538 



Dr. J. Stenhoase on [Jane 1G, 



also produced by boiling any kind of madder with solution of sulphate of 

 aluminium. 



Crude furfurol, whether obtained from madder, bran, sawdust, or any 

 other of its usual sources, is always contaminated with another aromatic 

 oil, which I called metafurfurol *. This has a higher boiling-point, and 

 oxidizes more readily than furfurol, so that by repeated rectification almost 

 the whole of it is converted into a brown resinous matter, which remains 

 in the retort. It is owing to the presence of this impurity that crude fur- 

 furol so rapidly changes its colour when kept, the metafurfurol not only 

 being itself decomposed, but superinducing the oxidation of the furfurol. 



A much simpler and more effective method, however, of purifying fur- 

 furol from this substance consists in digesting it for some hours with very 

 dilute sulphuric acid, to which small quantities of acid potassium chro- 

 mate are added from time to time ; this effectually destroys the metafur- 

 furol and other impurities, so that the furfurol which distils over after 

 being separated from the water and dried over fused chloride of calcium 

 has a constant boiling-point of 161" C. It has a much more agreeable 

 odour than before, is nearly colourless, and may be exposed to the air 

 under a layer of water for months, without any considerable increase of 

 colour. Its refractive index for the D line at 20 3 C. is }*520i. 



Action of Furfurol on Aniline Furfuraniline. 



Twenty years ago J I stated that when aniline was added to furfurol, 

 the mixture acquired a rose-red colour, which it communicated to the 

 skin, and likewise to paper, linen, and silk, but that these rapidly lost 

 their colour, becoming of a brownish yellow, even when light was excluded. 

 I was unable, however, to obtain this red substance in a crystalline state. 



In 1S60 the subject was again examined by M. Jules Persor§, who dis- 

 solved aniline in acetic acid, and then added an excess of aqueous solution 

 of furfurol ; after some time a deep red viscid mass was deposited on the 

 sides of the vessel, which communicated to silk and wool a fine but very 

 fugitive red colour. He was not more fortunate than I had been in ob- 

 taining this substance in a crystalline state. 



A few months ago I resumed the investigation of this subject, and 

 although I was unable to obtain definite compounds either -by the action 

 of furfurol on aniline itself or on its salts when in a pure state, yet when 

 furfurol was added to a strong alcoholic solution of aniline hydrochlorate 

 containing an excess of aniline a deep red colour was produced, and in the 

 course of a few minutes the mixture solidified to a crystalline mass of a 

 fine iridescent purple colour. 



* Ann. Chem. Phar. lxxir. 2S2. 



t I am indebted to the kindness of Messrs. 'T. and H. Smith, of Edinburgh, for the 

 greater portion of the furfurol employed in this investigation. This firm has long been 

 in the habit of manufacturing it for preparing furfurine for medical purposes. 



% Ann. Chem. Pharm. lxxiv. 2*2. § Rep. Chem. App. I860, p. 220. 



