Thermometers, mercury

Beckmann thermometer A very sensitive mercury thermometer with a small temperature range which can be changed by transferring mercury between the capillary and a bulb reservoir. Used for accurate temperature measurements in the determination of molecular weights by freezing point depression or boiling point elevation. 

In the late fifteenth century AD mercury was successfully used as a treatment for syphilis. In the late sixteenth century the development of the Patio process for the recovery of silver by amalgamation (see Silverand silveralloys) greatiy increased the consumption of mercury. Usage of mercury increased in 1643 when Torricelli invented the barometer, and again in 1720 when Fahrenheit invented the mercury thermometer. Other scientific and medical appHcations foUowed. Industrial usage after 1900, particularly in electrical appHcations, expanded rapidly, offsetting the sharp decline in its use in amalgamation. 

Ammonia is corrosive to akoys of copper and zinc and these materials must not be used in ammonia service. Iron or steel should usuaky be the only metal in ammonia storage tanks, piping, and fittings. It is recommended that ammonia should contain at least 0.2% water to prevent steel stress corrosion. Mercury thermometers should be avoided. 

Mercury thermometers are subject to separation of the mercury column or to inclusion of bubbles of the fiU gas. These may result from shipping and handling and cause a scale offset which can usually be seen upon visual examination, and they are always recogni2ed by a 0°C verification check. Manufacturers will suggest means by which these temporary defects may be cured. 

When bulb thermometers are employed where there is a likelihood of a magnetic field, alcohol thermometers shotdd be preferred to mercury thermometers, as the latter ire unreliiiblc under stich conditions. 

The ambient temperature should be measured during the last quarter of the test by at least three thermometers or thermocouples placed equally around the switchgear assembly, at almost the centre level and at about I metre from the body of the enclosure. The ambient temperature to be considered must be the average of these readings and should be within 10-40°C. To ensure that the ambient temperature is unaffected by ntagnetic field, alcohol thermometers must be used and not mercury thermometers. 

Sources of mercury (e.g., mercury thermometers) should be avoided in the vicinity of aluminum and copper alloy equipment. 

Liquid-in-glass thermometers measure the thermal expansion of a liquid, which is placed in a solid container, on a length scale. The mercury thermometer is one example of liquid thermometers. Alcohol is also used with this type of instrument. The temperature range is -80 to a-330 °C depending on the liquid. The quality, stability, and accuracy vary considerably. The advantages are a simple construction and low price. A disadvantage is that they are not compatible for connection to monitoring systems. 

Mercury thermometers, both for laboratory and clinical use, have been replaced by digital ones. 

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 ... 

Mercury (II) oxide, 3-4 Mercury-in-glass thermometers, 7-8 Mercury thermometers, 2 Metabolic energy, 218 Metal A substance having characteristic... 

The Nernst equation shows that the glass electrode potential for a given pH value will be dependent upon the temperature of the solution. A pH meter, therefore, includes a biasing control so that the scale of the meter can be adjusted to correspond to the temperature of the solution under test. This may take the form of a manual control, calibrated in 0 C, and which is set to the temperature of the solution as determined with an ordinary mercury thermometer. In some instruments, arrangements are made for automatic temperature compensation by inserting a temperature probe (a resistance thermometer) into the solution, and the output from this is fed into the pH meter circuit. 

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. 

Infrared radiation was discovered by Herschel [58] in 1800, using a mercury thermometer to detect sunlight dispersed by a prism. However, the Latin poet Lucretius in his De rerum Natura (On the Nature of Things, about 50 BC) clearly showed a clear feeling of the infrared radiation. Of course Lucretius s terminology was far from the modern one, and he had no thermometer at his disposal ... 

A mercury thermometer having first-order dynamics with a time constant of 60 s is placed in a bath at 308 K (35°C). After the thermometer reaches a steady state it is suddenly placed in a bath at 313 K (40° C) at / = 0 and left there for 60 s, after which it is immediately returned to the bath at 308 K (35°C). 

Mercury-switch thermostats, 16 42 Mercury-thallium amalgam, 24 628 Mercury thermometers, 24 464, 465 Mercury vapor intoxication, chronic, 16 51 Mercury vapor lamps, vitreous silica in, 22 441... 

Stiction, in mercury thermometers, 24 465 Stiff differential equation, 25 285 Stiffness loss, in fatigue, 16 187-188 of fibers, 11 181, 182 Stiffness values, of paper, 18-101 Stilbene(s), 25 181... 

Temperature measurement was historically done with a mercury thermometer. Modern instruments have electronic temperature sensors that can be coupled with digital temperature readouts. Digital temperature monitoring also allows the operator to record the observed melting point with the press of a keypad button. Data can be stored within the instrument or transmitted to a computer or laboratory information management system (LIMS). 

Mercury thermometers have been used for decades. In some instances their use has been discontinued, such as in infant incubators where it was found that significant mercury vapor concentrations could be achieved if the thermometers were broken in this enclosed environment. Disposal of thermometers and thermostats continues to add significandy to the toxicity of municipal waste. In 1995, discarded thermometers contributed 16.9 tons of mercury to municipal solid waste stream. 

Use naturally occurring (mold, radon) and purchased household products (medicines, pesticides, cleaning agents, paint, mercury thermometers) Source natural and manufactured Recommended daily intake usually not recommended Absorption skin, oral, inhalation... 

In a mercury thermometer, atmospheric pressure, P, forces mercury to rise in the tube to a height of approximately 30 inches... 

However, it is now recommended that thermometers be calibrated in °C. More recently, thermistors have been used instead of mercury thermometers. Cryoscopes based on dew point depression have also been approved for use. These latter instruments also use thermistors and are based on changes in osmotic pressure. Thermistor cryoscopes are now used more widely than Hortvet instruments. 

Thermometers. Conventional mercury thermometers are used to measure temperatures not exceeding 300 °C. Special thick-walled glass thermometers make it possible to determine temperatures up to 500 °C. 

The determination of the temperatures of crystallization of the mixtures was carried out in a closed glass apparatus with a manual stirrer. This entered the vessel through a hole of tight bore in the rubber stopper, which was greased with vaseline, so that the accession of atmospheric moisture was reduced to a minimum. Temperatures above 0°C were measured with a mercury thermometer with scale divisions of 0-1°, which was calibrated by the ice-water mixture at 0° and by the Na2S04 0H2O transition point at 32 38°. For temperatures below 0° an alcohol thermometer with 0 2° scale divisions was used. It was calibrated also at 0° with the ice-water mixture. Since the thermometer capillary was at room temperature in the course of the determinations, a correction for its expansion was applied. The low temperatures were obtained by means of dry ice-acetone mixtures. 

When very low temperatures, under —40° Fahr., have to bo estimated, a mercurial thermometer cannot be employed, since this metal solidities at that point in such cases, alcohol colored by some matter is used in the bulb of the instrument. On the other hand, mercury boils at about 600° Fahr., and, therefore, when, very high temperatures are to he estimated, a different instrument, termed the pyrometer, is employed, which Will be described in the sequel. 

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