How should general purpose glassware be cleaned?

I've just purchased a water distillation setup for my plant tissue culture project. I've got a copy of that excellent book Organic Chem Lab Survival Manual by Zubrick so I have an idea about clamps, setup etc. But while the book mentions greasing, cleaning and storing pyrex glassware it doesn't actually tell you what products to use. Some of this glassware here looks pretty obscure and I need SD water to work with so I can't risk losing any of it ( I live away out in the bush... ) Can you help me with some guidelines on cleaning, greasing and storing lab glassware? Allison Wiseman

For any piece of special apparatus, I'd ask the manufacturer for their recommendations. But here are some tips for general purpose laboratory glassware.

How to tell if glassware is clean. The glass should wet uniformly. If the meniscus pulls way from the side as the glassware drains, it isn't clean.

How to clean glassware. A bottle brush and ordinary lab detergent (trisodium phosphate or organic sulfonate based detergents work great). If you're doing phosphorus assays with the molybdenum blue method, it's better not to use a phosphate based detergent.

To clean silicone-based stopcock grease off the glassware, you should soak it in hot saturated NaOH in ethanol for about 15 minutes, and then rinse thoroughly with water.

How to really clean glassware. Sometimes detergent and elbow grease isn't enough, and you have to get mean. Take 20 g of ammonium peroxydisulfate (NH₄)₂S₂O₈, put it in a clean 4 L glass lidded vat (like a dessicator), and add 1 L of 98% sulfuric acid. A 15-30 minute soak in this stuff will eat anything- dirt, grease, organics, clothes, and you, too. Keep it under the hood and please, wear gloves and eye protection. You want it to contact only the inside surfaces of the glassware; it will attack pigments used for fiducial marks and gradations on burets and pipets. Let the solution gravity drain off the glassware, and then rinse it with copious amounts of water. The final rinse should be with distilled water.

Dry glassware before putting it into this stuff. Take apart your stopcocks and degrease them as outlined above, and please make sure the alcoholic NaOH is completely washed off before they come anywhere near the peroxydisulfate solution.

It does weaken over time. You'll have to add a few grams of peroxydisulfate every other week.

This sounds like the cleaning solution from hell, and it is; but it's not as bad as the chromic acid witch's brew chemists used to use, which was just as corrosive and also carcinogenic.

How to dry glassware. Let glassware gravity-drain once it's cleaned. A final rinse with distilled water is always recommended. Don't dry it with an air hose; that can spray microscopic droplets of grease and other gunk from the airline on your clean glass.

You don't need to dry the glassware if you've just cleaned it; just rinse it with the solution you want to fill it with a couple of times. Small rinses are more effective than large ones.

How to store glassware. It's best to just let glassware dry and store it in a closed cabinet so it won't get dusty. Some people fill burets with distilled water and put an inverted beaker on top and store them that way.

How to grease glassware. Use a silicone lubricant, like Dow Corning stopcock grease. Use as little grease as you possibly can; less is more.

You can find specific recommendations for many specialized pieces of glassware by following the "Glassware Gallery" link given below.

Web Resources

Glassware Gallery (Rob Toreki, University of Kentucky)

Want to know what a skull melter looks like? Wondering what exactly to do with your brand new ball mill? Find what you need at the Glassware Gallery, which includes drawings, descriptions, usage, and maintainence information of most common pieces of glassware and equipment found in synthetic inorganic and organic laboratories.
http://www.ilpi.com/inorganic/glassware/ (07/16/01)

Author: Fred Senese senese@antoine.frostburg.edu

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