Temperature Indicator Thermometers Below

Heat the bath from below so that the temperature indicated by the thermometer rises at a uniform rate of 5"C (9 F)/min (Note 7). Protect the bath from drafts, using shields if necessary. Do not average the rate of temperature rise over the test period. The maximum permissible variation for any 1-min period after the first 3 min shall be 0.5 C... 

A dry reflux set-up is used with a three neck flask allowing a thermometer and sep funnel to be attached to the reaction flask. The thermometer is placed well below the surface of the flask contents. If the temperature rises above 55°C ice will need to be used to cool things down a bit So the three neck flask will be sitting in an ice bath on the stir plate before we begin. If ether is used instead of THF the ether will boil well before 50°C is reached giving a better indication of how hot things are getting. 

Cloud point. Measures the solubility/compatibility of a resin with solvents. The value reported is the temperature at which a specific mixture of a resin and a solvent or solvents blend gives a cloudy appearance, having been cooled from a temperature at which the mixture was clear. Commonly, a test tube of a given diameter is used and the temperature is noted when the lower end of the thermometer, placed at the bottom of the tube, disappears. Resins with cloud points below 0°C are commonly regarded as soluble and cloud points greater than 10°C indicate poor solubility/compatibility. White spirit with various aromatic contents is a widely used solvent in the determination of cloud point, but other solvents or solvents mixtures are also used. 

Low-voltage electric resistance heater cables fixed to the structural floor slab and then protected within a 50 mm thickness of cement and sand to give a suitable surface on which the floor vapour barrier can be laid. The heating is thermostatically controlled, and it is usual to include a distance reading or recording thermometer to give visual indication of the temperature of the floor at several locations below the insulation. 

The pH (or pI) term of the Nemst equation contains the electrode slope factor as a linear temperature relationship. This means that a pH determination requires the instantaneous input, either manual or automatic, of the prevailing temperature value into the potentiometer. In the manual procedure the temperature compensation knob is previously set on the actual value. In the automatic procedure the adjustment is permanently achieved in direct connection with a temperature probe immersed in the solution close to the indicator electrode the probe usually consists of a Pt or Ni resistance thermometer or a thermistor normally based on an NTC resistor. An interesting development in 1980 was the Orion Model 611 pH meter, in which the pH electrode itself is used to sense the solution temperature (see below). 

In the flask are placed 240 g. (2 moles) of acetophenone and 1 1. of glacial acetic acid. The thermometer is adjusted so that it extends considerably below the surface of the solution, and chlorine is admitted at such a rate that the temperature does not exceed 60° (Note 1). Chlorination is continued until an excess of the halogen has been absorbed. This requires about five hours completion of the reaction is indicated by the development of a yellow color. The reaction mixture is poured over 6 1. of crushed ice in a 2-gal. jar. The mixture is stirred several times (Note 2) and allowed to stand until the ice has melted. The dichloroacetophenone, which separates as a heavy lachrymatory oil, is removed. The yield is 340-370 g. (90-97 per cent of the theoretical amount). This product, containing only a few per cent of water and acetic acid, is pure enough for the preparation of mandelic acid. It may be purified by adding about 100 cc. of benzene, removing the... 

But the temperature is measured by the number of divisions contained iff equal portions of the stem of the respective thermometers. Now, the zero point of Fahrenheit s is 32° below freezing point. If, therefore, F.° — 32, R.°, C.° indicate the same temperature on. each of the three thermometers, one has the proportion — ... 

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