Thermometer calibration apparatus

Krell s thermometer calibration apparatus for ground-in thermometers and thermocouples... 

Softening ranges were determined using a Fisher Mel-Temp apparatus equipped with a thermometer calibrated to 300 C. 

Any thermometer with 0.0°C on either its main or auxiliary scale can be calibrated with an ice-bath calibration apparatus that can be assembled with the following material ... 

The object of the experiment described below is to set up a gas thermometer, calibrate it at the ice point (in lieu of the experimentally more difficult triple point), and use it to determine the temperatures of one or more other fixed points. These may include the steam point, the boiling point of liquid nitrogen, the sublimation temperature of solid carbon dioxide (Dry Ice), the transition temperature of sodium sulfate decahydrate to the monohydrate and saturated solution, etc. The experiment will be performed with an apparatus that... 

Thermometer correction. The temperature which is read on the thermometric scale must be corrected because there are several errors in such determinations. One source of error arises from the construction and calibration of the thermometer. The bore of the capillary may not have the same diameter throughout further, the scale graduation and the calibration of low-priced thermometers are not very accurate. A second source of error is the method used in the common melting point apparatus. The common thermometer has been calibrated while totally immersed in a bath. In the melting-point apparatus described, only a part of the stem is immersed. The column of mercury above the oil bath has a lower temperature than that at which the thermometer was calibrated. Therefore either a thermometer calibrated by partial immersion should be used or a correction must be made for the unequal heating of the mercury in the stem of the thermometer. Although thermometers calibrated by partial immersion are available, the latter practice is the more common. 

Determination of melting points (a-naphthylamine, a-naphthol, benzoic acid, succinic acid and p-nitrobenzoic acid). Use the apparatus shown in Fig. II, 10, 2, a. Construction of calibration curve for thermometer. Determination of m.p. of unknown compound. 

Most of the instruments, commonly used in an analytical laboratory, such as UV-Spectrophoto-meter, IR-Spectrophotometer, single—pan electric balance, pH-meter, turbidimeter and nephelometer, polarimeter, refractometer and the like must be calibrated duly, before use so as to eliminate any possible errors. In the same manner all apparatus, namely pipettes, burettes, volumetric flasks, thermometers, weights etc., must be calibrated duly, and the necessary corrections incorporated to the original measurements. 

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. 

The thermometer should be inserted so that the thermometer is immersed to the 0.0°C level (if calibrating a complete-immersion thermometer) or inserted to the immersion line (if calibrating a partial-immersion thermometer). The thermometer is likely to require support to maintain its proper position. Let the entire apparatus sit for 15 to 30 minutes, to reach equilibrium. Periodically add more ice, as needed, and remove any excess water with the siphon. If the ice is kept clean and... 

Apparatus for cryoscopic determination of molar mass. The cryoscopic mercury thermometer can be replaced by a resistance thermometer or a calibrated thermistor. 

The apparatus used in this experiment is shown in Fig. 1. The thermometer is either a special cryoscopic mercury thermometer of appropriate range, with graduations every 0.01 or 0.02°C, a resistance thermometer with a resolution of 0.01°C, or a calibrated thermistor. In this experiment an aqueous solution of a weak or strong acid is mixed with crushed ice until equilibrium is attained. The temperature is recorded, and two or more aliquots of the liquid phase are withdrawn for titration to determine the equilibrium nominal concentration iiiq. The ice to be used should preferably be distilled-water ice. 

Figure 1 depicts the experimental apparatus used in the determination of heat and mass transfer coefficients.A compressor (A) feeds the air to a tank (B), to minimize pulse fluctuations in flowrate. The air is dried as it passes trough a bed of silica gel (C). Air flowrate is measured with a rotameter and in addition with a calibrated capillary meter(E). The inlet air moisture content is measured by means of a dry and wet bulb thermometer system (D) prior to its entrance to a coil submerged in a constant temperature bath (F). From here, the air enters the bottom of the fluidized bed (G) where its temperature is measured.The fluidized bed consisted of an insulated QVF glass tube 2 inches in diameter and 12 inches in length. A system for the collection of fines(I) was installed after the bed to evaluate entrainment, although at all experimental conditions used in this work entrainment was absent. A thermometer placed on top of the bed of solids was used to measure the temperature of the bed exit.Air moisture content was also determined at the outlet of the fluidized bed by means of a hygrometer and a wet and dry bulb temperature system(J). 

Comments. Methods for obtaining melting-points are not usually given in the specifications, but it is absolutely necessary that a definite procedure and definite apparatus be agreed upon. The following points should be taken into consideration calibration and stem correction of thermometers, size of tubes, amoimt of substance taken, rate of melting and vessel of liquid to be used as bath. 

The boiling point is one of the most important physical constants of a liquid. It is also easily determined with sufficient accuracy for most purposes if a reasonable quantity of a pure substance is available, for then it is only necessar to carefully distill the sample, noting both the vapor temperature and the barometric pressure. A particularly convenient apparatus for distillation of small quantities is shown in Fig. 1-10. The shape of the flask here is a desirable one because it confines the liquid to a smaller area than does a round-bottom flask. Thermometers with standard taper joints (1-in. immersion) are very convenient and reduce the possibility of contamination, and in vacuum distillation, of leakage. They are also calibrated for partial immersion, thus making emergent stem corrections (page 83) unnecessary. They... 

If one considers the amount of time usually spent in the preparation of a new compound, the few minutes required to obtain a good melting point seems little enough to make it inexcusable to report carelessly determined melting points. For this purpose, the use of the Hershberg apparatus and calibrated Anschutz thermometers is strongly recommended. 

---