Greaseless valve

More recently, a system using greaseless valves and a magnetic lifting mechanism was used (135), but no differences were found in the behavior of solids activated in either type of reactor. The activation procedure consists in the evacuation (10 s Torr) of the system at the position L at 430°C for 8 h ... 

Fig. 2. Pyrex glass apparatus used (a) for the synthesis and sampling of a base-free gallane and (b) for the admission of the gallane vapor to the chamber of the electron-diffraction apparatus. In (a) A is a sample of [H2GaCl]2 Bj, B2, and B3 are greaseless valves C is freshly prepared LiGaH4, LiBH4, or [Bu"4N][B3H8] Dj, D2, and D3 are U-tube traps for fractionation of the volatile components of the reaction mixture and E is an NMR tube (reproduced with permission from Ref. 56 copyright 1991, American Chemical Society).

A more direct study of the reaction between CO and NO2 was made by Brown and Crist [485], who used a KCl coated Pyrex reaction vessel fitted with a greaseless valve to avoid decomposition of the NO2. In order also to avoid complications due to gas phase dissociation of the NO2, its pressure was kept very low (<0.5 torr), and the reaction times were kept comparatively short. Amounts of reaction were measured by freezing and then analyzing for the product CO2 by vacuum sublimation from the nitrogen oxides. In order to obtain measurable amounts of reaction under the conditions stated, it was necessary to employ high concentrations of CO. Even then the partial pressures of CO2 in the products were less than 30 microns, and often as little as 5 microns, so that good experimental technique was required. It was confirmed that the reaction was second order over some two- to three-fold variation of the partial pressures of CO and NO2. Mean rate coefficients between 500 and 563 K are given in Table 57. 

Atmospheric pressure apparatus. Isomerization experiments at atmospheric pressure were carried out in an all-glass system equipped with greaseless values, a flow meter, a U-shaped silica reactor, a double TCD system recording the pressure of reactant (provided by a saturator) before the reactor and the pressure of the products after the reactor, a system to extract the products for GC analysis and a needle valve to regulate gas flow. The catalyst was placed on a silica fritted disc and the reactor was operated as a fixed bed at constant pressure and temperature. Hydrocarbons were introduced at a set pressure and hydrogen was used as complement to the atmospheric pressure on the catalyst. 

Fig. 1.29. Double-ended filter. This type of apparatus is a good alternative to the more standard Schlenk filler. The version illustrated is based on greaseless joints and valves. 

FT-NMR spectrometer, with 10- or 15-mm-diameter probe capability if possible gas NMR tube with concentric Teflon valve (e.g., J. Young NMR-10) 1-L reaction flask with greaseless stopcock 0- to 1-bar pressure gauge vacuum line Ultra-Torr fittings microsyringes hot plate and oil bath with 0 to 200°C thermometer liquid N2 and ice baths benzoyl chloride and bromide, D2O (95 percent) fume hood. 

Reactors. Pyrex reactors were made by joining a heavy-walled Pyrex vessel to a greaseless J. Young glass valve provided with Teflon O-rings. The Pyrex reactors were flame-dried under a vacuum of lO" torr. The reactors were made of Vi diameter... 

Very unreactive, nonstick, relatively high softening point liners for pots and pans, greaseless bearings, artificial joints, heart valves, plumbers tape, fabrics... 

The checker used a 2.5 cm OD double-chamber ampule with a 15 cm length reaction chamber, a 10 cm receiver chamber, and a 0.95 cm OD end tube to which a greaseless vacuum valve was attached via a Cajon fitting. The ampule was flame sealed under vacuum between the receiver chamber and the Cajon fitting. 

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