210 REPORT — 1901. 



of iso-cyanuric acid (Formula II.) would behave like piperidine and other 

 bodies composed of a closed chain of singly linked carbon atoms or of 

 carbon and nitrogen, where one or more carbons are replaced by nitrogen 

 atoms, and which exhibit general absorption only. All the cyanuric 

 compounds, however, which we have examined show only general absorp- 

 tion, and give no indication of the presence of absorption bands. 



This result is what was anticipated in the case of derivatives of iso- 

 cyanuric acid ; but so tar as cyanuric acid and its esters are concerned it 

 is remarkable — especially when considered in connection with the fact 

 that no strict experimental evidence has yet been advanced in support of 

 the commonly received structural formula for cyanuric acid. Methyl cyan- 

 urate (ra.p. 135°) yields on saponification with alkalies cyanuric acid and 

 methyl alcohol. It is therefore regarded as the ester of normal cyanuric acid 

 (Formula I.), a conclusion which is supported by its method of formation 

 from sodium methylate and cyanuric chloride. Trimethylcarbimide 

 (m.p. 175°), on the other hand, yields methylamine on treatment with 

 alkalies, and is therefore regarded as a derivative of iso-cyanuric acid 

 (Formula II.). It is generally admitted, however, that chemical evidence 

 of this kind and in such cases is frequently unreliable. ^ 



In this instance the spectrographic examination confirms tlie result 

 arrived at on purely chemical grounds. The spectra of methyl cyanurate 

 (m.p. ISS'^^) bear a close resemblance to those of cyanuric acid, the 

 absorption being somewhat greater owing to the replacement of three 

 hydrogen atoms by three methyl groups. On the other hand the spectra 

 of trimethylcarbimide (m.p. 175°), notwithstanding a similar replacement 

 of hydrogen by methyl groups, show considerably less absorption of the 

 more refrangible rays. 



Melamine and its esters show only general absorption, the amount 

 being somewhat greater than in the case of cyanuric acid. Melamine is 

 regarded as the triamide of normal cyanuric acid (Formula I.). 



NHa NH 



I II 



N.C : N HN.C.NH 



II I II 



H2N.C.N : C.NHa HN=C.N.C=NH 



H 



Melamine or Iso-melamine or 



cyanurtriamide. Iso-cyanurtriimide. 



The triethyl ester (m.p. 74°), which is obtained by the action of 

 ethylamine on cyanuric chloride, is, from its method of formation, con- 

 sidered to be a derivative of melamine ; the ethyl derivative (m.p. 92°), on 

 the other hand, which is prepared by the desulphurisation of thiourea, is 

 regarded as a derivative of iso-melamine. Here again the results of the 

 spectrographic investigation are in accord with the conclusions arrived at 

 on chemical evidence. The spectra of melamine and the triethyl ester 

 (m.p. 74°) are almost identical, while the general absorption exhibited 

 bv the spectra of the isomeric ester is considerably less. 



The general result of the examination of these bodies is in complete 



» Goldschmidt and Meissler, Ber., 1«90, 23, 253 ; A. Michael, J. j;r. Chem. [ii.], 

 1S85, 3?, 513 ; Hartley and Dobbie, Trails. Chem. Soc, 1899, 75, 640. 



