Clean Laboratory Glassware Keeping glasswae clean has always been a problem in our organic chem~strylab. The most common sod has been silicone greases on t h e standard taper lab sets, althourh we sometimes need t a remove skin oils and biolorical soils from glassware without using abrasive cleaners or acid chru&te baths. We have been using the standard lab reagent known as "alcoholic potassium hydroxide" for our cleaning. T h e result has heen elass entirelv free of all creases. excent for the netroleum-hased ones. and free of anv biolorical contaminants. T h e glass surf& is clean "enough to '{heet upon rinsing. Our cleaning vat is a 6-gal. plastic paint bucket with a plastic cover to retard evaporation. This vat is filled with four gallons of a solution of potassium hydroxide in alcohol, usually 2 M, made by dissolving the potassium hydroxide pellets into a minimum amount of water then pouring this hot solution into the vat of alcohol. There is no difference in effectiveness found if the concentration varies (1-6 M ) and if the alcohol identity varies (0-50% methanol in ethanol). Furthermore, no significant effect upon glass surfaces has been observed as long as the piece is completely submerged in the solution and as long as it is not left for long periods of time. Any glass out of the solution may be etched on that part of the surface not covered. I was concerned whether any glass was dissolved by this solution. Time Weight Volume New, unused 250~mlbeakers as they came from their shipping carton in Vat Loss ChangeS were tested far weight loss. No significant loss was measured. Brand (days) (mg) (mi) The health hazard associated with this cleaning method is what would be expected for the handling of a caustic or strongly basic s o Pyrex #I000 6 2.1 9.4 X lo-' lution. Periodic or brief skin contact will wash off completely with Kimax #14000 6 1.6 7.0 X 10W water. Serious spills may be neutralized with either dilute acetic acid Pyrex #I000 22 1.3 5.8 X lo-' or very dilute hydrochlaric acid. Furthermore, the used solution may Kimax #I4000 22 0.1 0.4 X 1 0 P be disposed of by pouring down t h e drain, provided there are no Using the density reported for Corning Code 7740 glass (2.23 dangerous contaminants present. 9Imil gives the volume change. These amounts would revresent Based two years of with this cleaning system, virtually no change far even class A volumetric equipment. it is recommended for cleaning any normal laboratory glassware including standard taperware and volumetric equipment. Since I have made no tests on optical glass other than a n occasional cleaning of tube-type cuvets for the Spectronic-20, general cleaning of euvets is not recommended until tested further. ~~~
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James W. Hill Panhandle State University Goodwell, OK 73939
304
Journal of Chemical Education
