Why were no crystals formed when urea phosphate was prepared in the laboratory?
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85% thermal phosphoric acid was diluted with water to obtain 70% phosphoric acid, which was then reacted with urea in a water bath at 80 degrees Celsius in a molar ratio of 1:1. After stirring for 20 minutes, the mixture was cooled; however, no crystals formed even after 24 hours of cooling. What could be the reason?
Phosphoric acid reacts with urea to form urea phosphate; after the reaction is complete, concentration under reduced pressure is required, followed by cooling for crystallization. Analysis of the reasons for no crystallization: On one hand, the reaction did not proceed to completion; you can extend the reaction time and observe again. Relevant literature indicates that the reaction time is approximately 45 minutes ； On the other hand, at your experimental crystallization temperature, no supersaturated solution was formed because concentration was not carried out.