Tap greases

Bromine trifluoride, though it reacts explosively with water and hydrocarbon tap greases, is somewhat less violent and vigorous a fluorinat-ing agent than is CIF3. The sequence of reactivity usually quoted for the halogen fluorides is ... 

Mercury cut-offs are used in vacuum apparatus instead of taps when tap grease is undesirable. A frequently used type is shown in Figure 63. A two-way tap is attached at the top of a reservoir for mercury. 

Storage of monomers and solvents also requires special precautions. The vessels must be specially constructed and be closed with a self-sealing cap through which the distilled contents can be transferred with a pipette or hypodermic syringe under inert gas. The contents should also not come in contact with tap grease. 

About 10 g. of pure sulfur(VI) oxide is prepared in the apparatus shown in Fig. 13. Concentrated oleum is placed in flask A which is cooled, evacuated, and sealed at point 1. Tube B is cooled in liquid air until the required amount of sulfur(VI) oxide has distilled over it is then sealed at point 2. Further purification of the trioxide by vacuum distillation is usually unnecessary. The procedure for reaction of the oxide with the required amount of heavy water (2.5018 g./lO g. SOs) is similar to that described in the preparation of deuterophosphoric acid except that sulfur(VI) oxide, being more volatile than phosphorus (V) oxide, should be cooled to —78° before being placed in the side arm of Fig. 14. An inert Fluorlube tap grease is recommended. Limb E is cooled and the apparatus evacuated slowly to prevent volatilization and entrainment of sulfur (VI) oxide in the vacuum line. When the oxide has been completely... 

By-products formed during their preparation (e.g., ethylbenzene and divin-ylbenzenes in styrene acetaldehyde in vinyl acetate) added stabilizers (inhibitors) autoxidation and decomposition products of the monomers (e.g., peroxides in dienes, benzaldehyde in styrene, hydrogen cyanide in acrylonitrile) impurities that derive from the method of storage of the monomer (e.g., traces of metal or alkali from the vessels, tap grease etc.) dimers, trimers, and polymers that are generally soluble in the monomer, but sometimes precipitate, for example, polyac-rylOTiitrile from acrylonitrile. Likewise, in polycondensation reactions it is important to remove reactive impurities because they can cause considerable interference during the polyreaction. 

Pb(CH3)4 vapor is absorbed by tap grease [11], and on most organic surfaces such as rubber stoppers and tubing [7]. 

In filling the tube R, one tap is inserted after being carefully greased with a high-vacuum or silicone grease. The taps are provided with scored grooves (that run completely around them near their outer end) which act as a trap to prevent... 

The ground runs are greased witli vaseline or a mixture of bees-wax and vaseline, and the ail is exhausted by attaching the tube of the watei-pump to the glass tap of the desiccator. 

Measure 5 mL of tap water into the graduated cylinder. Pour the water into one of the test tubes. Use the grease pencil to mark the test tube at the 5-mL level. Discard the water. Repeat for the other two test tubes. 

In the schematic diagram of the vacuum line (Fig. 2.1) a U-bend is shown between the main tap T, and the manifold, which has two functions (a) It lends an extra element of mechanical flexibility to the system by absorbing small movements at the traps or along the main manifold (WL or WL ) which might otherwise lead to fracture and (b) it acts as a sink for non-volatile residues in the line and for grease which may be washed away from the taps 7, 7 and 7. ... 

Glass taps Glass taps should only be used at the pumping end of a vacuum system or where there is no likelihood of them coming into contact with liquids since, whatever grease is used, it will tend to be washed away... 

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