h ALKALINE CLEANING SOLUTION SHIRLEY GADDIS
THE problem of cleaning glassware in the chemistry laboratoj has been neglected in many schools. While i t is true that the student in quantitative analysis is given a bottle of chromic acid cleaner, the struggling freshman has been piven a test-tube brush and our best wishes. To solve this problem we have tried a number of mixtures of detergents, and to o w mind the following procedure is to be recommended: At strategic points, determined by a study of the traffic flow in the freshman laboratory, there are placed small enamel dishpans containing about two quarts of a detergent solution. Under each pan are a Bunsen burner and a micro burner. The solution is heated to 70°C. with the Bunsen and maintained a t that temperature with the micro burner. Usually the most convenient location for the cleaning unit will be the hood, since i t is usually equipped with the gas outlets. If the water in the laboratory is unusually hard, it is advisable after the cleaning to rinse the glassware in soft water. For this purpose there should be provided beside the hot detergent solution a large dishpan full of soft water. A homemade zeolite softener can be made by placing five pounds of zeolite in a gallon jar. The cleaning mixture has been empirically formulated by actual experience. Since the problem in cleaning glassware is to cut the film of grease, the detergent is mixed with the usual alkaline detergents of TSP, TSPP, and Metso as the principal ingredients. To give a good suds Dreft is added. To inactivate the alkaline earth ions Calgon is used. Finally, to reduce the surface tension a wetting agent of the alkyl aryl sulfonate type is added.
2$/, 1
10
12
36
1
Eureko College,Eureka,Illinois
pounds o f Calgon pound o f wetting agent pounds o f sodium metasilicate pounds o f tetrasodium pyrophosphate pounds o f trisodium phosphate pound o f Dreft
$1.00 0.60 0.50 0.70 1.50 0.40
Thus a total of 63 pounds of the detergent costs $4.70. Since only one ounce of the detergent is added to two liters of water for use in the laboratory, it is apparent that the cost of the detergent is of no consequence when compared to the cost of the chromic acid cleaner. The alkaline detergents have proved so satisfactory, compared to chromic acid, that they are used in all o w laboratories. In quantitative analysis the beakers, flasks, and burets come out of a one-minute soak in hot detergent free from all grease. A rinse with soft water and then distilled water leaves them sparkling. In the organic laboratory the hot alkaline detergent is especially useful in cleaning partially carbonized residues out of distilling flasks. Other advantages of the use of an alkaline detergent are: 1. The use of hot chromic acid cleaner is a potential accident hazard. 2. The storeroom inventory of test-tube brushes can be greatly reduced. Brushes need not be issued to individual lockei-s. A brush is always left a t the pan of the hot detergent solution. 3. It has always seemed an anomalous teaching practice to spend a period of lecture time extolling the virtues of the newer types of detergents and to ignore their practical application in the laboratory. Here is an opportunity to do a realistic teaching job by making available a really efficient cleaning aid.
