Stopcocks greasing

The stopcock should preferably be lubricated with Sihcone stopcock grease, and held in position by a rubber band. 

Lubrication of all ground glass surfaces is essential for distillations under reduced pressure. Suitable lubricants are Apiezon grease L, M or N and Silicone stopcock grease also Alkathene (a polyethylene plastic), which is especially suitable for high temperatures. 

Hahnen-fett, n. stopcock grease, -fuss, m. lit., cock s foot Ceram.) cockspur Bot.) crowfoot, ranunculus. 

Kel-F grease is recommended for ground-glass joints. Nitronium tetrafluoroborate slowly attacks silicone stopcock grease, causing air to enter the flask. 

In particular, if a latex is to be used for coatings, adhesives, or film applications, no silicone-base stopcock greases should be used on emulsion polymerization equipment. Although hydrocarbon greases are not completely satisfactory either, there are very few alternatives. Teflon tapes, sleeves, and stoppers may be useful, although expensive. 

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). 

System arranged so that all parts up to and including one cold trap may be baked out at 400-450°C for at least an hour. This means no stopcock grease beyond the first cold trap (which may be kept cold during the out-baking of the system and other trap). 

Ground glass joints were connected using Teflon sleeves or a chlorofluorocarbon stopcock grease. 

Silicone, fluids, 59, 1020 resins, 1020 stopcock greases, 225 Silver maleate, 388 Silver nitrite, 201 Simon s test, 421 ... 

Oxygen can also be detected chemically. Tetrakis(dimethylamino)ethylene forms a luminescent compound with oxygen and is very sensitive to trace amounts of oxygen [4]. One drawback of this compound is that it has a high affinity for silicone stopcock grease, which it deteriorates quite rapidly. A small bottle of diethylzinc mixed with heptane is also useful. The absence of a vapor cloud indicates less than 5 ppm of oxygen. (Caution This material is pyrophoric use extreme care in handling.)... 

A few drops of water may generate sufficient heat to initiate the explosion. Contact with organic matter such as stopcock grease in a separatory funnel has had the same effect (Ref 5D... 

Never use rubber or cork with apparatus when working with HC104- Use an all-glass apparatus, and do not use stopcock grease. Thoroughly clean all apparatus which has been in contact with HC104... 

Table 1.1 Spectral Signatures of Impurities from Stopcock Grease and Rubber and Plastic Items...

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