Stopcock grease silicone

Si—CHj Silicone stopcock grease is attacked by aromatic and chlorinated solvents. The presence of a sharp 1266 cm" band along with broad absorption in the 111 1-1000 cm" range is characteristic of the silicones in stopcock greases. Silicone greases should be rigorously excluded in all careful separations work. 

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. 

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

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

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. 

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.)... 

Silicon tetrafluoride is a colorless, pungent, fuming gas at room temperature. The triple point is at —90.2° and 1318 mm.3 The critical temperature and pressure are —14.5° and 36.66 atm., respectively.5 The sublimation temperature3 at 1 atm. is —95.7°. The gas liquefies under pressure to form a colorless, mobile liquid. Distillation of the liquid can be used for purification.1,5 In the absence of moisture, pure silicon tetrafluoride does not attack glass, mercury, stopcock grease, or rubber. 

Silicon-based stopcock grease maintains constant viscosity over a wide range of temperatures (-40°C to 300°C). These greases are water insoluble and inert to most chemicals and gases. Silicone grease is inexpensive compared to many other stopcock greases. 

Pldbielniak Silicone Stopcock grease Contains silicone and carbon particles as lubricants, which may provide a more slippery lubricant. Because of the carbon, it should not be used with Teflon because there is a potential of scratching the Teflon. It should also not be used with compressed oxygen as it could detonate. 

Silicone stopcock grease requires cleaning and replacement every month or two whether the stopcock is used or not (see page 198). 

Both gallium trichloride and chlorine attack silicone stopcock grease. It is important that all stopcocks and joints be of the grease-free, Teflon variety or if this is not possible that Kel-F grease be employed. 

Outer 19/38 joints are used on the manifold and 19/38 inner joints are used on the associated equipment. Dow-Corning silicone stopcock grease is used throughout because of its relatively high resistance to erosion by common organic solvents. 

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