MICK CHE MIS TR V. 99 



which is soluble in acetic acid. The substance does not 

 directly reduce Fehling's solution, but does so after heating 

 with dilute sulphuric acid. 



Since the isolation of this questionable substance has not 

 yet been accomplished, it must remain doubtful, in case of 

 several of the reactions described, how far they are influenced 

 by other substances also containe t d in the drops of fluid. 



7. Bitter Principles and Indifferent Substances. 

 a. Calycin, C 18 H 12 O 6 . 



165. Calycin occurs in the form of small yellow crystals 

 deposited on the membranes of Calycium chrysocephalum 

 and various other lichens. For its microchemical recog- 

 nition it is best, according to Bachmann, to treat with gla- 

 cial acetic acid a bit of the lichen under examination, which 

 has been rubbed as fine as possible, then to bring the whole 

 together into a drop and let it evaporate. The calycin crys- 

 tallizes out in long, acicular, strongly doubly refractive 

 crystals. 



It is also characteristic of calycin that it is not dissolved 

 by caustic potash solution and suffers no change of color 

 by it. 



b. Spergulin, (C 5 H 7 O 2 ) X . 



166. Harz (II) has isolated from the seed-coats of Sper- 

 gula vulgaris and S. maxima a strongly fluorescent sub- 

 stance which he calls spergulin. It is readily soluble in 

 absolute and dilute alcohol and appears colorless or faintly 

 greenish or olive-brown in this solution, showing an in- 

 tense, dark-blue fluorescence, while a beautiful emerald- 

 green fluorescence appears after the addition of a small 

 quantity of alkali. It cannot be obtained in crystalline 

 form from this solution. 



It is also characteristic of spergulin that it dissolves in 

 concentrated sulpJmric acid with a beautiful dark blue color. 

 It is readily soluble in methyl alcohol, less so in amyl alco- 

 hol, and hardly so in petroleum and ether. 



