Letter from Melbourne

摘要

I underwent some medical procedures last year and, as you might expect, took an interest in the chemistry of what was being done to me. Perhaps the most 'chemical' of these procedures involved what is politely known as 'colonic lavage', a procedure that I find many of us have undergone...but few care to talk about. If you've had it, you'll know what I mean. The first potion involved three litres of water and an active ingredient called sodium picosulfate, which turns out to be a triaryl methane derivate in which one of the aryls is alpha-picolinyl, and the other two are benzene-4-sulfonic acid sodium salts. The molecule is similar to that of phenolphthalein, a well-known laxative. In that case, two of the aryl groups are 4-hydroxyphenyl and the third one is 2-carboxyphenyl with its oxygen hooked back to the central carbon.