THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



AUGUST 1855. 



X. On the Formation of Indigo-blue. — Part I. 

 By Edward Schunck, Ph.D., F.R.S.'-^ 



INDIGO, one of the most important and extensively used 

 dyes, owes its value entirely to a peculiar colouring matter 

 contained in it, to which the name of indigo-blue or indigotine is 

 applied by chemists. This substance has been repeatedly sub- 

 jected to investigation, and several distinguished chemists have 

 bestowed their attention and labour upon it. Its properties, 

 composition, and products of decomposition, have been so care- 

 fully examined, that it may safely be asserted that there are few 

 organic substances whose nature is more accurately known than 

 that of indigo-blue. If, however, we inquire into the state of 

 our knowledge regarding the origin and mode of formation of 

 this body, it will be found that our information on this part of 

 the subject is extremely defective. Indigo-blue may be obtained 

 from a variety of ])lants, which, though belonging to the most 

 different genera and orders, are rather limited in number. It 

 has sometimes been observed to form in the milk of cows, espe- 

 cially such as have been fed exclusively on saintfoin \. Latterly 

 it has been discovered by HassallJ and others § in human urine, 

 where its occurrence is attributed to a morbid state of the system. 

 It is therefore a substance which is formed sparingly indeed, but 

 in widely distant parts of the organic world. The properties of 

 iudigo-blue, which arc so peculiar as almost to separate it from all 



* From the Memoirs of the Literaiy and Philosophical Society of Man- 

 chester, vol. xii. ; read April '.i, 1855. 



t Annates de Cfiimie et de Pliysique, vol. iii. p. 26f). 



X Philosophical Transactions for 1854. 



§ Anil, der C/iem. und Pfiarm. vol. xc. j). 120. 



Phil. Mag. S. 4. Vol. 10. No. G4. Aug. 1855. G 



