Chemistry of water -Part 27-

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2 - Calibration of nitrate ions:

Nitrates, together with phenolic compounds and sulfuric acid, form nitrite derivatives of phenol that can be extracted with an organic solution, which is toluene. These formed compounds give a yellow colour in an alkaline medium, the density of which can be measured by spectroscopic method.

Reagents used:

  • Mercuric sulfate solution: 2 mg of mercuric sulfate and 20 ml of concentrated sulfuric acid are placed in 400 ml of distilled water.
  • Sulfuric acid reagent: It is prepared by dissolving 42 ml of the previous solution in 158 ml of concentrated sulfuric acid, and it is renewed daily.
  • Xylenol reagent: It is prepared by dissolving 1 g of xylenol in 100 ml of acetic acid.
  • Sodium hydroxide solution.
  • Toluene.
  • Sulfamic acid solution.
  • Potassium nitrate solution.

Standard Curve:

  • The solutions indicated in Table 1 are prepared to obtain the standard curve:

    [Table1(Created by using Word Microsoft)]

The solutions referred to in Table 1 are cooled by placing them in cold water, then 1 ml of xylenol reagent is added to each of them and placed in a water bath at a temperature of 35 ° C for half an hour, and the contents of the vials are poured into a series of separation funnels and washed with water Distilled, where the wash water is added to the separation funnels. 10 ml of toluene is added to each separation funnel, and it is mixed well with the aqueous solution, and the organic layer is separated and washed with distilled water several times, then mixed with 20 ml of sodium hydroxide solution and the mixture is shaken well before we leave it for twenty minutes. We extract the aqueous layer and measure the absorbance at the wavelength of 432 nm using the spectrophotometer, and the result of the absorbance is in terms of concentration.


  • [AQUAPROX- Livre: Traitement des eaux de refroidissement. Imprimé en France par EMD S.A.S- 53110 Lassay-les-Chateaux. N° d'imprimeur: 15566- Dépot légal: juin 2006. N° 842- Cyclus print 90°]

  • [Introduction to Water Chemistry (Pollution- Treatment- Analysis). Dr. Nasser Al-Hayek. Publication of the Higher Institute for Applied Sciences and Technology (HIAST). Syrian Arab Republic, 2017.]

  • Folco Laverdière, Anja Holstein, Laurent Thiebaut, Robert Mallee, Guillaume Gravejat, Benjamin Des clozeaux: Les principales methodes d’analyse,1999, p5.