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A3631 

 A3631 1 Dupre's Constant Temperature Apparatus, with heavy copper boiler, etc., soldered 



joints for temperatures under 100 C. 

 B3631 T Dupre's Apparatus, as above, with heavy copper boiler and bulb condenser, etc. All 



joints brazed for temperatures 100 C. and over 



DESCRIPTION. 



This apparatus is for the purpose of maintaining a constant temperature, within very narrow limits, and can 

 /be used for temperatures ranging roughly from 30 C. to 150 C. The principle employed is the constancy of the 

 temperature of water boiling at a constant pressure. 



The apparatus consists of a boiler A, water jacketed bulb B, and reflux condenser c, connected as shown in 

 illustration ; the whole being closed by a screw valve D ; this valve being the only opening to the air. 



The boiler A, which is about one quarter filled with water, is heated by a gas flame or other suitable means. 

 When the water boils the air in the boiler is driven over into the bulb, creating therein a pressure varying in accord- 

 ance with the amount of air originally in the apparatus. The steam generated being condensed and returned to 

 the boiler does not affect the pressure in the bulb, and the vapour in the boiler will therefore remain at a constant 

 temperature dependent on the said pressure in the bulb for any length of time desired. 



The actual adjustments are made as follows : 



For temperatures below 100 C. The nozzle of the screw valve is connected with a vacuum pump, the valve 

 opened and the apparatus exhausted so as to give a lower temperature than that required. The valve is then 

 screwed down ; the cooling water (which passes first round the jacketed bulb and then through the condenser) 

 is turned on and the boiler heated. A constant temperature is soon reached which can readily be raised to the 

 point required by cautiously admitting air through the screw valve. The valve is then screwed down tightly, 

 when the temperature will remain constant as long as heat is applied to the boiler, and unless the valve be unscrewed 

 the apparatus will always maintain this temperature when used at any subsequent time. 



For temperatures above 100 C. The valve is opened so that the apparatus is filled with air at atmospheric 

 pressure, and is then closed, the cooling water started, and the boiler heated as before. The temperature will 

 now become constant at the highest safe point for which the apparatus is designed. The desired temperature 

 is then obtained by cautiously allowing the necessary amount of air to escape by means of the screw valve. 



Without any special precautions as to gas regulation or nature of cooling water desired temperatures can be 

 maintained within + 0.1 C. With an efficiently regulated gas supply and a supply of cooling water of constant 

 temperature such as that direct from a main this apparatus can be designed to maintain desired temperatures 

 within 0.001 C. for any length of time. 



The exact form of the boiler depends on the purpose for which the apparatus is required, the illustration 

 showing the form of apparatus designed for heat test work. 



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-CROSS STREET HATTOTST GARDEN, E-C 



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