This method describes how to determine the chemical oxygen demand in wastewater through oxidation with potassium dichromate.
Potassium dichromate is added to the acidified sample as an oxidizing agent along with silver sulfate as a catalyst; mercury sulfate is also added to prevent the formation of elemental chlorine from chlorides. After oxidation of the organic substances in the sample (the dichromate ion is reduced to the chromium(III) ion in an acidic solution), the chromate required to achieve this is determined through reverse titration of the excess potassium dichromate with iron(II) solution (adjusted) against ferroin as an indicator [1].
Cr2O72- + 6 e- + 14 H3O+ → 2 Cr3+ + 21 H2O
Cr2O72- + 6 Fe2+ + 14 H3O+ → 2 Cr3+ + 6 Fe3+ + 21 H2O
Determination of the total oxygen content (dissolved and in the headspace) in filled containers
The bottled or canned beer is brought to 20 °C and mechanically shaken, thereby achieving equilibrium between the oxygen dissolved in the beer and the oxygen present in the headspace (Henry’s and Dalton’s laws). By directly measuring either the oxygen in the beer or in the headspace, the total oxygen can be calculated through referencing a table of values, which includes the headspace volume as a percentage of the fill volume.
Wastewater generated in the industrial production of beer and food
The water sample is diluted with oxygen-rich water “free of oxidizable organic substances” so that after the incubation period there is still at least 2 mg oxygen per liter left in the water. Afterward, the dissolved oxygen in the diluted sample should be determined immediately and then again after five days using an iodometric method or with oxygen electrodes. The difference between the two values yields the BOD5 (taking into account the dilution factor).
Boiler water for use in the production of beer and other foods
Hydrazine and p-dimethylaminobenzaldehyde in an aqueous solution containing alcohol form a compound which is yellowish red in color.
This method describes the determination of the chemical oxygen demand in wastewater photometrically with a cuvette test.
Oxidizable substances in the water sample react with the sulfuric acid potassium dichromate solution in the presence of silver sulfate as a catalyst. Chloride is masked with mercury sulfate. The decrease in the yellow color of Cr6+ is measured.
Hops and hop products intended for use in beer brewing or elsewhere in the food industry
The volatile constituents in hops or hop products are obtained by means of steam distillation. The hydrocarbon and oxygen fractions are separated using a process involving column chromatography.