Thermometer, calibration

The capillary tube method initially involves packing a powdered sample into a glass capillary tube of uniform diameter and length, carefully sealed at one end so that it forms a rounded tube of uniform thickness. The tube is then attached to a standardized thermometer so that the end of the tube reaches the middle of the thermometer reservoir bulb. This assembly is then inserted into a vessel contg a suitable liq which is uniformly heated so that the temp rises at a rate of about 1° per minute. Ref 1 discusses in detail equipment design and thermometer calibration. It should be noted that this technique is the method most widely used by organic chemists... 

The thermometer used in the large temperature interval between 13.8033 and 1234.93 K is a platinum resistance thermometer calibrated at fixed reference points. Temperatures are expressed in terms of W(T90), which is the ratio of the resistance R(T9q) of the thermometer at temperature T9o and the resistance at the triple point of water / (273.16), as seen in equation (A2.4) ... 

Last, we wish to remind that thermal cycling may spoil the thermometer calibration. The frequent check of the calibration by means of reference fixed points (see Section 8.5) is advisable. 

The relative errors on Ph, of the order of 0.1%, have been disregarded in the computation of K. We have checked for the presence of non-linear terms in the curves of T2 vs Ph, but the contribution of higher-order terms was found to be within the errors due to thermometer calibration. 

Between the triple point of equilibrium hydrogen (13.8033 K) and the freezing point of silver (1234.93 K), Tgo is defined by means of platinum resistance thermometers calibrated at specific sets of defining fixed points. The temperatures are given in terms of the ratio of the resistance of the thermometer at temperature Tgo to the resistance at the triple point of water ... 

Fixed-point realization, procedures for achieving, 24 444 Fixed points, secondary, 24 442t Fixed-point thermometer calibration,... 

Temperature measurement(s), 24 433-467, 75 469, 77 783-784 of critical current density, 23 847-848 fixed-point thermometer calibration,... 

Cla5don R. N. and KieflTer S. W. (1991). Oxygen isotopic thermometer calibrations. In Stable Isotope Geochemistry A Tribute to Samuel Epstein, H. P. Taylor Jr., J. R. O Neil, and I. R. Kaplan, eds.. The Geochemical Society, Special Pnblication n. 3. 

Clayton RN, Epstein S (1958) The relationship between 0/ 0 ratios in coexisting quartz, carbonate and iron oxides from various geological deposits. J Geol 66 352-373 Clayton RN, Kieffer SW (1991) Oxygen isotope thermometer calibrations. In Taylor HP, O Neil JR, Kaplan IR (eds.) Stable isotope geochemistry A tribute to Sam Epstein. Geochem Soc Spec Publ 3 3-10... 

Figure 11.5 Schematic representation of a Hortvet cryoscope. 1,4, Inlet and outlet for air or vacuum supply 2, thermometer calibrated at 0.001 °C intervals 3, agitator 5, milk sample 6, glass tube 7, alcohol 8, ether cooled by evaporation 9, insulated jacket.

Vapor-liquid equilibrium experiments were performed with an improved Othmer recirculation still as modified by Johnson and Furter (2). Temperatures were measured with Fisher thermometers calibrated against boiling points of known solutions. Equilibrium compositions were determined with a vapor fractometer using a type W column and a thermal conductivity detector. The liquid samples were distilled to remove the salt before analysis with the gas chromatograph the amount of salt present was calculated from the molality and the amount of solvent 2 present. Temperature measurements were accurate to 0.2°C while compositions were found to be accurate to 1% over most of the composition range. The system pressure was maintained at 1 atm. 1 mm... 

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

The BurStds thermometer and other thermometers calibrated for total immersion should be used only for detn of sp of TNT by the Specification Method, while for routine tests the thermometers calibrated to partial immersion should be used. F or calibration of such thermometers proceed as follows a)Make a mark ca 5cm from the bottom of the bulb and at least lcm above the upper (small) mercury bulb on each special thermometer graduated in 0.1 or 0.05° b)Tie thermometers together in pairs (with a strip of rubber tubing) and be ready for calibration by custard cup method c)Wash and dry a Pyrex custard cup ca 2.5 in diam and ca 2.5 deep. In order to hold the cup and thermometers in place, use a wooden stand as shown in Fig... 

Fill three small test tubes half full with water. Place a thermometer calibrated to 0.1° in each test tube. Record each temperature to 0.1°. Using identical penlight flashlights, shine a violet light into one test tube and a red light into another test tube. Let them stand for half an hour and then record the temperatures in all three test tubes. Continue to record temperatures for four hours at half-hour intervals. Explain your results. Why was one test tube prepared with water and a thermometer but no flashlight ... 

We will assume that Charles measured temperature with a mercury thermometer calibrated for the centigrade (Celsius) scale. 

Example 1.2 Table 1.3 lists the specific volumes of water, mercury, hydrogen at l(atm), and hydrogen at lOO(atm) for a number of temperatures on the International Practical Temperature Scale. Assume that each substance is the fluid in a thermometer, calibrated at the ice and steam points as suggested at the beginning of this section. To determine how good these thermometers are, calculate what each reads at the true temperatures for which data are given. 

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... 

Since the mercury in the thread, as well as that in the bulb, is susceptible to thermal expansion, it is important in precise work to take account of the temperature of the thermometer stem. Most thermometer calibrations, especially those for enclosed-stem types, are for total immersion—it is assumed that the thread is at the same temperature as the bulb. Other thermometers are meant to be used with partial inunersion, often to a ring engraved on the stem, and the remainder of the stem is assumed to be at room temperature (say, 25°C). For precise work, stem corrections should be made if the stem temperatures differ significantly from those assumed in the calibration. The correction that should be added to the thermometer reading is given by the equation... 

Table 12.1 A typical series of standards for thermometer calibration...

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. 

Thus, it has been found that the high temperature scale defined by the platinum resistance thermometer calibrated in terms of the melting point of ice, 0°C., the boiling points of water, 100°C., and of sulphur, 444.6°C., at a pressure of 760 mm. Hg.,... 

Use Solvent, especially for vegetable oils low- temperature thermometers calibrations polymerization reaction medium paint diluent alcohol denatu-rant. 

---