Removing Stopcock Grease

Pre-preparation. Stopcock grease on a joint or stopcock must be removed before adequate soap and water cleaning can begin. It is always best to remove excess stopcock grease physically with a Kimwipe. Then, any film of stopcock grease remaining can be removed with less solvent. 

Fluorocarbon greases (Krytox) originally required a chlorinated fluorocarbon for removal. In the last few years, it was found that an industrial solvent (such as BH-38 from Spartan Chemical Co. ) can remove Krytox. Tests that this author has conducted seem to show a film of some kind remains on the joint, so it is unknown exactly how safe it is to heat a joint or stopcock that has been cleaned with this technique. Do not use heat to remove Krytox because heating ( 260°C) will produce fumes (lethal fluorine compounds, such as HF) that are highly toxic. For more information on cleaning these greases, see Sec. 3.3.3. 

After the various greases are removed from the apparatus, it is then possible to continue with soap and water cleaning. However, whether organic solvents were used or not, glassware should be rinsed out first with a small amount of acetone and then water, before being placed in a soapy water solution. 

Material. There is a variety of powdered and liquid washing compounds available on the commercial market that, when mixed with water, provide excellent cleaning. There are a few superconcentrated cleaners (that come as liquids) which 

Preparation. Because there are as many different preparation techniques as there are commercial brands, it is best to read the instructions on the container of the cleaner you are using. 

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Cool the flask. Remove stopcock grease from all the joints of the flask. With suction, filter off the poly(vinyl alcohol) that has formed. Wash the product repeatedly with methanol until a sample of the methanol washings, diluted with deionized water, have a pH below 7.5 (i.e., until residual alkali has been removed). 

NOTE Instruction in the operation and principles of operation of pH meters may be necessary. Provide burette brushes and solvent (CHCI3) for cleaning burettes and removing stopcock grease, unless burettes with Teflon stopcocks are used. 

Your objective is to soften, not remove, any grease between the mated members. Never perform cleaning operations with solvents on mated stopcocks or joints. Never let mated stopcocks or joints bake in a drying oven or soak in solvents that can dissolve the grease. If there is no grease, there is little hope in separating the pieces. 

Any small-sized stopcock that requires heat to turn should be removed, cleaned, and regreased at the first opportunity. Large stopcocks may require a hot air gun for all rotation. Because heat ages stopcock grease faster than normal, the grease should be replaced two to three times more often than the other stopcock grease. 

The catch to the vacuum method is that you must have a controlled boil without which the material and/or solvent are liable to be sprayed all over your vacuum system. Although a solvent can easily be pumped out of a vacuum system, it can cause serious problems if it remains in contact with stopcock grease, O-rings, or mechanical and/or diffusion pump oils. Any particulate material deposited within a vacuum line can only be removed from the vacuum line by disassembly and cleaning. With a glass vacuum system, such a cleaning may be difficult or impossible. 

Sample Introduction and Distillation Remove the separatory funnel, and quantitatively transfer the sample in aqueous ethanol to the flask. Wipe the tapered joint clean with a laboratory tissue, apply stopcock grease to the outer joint of the separatory funnel, and return the separatory funnel to the tapered joint flask. The nitrogen flow through the 3% Hydrogen Peroxide Solution should resume as soon as the funnel is reinserted into the appropriate joint in the flask. Examine each joint to ensure that it is sealed. 

The funnel must be thoroughly cleaned to remove all stopcock grease. 

If a sep funnel is used for the purification of nitro, one should make sure that the stopcock and the stopper are both well greased. If regular stopcock grease is unavailable, substitute Vaseline. This will prevent grinding friction during the use of the sep funnel, and make accidents less likely. When one is finished with the sep funnel work, it should be cleaned out. A cold water rinse followed by a rubbing alcohol rinse will remove nitro residue from the glassware. 

A solution of CI3O in CCl, cooled to 0°C, is mixed with water (0°C) in a separating funnel (the stopcock of which must under no circumstances be coated with stopcock grease) and shaken vigorously for three minutes. The CCl layer is removed the aqueous solution contains HClO which is free of CI3. 

Lightly coat a watch glass with stopcock grease. Pour some of the hot polymer from the tube containing ethylene glycol use a wooden applicator stick to spread the polymer on the surface to create a thin film of the polymer. Remove the polymer from the watch glass and save it for Experiment 46D. 

If the glassware is contaminated with stopcock grease (unlikely with the glassware recommended in this book), rinse the glassware with a small amount (1-2 mL) of methylene chloride. Discard the rinse solution into an appropriate waste container. Once the grease is removed, wash the glassware with soap or detergent and water. 

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