STUDIES ON THE METABOLISM OK I'lIOSl'HOKlS IN ANIMALS l.lli 



PREPARATION OF RADIOACTIVE PHOSPHORUS 



Radioactive ])lu)spli()rus ffP can ])v prepared from chlorine or IVom 

 sulphur undei- ihe action of last iKHitrons, or from ordinary phosphorus 

 under the action of slow neutrons; the nuclear reactions are: 



?fCl +ln = ?iP + file 



IIP +5n = ?fP 



Using neutrons liberated from mixtures of radium and beryllium. 

 3^P can be prepared most conveniently from sulphur. We found it advis- 

 able to use carbon disulphide instead of the elementary sulphur used 

 by Fermi and his colleagues in their original experiments. About 10 

 litres of carbon disulphide were exposed to neutrons from radium- 

 beryllium mixtures and a fortnight later the carbon disulphide was 

 distilled off. The residue contained the radioactive phosphorus formed, 

 along with some of the decomposition products of carbon disulphide. 

 The residue was oxidized and the phosphoric acid obtained converted 

 into the phosphate compound wanted. We used chiefly sodium radio- 

 phosphate in our experiments. The weight of the radiophosphorus 

 produced is extremely minute; using a source containing 100 mgm 

 of radium, less than 10" ^^ gm of radiophosphorus is obtained. By adding 

 a suitable quantity of sodium phosphate to the sodium radiophosphate- 

 solution we obtain the "radioactive" ("labelled") sodium phosphate 

 desired. 



To concentrate the radiophosphorus ol)tained by neutron bombard- 

 ment of carbon disulphide other methods besides that outlined above 

 were used. A very convenient way to prepare nearly pure radiophos- 

 phorus is the following. Under the action of the radiation some decompo- 

 sition of the carbon disulphide takes place and a partly orange-coloured 

 precipitate is formed which settles on the glass walls. This slight preci- 

 pitate contains a large part of the radioactive phosphorus formed. 

 The precipitate is possibly identical with the red sulphur described 

 by Magnus as far back as 1954, which was found to consist of a mixture 

 of sulphur and organic sulphur compounds. We are engaged on the 

 investigation of this precipitate. 



In a third method of preparation the phosphorus formed was removed 

 from the carbon disulphide solution by shaking the lattei' with diluted 

 (20 : 1) nitric acid. 



