CLEANING BATHS FOR GLASSWARE

See CLEANING BATHS FOR GLASSWARE See other glass incidents... 

See Nitric acid Glassware, Hydrogen peroxide, 5-Bromo-4-pyrimidinone See also CLEANING BATHS FOR GLASSWARE, FRICTIONAL INITIATION INCIDENTS... 

For many years, sulfuric acid—dichromate mixtures wo-e used to clean glassware (a sulfuric acid—peroxy-disulfate solution is now recommended because disposal of chromate is a problem). Confusion about cleaning baths... 

Removing Tar from Distillation Flasks. As mentioned in the beginning of this section, the best time to clean glassware is immediately after it is used. The hardest glass pieces to clean are those that have been left for someone else to clean. Tar, however, is always hard to clean and is always left for last (which also makes it more difficult to clean). A simple solution for cleaning tar from the bottom of flasks is to invert the flask into a beaker of acetone and let the vapor of the solvent dissolve the tar (see Fig. 4.4). This technique can remove most of the tar deposit in a few hours. It can be hastened by heating the solvent in a steam bath (do not use an open flame). 

Special cleaning of glass - for an acid wash use dilute acid, rinse with tap water (three times) to remove the washing solution and then rinse thoroughly at least three times with distilled or deionized water. To remove acidic deposits, wash with KOH/ethanol solution followed by rinsing with deionized water. Glassware, which must be exceptionally clean, should be washed in a chromic acid bath, but this must only be made up and used under supervision. 

Swirl the acid mixture in the container for a few minutes. If necessary, place the glassware in a warm-water bath and heat cautiously to accelerate the cleaning process. Continue heating until any sign of a reaction ceases. When the cleaning procedure is completed, decant the mixture into an appropriate waste container. 

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