indicate a difference in composition, though the physical proper- 

 ties are the same. 



It is evident that the urushic acid of Yoshida consists of at 

 least four, if not five substances, differing in their solubilities as 

 well as in other respects, for I have already shown that some dry 

 in air to an insoluble substance, while others remain for months 

 without drying; one is piosonous and the others not. However 

 it is a remarkable fact that all may be converted into an end pro- 

 duct having practically the same properties, resisting the action 

 of all ordinary solvents, are black when heated with alkalies and 

 red when heated with acids. The product seems to be the same 

 whether obtained by drying with heat, by the action of the enzyme, 

 or by the action of alkalies. 



ORIGINAL RESIDUE INSOLUBLE IN ALCOHOL OR WATER. 



The residue from the lac which was insoluble in alcohol or 

 water consisted largely of hardened lac. By boiling this with 

 caustic alkali a dark brown solution was obtained which, on neu- 

 tralization and evaporation, left a hygroscopic residue, soluble in 

 water but insoluble in alcohol or ether. All attempts to obtain 

 a crystalline product failed. 



The residue insoluble in alkali was dissolved by continued 

 heating with fuming nitric acid, concentrated, and precipitated 

 by pouring into water. The precipitate formed a gummy, plastic 

 mass, soluble in alcohol but non-crystallizable. 



The watery solution contained oxalic acid, but no picric or 

 styphnic acid. 



Oxyurushin when treated with fuming nitric acid gave the 

 same results as above. 



PREVIOUS INVESTIGATIONS OF SOLUBLE FERMENTS. 



The first observation recorded upon the color action of Gums 

 and of guaiac was made in 1809 by Goettling 18 who observed a 

 bluish-gray color when compounding a mixture of resin of guaiac, 

 sugar, acacia, and peppermint water. In the same year Boulay 17 

 observed the same color reaction when syrup, gum arabic and tr. 

 of guaiac were mixed and by experiments proved that the color 



16 Bulletin de Pharmacie t. I. p. 220, 1809. 



17 Bulletin de Pharmacie t. I. p. 225, 1809. 



