Chemistry and Physics. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistey and Physics. 



1. On the synthesis of indigo i^we.— The beautiful discovery of 

 till' artificial production of alizarin is now followed l>y that of 

 iiiditro blue. The path to this discovery was opened b^ liaeyer, 

 who by the action of a new reducing agent suiceedtd m forming 

 the first derivative of indigo free from oxyg^ n — imlfJ, and snl)st - 

 quently in preparing this artificially. Tlie same rhi mist also i. .la- 

 ced isatin to indigo blue, giving thereby fiutlur (.■nc-onriiLrciiu nt to 

 the hope of artificially forming indigo blur itself. \\\ \\\v A\\ ilis- 

 tillution of equal molecules of calcic acetate and bcn/.oaU', Ktinutr- 

 liiiU' and Engler obtained acetophenon, the nirtliyl-ki-tcmc of l.cn- 

 zoic acid, CgHgO. Nitric^ acid converts this into two i<o„Hric 



low syrupy compound with the same empiriral fornnila. As the 

 t'uipirioal 'formula shows, two molecules of this body l.y losing 2 



cuk- of indigo blue. 



2€8H7N03— 2H2e-2e=€, JIi .XsO,. 

 By using a mixture of zinc-dust and soda-lime at a higli tempera- 

 ture, both these changes occurred, the heat serving to remove the 

 water. Afterward it was found that the water n 

 expelled by a carefully regiilated heat. When small 

 the mixture are heated over a good Bunsen's lamp, v. 

 tubes, a dark sublimate is fornied on the colder parts of tlic tube, 

 which on heating gives the characteristic violet vapors ot mdigo 

 blue. The sublimate also gave with lime and ferrous sulphate a 

 solution of indigo-white, wdiich again by oxidation gave the char- 

 acteristic purple film. The artificial production of mdigo-blue, 

 although in extremely small quantity, is thus rendered certain. 

 The authors give for the structural formula of indigo-blue the tol- 

 lowing scheme: N-^eH, -€0-€H 



?o that it represents the azo-derivative of a peculiar ketone, hav- 

 ing the formula : , €eH5-€0-€H | 

 ^€gH5-€0-€II, ) 

 but not yet prepared. In view of the facility with which azo- 

 compoundsare converted into hydrazo-compounds, mdigo-whitc 



ities of 



i the formula : 



j NH~€,H,-Ce-€H I 

 (NH-€eH,-€0-€H. f 



The constitutions of the other bodies belonging to the mdigo 



