The Result 4 calculation in the Titration Application for Biogas (FOS/TAK) does not include the titrant concentration. Is this a mistake?

Document ID

Document ID TE3359

Version

Version 3.0

Status

Status Published

Published Date

Published Date 04/10/2018
Question
The Result 4 calculation in the Titration Application for Biogas (FOS/TAK) does not include the titrant concentration. Is this a mistake?
Summary
Explanation of Nordmann method calculation.
Answer
This application is following/based on the Nordmann method. It is an empirical relationship.

The calculations for result 4 are taken directly from the Nordmann method. Which is, in summary,with the volume from pH 5.0 to 4.4, a 0.1 N H 2SO 4 titrant, and 20 mL of sample; FOS= ((Volume*1.66)-0.15)*Molecular weight and unit factor. 500 would be the molecular weight and unit factor to get the result from eq/L to mg/L CH 3COOH. And since 5 mL of sample is used instead of 20mL, an extra factor of 4 is added in the equation which gives:

FOS= 500*((R3*4*1.66)-0.15);
R3 is just the difference in volume from EP1 and EP2 so it’s the volume from pH 5.0 to 4.4.

This is not a mistake and is taken directly from the referenced material. The reason that the titrant concentration used in the method is 0.1 N is because that is what is used in the Nordmann method, and is required for that empirical formula to work to calculate FOS. The reason that the sample volume was changed to 5 mL and the factor of 4 was added was to increase the range of the test. This was done in order to make it more accessible to more customers with higher concentration samples.
 

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