Thermostatic box

To run a front, a polymer slice (or seed) was placed in the bottom of a standard glass cuvette, and monomer solution of the concentration of interest was poured on top. The cuvettes were capped with inverted polyethylene caps (Fisher Scientific) to minimize the air/liquid interface. (If an air layer were present on top of the samples, the oxygen in the air would, over time, have diffused into the upper layer of monomer solution and would have inhibited polymerization in this layer.) The cuvettes were then placed in the cuvette holder in the pre-heated thermostatic box (Figure 7), and the fronts were run at the desired temperature until completion. 

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box. 

The thermostatic mortar P, whose function is described below, is a small electrical heating unit (1 5 cm. in diameter and 7 cm. long) kept constant at 180 . The temperature is kept constant by another Simmerstat. The mortal may be supported on its Simmerstat box or alternatively screwed on to the end of the furnace, a gap of 1 cm. being left between the furnace and the mortar in each case. The right-hand end of the mortar bore is only wide enough to take the drawn-out beak end of the combustion tube, which is thus held in place. 

For measurements at temperatures other than ambient, cells with double walls, which can be thermostatted, are also available commercially. If measurements are required at temperatures between ca. —5°C and room temperature, the sample compartment of the spectrometer can be flushed with dry air or nitrogen to reduce condensation on the cell windows. Below ca. — 5 °C the windows can be covered with a thin polythene film, but measurements below —25 °C are very troublesome. The problems associated with low temperature spectroscopic measurements were solved by enclosing the cell in an air-tight box fitted with glass windows (Dadley and Evans, 1967). The box was so designed that it fitted into the spectrophotometer and the air inside the box was dried with phosphoric oxide which, it is claimed, stopped condensation even at temperatures as low as — 60 °C glass windows could be used because only absorptions above 380 nm were of interest. 

The thermostat is an iron box about thirty centimeters square filled with molten lead. An iron blade keeps the lead stirred and a platinum resistance thermometer functions both as a thermometer and as a thermoregulator. The Wheatstone bridge, which contains the resistance thermometer as one arm, is adjusted for a given temperature, and the beam of light from the galvanometer strikes a zero reading on the scale. At this position is introduced a photoelectric cell connected with a radio tube and amplifier, which in turn actuates an electro-magnetic relay. When the temperature reaches the predetermined value, the beam of... 

Figure 6.118 Electrical heater, formed by a bundle of single U-shaped heating elements. A flameproof enclosure contains the thermostatic controller and the interconnection wiring of the single heaters. The terminal box complies with increased safety - e...

A Dewar flask, in which 400 cm of kerosene, one CA thermocouple to measure the Tug and a Nichrome wire of about 1.7 Q are contained, is set under conditions of no air circulation in an aluminium box settled in a fairly large thermostat, which in turn is placed in an air-conditioned room maintained at an almost constant (room) temperature. In this connection, the temperature of the thermostat is maintained at a constant temperature 2 3 K higher than the The other thermocouple to measure the T i-up is held outside the flask set in the aluminium box. The thermocouples used are calibrated in the range of 40 to 60 °C before the measurement (Figs. 48-53). 

Figure 48, The set-up to measure the main heat transfer data of 400 cm of kerosene charged in a Dewar flask used in the BAM test. The flask is set under conditions of no air eireulation in an aluminium box settled in a fairly large thermostat,...

Thermostat (transite box with external heater winding and insulated with glass wool)... 

Figure 13 illustrates a multiple thermocouple installation connected to a single indicator. Compensating lead wires are carried from the couples to a conveniently located cold-junction box. The temperature of this box is thermostatically controlled. From the cold-junction box copper wires are carried to the terminal block and selective switch illustrated. A common return has been employed between the cold-junction box and the switchboard. In general it is preferable to use individual return wires for each couple. The switchboard illustrated is designed for six couples. By pressing one of the buttons shown any desired couple is connected directly to the indicator. 

---