254 SCIENCE PROGRESS. 



which is concerned in the production of lacquer from the 

 crude sap of the lac tree of South-east Asia. 



The existence of this oxidase was first pointed out 

 in 1883 by a Japanese chemist, Yoshida (1), who in- 

 vestigated the latex of that plant and ascertained the 

 nature of the changes occurring in the production of the 

 varnish. 



The crude juice is obtained by making incisions into the 

 trunks of several species of Rhus, and collecting the viscous 

 matter which exudes. It has the appearance of a nearly 

 white creamy liquid, with a faint odour resembling that of 

 butyric acid. On exposure to air it rapidly changes colour, 

 becoming brown and ultimately black. Spread on a flat 

 surface it dries with a brilliant black lustre. The juice is 

 very difficult to experiment with, as it possesses a very 

 irritating property which affects the skin, causing painful 

 eruptions and sores. 



Yoshida states that the juice, known by the name of 

 uruski, consists in great part of a peculiar acid, which he 

 has called urushic acid, and to which he ascribes the formula 

 C 14 H 18 2 . Separated by appropriate methods from the 

 crude latex and dried at 1 io° C. it forms a dark pasty sub- 

 stance, smelling of the original juice ; it is then soluble in 

 benzol, ether, alcohol and carbon-disulphide, but insoluble in 

 water, and has a specific gravity of '9851 at 23 C. When 

 exposed to the air it does not dry or show signs of change 

 such as the orioinal latex does. 



Besides urushic acid the crude sap contains a certain 

 proportion of gum, and about 3*8 per cent, of a peculiar 

 nitrogenous body, which coagulates on heating to 63 C. 

 If the latex is treated with excess of alcohol the gum and 

 the nitrogenous constituent are precipitated and can be re- 

 moved by filtration, and the latter can be separated from the 

 former by the action of cold water, in which it dissolves, 

 while the gum only becomes swollen. 



This nitrogenous constituent is the source of the enzyme, 

 and on the addition of a small quantity of it to the urushic 

 acid the latter becomes changed into the varnish. If 

 the solution of this albuminoid matter is heated to 63 C, 



