Vapor thermometer

The metal is widely used in laboratory work for making thermometers, barometers, diffusion pumps, and many other instruments. It is used in making mercury-vapor lamps and advertising... 

It is one of four metals — mercury, cesium, and rubidium — which can be liquid near room temperature and, thus, can be used in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. 

Table 11.4 Solutions for Maintaining Constant Humidity Table 11.5 Concentration of Solutions of H2SO4, NaOH, and CaCi2 Giving Specified Vapor Pressures and Percent Humidities at 25°C Table 11.6 Relative Humidity from Wet and Dry Bulb Thermometer Readings Table 11.7 Relative Humidity from Dew Point Readings...

The fixed points in the lTS-90 are given in Tabie 11.39. Platinum resistance thermometers are recommended for use between 14 K and 1235 K (the freezing point of silver), calibrated against the fixed points. Below 14 K either the vapor pressure of helium or a constant-volume gas thermometer is to be used. Above 1235 K radiometry is to be used in conjunction with the Planck radiation law,... 

Most thermometry using the KTTS direcdy requites a thermodynamic instmment for interpolation. The vapor pressure of an ideal gas is a thermodynamic function, and a common device for reali2ing the KTTS is the helium gas thermometer. The transfer function of this thermometer may be chosen as the change in pressure with change in temperature at constant volume, or the change in volume with change in temperature at constant pressure. It is easier to measure pressure accurately than volume thus, constant volume gas thermometry is the usual choice (see Pressure measurement). 

Fig. 2. A water triple-point ceU. A, handle B, water vapor C, Hquid vapor, D, soHd water (ice mande) and E, thermometer weU.

VP = vapor pressure point CVGT, constant volume gas thermometer point TP, triple point MP, melting point FP, freezing point. Note MP and FP at 101.325 Pa (1 atm) ambient pressure. 

The ITS-90 has its lowest point at 0.65 K and extends upward without specified limit. A number of values assigned to fixed points differ from those of the immediately previous scale, IPTS-68. In addition, the standard platinum resistance thermometer (SPRC) is specified as the interpolation standard from 13.8033 K to 961.78°C, and the interpolation standard above 961.78°C is a radiation thermometer based on Planck s radiation law. Between 0.65 and 13.8033 K interpolation of the scale rehes upon vapor pressure and constant-volume gas thermometry. The standard thermocouple, which in previous scales had a range between the upper end of the SPRT range and the lower end of the radiation thermometer range, has been deleted. 

A descriptive flowchart has been prepared by Sparks Materials at Low Temperatures, ASM, Metal Park, OH, 1983) to show the temperature range of ciyogenic thermometers in general use today. Parese and Mohnar (Modem Gas-Based Temperature and Pres.sure Measurements, Plenum, New York, 1992) provide details on gas- and vapor-pressure thermometiy at these temperatures. 

Ambient Wet-Bulb Temperature The temperature in degrees Fahrenheit to which air can be cooled, making it adiabatic to saturation by the addition of water vapor, in practical terms, the wet-bulb temperature is the temperature indicated by a thermometer, the bulb of which is kept moist by a wick and over which air is circulated. 

There were placed 120 g of Lthree-necked flask equipped with a stirrer thermometer and methanol/dry ice cooling and 1.5 liters of liquid ammonia were allowed to enter at -40°C. Then there were added under continuous cooling 50 g (2.17 mols) of sodium metal in portions of 1 to 2 g during the course of one hour. The end of the reaction was recognized by the continuation of the blue color. After the end of the reaction the excess sodium was destroyed by the addition of ammonium chloride and the ammonia vaporized at normal pressure. The residue was taken up in 500 ml of water and concentrated in a vacuum to 200 ml in order to remove residual ammonia, and again treated with 300 ml of water. The entire operations were carried out under a nitrogen atmosphere. 

A) Preparation of 6-(3-dimethylammopropYl)-6-hydroxybemo[b]bemofurano[2,3-e]axe-pin — In a 250 ml flask equipped with a vertical condensar, a dropping-funnel, a dip thermometer and a stirrer, 1 g of magnesium turnings and a crystal of iodine were heated until vaporization of the iodine and then cooled, after which 20 ml of dry tetrahydrofuran were added. 

Psychrometry has to do with the properties of the air-water vapor mixtures found in the atmosphere. Psychrometry tables, published by the US Weather Bureau, give detailed data about vapor pressure, relative humidity and dew point at the sea-level barometer of 30 in Hg, and at certain other barometric pressures. These tables are based on relative readings of dry bulb and wet bulb atmospheric temperatures as determined simultaneously by a sling psychrometer. The dry bulb reads ambient temperature while the wet bulb reads a lower temperature influenced by evaporation from a wetted wick surrounding the bulb of a parallel thermometer. 

Mercury thermometers are being phased out because of the toxicity of mercury vapor. A common replacement for mercury is the organic liquid iso amyl benzoate, which boils at 262°C. What is its boiling point in °F K ... 

The international temperature scale is based upon the assignment of temperatures to a relatively small number of fixed points , conditions where three phases, or two phases at a specified pressure, are in equilibrium, and thus are required by the Gibbs phase rule to be at constant temperature. Different types of thermometers (for example, He vapor pressure thermometers, platinum resistance thermometers, platinum/rhodium thermocouples, blackbody radiators) and interpolation equations have been developed to reproduce temperatures between the fixed points and to generate temperature scales that are continuous through the intersections at the fixed points. 

Temperature Tgo in the range between 3.0 and 24.5561 K is defined in terms of 3He or 4He constant volume gas thermometers (CVGT), calibrated at the triple points of Ne and H2, and at a temperature between 3.0 and 5.0 K that has been obtained from vapor pressure versus temperature relations for He. 

Two additional points near 17.0 and 20.3 K are required. These may be determined by using either ihe constant volume gas thermometer or by vapor pressure measurements of H . 

A. Trichloromethyl chloroformate. A 100-ml., three-necked, round-bottomed Pyrex flask is equipped with a thermometer, a reflux condenser protected at the top with a calcium chloride tube, and a gas-inlet tube with a coarse fritted-glass tip extending almost to the bottom of the flask. In the flask are placed 37.8 g. (0.4 mole) of freshly distilled methyl chloroformate (Note 2) and a Teflon-coated magnetic stirring bar. The flask is illuminated with a 100-W. high-pressure, mercury-vapor lamp (Note 3) which is placed beside... 

Flash point temperatures are determined using an open-cup apparatus, shown in Figure 6-3. The liquid to be tested is placed in the open cup. The liquid temperature is measured with a thermometer while a Bunsen burner is used to heat the liquid. A small flame is established on the end of a movable wand. During heating, the wand is slowly moved back and forth over the open liquid pool. Eventually a temperature is reached at which the liquid is volatile enough to produce a flammable vapor, and a momentary flashing flame occurs. The temperature at which this first occurs is called the flash point temperature. Note that at the flash point temperature only a momentary flame occurs a higher temperature, called the fire point temperature, is required to produce a continuous flame. 

A plant having a shelf area of = 30 m2 has been loaded with 300 kg of water in trays and frozen on the shelves. Water vapor transport and condenser temperatures have been measured in this case between 0.4 and 0.6 mbar, which is approx, two to three times higher than the normally expected operation pressure of the plant (to get an measurable quantity of ice sublimed in a reasonable test time). The data of the test are shown in Fig. 2.19. Three Pt 100 (resistance thermometers) have been frozen in the ice. One CA each have been... 

A round-bottomed, standard-taper flask with a Claisen head carrying an ebullition capillary and a thermometer and attached to a two-necked flask with one neck for vacuum takeoff is satisfactory. It is important that the setup allow for heating by either flame or infrared lamp to melt the solid distillate and prevent its clogging the vapor passage. 

So as you fractionally distill, not only does your boiling liquid get richer in the higher-boiling component, so also does your distillate, your condensed vapor. Don t worry too much about this effect. It happens as long as you have to collect a product for evaluation. Let your thermometer be your guide, and keep the temperature spread less than 2°C. 

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