of Edinburgh, Session 1884-85. 
189 
I. 
II. 
Mean. 
Numbers calcu- 
lated from the 
constituents of 
the juice. 
Carbon, . 
75-47 
75-61 
75-54 
75-54 
Hydrogen, 
8-93 
9-01 
8-97 
9-14 
Nitrogen, 
0-11 
o-ii 
o-io 
Ash, 
0-21 
0-21 
0-21 
Oxygen, . 
15-28 
15-17 
15-01 
100 00 
100-00 
100-00 
The lacquer dried (naturally hardened) in the usual manner, and 
afterwards heated at 100° C. had the following composition: — - 
I. 
II. 
Mean. 
Carbon, . 
70-90 
70-84 
70-87 
Hydrogen, 
8-55 
7-90 
8-225 
Nitrogen, 
0-092 
0-092 
Ash, 
0-032 
0-032 
Oxygen, . 
20-426 
20-781 
100-000 
100-000 
The comparison of these two results indicates that the lacquer in 
hardening had taken up oxygen ; and we see that, cceteris paribus , 
the amount of oxygen thus taken up is almost quite accounted for 
on the supposition that each molecule of urushic acid (C 14 I1 18 0 2 ) in 
the juice has taken up one atom of oxygen, and changed into 
another body, C 14 H 18 0 3 . 
Further proof of this theory has been reached by the preparation 
of oxy-uruskic acid (C 14 H 18 0 3 ), ivhich showed all the properties of a 
dried lacquer. Urushic acid was repeatedly subjected to the action 
of strong chromic acid mixture containing some excess of sulphuric 
acid to prevent the precipitation of chromic oxide. The product, 
cohobated with strong alcohol to dissolve away the unattacked 
urushic acid, gave, on drying at 106° C., a brownish powder of the 
following composition : — 
