Spiral manometer

The pressures were obtained with a glass spiral manometer. 

Where high strength is important, wrought iron, ingot iron, or steel must be used. These are used for the drawbars of filter presses and hydraulic presses. (The head pieces of the latter must be of cast steel because cast iron is too weak.) Recently, welded electrosteel has also been used. Steel is also used for the spiral manometer tubes where ammonia is involved. Wrought iron is used for the bands on vats and for the reinforcing iron for concrete. 

Fig. 39. Circulating system for studying exchange reactions. A, to quartz spiral manometer B, device for loading sodium chloride into reaction vessel in vacuo C, long path envelope of...

Fig. 26. Quartz-spiral manometer, Boden-stein type.

The most frequently applied mechanical manometers in ventilation applications are fluid manometers, bur the following types are also used. The Bourdon tube is a small-voiume tube with an elliptic cross-section bent to the shape of a circular arc, the C-type. One end is open to the applied pressure while the other end is closed. The pressure inside the tube causes an elastic defonnation ot the tube and displaces the closed end, which is then converted, by means of a linkage mechanism, into the movement of a pointer. The Bourdon tube may be of a spiral or helical design as well. 

Premier and Schupp have made vapour-density measurements with sulphur enclosed in a quartz bulb heated electrically and connected with a manometer consisting of a spiral of silica tubing attached to a small mirror. The pressure was measured by the amount of unwinding of the spiral. The same method has been used by Bodenstein and Katavama in studving the equilibrium ... 

G. Bourdon Gauges. As an alternative to mercury manometers there is a variety of gauges based on mechanical or electrical pressure transducers. This section presents a description of purely mechanical gauges which still find use in this electronic age.4 The metal Bourdon gauge (Fig. 7.5) is fashioned around a semicircular thin-walled metal tube with mechanical linkage to a pointer. Fused-quartz spiral gauges are also available. In this case, a thin spiral is sensitive to a pressure differential, and the deflection is balanced with air pressure in the surrounding envelope. The air pressure is then measured with a manometer. 

In the following procedures a standard glass vacuum line with high-vacuum stopcocks (lubricated with Kel-F-90 grease ) is used. Because of the reactivity of many of the compounds with mercury, it is convenient to use a null-point pressure device, such as a Booth-Cromer16 pressure gage or spiral gage. A mercury manometer covered with Kel-F-3 oil can be used. 

For work with low-boiling fluorides it is useful to have on hand a part-glass, part-quartz vacuum system provided with a spiral quartz manometer. 

The analysis vessel B is cylindrical. It contains a thin spiral of Pt wire supported by two sealed-in current leads. The wire glows when the current from a small line transformer is passed through it. The analysis vessel is connected via stopcock with an HsSO manometer M. Stopcock Is connected to the hood through tube D, which will be discussed later. The analysis vessel is placed in a water bath, which must be large enough to prevent temperature fluctuations during the measurement (the bath temperature may be checked with a thermometer). 

Measurement of Pressure and Rate of Flow.—Great attention is paid to the measurement of the rate of flow of gas, which is arrived at by counting with a stop-watch the number of bubbles of gas per minute in a small sulphuric acid wash bottle. A mercury manometer is introduced here, and is useful for detecting a leak in the apparatus. The rate of flow that gives the most satisfactory results is 1,000 c.c. per hour. If too rapid it does not become sufficiently preheated in the glass spiral, and if too slow there is a more rapid decomposition of the nitro-cellulose by the oxides of nitrogen which are not removed. 

---