How to determine free water and bound water in polyformaldehyde?
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When measuring the content of paraformaldehyde, a dry sample is required; in other words, free water must first be removed. (1) How can free water be removed? By vacuum drying? What should the temperature be? (2) How is the bound water determined? Thank you!
Do you want to remove the water? When heated, formaldehyde gas is released, which is harmful to both people and the environment. It seems that it’s sufficient to use a sodium sulfite solution along with polyformaldehyde, and then use the sodium hydroxide generated through back-titration with an acid.
Since it is related to water and degree of polymerization, free water can be determined using the Karl Fischer method. Spray granulated products can be dried using vibrating beds, fluidized bed dryers, belt dryers, etc.; it is possible to consult manufacturers of drying systems for this purpose. Vacuum drying and scraper crushing in a reactor is also possible, though the degree of polymerization will be higher.
It’s only now that I realize everything I said on the second floor was complete nonsense. The polyformaldehyde I was exposed to in the past was used only for measuring the total amount of aldehydes; there was no requirement to measure moisture, and at that time I thought it was impossible to determine the bound water. I just looked up the concept of bound water online; it was very informative. I need to keep studying more on this topic in the future. The image below provides an introduction to bound water.
Haha, bro, reflect on yourself three times a day!