Analytical Method: Nitrite in cooling lubricants (Photometry)

Instruments and Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or

Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or

Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or

Cat.No. 109748  Spectroquant® Photometer NOVA 30 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60 or

Cat.No. 173632  Spectroquant® Colorimeter Move 100

Cat.No. 114946  Rectangular cells 10 mm and/or

Cat.No. 114947  Rectangular cells 20 mm and/or

Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 114547  Spectroquant® Nitrite Cell Test
Cat.No. 114776  Spectroquant® Nitrite Test
Cat.No. 100716  Sulfuric acid 25 % for analysis
Cat.No. 105588  Sodium hydroxide solution 10 % for analysis
Cat.No. 109533  MColorpHastTM pH-indicator strips pH 5 - 10
Cat.No. 110537  Carrez Clarification
Cat.No. 116754  Water for analysis
As samples can be either acid or alkaline, the pH of the ready-to-use emulsion must be adjusted to neutral with acid or alkali prior to determining NO2-. This facilitates precipitation.
Sample preparation:
Adjust the ready-to-use emulsion to pH 6 - 8 with either  sulfuric acid 25 % or sodium hydroxide 10 % solution for analysis. Place approximately 10 ml of the sample in a 200-ml volumetric flask, add approximately 100 ml water for analysis and mix. Add 2 ml of Carrez solution-1 and -2 consecutively, mixing well after each addition. Make up to the mark with water for analysis and mix well. Allow the precipitate to settle. Filter the supernatant through a paper filter; the filtrate must be clear.
Determine with the above mentioned test kits.
Nitrite content in mg/l NO2 = analysis value in mg/l NO2 x 20


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