( 644 ) 



dissolved o-iiitrolicii/aldoliydr is (•()ii\oi-l('d, iiiidr-r tho iidlueiice of tlio 

 blue niys of sunli.ulit ') into o-iiilrosol)e]izoic ;u-id : 



\(>., / \\u 



\/c;; \/r..,. 



«^ii<l wlierc ('oiis('(|iioiillv nil oxv,ueii aloiii of llic iiilrouroiii» iiiiirrales 

 to llie iieighlioui'iiii'' aldclixde ,uroii|» and oxidises tlic same l(» carlioxvl. 

 (ylAMiciAN and SiLHKK have iiivestiLialed diis reaelioii iiiofe closelv, 

 priiicipallv willi solutions in dilfereiil liquids; as regards llie Ii-aiis- 

 foi'iiuitioii lakiiiu' plaee in the solid coiidilioii, in whieli we lia|i|ieii 

 to be partieidarlv interested, they merely say: -/dass die Kryslalle 

 naeh nnd Jiaeh ilire lielitgelbe Farbe verliercii, nn<hiiriisiehtig, gi-iiii- 

 beh nnd sehliesslieh weiss werden". 



The said changes in eohnif, llie oeeiirrenee of the green colorali^m 

 and the sidiseqiient turning \\ hile reinier I he |iheiionienon preeisely signi- 

 ficant for the knowledge of the |»ro|H'ili('> of solid ^olnlions. This 

 will lieecnne exidcnl when nnc lliink of llic general and \'ery interesting 

 properly of the oiganie nilrosoderix alives to sn Her polymerisation and 

 become colonrless when in a solid condition; in solution, however, 

 they are nniniolccnlar and cohinixMl (generally bine or green). This 

 belia\ionr is (|tiil(' coinparablc lo that of nitric ])eroxide. In a certain 

 number of cases the depoly inerisalion has been traced iiy ciyoscopic 

 means, as il often takes place \ery slowly : the lowering of the 

 freezing point then gradually beconu>s greater while the colonr becomes 

 more and more inlense. In this way it has been ascerlained that in 

 the colourless solid niiroso-componnd two molecules have become 

 united showing that an intense colour must be attributed to the single 

 niolecnles. The same happens with NO.^ (the nitroso-com[>onnd of 

 oxygen) ^vhich has an intense colour, whilst its jiolymcrisation pi-odnct 

 NjO, is colourleöö. 



After these remarks ii is not <lil"licnlt to see in what manner the 

 transformation of solid o-nitrobenzaldehyde into solid o-n it rosobenzoic 

 aci<l mnst be conceived. The displacement commences as soon as 

 the crystal is exposed lo sunlight; after about 15 minutes a faint 

 green tinge is perceptible which gradually deepens ; the nitrosobenzoic 

 acid, which is formed from and in the solvent, first renuiins in solid 

 solution and, lo judge from the green colour, in the unimolecnlar 

 condition. On continuing the exposure to sunlight the colour becomes 

 more hitense, until finallv the saturation [toint is reached; the outer 



^) We have ascerlaiiir.l Ihat an elevation of tcmpeialure doos not cause tlu 

 displacement. 



