Figtjke 8. — A schematic diagram of the chamber, showing the water recirculation equipment. 



ENVIRONMENTAL CONTROLS 



Temperature 



For temperature control of the room in which 

 the chamber is located, a 10-horsepower, water- 

 cooled air-conditioning compressor was installed 

 in the equipment room with the cooling tower 

 located outside the building. Two 5-ton capacity 

 evaporator coils are located in opposite ends of 

 the room, and the temperature is controlled by 

 adjustable thermostats. Safety controls turn off 

 the lights in case the air conditioners cease func- 

 tioning, which prevents high-temperature damage 

 to the plants. 



Temperature is controlled in the biosynthesis 

 chamber by a 34-horsepower compressor installed 

 in the equipment room and an evaporator coil 

 in the chamber. A large-bulb thermostat controls 

 a solenoid in the liquid Freon line, and the com- 

 pressor is operated on back-and-head pressure 

 controls. Temperature in the chamber is main- 

 tained within ±1.5° F. 



A 500-watt strip heater is operated continu- 

 ously in the chamber to increase the heat load 

 for the compressor to reduce humidity. 



Lighting 



The biosynthesis chamber is illuminated by a 

 bank of 80 fluorescent 96-inch tubes and 24 incan- 

 descent 60-watt lamps. These produce a light 

 intensity in excess of 1,000 foot-candles at the 

 floor of the chamber. Readings of about 1,500 

 foot-candles at the horizontal midline and be- 

 tween 2,500 and 3,000 foot-candles at the top 

 inside the chamber have been observed. These 

 values are sufficiently high to give excellent 

 growth of soybeans, wheat, corn, and tobacco. 



The controls for the lighting and refrigeration 

 are installed in the machinery room. The ballasts 

 for the fluorescent lights are mounted on a rack 

 and covered with a vented hood. A thermostati- 

 cally controlled exhaust fan removes excess heat. 



Carbon Dioxide 



Radioactive carbon (C-14) is available at mod- 

 erate cost only in the form of barium carbonate. 

 It is necessary for automatic handling and reac- 

 tion to have the carbonate in a soluble form. A 



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