April, '10] COTTON : LOW TEMPERATURE APPARATUS 145 



through which the brine circulates. The flow of brine through each 

 of these coils is controlled by a balanced valve operated by a thermo- 

 regulator. 



The compressor is of the two-cylinder upright type and when in 

 operation the high and low pressure sides stand at 70 and 30 atmos- 

 pheres respectivelj'. The machine is so strongly constructed that 

 there is no special danger attendant upon its operation at these high 

 pressures. A motor of G^/o-horse power is required to operate this 

 machine and a reserve of at least 1-rated horse power should always 

 be allowed for a compressor of this size, more for larger sizes. 



The brine system consists of a brine tank, pump, coils and the nec- 

 essary piping to connect them. The brine tank is constructed of 3-16- 

 inch boiler plate, is 3 feet in diameter and 4 feet high and contains 

 200 lineal feet of expansion coils giving a radiating surface of about 

 68 square feet. This tank holds approximately 200 gallons of calcium 

 chlorid brine, which we are using in preference to sodium chlorid 

 brine because the latter is so destructive to iron piping. The brine 

 piping, with the exception of the coils in the chambers, which are 

 1 inch, is %-inch galvanized water pipe (PI. 7.). The brine tank, 

 piping and pump are well insulated against loss of cold by a wrap- 

 ping of two thicknesses of 1-inch hair felt with one layer of water- 

 proof insulating paper between. A tight-fitting cloth cover is then 

 fastened over the whole and painted to keep out moisture (PI. 6). 



The brine is circulated by an automatic water lift or pump, operated 

 by city water pressure. The pressure of the brine in the pipes^ 

 between the pump and the balanced valves, is automatically main- 

 tained equal to that of the water acting on the pump. When any 

 one of the four valves is opened the brine flows through, reducing 

 the pressure and starting the pump, which continues to operate until 

 the valve closes and the pressures in the water and brine systems 

 again balance. The brine tank thus serves as a storage reservoir for 

 cold, which is automatically fed into the coils as needed to maintain 

 the desired temperatures in the chambers. 



The insulated chambers consist of a box 10 feet long, 3 feet wide 

 and 3 feet high, the interior of which is divided into four compart- 

 ments, each 2 feet square inside. The outside walls consist of an 

 outer and an inner casing of yg-i^ch matched pine ceiling with four 

 thicknesses of 1-inch hair felt and five layers of waterproof insulat- 

 ing paper alternating between. The inside partitions, between the 

 chambers, are built up of two walls of yg-inch matched pine ceiling 

 with three thicknesses of 1-inch hair felt and four of paper alternat- 

 ing between. Each of these chambers is to be maintained at a dif- 



