Key points of Karl Fischer method for moisture detection of n-butyl acrylate?

Key points of operation for moisture detection of n-butyl acrylate by Karl Fischer method

with the continuous development of industrial production, n-butyl acrylate as an important chemical raw material, in the production process of its quality control is particularly important. As one of the key indicators affecting the performance of n-butyl acrylate, the detection method of moisture has attracted much attention. Karl Fischer method, as a classic moisture detection method, is widely used in chemical industry because of its high sensitivity and simple operation. This paper will analyze the operation points of Karl Fischer method to detect the moisture content of n-butyl acrylate in detail, in order to provide reference for relevant workers.

1. the Fundamentals of Karl Fischer's Law

karl Fischer method is a kind of moisture detection method based on chemical reaction. Its core principle is to use iodine and sulfur dioxide to react in methanol solution to generate potassium iodine bisulfite. The reaction needs the participation of water to complete. From the volume of Fischer reagent consumed during titration, the moisture content of the sample can be calculated.

Preparation before 2. experiment

before the Karl Fischer method is used to detect the moisture content of n-butyl acrylate, it is necessary to make sufficient preparations to ensure the accuracy and repeatability of the experiment.

1. Selection and preparation of reagents

• fischer Reagent it is usually composed of iodine, sulfur dioxide, pyridine and methanol, and should be prepared strictly according to the instructions. After the preparation is completed, it should be kept away from light and its effectiveness should be checked regularly.
• Methanol as the reaction solvent, analytically pure or chromatographically pure methanol should be selected to avoid the influence of impurities on the experimental results.

1. Calibration of instruments and equipment

• the calibration of the burette is one of the key steps in the experiment. Make sure that the scale of the burette is accurate and the titration head has no leakage.
• The adjustment of the titration table is also very important. It is necessary to ensure that the titration head is aligned with the receiving container to avoid bubbles during the dripping process.

1. Preparation of samples

• when weighing n-butyl acrylate samples, use dry weighing instruments and minimize the introduction of moisture during weighing.
• The sample should be shaken evenly to ensure the adequacy of the reaction during titration.

3. titration procedure

1. preparation before titration

• add the prepared Fischer reagent to the titration head and adjust to zero scale.
• The methanol solution was added to the receiving vessel and gently shaken to remove air bubbles.

1. titration process

• slowly add the Fischer reagent dropwise while continuously shaking the receiving container to ensure complete reaction.
• When the solution appears blue-green, gradually slow down the titration speed until the solution becomes light yellow, and keep it for 30 seconds without fading, which is the end point of titration.

1. Recording and calculation

• record the volume of Fischer reagent consumed during the titration.
• Calculate the moisture content in n-butyl acrylate according to the formula:
  [ \text {moisture content} = \frac{V \times C \times 0.018}{m} ]
  V is the volume (mL) of the Fischer reagent consumed in the titration, C is the concentration (mol/L) of the Fischer reagent, 0.018 is the millimolar mass (g/mmol) of water, and m is the mass (g) of the sample.

4. Result Analysis and Precautions

1. analysis of results

• judgment of titration end point: Karl Fischer titration endpoint color change is more obvious, but due to personal visual differences, it is necessary to ensure accurate judgment of the titration endpoint.
• Purity of Reagents: The preparation of Fischer reagent should be carried out in strict proportion. Insufficient purity or improper proportion of any reagent will affect the experimental results.

1. Precautions

• control of environmental humidity during the experiment, changes in ambient humidity may affect the titration results. It is suggested to carry out the experiment under the condition of constant temperature and humidity.
• Maintenance of instruments the burette and titration head should be cleaned and maintained regularly to avoid the influence of residual reagents on subsequent experiments.
• The Necessity of Blank Experiment: Before the start of each experiment, a blank experiment is required to correct the purity of the reagent and the stability of the experimental conditions.

5. Summary

karl Fischer method is a classical moisture detection method, which has the advantages of high sensitivity and simple operation. During the experiment, we need to pay attention to the key links such as the preparation of reagents, the calibration of the instrument and the judgment of the titration end point. By strictly complying with the operation points, the accuracy and repeatability of the test results can be effectively improved, and a reliable guarantee for the quality control of n-butyl acrylate can be provided.