772 



We purchased a two-ton machine; i. e. machine whose refrigerat- 

 ing capacity in 24 hours is equivalent to 2000 kg of ice. This 

 machine much more than fulfills our requirements and may ultimately 

 be used for cooling a number of working rooms in the summer. Yet 

 it is very desirable in the construction of any apparatus to have an 

 excess of force at hand. 



In our apparatus anhydrous ammonia is allowed to expand in 

 a coil immersed in 5000 kg of saturated calcium chloride solution 

 which in turn is forced through the cooling pipe suspended from 

 the ceiling of the room. The tank of calcium chloride brine is placed 

 within the vault and when the engine is not running this great 

 quantity of brine absorbs the heat which gradually enters through the 

 insulated walls. The figure explains the arrangement. 



The vault is well constructed with a number of layers of boards, 

 air-spaces and mineral wool as the diagram shows. Each layer of 

 boards is covered with one or two layers of paper, the outermost layer 

 being tarred. The door is insulated in the same way and is 30 cm 

 thick. The interior is illuminated with electric light. There are 

 thermometers on the outside which read the temperature of the brine 

 as the air of the vault. 



We found that in the beginning it was necessary to operate the 

 machine for 36 hours continuously to reduce the temperature of the 

 vault to O** C. After this an additional run of the machine for 

 8 hours reduced the temperature of the vault to — 5 ° C. During this 

 time the brine was circulating constantly through the tubes suspended 

 from the ceiling of the vault. The temperature of the brine at this 

 time had fallen to — 20 ° C. Throughout the year we have not attempt 

 to reduce the brine below — 20^ C. With the vault at — 6 degrees 

 and the brine at — 20 degrees the machine may remain quite for a 

 whole week at the end of which time the temperature in the vault 

 is 0" and that of the brine —4" C. When the temperature of the 

 vault has risen to " it is desirable to cool it again because opening 

 the door of the vault easily causes thawing which makes the room 

 very sloppy. 



I have now taken the temperature of the vault, brine and outside 

 room twice a day during a whole year including the time the machine 

 has been running. The following table is a portion of this record 

 taken at random. (Table p. 774.) 



The table is not as complete as might be desired for the brine 

 temperature is not given for the time in which the machine was not 

 running. This is not easily obtained for it is necessary to start the 

 engine to obtain the temperature of the brine. Our method of man- 



