The newly purchased ethylene glycol had a freezing point of -32°C as determined by a condensation thermometer, yet the quality inspection report indicated a purity of 99.95%
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Recently, the factory purchased a batch of ethylene glycol. The test report indicated that it was industrial-grade ethylene glycol with a purity of 99.95%. However, when it arrived at the factory, a freezing point test was conducted, and it took until -32°C for it to solidify. By referring to the freezing point chart for ethylene glycol solutions, the purity was estimated to be around 90%; yet the manufacturer’s chromatography test showed a purity of 99.95%. What’s going on here? Does anyone know the answer? There’s another issue related to the handshake phenomenon: when using a mixture containing ethylene glycol at a concentration of 10%~20%, the freezing point is measured using a freezing point detector, and sometimes the mixture starts to freeze slightly halfway through, only to thaw out again immediately; the temperature then continues to drop. I’ve been puzzled by this for a long time.
This post was last edited by qugd on 2020-12-23 at 15:00. The purity of this substance is questionable, as the freezing point of pure ethylene glycol is around -13 degrees. There must be a certain amount of water in this ethylene glycol, as adding water lowers the freezing point; this is also the method used to prepare antifreeze. Purity is measured by chromatography; water is certainly not counted as an impurity, and only the amounts of other alcohols are recorded. It is possible that a FID detector is being used, and it does not respond to this detector. Detecting water requires a thermal conductivity detector. The water content of ethylene glycol can be accurately measured using the Kjeldahl titration method or the Kjeldahl electrical method.
Experiments have shown that if the confidence level of the test report is low, one should first file a complaint with the supplier, informing them of potential quality issues and requesting that they take action. These days, many suppliers use a test report – which may be from a third party – to sell their products. The batch number on the test report does not correspond to the batch of products that are actually shipped; as a result, it is possible for the product quality to be unstable and not meet the required standards.