PRESSURE 



EQUALIZATION 

 TUBE (COPPER) 



STAINLESS STEEL TUBE 



SPAN ZERO 



ANALYZER CALIBRATION GAS CYLINDERS 



Figttbe 9.-A schematic diagram of the carbon dioxide control equipment for the biosynthesis chamber. 



reaction vessel was constructed from a 200-ml. 

 round bottom flask with a side-arm outlet and a 

 ground glass joint inlet with stopcock. A 

 weighed quantity of C-14 barium carbonate was 

 placed in the flask, the inlet and outlet systems 

 connected, and a mixture of sulfuric acid and 

 fuming sulfuric acid admitted dropwise through 

 the stopper in the top. A slight vacuum was 

 applied to sweep out the evolved C0 2 , which was 

 captured in a train of bubblers containing sodium 

 hydroxide solution. The radioactive carbonate 

 solution thus prepared was then mixed with a 

 large volume of sodium bicarbonate solution to 

 produce the desired specific activity. This radio- 

 active solution then became the "stock" from which 

 a given crop of plants derived its carbon. 



The carbon dioxide concentration in the bio- 

 synthesis chamber was continually monitored. 

 Air from the chamber was pumped through a flow 

 system to an infrared carbon dioxide analyzer 

 and back into the chamber. The C0 2 content of 

 the air was recorded on a strip chart recorder. 

 (See fig. 9.) A special switch installed on the 

 recorder was set to actuate the controller when 

 a preset C0 2 concentration was reached. This 

 opened a solenoid for a given time and emptied 

 the contents of a metering vessel into a reaction 

 vessel in the chamber. The reaction vessel con- 

 tained sulfuric acid that reacted to evolve a quan- 

 tity of carbon dioxide. During normal operation 



10 



C0 2 content was automatically maintained be- 

 tween 0.03 and 0.10 percent. Figure 9 gives a 

 schematic layout of the carbon dioxide control 

 apparatus. This system has proved to be satis- 

 factory and has overcome the major problem 

 involved in the operation of this facility. 



The metering vessel (dispenser in fig. 9) is a 

 special fabricated glass vessel designed to fill by 

 siphon from the storage vessels. It has a filling 

 tip that is restricted to require 20 to 30 minutes 

 to fill the vessel, depending on head. The solenoid 

 is controlled so that it opens and remains open 

 only long enough for the vessel to empty (about 

 30 seconds), then closes. This delivers 300 ml. of 

 7-percent sodium bicarbonate solution, which upon 

 reaction with H 2 S0 4 will increase the C0 2 content 

 of the chamber about 0.06 percent. 



The cultures were aerated by recirculation of 

 air within the chamber by a sigmoid pump. The 

 air was pumped through a manifold and the flow 

 rate regulated by needle valves for each vessel and 

 through air dispersion tubes made of porous glass 

 into the solutions (fig. 10) . 



Pressure Regulation 



Strain imposed on the glass during installation 

 may have weakened some of the panes; therefore, 

 a maximum pressure well below theoretical maxi- 

 mum was maintained. A pressure variation of 



