260 SKATOXYL-PIGMENTS. 



The numbers just given refer to the method (Vierordt's) frequently used for 

 indicating the position of an absorption band. In this the distance between any 

 two of the fixed lines of the solar spectrum is regarded as being divided into 100 

 equal parts and the extent of the band is given by reference to these divisions. 

 Thus if a band is described as lying between D 50 E and D 77 E it implies that 

 the band begins half way (^ of the distance) between D and E and extends to Jfo 

 of the distance between the same two lines 1 . (See also above note 1. p. 229. ) 



Variable amounts of the above pigments may be obtained from 

 urines during their spontaneous decomposition or when treated with 

 hydrochloric acid or oxidising agents, the amount being greatest in 

 herbivorous urine and especially great in certain pathological urines 

 (see p. 200). They have also been met with in urinary sediments and 

 calculi 2 . 



7. Skatoxyl-pigments. 



The skatol formed in the alimentary canal gives rise, like indol, to 

 compounds of skatoxyl with either sulphuric acid or glycuronic acid 

 (see p. 204). These compounds when decomposed by hydrochloric acid 

 or oxidising agents give rise to a colouring-matter which is more or less 

 red and may exhibit a distinct and strong purple tint 3 . The pigment 

 is insoluble in water, but soluble in either alcohol or chloroform, also 

 when freshly prepared in ether but less so if it has been kept some 

 time. Alcoholic solutions are of a reddish- violet colour; ethereal 

 solutions may show a green fluorescence, which on exposure to the 

 air takes on a reddish tinge. It is also soluble in hydrochloric and 

 sulphuric acids, giving bright red or pink solutions, and in alkalis 

 yielding yellow solutions. No absorption bands for this substance 

 have as yet been described and the whole subject requires further 

 investigation. 



A considerable number of red or reddish-purple pigments have 

 at different times been obtained and described under specific names 

 as derived either from pathological urines when first voided or from the 

 spontaneous decompositions of or action of mineral acids on different 

 urines. The remarks which have been made on the indoxyl and 

 skatoxyl pigments indicate a possibility that they may all have a 

 common origin and thus be closely related if not in many cases 

 identical. In the absence of any guarantee of the purity of the 



1 A table for the conversion of these data into wave-length limits is given by G. 

 u. H. Kriiss, Kolorimetrie u. quant. Spektralanalyse, 1891, S. 290. 



2 Ord, Berl. klin. Wochensch. 1878, S. 365. Chiari, Prager med. Wochensch. 

 1888, S. 541. 



3 Otto, Pfliiger's Arch. Bd. xxxni. (1884), S. 613. Hester, Zt. f. physiol. Chem. 

 Bd. xii. (1888), S. 130. 



