P.\KT IV.] Pl'eaa Si.n'c; : on Bunneae VurnisiL. 
291 
was further shown that the activity of this fliastatic or alhmninous 
substance diminishes with increasing temperature till at 63°C., 
when the albuminoid coagulates in the form of a white precipitate, 
its drying power entirely disappears. 
The hardening of the Uru.shi when expo.sed to a moist unwarmed 
atmospliere was shown to be due to a process of oxidation, which 
fakes place by the aid of diastatic matter present in Uru.shi in the 
])resence of oxygen and moisture fmoi.st air), and which brings 
about the conversion of the pasty Urusliic acid into a solid brown 
neutral substance according to the equation 
This ultimate brown sub.stance, to which the name oxy-urushic 
acid has been given, is an exceedingly stable body, which is abso- 
lutely unaffected by any of the solvents of Uru.shic acid, and it is to 
the presence of this oxy-urushic acid that the dry lacquer work owes 
its great power of resisting all disintegrating influences. Its 
chemical composition is represented by the formula Cj^H,gO,. 
BURMESE VARNISH. 
General Properties. 
Pure Thitsi or the Burmese Varnish is a thick sticky greyish 
fluid of glutinous consistence, which at first darkens to a brown and 
finally assumes a jet black colour on exposure to the air. It has a 
peculiar sweetish odour and specifically is heavier than water but 
only slightly so. The specific gravity at 20°C. of a pure fre.sh .sample 
derived from the M. Usitata of the Mawhan Forest was found to be 
1‘OOIG fsp. gr. at 23°C. of Pure Japanese lacquer= 1'0020). 
So far as I know. Sir David Brewster^ is the only inve.stigator 
who has ever examined the Burmese Varnish from a scientific point 
of view. Brewster experimented with the varnishes of Sylhet and 
Burm.a, and his experiments which were very simple were conducted 
as follows : — A thin transparent film of the varnish was obtained by 
pressing a small quantity of it between two glass plates. This film 
then examined under a powerful micro.scope showed the fluid to be 
an organised and not a homogeneous structure, as it was seen to 
consist of “ immense congeries of small parts which exhibited the 
finest example of mottled or striated colours, (and which) dispersed 
’ Edinburgh Journal of Science (Vol. VIII, 1828) quoted by Sir George Watt 
