Benzyl halides are lachrymators. Their presence in a reaction mixture even as a residue makes work-up troublesome. In some cases, human exposure can cause serious skin problems and so a method for removing them from a reaction mixture before work-up and a simple method to separate the resultant materials in the isolation would be valuable. This is an unproven suggestion. Thiourea is a relatively inexpensive and innocuous material that reacts readily with benzyl halides upon heating together. The products are called phenylmethyl isothiuronium salts and they form insoluble salts with carboxylic and sulfonic acids which can be easily filtered off.
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