SU968754A1 - Method of separate determining formaddehyde and oxymethyl-containing compounds in their mixtures - Google Patents

Description

The invention relates to the quantitative determination of free formaldehyde and hydroxymethyl compounds when they are present in the mixture.

Oxymethyl compounds are. intermediate products of a large number of organic syntheses, for example, the preparation of formaldehyde-containing polymers, tris (hydroxymethyl) aminomethane and other important organic compounds.

A known method for the determination of formaldehyde by potentiometric titration with a solution of hydroxylamine hydrochloride [1].

The disadvantage of this method is the inability to use it for separate determination of formaldehyde and oxymethyl-containing compounds.

The closest to the proposed technical essence and the achieved results is a method for separate determination of formaldehyde and oxymethyl-containing compounds by dissolving one sample of the analyzed. substances in a saturated solution of sodium tetraborate and titration with a solution of hydroxylamine salt in dimethyl sulfoxide; the second sample of the analyte is treated first with ¹ secondary amine, then with 0.1 N rust2 with a potassium hydroxide thief, followed by potentiometric titration of the resulting mixture with 0.1 N alcohol solution, ¹ rum of perchloric acid [2].

The disadvantage of this method is its complexity and duration.

The purpose of the invention is to simplify the method and reduce its duration.

This goal is achieved 1θ by the method of separate determination of formaldehyde and hydroxymethyl compounds by dissolving the analyzed sample in a saturated solution of sodium tetraborate and titration with a solution of a hydroxylamine salt in dimethylformamide followed by processing of the solution obtained after titration with a 30-40% alkali solution and repeating. titration with the same titrant. 20 - Simplification of the process is achieved by the fact that the determination of formaldehyde and hydroxymethyl compounds is carried out sequentially in one solution, and for the determination of both components 25 one titrant is used - a solution of hydroxylamine salt in dimethyl sulfoxide ·.

The acceleration of the process is achieved due to an increase in the decomposition rate of oxymethyl compounds with a 30-40% ^ ^υ hydroxide solution (the concentration of hydroxide is 50-60 times higher than in the known method).

A decrease in the concentration of hydroxide leads to a decrease in the accuracy of determination due to the non-quantitative decomposition of oxymethyl compounds, and a 5 increase in the concentration of hydroxide leads to adverse reactions of titanium. those with a titration medium and distort ¹ determination results.

The method is as follows. Щ To the sample sample containing 0.0010-0.0015 mol of the compounds to be determined, add 29 ml; saturated aqueous sodium tetraborate, a pair of electrodes immersed in a solution (platinum and a calomel) and potentiometrically titru- ¹ dissolved 0.1-0.15 M solution of hydroxylamine in dimethyl sulfoxide salt until the potential drop on the titration curve. Then, 5-7 ml of a 30-40% aqueous hydroxide solution is added to the solution and titration is continued until a second potential jump appears on the titration curve. The first jump corresponds to the quantitative titration of free formaldehyde, and the second corresponds to the titration of formaldehyde released during the decomposition of oxymethyl-ethylene.

Example 1. Quantification of formaldehyde and dimethyl urea.

A sample of the analyzed sample 0.0965 g is placed in a glass for: titration with a capacity of 100 megapixels; 20 ml of a saturated aqueous solution of sodium tetraborate are added, stirred until the sample is completely dissolved. A pair of electrodes is immersed in the solution (platinum and calomel) and potentiometrically titrated with 0.1496 M with a solution of ¹ hydroxylamine hydrochloride in dimethyl sulfoxide until a potential jump appears on the titration curve. Then, 5 MP of a 30% aqueous sodium hydroxide solution is added to the solution and titration is continued until a second potential jump appears.

The content of free formaldehyde was calculated by the first potential jump (titrant consumption 2.17 ml),%?

35 * y - 2.17-0.030-0.1496 _χ

- ----- η gloss ιυ, ι

0.0965

The content of dimethylolurea was calculated by the second potential jump (titrant consumption 9.62 mp),%:

9.62-0.120-0.1496

0.09'65 / · 2 • 100 = 89.6.

Example 2. Quantification of formaldehyde and tris (oxymethyl) nitromethane.

A sample of the analyzed sample 0.1484 g is dissolved in 20 ml of a saturated aqueous solution of sodium tetraborate and potentiometrically titrated with a 0.1228 M solution of hydroxylamine acetate in dimethyl sulfoxide until a potential jump appears on the titration curve. Then, 6 ml of a 40% aqueous potassium hydroxide solution are added to the solution and titration is continued until a second potential jump appears. The titrant consumption for titration of formaldehyde is 7.05 ml, and for titration of tris (hydroxymethyl) nitromethane 6, 59 ml.

The formaldehyde content,%:

„_ 7 / 05-0.03-0.1228 X _d -100 = 17.5.

Standard deviation ± 0.9%

The content of tris (oxymethyl) nitromethane,%:

_v _ 6.59-0.151 -0.1228

---------- 100 = 82.3.

Example 3. Quantification of formaldehyde and N-hydroxymethylbenzamide.

A sample of the analyzed sample 0.12483 g is dissolved in 20 ml of a saturated aqueous solution of sodium tetraborate and potentiometrically titrated with 0.1015 m solution of hydroxylamine sulfate in dimethyl sulfoxide until a potential jump appears on the titration curve. Then, 7 ml of a 35% sodium hydroxide solution was added to the solution and titration was continued until a second potential jump appeared. The titrant consumption for titration of formaldehyde is 1.97 ml, and for titration of N-hydroxymethylbenzamide 7.74 ml.

The formaldehyde content,%:

1.97-0.03-0.1015

0.12483 • 100 = 4.8.

Standard deviation + 0.5%. The content of N-hydroxymethylbeneamide,%:

„_7.74-0.151-0.1015

0.12483

100 = 95.1.

Standard deviation + 0.9%.

Claims (2)

1.M.F.Eshworth. Titrimetric methods for the analysis of organic compounds. M., Himi, 1968, p. 258. 2. Veveris L.YA ,, Spinets B.A. et al. Determination of formaldehyde and tris (oxymethyl) nitromethane in a condensate produced by tris (oxyme III) aminomethane. Ref. Sat NINTECHIM Methods of analysis and quality control of products in the chemical industry, 1980, 8, p. 21-25 (prototype).