Stopcock grease fluorocarbon

A carefully dried, 500-ml., three-necked, round-bottomed flask is fitted with a compact distillation head and condenser, a pressure-equalizing addition funnel, and a nitrogen gas inlet tube. TTie nitrogen passes out through the distillation head. If conventional stopcocks are used, they should be lubricated with fluorocarbon or silicone grease. 

The reaction vessel is a 3-1. round Pyrex bulb equipped with a 2-mm. stopcock and a quartz tube insert (20 cm. in length and 2.5-cm. i.d.) which is sealed into the bulb by means of 45/50 S.T. joints.1,1 Fluorocarbon grease is used for lubricant. The bulb is evacuated and charged with tetrafluorohydrazine f (100-mm. pressure, 16 mmoles), which is used without purifica-... 

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. 

Gases are transferred in a standard Pyrex glass vacuum line equipped with high-vacuum stopcocks (lubricated with a fluorocarbon grease [Halocarbon]) to which is attached a four-trap system used for low-temperature trap-to-trap distillation (Fig. 1). Because of the reactivity of the compounds, a Heise-Bourdon tube gauge [Dresser Ind.], is used for PVT measurements. 

The stopcocks must be greased with fluorocarbon lubricant because of the corrosive effect of Cl30g, unless one prefers to use the glass valves su ested by Bodenstein. 

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