646 REPORT — 1895. 



N 

 ty Curtlus, that the group V,!!>N- functions in chemical molecules like the atom 



ol chlorine is certainly among the most striking of recent discoveries. Only last 

 year the list of nitrogen compounds was enriched by the addition of COCNjjj, the 

 nitrogen analogue of phosgene.^ 



These illustratiojis, drawn from the compounds of nitrogen, will serve to bring 

 out the wonderful development which our knowledge of the chemistry of this 

 element has undergone within the last few years. I might be tempted here into a 

 digression on the general bearing of the very striking fact that an element com- 

 paratively inactive in the free state should be so remarkably active in combination, 

 but I must keep to the main topic, as by means of these compounds it is possible 

 to ilhistrate still further both the strength and the weakness of our modern con- 

 ceptions of chemical structure. Consider some of the undiscovered compounds 

 which are foreshadowed by the process of ideal abstraction of types. The azoxy- 



, . , -N-N- -N=N- 



compounds contain the complex \^ y ov •• . The types would be 



HN-NII HN = NH 



\ / or •• . The first of these formulae represents the unknown 



dihydro-nitrous oxide. The azo-compounds are derivatives of the hypothetical 

 diimide HN:NH. An attempt to prepare this compound from azodicarbonic 

 acid" resulted in the formation of hydrazine. The diethyl-derivative may 

 have been obtained by Harries,^ but this is doubtful. It is at present inex- 

 plicable why compounds in which the group • N : N • is in combination with 

 aromatic radicles should be so remarkably stable, while the parent compound 

 appears to be incapable of existence. The addition of two atoms of hydrogen 

 converts this type again into a stable compound. There is nothing in the 

 structural fornnil.ie to indicate these facts. The amidines are stable compounds, 

 and the so-called ' anhydro-bases,' or imidazoles, are remarkably stable ; the 



parent compound, HC-^^tt , has not been obtained, while its amido-derivative, 



NTT i^n.^ 



HjN.C <^-vT-TT , is the well-known substance guanidine. The isodiazo-compounds 



recently discovered by Schraube and Schmidt and by Bamberger'* are pos- 

 sibly derivatives of the hypothetical substance OrN.NH.,, which might be 

 named nitrosamide. Why this compound should not exist as well as nitramide 

 is another question raised by the principle of abstract types. The carhi- 



TU'LT 



zines were formerly regarded as derivatives of the compounds C0<' • and 

 CS-^ • .5 Although this structure has now been disproved the possible existence 



f'f the types has been suggested. Carbizine and thiocarbizine differ from urea and 

 thiocarbamide only by two atoms of hydrogen. These types have not been isolated ; 

 if they are incapable of existence the current views of molecular structure give no 

 suggestion of a reason. The diazoamides are derivatives of the hypothetical 

 HoN.NPI.NITj or HN:N.NH„, compounds which Curtius speaks of as the propane 

 and propylene of the nitrogen series. The latter complex was at one time thought 

 to exist in diazohippuramide,*' and a biacidyl derivative of the former type has also 

 been obtained.'' Both these types await isolation if they are capable of existence. 

 I may add that several attempts to convert diazoamides into dihydro-derivatives 

 by mild alkaline reduction have led me to doubt whether this nitrogen chain, can 



> Curtius, Ber., 27, 2G84. "- Thiele, A7m., 271, 130. = Ber., 27, 2276. 



* Ibid., 27, .514, C.Tl). &c. 



* Fischer, Ann., 212, 326 ; Freund and Goldsmith, Ber., 21. 2456. 



* Bf'r. 24, 3342. This has since been shown to be hippurazide, i.e., a derivative of 

 N,H iBer., 27, 779). ' Jbid., 3344. 



