SUBJECTS manometer

With the reaction flask closed off from the vacuum line, the bath at -196° is replaced by a bath at -111° (CS2 slush bath), which results in a gradual increase in pressure to approximately 50 torr as observed on the blow-out manometer. As the reaction proceeds, the pressure slowly diminishes and stabilizes after about 2 hours. When no further pressure change is observed, the reaction mixture is frozen again at -196°. The reaction vessel is then warmed by removing the cold bath, while the contents are subjected to pumping of the volatile products through successive cold traps at -126 (methylcyclohexane slush bath), -140, (Skelly F) and-196°. 

Strain Gages. Essentially, they are based on electrical measurements of strains produced by the action of stress. There are several ways for measuring strains, but the most convenient is the resistance method. The apparatus used for these measurements, known as "resistance manometer , depends upon the change in resistance of a metal (such as platinum, manganin or mercury) when subjected to pressure. The change in resistance is usually measured by means of a very sensitive Wheatstone bridge, but it may also be measured by a potentiometer or by an... 

The pressure of a gas, the force it exerts divided by the area subjected to the force, arises from the impact of its molecules. Pressure is measured with a barometer or a manometer. 

Any increase in pressure, whatever the cause, may be sufficient to blow ground glass joints apart, or to cause some part of the line to explode, usually that part of the line with the greatest diameter of tube. Safety spectacles should always be worn by everyone in the vicinity of a glass vacuum line. When the chemicals handled in any vacuum line are known to be poisonous, the line should be in a fume cupboard. Pressure release devices such as mercury manometers with one limb open to the atmosphere, or "0"-ring cup joints, should be included in ail sections of a vacuum line which may be subject to excessive internal gas pressures. 

We use the total pressure of the two gases in the pressure uncertainty since that is what the manometer is measuring with an uncertainty of 1 mmHg (according to our subjective eye) and even though we measure the temperature to the nearest degree (low-precision thermometer) we need to remember we are using the Kelvin temperature in the calculation. Now all the variables are in the same units of percent. In this case we have three variables so we can plot them on a (P, V,T) axis and display the value calculated for the moles as a vector. The relative uncertainties can be displayed as +/— deviations about the tip of the calculated vector result. 

A2.2.6.2 The manometer system, by nature, includes a bias due to the presence of fuel instead of the usual air over the mercury. This changes the value of pressure expressed in terms of column height of mercury such that a result about 6 % higher than true occurs. The transducer is not subject to... 

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