S. DILLI AM) J. H. GREEN 



Neither did it appear to be what was thought to Ije a xanthyl-derivative of 

 the diamine. The analyses ^vere as follows: 



Figures are expressed as percentages 



C H N O 



(by diff.) 



1. Dixanthylurea — — 6-66 — 



2. Mono-substitute Xanthyl 



derivative of w-phenylene- 79-3 5-6 9-7 5-6 



diamine (Hypothetical) 



3. Di-substitute Xanthyl 



derivative of m-phenylene- 82-0 5-1 6-0 6-8 



diamine (Hypothetical) 



4. Derivative obtained 80-5 4-9 3-6 11-0 



These results give an empirical formula for the derivative of 

 C6.7H4.s,No.260o.6i or approximately CgiHjgN.pe. 



The empirical formulae for the other three derivatives are : 



1. C27H20N2O3 



2. C19H16N2O 



3. C32H24N2O2 



In an endeavour to increase the limiting sensitivity of the urea detection, 

 a method using paper chromatography was sought. It was not difficult to 

 detect as little as 10 y of urea by this approach, and methods are available 

 for the quantitative estimation of urea by this means^^. Numerous solvent 

 systems were used but were found quite unsuitable for a number of reasons. 

 In all the suggested solvent systems, the very reactive, polar m-phenylene- 

 diamine failed to migrate as a compact spot and in fact showed a marked, 

 although varied, degree of 'tailing'. Coupled with greater reactivity of the 

 diamine with the chromogenic reagent to produce a highly coloured (orange- 

 brown) area, the tailing made the uni-dimensional technique less sensitive. 

 By using the two-dimensional technique however, it was possible to detect 

 as little as 50 y urea with ease using as solvent, butanol-ethanol-water 

 (4:1:1). However, the effect of the diamine was still apparent in the form 

 of a rectangular coloured area. Viewing with u.v. light helped to define the 

 urea spot further, showing it as a black spot on a rather strong fluorescent 

 (pink) area to m-phenylenediamine. 



This solvent was used until it was found that aqueous pyridine (4:1) gave 

 good separations using the uni-dimensional, ascending technique. The 

 chi'omogenic reagent was dimethylaminobenzaldehyde as a one per cent 

 solution in ethanol and containing one ml. concentrated hydrochloric acid. 

 After spraying, the chromatogram was heated in an oven at 100°C for five 

 minutes to increase the intensity of the yello\v urea spot. 



RESULTS AND CONCLUSION 



The results showed that no urea was obtained from the solution after 

 irradiation under the conditions of the experiment described. The irradiation 

 periods extended to twelve hours, at one hour intervals for the first six. In 



113 



