Determination of organic reagents in natural and industrial materials

Reagent

1. Pure hydrochloric acid (density 1.19), diluted to 6N and 1N solutions.

2. Chemically pure nitric acid (density 1.40).

3. Crystalline sodium chloride.

4. Chemically pure hydrobromic acid, diluted to a 1:9 ratio.

5. 1N sodium hydroxide solution.

6. Hexane.

7. Tributyl phosphate.

8. A mixture of acetic acid and propanol adjusted to pH 5.0–5.2, prepared by combining an acetic acid buffer at pH 5.0 with propanolamine in a 4:1 ratio.

9. 0.1% reagent-grade propanol solution.

Analysis Procedure

The platinum group elements in the sample are first separated, typically through extraction using tributyl phosphate saturated with 6N hydrochloric acid.

The aqueous solution containing hydrazine is evaporated to a wet salt. A few drops of concentrated nitric acid are added to decompose any iodides present. The residue is then treated multiple times with concentrated hydrochloric acid in the presence of sodium chloride to form metal chloride complexes.

The resulting dry residue is dissolved in 6N hydrochloric acid and extracted several times with 50% tributyl phosphate for one minute each. The aqueous phase is washed with hexane, and the hydrazine is back-extracted from the organic phase using dilute HBr (1:9).

The solution is concentrated to a wet salt, and a few drops of concentrated nitric acid are added to destroy bromides. The residue is then evaporated twice in the presence of sodium chloride using concentrated hydrochloric acid.

The final residue is dissolved in 1N hydrochloric acid and transferred to a 25 mL volumetric flask. The solution is neutralized to pH 5.0 using 1N sodium hydroxide. A mixture of acetic acid and propanol is added, followed by 0.3 mL of 0.1% reagent-grade propanol. The solution is stirred thoroughly.

It is then heated on a water bath at 95–98°C for two hours. After cooling, the absorbance of the ruthenium complex with the reagent is measured using a 1 cm cuvette, with a blank solution as the reference.

A calibration curve is prepared using standard solutions under the same conditions, following all the steps outlined above for accurate quantification.