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enamine nature of structure 1, which Heinert and Martell have shown to predominate in aqueous solution.4The hydrogen bonding is assumed to hold the molecule in conformation 1. However, a second conformation, 2, in which the imine double bond and the pyridine ring are again coplanar, is also possible, and doubtless exists at high pH where the chelated hydrogen has dissociated.

Recently we were faced with the task of purifying a vitamin derivative by preparative thin-layer chromatography. We quickly discovered that spotting the sample manually yielded such irregular bands that isolation of the desired compound was unfeasible. The prohibitive expense of commercially available TLC spotters (about $1000) encouraged us to devise our own apparatus. Although the components of our apparatus are several times as expensive as a TLC spotter, they (or comparable equipment) are often already available in a well-equipped laboratory. The expensive components are a Moseley (Hewlett-Packard) 7030AM X-Y recorder and a Sage Model 341 syringe pump. The remainder of the apparatus is constructed as described below.A 2.5-cm segment of %gauge tubing was cut from a stainless steel syringe needle; the end was deburred and filed flat. The needle was then soldered to a Fahnestock clip in such a way that the flat end of the needle projected slightly below the recorder pen tip when the needle was attached to the pen by means of the clip. The other end of the needle was attached

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