An Improved T-Tube Pressure Regulator. William N. Carson,
Only a small amount of liquid is needed in the primary regulator, as the secondary regulators provide ample pressure in the outer annular space. The range is readily adjusted by the addition or removal of one or more of the secondary regulators. The trap used in the secondary regulators is self-emptying, and readily removes liquids hard to trap from the outgoing stream of gas. The dimensions of the regulators given are those used in the author's laboratory. In the primary regulator, a large free space above the surface of the liquid in both of the annular spaces is necessary, and a large enough trap, A , must be provided. In the secondary regulator, the liquid surge must never cover the tip of the inlet tube, and the tip must be below the outlet tube. The former requirement is met by allowing a t least 30-mm. length between the tip and the top of the return tube. Pressure regulators of this type have been used in the author's laboratory for the past 2 years on systems requiring a constant pressure coupled with large sudden changes in demand for gas. S o attention is required after the initial adjustment.
Jr.1, The Ohio State University, Columbus, Ohio. open end is immersed in a column of liquid A is oftenwhose used for the regulation of pressure. As usually T-TUBE
made, the device has several limitations: The liquid is likely to be spattered out with sudden line surges, or is sucked back in the line whenever the pressure falls below atmospheric, and the range of pressure controlled by any one device is limited. The regulator described is simple to build and use, and overcomes these objections. f O PRIMARY
HIGH
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7 PRESSURE -
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A Useful Stopcock Lubricant. I. E. Puddington, National Research Council, Ottawa, Canada. that will not absorb appreciable quantities of A certain organic vapors is frequently required for stopcocks and ground-glass joints in exposed positions. Because it is often LVBRICANT
B C 0
The regulator is divided into two basic components: the primary regulator (left) and the secondary regulator (right). I n the primary regulator high pressure gas enters through trap
A , which prevents the liquid in the regulator from entering the line on a suck-back, and continues through the inner tube, B.
The emerging gas is oollected for the most part in the inner annular space between tubes B and C. This gas is compressed by a combination of hydraulic and pneumatic pressure in the outer annular space between tubes C and D. If sufficient gas is flowing to allow a small excess to be discharged through the outer annular space, the pressure in the inner annular space is held constant to within a small percentage. This pressure is equal to the head of liquid in the outer annular space, plus the pressure developed by the secondary regulators. Splashing of the liquid into the discharge line is avoided by use of the long tube of large diameter, which provides a large free space above the surface of the liquid. By using only a small amount of liquid in the regulator, splashing through the vent is avoided. ' 1 Present address, Reaearch Laboratory, Hanford Engineering Works, General Electric Company, Richland, Wash.
inconvenient to regrease these stopcocks, the lubricant should prevent the seizure of the moving parts for long periods of time, and in addition should possess a low vapor pressure. Anhydrous glycerol which has been thickened with dextrin, bentonite, mannitol, and the like has been suggested frequently for this purpose. The vapor pressures of these preparations are probably satisfactory for most uses, as the vapor pressure of anhydrous glycerol is about 4 X 10-4 a t 20" C.; their life in frequently turned stopcocks, however, leaves much to be desired. In an attempt to overcome this difficulty, it was found that finely divided silica incorporated into the glycerol produced remarkable results. The silica used was in the form of an aerogel (Santocel C, obtained from the Monsanto Chemical Co.). This material was ignited a t a temperature of 450' C. overnight to remove traces of volatiles, and then incorporated in small portions into the glycerol until a uniform dispersion containing 20 to 25% by weight was obtained. -4 Waring Blendor or other stirring device will produce the dispersion conveniently. The glycerol may be rendered anhydrous by heating to about 70" C. for 2 hours in a diffusion pump vacuum. Although this drying procedure may seem somewhat elaborate, it is a worth-while precaution, as it eliminates the annoying and time-consuming dehydration process which occurs a t the stopcocks in low pressure systems, when a lubricant prepared from commercial silica and laboratory grade glycerol is used. After about 20% of silica has bern incorporated, the glycerol is an extremely viscous fluid and is sufficiently stringy to resemble a concentrated polymer solution. This dispersion has excellent lubricating properties. In one instance a 6-mm. bore stopcock which had received an application of it was exposed continuously do benzene vapor a t 6-cm. pressure for 6 months; a t the end of this time, although it had been turned frequently, the stopcock showed no detectable increase in friction and at no time was any streaking visible.
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