BAIRD &TATLOCK (LONDON) LTD. 



5285 



5285 T Thermostat, new pattern, designed by Dr. Lowry to supply a rapid stream of water 

 heated to constant temperature. 



This bath gives a flow of water, the temperature of which does not vary by more than a few thousandths 

 of a degree, even when a maximum rate of 4 litres (water) per minute is maintained. 



The apparatus, as shown, consists of a large zinc-lined wooden box, 20 by 18 by 16 in., with a capacity of 

 over 70 litres, stirred by means of a propeller driven by an electric motor. The large bulk of well-stirred water 

 and the heat insulation of the wooden box and cover render the regulation of the bath temperature exceptionally 

 easy, with the result that when the gas flame is controlled by a 4 in. spiral regulator the variations are so small 

 that they escape detection even with a thermometer graduated in 1-100. The heating is effected by means of 

 a small burner placed beneath a copper plate which forms the bottom of the central well of the water bath ; the 

 supply of gas to the burner is controlled on one hand by the bye-pass tap B, and on the other by the spiral s. 



The bath is provided with an adjustable overflow. In cold weather it is only necessary to allow an occa- 

 sional drop of water to drip into the side tube of the bath to maintain the level ; but in summer the flow is diverted 

 into the bath itself and greatly increased. Ideal conditions are reached when the air temperature is up to 20 C., 

 the water temperature a few degrees below. 



The water circulation is maintained by means of an electric driven pump, which sucks the water out of the 

 bath from a point near to the centre of the regulator, and draws it through the various jackets, and returns it 

 to the bath. 



The temperature of the return flow can be read by means of a standard thermometer T, graduated in i-iooths, 

 which dips into a tube of mercury round which the circulating water passes on its way back to the pump. The 

 rubber bulb serves to take up a part of the thrust of the pump. It usually becomes flattened, but continues 

 to pulsate when the flow of water exceeds I litre per hour. 



The pump is driven from an electro-motor through the gearing, which carries the propeller and is provided 

 with several adjustments. 



The speed of the motor is controlled by a lamp resistance. When this is short circuited the pump pro- 

 duces a maximum flow of 4 litres per minute. Under normal conditions a 180 v. 16 c.p. lamp resistance on a 

 200 v. circuit gives a flow of about i litre per minute, the temperature gradient with the bath at 208 and the 

 | room at 15 C. is then 0.01 C. per jacket unless the apparatus where temperature is to be maintained constant 

 can actually be immersed in the water bath, it is necessary. 



Whatever scheme is used to effect the regulation at a distance of a foot or two from the observation tube. 

 In the apparatus described above, the temperature gradient in the leads and the jackets is reduced to a minimum 

 by the rapid flow of water, which can be increased to any desired extent by speeding up the pump or by increasing 



its size. 



Price, complete with electro-motor, pump, etc., as figured 



Please state voltage of current available. 



17 10 



ICHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



959 



