188 
Proceedings of the Royal Society 
of hydrogen or of carbonic acid, when kept in a eudiometer standing 
over mercury. These conclusions bear out the practical experiences 
of our lacquer men, viz., that lacquer dries most readily in the rainy 
season, and better in summer than in winter — a damp atmosphere 
at a temperature of 20° to 30° C. being usual during the rainy 
season. 
The nitrogenous matter in the juice, if it be really possessed of a 
peculiar kind of diastatic action upon urusliic acid, ought to be able 
to cause the change upon a comparatively large quantity of the acid. 
To study this property, and to find out the limit of the quantity of 
that substance within which the action can still take place upon 
the acid, certain experiments were made. Various mixtures of a 
known quantity of Hachioji juice with a weighed quantity of pure 
urushic acid were made ; after each mixture had received the 
requisite quantity of water, it was thoroughly mixed in a mortar, 
and left to dry in a thin layer on glass plates in a moist chamber. 
The practical limit within which the action can take place was 
found to be 1 of the nitrogenous matter to 413 of urushic acid. 
Although a much less quantity of the diastatic matter can effect 
the drying of the acid after the lapse of many days, such length of 
time will unquestionably be considered inconvenient in practical 
working with the juice as a varnish. These experiments also show 
that the amount of gum in the juice can be brought down to a small 
percentage without bad effect. A large quantity of it, as it exists 
in bad juice, is always injurious, as it produces blisters upon the 
newly lacquered ware when it is brought into contact with water 
for any length of time. Knowing these facts, we are now able to 
prepare any good quality of the juice for varnish making, by mixing 
a regulated quantity of pure urushic acid with the natural juice. 
The question still remains, How does the diastase act upon the 
urushic acid, or what is the change which urushic acid undergoes in 
drying'? To solve this question, the states of the lacquer before 
and after drying have been examined and compared. 
A quantity of the fresh juice (Yoshino sample) was rapidly heated 
on a water-bath, so as to coagulate the albuminoid, and put a stop 
to its further action upon the urushic acid. The heat was continued 
till all the water was expelled from the juice; the substance was 
then analysed, with the following result : — 
