Mercury piston

A Toepler pump is a piston pump with mercury as the piston. The mercury piston is powered by both the vacuum from a vacuum system and the atmosphere. The actual operation of a Toepler pump involves evacuation followed by readmission of air out of, and into, the Toepler pump. There have been a wide variety of techniques to automate this process because manual operation can be quite tedious. 

The natural frequency at which the mass inertia of the mercury piston would interfere with the column s usefulness for inducing volume variations is calculated using the laws of elementary physics. 

Static methods. In which the system of interest is enclosed in a magnetically stirred variable volume cell [64, 76] which in some cases contains a window. The temperature and pressure within the cell are accurately metered. The cell volume may be changed either using a mercury piston or a mechanical piston and samples of the fluid phases present may be obtained, if required, under conditions of constant temperature and pressure by suitably reducing the cell volume. In the windowed cell version [76] sampling is unnecessary for binary systems since the cell may be charged with known amounts of the two components and conditions adjusted to obtain trace presence only of one of the phases. In this way the dew- and bubble-point curves for binary systems may be established and similarly the solubilities of solids in compressed fluids may be determined. 

The traditional arrangement of simple spherical glassware and Isomantles with full-power on-off controllers monitored by mercury thermometers, would still be widely recognised. So too would be the plug-shot piston pumps set up and monitored by use of measuring cylinders. Although tried and tested this hardware system requires constant attention by a skilled lab. technician to achieve control and reproducibility of even the first-order process parameters manual data collection is hardly feasible at better than 10-15 minute intervals. 

Fig. 15 Instrumented Zanasi LZ-64 showing mercury swivel for signal removal (A) dosator containing strain-gauged piston (B) mercury swivel. (From Ref. 38.)... 

The mercury values obtained by the Teflon-piston sampler were high at 0.21 0.2 nmol/kg due to malfunction with incomplete filling and previous contamination, as indicated by the very low salinity in this set. The values inside the bag were higher than those outside, measured about one month after intercomparison to be 0.02,0.03, and 0.04 nmol/kg. There was a subsampling problem. The first and second draw of the sampling bottle usually showed a very wide spread of values, as much as 0.07 nmol/kg, e.g., between 0.05 and... 

By turning the threaded steel piston (2 mm diameter) a fixed angle, for instance, 90° or 180°, mercury will be pushed out of the capillary and will hang as a drop from its end. It is important that the piston screw be set tight in the polyethylene part shown in Figure 14.3b. 

In this experiment, a volume of air is trapped in a capillary tube by a column of mercury. The mercury acts as a movable piston. Depending on how the capillary tube is tilted, the mercury column moves and thus causes the volume of trapped air to change. The pressure of the trapped air supports not only the pressure exerted by the atmosphere but also the pressure of the mercury column. The pressure exerted by the mercury column varies depending on the angle of the tilt. If 0 is the angle of the tilt, the pressure of the mercury column can be calculated by the following equation ... 

Rather than using mercury as a piston that is pushed about by the forces within a vacuum system, the McLeod gauge traps a known volume of gas of unknown pressure and compares it to a known volume of gas at a known pressure using Boyle s law ... 

K Measurement of volume change as a function of pressure a. Dilatometer method (Bekkedahl, 1949) (sample immersed in mercury) b. Piston-cylinder method (Warfield, 1980) (cylindrical sample in bore of rigid container under varying pressure) Combined measurement of speed of longitudinal and shear waves (Hartmann, 1980) K = p(ul lush)... 

A vertical cylindrical tank of length 77 cm has its top end closed by a tightly fitting frictionless piston of negligible mass. The air inside the cylinder is at an absolute pressure of 1 atm. The piston is depressed by pouring mercury on it slowly, so that the temperature of the air is maintained constant. What is the length of the air column when mercury starts to spill over the top of the cylinder ... 

The nature of the phase rule can be induced from some simple examples. Consider the system represented in Figure 24-3. It is made of water-substance (water in its various forms), in a cylinder with movable piston (to permit the pressure to be changed), placed in a thermostat with changeable temperature. If only one phase is present both the pressure and the temperature can be arbitrarily varied over wide ranges the variance is 2. For example, liquid water can be held at any temperature from its freezing point to its boiling point under any applied pressure. But if two phases are present the pressure is automatically determined by the temperature, and hence the variance is reduced to 1. For example, pure water vapor in equilibrium with water at a given temperature has a definite pressure, the vapor pressure of water at that temperature. And if three phases are present in equilibrium, ice, water, and water vapor, both the temperature and the pressure are exactly fixed the variance is then 0. This condition is called the triple point of ice, water, and water vapor. It occurs at temperature +0.0099 C and pressure 4.58 mm of mercury. 

For the determination of the differential values of r and / the PVT cell containing mercury and a known volume of reservoir fluid is immersed in the constant temperature bath at reservoir temperature and the pressure is reduced 200 psi below the saturation pressure by withdrawing mercury from the cell through the mercury pump. The cell and its contents are thoroughly agitated until equilibrium is established and the volume of the gas-oil system is recorded. The gas is bled off through the metering device and at the same time the piston of the mercury pump is slowly advanced to keep the pressure in the cell constant. When the gas has been bled off, the volume of the residual oil in the cell is measured and recorded. The volume of the... 

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