Determination of sodium methoxide in methanol, sodium methoxide solution and free base

HG/T 2561-2014 Industrial Methanol Sodium Methanol Solution

range

This standard specifies the requirements, test methods, inspection rules and signs, packaging, transportation, storage, etc. of sodium methoxide methanol solution.

This standard is applicable to the sodium methoxide methanol solution prepared by the reaction of methanol and sodium hydroxide by dehydration. It is also suitable for the sodium methoxide methanol solution formed by the reaction of methanol with sodium metal.

Molecular formula: CH3ONa

Relative molecular mass: 54.02 (according to 2017 international relative atomic mass)

Claim

Appearance: Colorless to pale yellow micro-belt viscous viscous liquid.

Industrial methanol sodium methanol solution should meet the technical requirements shown in Table 1.

experiment method

Determination of sodium methoxide content

Method principle

In industrial sodium methoxide methanol solution, sodium methoxide is decomposed into methanol and sodium hydroxide by water and a standard titration solution of hydrochloric acid of known concentration is used for quantitative determination. The content of sodium methoxide was calculated by subtracting the amount of free base from the volume of the hydrochloric acid standard titration solution.

Reaction equation:

Determination of free base (calculated as sodium hydroxide)

Method principle

The sample is neutralized with anhydrous acetic acid, and the sodium methoxide in the sample is neutralized with anhydrous acetic acid to become sodium acetate and methanol, and the sodium hydroxide in the sample is neutralized to become sodium acetate and water, and then known. The water equivalent of the Karl Fischer reagent is quantitatively reacted with the produced water.

Reaction equation:

Reagent

Methanol: Water is not more than 0.05%.

Glacial acetic acid: moisture is not more than 0.05%.

Glacial acetic acid-methanol solution: Prepared according to glacial acetic acid:methanol = 1:5 (volume ratio).

Karl Fischer reagent (one-component volume method moisture determination reagent).

Karl Fischer reagent calibration of water titer

Take 20 mL of glacial acetic acid-methanol solution in a dry 100 mL stoppered reaction flask, titrate with a Karl Fischer reagent to be calibrated to amber under stirring (excluding Karl Fischer reagent consumption), and then weigh 10 mg~ 20 mg of water, accurate to 0.0002 g, was placed in a reaction flask and titrated with a Karl Fischer reagent to be calibrated until the solution turned from pale yellow to amber (or the end point was determined by potentiometry). The titer T of Karl Fischer reagent for water, expressed in g/mL, is calculated according to formula (2):

In the formula:

V. The value of the physical test consumed by the Karl Fischer reagent, in milliliters (mL);

The value of the mass of m0-one water, in grams (g).

Result calculation

The mass fraction ω2 of the free base (calculated as sodium hydroxide), expressed as a percentage in %, calculated according to formula (3):

In the formula:

V - titration sample consumption volume of Karl Fischer reagent, the unit is milliliter (mL);

T - Karl Fischer reagent titer value for water, in grams per milliliter (g / mL);

m The value of the mass of the sample, in grams (g);

2.22 -1 mass ratio of 1 mol of sodium hydroxide to 1 mol of water.

The arithmetic mean of the results of two parallel determinations is the measurement result, and the difference between the results of the two parallel determinations is not more than 0.05%.