards for titer determination. We recommend the use of certified standards. They are simpler to handle, because larger sample volumes can be added here than with titer determination using distilled water.

Standard solutions can be obtained with the water contents 10.0 ±0.1 mg/g and 5 ±0.2 mg/mL, although the latter is not certified.

The possibility also exists of carrying out the titer determination with distilled water or with disodium tartrate dihydrate.

Karl Fischer - Determinação Fator

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Sample size for 5 mL buret

Sample size for 10 mL buret

Sample size for 20 mL buret