S. DILLI AND j. H. GREEN 



was sealed at the lower end and the source fitted neatly into it. The cell held 

 25 to 30 ml. solution and was supported in the vertical position in the centre 

 of a paraffin- wax cube as shown in Figure 1. 



The 5C i^'Cs source was held in a cylindrical lead castle approximately 

 30 cm high and 30 cm diameter. Access to the castle was by means of a 

 drawer fitted diametrically at its base, the inner compartment of which was 

 approximately an 8 cm cube. The paraffin block was then put into the 

 compartment, the cell positioned in the block and when the drawer was 

 closed, the source was lowered into the inner cell tube. 



To aerate the solution, a perforated coil of polythene capillary tubing 

 passed through to the bottom of the cell. A second tube led the air from the 

 cell compartment. A small electric blower supphed air at a controlled rate 



zr Air 



Figure 1. Apparatus used for irradiations with ^^'Cs 



(25 to 30 ml. per min) to the cell after passing first through a volume 

 of solution of the same composition as that under irradiation. 



The solution to be irradiated (CH3OH 32 ml, CH2CI2 4 ml, w-phenyl- 

 enediamine 250 mg, 30 per cent aq. ammonia 0-25 ml.) was freshly prepared 

 for each irradiation. Methanol and dichloromethane were fractionated in 

 500 ml. aliquots and then used as required without further purification. 

 The impure phenylenediamine was first purified by distilling in an atmo- 

 sphere of nitrogen. Although this represented a considerable improvement, 

 it was necessary to redistil the diamine each time, immediately before use, 

 as decomposition obviously occurred in less than twenty-four hours. Am- 

 monia (Sp. gr. 0-880) was diluted with distilled water. Reagent xanthydrol 

 as a 10 per cent solution in methanol was used. Later, the xanthydrol was 

 synthesized and used as a 10 per cent solution in ethanol'-^--^. 



The absorbed irradiation dose was determined by measuring the oxidation 

 of ferrous iron in 0-8n sulphuric acid^'". The value of GFe+++ was taken as 

 15-5 and accordingly, the dose was lO^^ eV/ml./min or approximately 

 200 rad/ml./min. The irradiation cell described above was used for X-ray 

 irradiation also. The cell was mounted in front of the window of an X-ray 

 generator operated at 20 mA and 40 k\ \vith a copper target. To determine 



111 



