| MadSci Network: Chemistry |
I'm not sure why this question keeps coming up in the queue, but it seems like a permanent answer needs to be posted: in my opinion, the best source for instant etymologic gratification is the Oxford English Dictionary (available online and in book form at most libraries); they give the following entry under definition #2 for policeman
2. Chem. A glass rod or tube with a short piece of rubber tubing on one end (see also quot. 1963).
1916 F. A. GOOCH Representative Procedures in Quantitative Chem. Analysis iii. 64 The precipitate, transferred from the container to the filter..with the aid of a rubber-tipped glass rod (the ‘policeman’). 1930 W. T. HALL Textbk. Quantitative Analysis xi. 149 This so-called policeman may be made by sticking together the end of a piece of rubber tubing that fits the rod tightly. 1963 N. L. PARR Lab. Handbk. vii. 103 Other means of separation [of solids] are sometimes adopted. Among them are dialysis, and the ‘policeman’ for dealing with solids in microchemistry, which is a small snipe feather mounted in a short length of glass tubing. 1974 Nature 6 Dec. 498/2 Attempts to passage stage 2 cells..by scraping with a rubber policeman, resulted in a rapid degeneration of the cells in a new flask.
Oxford English Dictionary, 2nd Edition, 1989
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