Temperature Control Thermometers Below

Fig. 48. Development chamber with mantle for temperature control. Right, below entry connection with dial-type thermometer above it. The exit is on the upper part of the opposite side. The cover tubulure contains a thermometer and a device for holding both TLC-plates (photograph of Firm 44)...

Dissolve 46-5 g. (45-5 ml.) of aniUne in a mixture of 126 ml. of concentrated hydrochloric acid and 126 ml. of water contained in a 1-htre beaker. Cool to 0-5° in a bath of ice and salt, and add a solution of 36-5 g. of sodium nitrite in 75 ml. of water in small portions stir vigorously with a thermometer (1) and maintain the temperature below 10°, but preferably at about 5° by the addition of a httle crushed ice if necessary. The diazotisation is complete when a drop of the solution diluted with 3-4 drops of water gives an immediate blue colouration with potassium iodide - starch paper the test should be performed 3-4 minutes after the last addition of the nitrite solution. Prepare a solution of 76 g. of sodium fluoborate (2) in 150 ml. of water, cool, and add the chilled solution slowly to the diazonium salt solution the latter must be kept well stirred (1) and the temperature controlled so that it is below 10°. Allow to stand for 10 minutes with frequent stirring. Filter... 

Synthesis of CHDM/BA and CHDM/PDA Polyester Resins Described in Tables III and IV. CHDM, brassylic acid (or dodecandioic acid) and "Fascat 4100 in a mol ratio of 2/1/0.005 and 5 wt % of xylene were placed in a three-necked, 250-mL round-bottomed flask fitted with line, a thermometer, an Ace temperature controller, a heating mantle, a mechanical stirrer, a steam-heated Allihn partial condenser with a xylene-filled Barrett moisture test receiver below the Allihn condenser and a total condenser above it. The mixture was heated to about 140 without stirring to melt the reactants and stirring was started. Heating was continued to 205 C. A slow N sweep was maintained throughout the reaction. About 95 to 100% of the theoretical water was collected in the Barrett receiver. Upon cooling the reaction mixtures partially solidified to white waxy solids which liquified when heated to about 40 C. Acid numbers were < 1 mg of KOH/g of resin. 

In a 1-1. three-necked flask equipped with a mercury-sealed stirrer, a reflux condenser protected with a calcium chloride drying tube, a separatory funnel, a nitrogen inlet tube, and a thermometer, is placed 0.51S mole of methylmagnesium bromide in 250-350 ml. of ether (a 1.5-2.0A7 solution). The mixture is cooled to a temperature below 10° by means of an ice-water bath, the stirrer is started, and a solution of 66.1 g. (0.50 mole) of cin-namaldehyde (Note 1) in 60 ml. of absolute ether is added, the rate of addition being controlled so that the temperature is kept below 10°. Throughout the addition, which takes about 1 hour, a slow stream of dry nitrogen is passed through the flask (Note 2). 

Contact thermometers of a maximum-minimum type are also manufactured these make contact both on exceeding an upper limit and on dropping below a lower limit. By means of a fine adjusting screw the temperatures may be set with an accuracy of 0.1 °C [23]. Temperature control may be arranged to follow a variable reference temperature by moving the thermometer contact with a synchronous motor. 

The small scale closed tester is a metal cup with a thermometer fitted below the bottom of the internal chamber with ahinge mounted cover having filling orifice. The sample is introduced to the cup and the cup is maintained at a constant temperature by means of temperature controller. After a specific time, a test flame is applied for 2.5 s and an observation is made whether or not flash has occurred. If flash did not occiu the cup is cleaned, a new sample is introduced and the temperature is increased by 5 C. The measurements are repeated until the flash point is determined with accuracy of 1 C. 

The must temperatme can be taken with a dial thermometer having a 1.5 m probe. This effective method can measure must temperature directly in different areas, especially just below the pomace cap in the hottest part of the tank. This zone has the most significant fermentation activity. The temperature can also be taken by thermoelectric probes judiciously placed in each tank. The probes are linked to a measmement system in the winery laboratory. With this system, the winemaker can verily the temperature of the tanks at any moment Certain temperature control systems automatically regulate tank temperature when the temperature reaches certain value. 

Equip a 1-litre three-necked flask with a powerful mechanical stirrer, a separatory funnel with stem extending to the bottom of the flask, and a thermometer. Cool the flask in a mixture of ice and salt. Place a solution of 95 g. of A.R. sodium nitrite in 375 ml. of water in the flask and stir. When the temperature has fallen to 0° (or slightly below) introduce slowly from the separatory funnel a mixture of 25 ml. of water, 62 5 g. (34 ml.) of concentrated sulphuric acid and 110 g. (135 ml.) of n-amyl alcohol, which has previously been cooled to 0°. The rate of addition must be controlled so that the temperature is maintained at 1° the addition takes 45-60 minutes. AUow the mixture to stand for 1 5 hours and then filter from the precipitated sodium sulphate (1). Separate the upper yellow n-amyl nitrite layer, wash it with a solution containing 1 g. of sodium bicarbonate and 12 5 g. of sodium chloride in 50 ml. of water, and dry it with 5-7 g. of anhydrous magnesium sulphate. The resulting crude n-amyl nitrite (107 g.) is satisfactory for many purposes (2). Upon distillation, it passes over largely at 104° with negligible decomposition. The b.p. under reduced pressure is 29°/40 mm. 

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. 

Callendar-van Dusen Equation. The complexity of the ITS-90 equations, especially for temperatures below 273.16 K, creates an awkward situation. For practical use, the Callendar-van Dusen equation, which was the basis for IPTS-48, is still a very convenient form. This is especially true if one wishes to determine the resistance R of a Pt thermometer digitally under computer control and convert it into a temperature with a reasonably simple algorithm. The general form of the Callendar-van Dusen equation is... 

Mantles are relatively slow to react to changes in the heater control setting and it is easy to overshoot the desired temperature. Therefore always make small incremental changes in the heating control and if a temperature below the boiling point of the liquid is required, make sure that a thermometer is incorporated in the apparatus. 

---