Glass stem thermometers

Mid-1600 Liquid-in-glass graduated thermometers are widely spread Famous are die alcohol thermometers of die Accademia del Cimento in Florence. Their graduation marks are made of coloured glass bits attached to die stem... 

To finish off the reaction, 200 grams (110 ml) of concentrated sulfuric acid is measured out. The sulfuric acid should be ice cold, fresh from the freezer. It is then added a drop or two at a time with an eyedropper (glass stem ) to the reaction mixture. Between each drop or two, the acid should be mixed in by mixing with the eyedropper or the thermometer. The temperature should be watched closely during the addition of the sulfuric acid to make sure the temperature does not go above 0° C. As the temperature nears 0° C, the addition of sulfuric acid should be stopped until the mixture cools off again. 

Liquid-in-glass thermometers are almost exclusively used to determine the temperature of fluids that are relatively uniform—that is, they contain no large temperature gradients. Conduction along the glass stem can affect the temperature of the glass as well as that of the liquid. Therefore, thermometers are usually calibrated for a specified depth of immersion. They should then show the correct temperature when inserted to that level in the fluid whose temperature is to be measured. When a thermometer is used in situations where the immersion is other than that for which it was designed and calibrated, a stem correction [8] should be applied. 

The electrolysis vessel consists of a glass cylinder, 5 cm. in diameter and 10 cm. high, such as, for example, a small Pyrex pressure vessel. This vessel is closed with a five-hole rubber stopper to accommodate the cathode stem, thermometer, diaphragm, and Ng inlet and outlet tubes. A suitable outlet tube is a small fermentation tube, which serves as protection against air and should, if possible, be drawn out into an outward-pointing capillary. 

The measuring range with liquid-filled thermometers (mercury with a glass stem) is situated between —200 and +370°C, with an accuracy of +1% of full scale, usually less than +0.5°C [4]. 

And remember Not only thermometers, but anything that resembles a glass tube can fit in here This includes unlikely items such as drying tubes (they have an outlet tube) and even a funnel stem (you may have to couple the stem to a smaller glass tube if the stem is too fat). 

Stellite-type aboys carbides in, 4 647 Stellite-type aboys, 7 220-226 Stelometer, 11 614 Stem corrections, in liquid-in-glass thermometers, 24 464-465 Stem cell technology, 11 13-14 STEM-drilling, 9 599-600 Stem bbers, 11 285... 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Fig. 2.30 The principle features of the solid-stem liquid-in-glass thermometer. From Figure 3 from the NBS Monograph 90, Calibration of Liquid-in-Glass Thermometers," by James F. Swindells, reprinted courtesy of the National Institute of Standards and Technology, Technology Adminstration, U.S. Department of Commerce. Not copyrightable in the United States.

By using two liquid-in-glass thermometers, you can verify the quality of both thermometers by their agreement in temperature readings. If the temperatures do not agree, one of the thermometers may have a bubble in the stem or some other defect. Unfortunately, this trick does not let you know which is the defective one, but it provides a clue to the problem. f Methanol is flammable and poisonous. 

Liquid in Glass Thermometers. Mercury-in-glass thermometers (or better yet, mercury-in quartz) function well between -25°C and 360°C their typical precision is 0.1 K. They must be corrected for (1) relatively small pressure effects and (2) a relatively large "exposed-stem correction," due to the different coefficients of thermal expansion of mercury and glass in the part of the thermometer not immersed in the system being measured. 

Laboratory thermometers are commonly available in two types solid-stem and enclosed-scale. The former has a stem of solid glass, with a scale engraved on the outside surface the latter has a slender capillary and a separate engraved scale, both enclosed in... 

II. The distillation is performed with the apparatus used in Exp. 30. Fill the flask half full of the liquid from I., add a few pieces of pipe-stem (or granulated zinc, or glass tubing) to prevent bumping, and distil about 50 cc. Save the distillate. Replace the residue in the flask by more liquid from I., distil again, and repeat this operation until all the liquid has been used. Replace the one-hole stopper with a two-hole stopper, insert a thermometer in one hole so that the bulb just touches the surface of the combined distillates which should now be distilled. Heat gently, and collect in a separate receiver the distillate which is formed when the liquid boils between 80° and 93° C. This distillate contains most of the alcohol. 

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