( (^77 ) 



§ 3. Circulation of calcium chloride solution at consta7it tempera- 

 ture behw zero C The theriiioslat is similar to that described in 

 Coiiim. No. 70 III May '01, but with the difference that at P^ a 

 side tube with cock and mercury resevoir is introduced, so that the 

 regulator can be set for high temperatures (very well to 60° C.) 

 and also for a low one by the choice of a suitable fluid. The spiral is 

 filled with benzene and, instead of water from the main (as in No. 70), 

 a cooled stream of calcium chloride solution is run into the heating 

 vessel. The solution is contained in a vessel ^ with filter and 

 float ??M and is driven through the refrigerator (?„ and regenerator ^'c 

 in winch the methylchloride evaporates and thus cools the circulating 

 calcium chloride solution. This is caused to move by a force pump S 

 with valves ^/- connected to one of the conjugated compressors S 

 while a bent tube prevents the cooled solution from fallinsj. 



In the refrigerator the liquid methylchloride runs through the 

 tube ^\j^ and regulating cock (Jj^ to the inner space, while the 

 calcium chloride solution runs spirally in the outer. The liquid 

 methylchloride running into the refrigerator is cooled by the vapour 

 evolved, which escapes by a wider tube <f è to the regenerator, from 

 which projected liquid returns by a narrow tube <?/,. finally the 

 danger which might arise when the cooled methylchloride, left 

 between the cocks d and the shut off cock of the tubing ^i, returned 

 to the ordinary temi)erature, is avoided by connecting a safety cap 

 with a closed tube '''k added above. At 12 Atm. the thin plate breaks 

 and sufficient space is produced without communication with the air. 



The walls are 

 methylchloride. 



all calculated to stand the ordinary pressure of the 



The pressure under w^hich methylchloride 



evaporates must not fall below a certain value, 



as the calcium chloride might then freeze out. 



It is kept constant by the pressure regulator l^ 



PI. II. When the pressure falls the mercury 



rises in b, see accompanying figure, and forces 



the float flTi upwards, so that the lever ƒ rotates 



about g and thus closes the suction channel by 



the double valve h^ h^. A safety tube 2' PI. II 



and a tube to receive spilt mercury complete 



the apparatus. The properly cooled calcium 



chloride solution runs from the refrigerator (f^ to the thermostat Tl, 



where it is rewarmed to the required low temperature and conducted 



to the apparatus which must be held at constant temperature. 



On PI. II a piezometer surrounded by a vacuumglass is shown, 



45* 



