## Biocide News

and general news relating to the regulation of biocide
products.In the News section you will find the last news
about biocides, including information on IRO new services
and press releases.

## 1. Determination of Acidity

### 1.1 Reagents and Solutions

a) Sodium hydroxide standard titration solution: 0.1mol/L.
b) Bromothymol blue indicator: 1g/L (ethanol solution).

### 1.2 Analysis

Weigh about 1g of the sample (accurate to 0.0002g) and place it in a 250ml Erlenmeyer flask pre-placed with 20ml of water. Add 3-4 drops of bromothymol blue indicator. Titrate with 0.1 mol/L sodium hydroxide standard solution until slightly blue.

### 1.3 Results

The acidity of glyoxal (in terms of acetic acid) is calculated in terms of mass fraction ω1%, and the number is expressed in %, which is calculated by the following formula:

where:

V——the value of the volume of sodium hydroxide standard titrant consumed by the sample, unit (ml);
C——the exact value of the concentration of sodium hydroxide standard titrant, unit (mol/L);
m——the value of the mass of the sample, in grams (g);
M – the value of the molar mass of acetic acid. The unit is grams per mole (g/mol) (M-60).

### 1.4 Allowable Error

Take the arithmetic mean of the parallel measurement results as the measurement result. The absolute deviation of parallel determination is not more than 0.05%.

## 2. Determination of Content

### 2.1 Method Principle

40% acetaldehyde reacts in potassium hydroxide medium to generate methyl glycolate. Excess potassium hydroxide was neutralized and titrated with a standard hydrochloric acid solution.

### 2.2 Reagents and Solutions

a) Potassium hydroxide solution: 1.5mol/L.
b) Standard titration solution of hydrochloric acid: 0.5mol/L.

### 2.3 Analysis

In the conical flask for measuring acidity in 1.1, accurately add 10ml of 1.5mol/L potassium hydroxide solution. Shake well for 15min. Titrate with 0.5mol/L hydrochloric acid standard solution until the solution changes from blue to yellow. At the same time do a blank test.

### 2.4 Results

The glyoxal content is calculated in mass fraction ω2, and the number is expressed in %, which is calculated by the following formula:

where:
V0——the volume value of the standard titrant of hydrochloric acid consumed in the blank test, in milliliters (ml);
V1——the volume value of the standard titrant of hydrochloric acid consumed in the measurement, the unit is milliliter (ml);
C——The standard value of the concentration of the standard hydrochloric acid titrant, the unit is moles per liter (mol/L);
m——the value of the mass of the sample, in grams (g);
M—the value of the molar mass of glyoxal, in grams per mole (g/mol) (M=58.04).

### 2.5 Allowable Error

Take the arithmetic mean of the parallel measurement results as the measurement result. The absolute deviation of parallel determination is not more than 0.2%.