XANTHORRHGA. 
wire netting into a second sieve shortly below, made of finer perforated 
sheet metal, which further sifts out smaller fibrous particles. The 
resin can thus be graded into two qualities. The Harrison steaming 
method melts out the resin, thus securing about one-third more gum 
than by the previous way.’ It also produces a purer product. ‘This 
process, however, does not save the tree. The present methods of 
collection generally result in the destruction of the plants, owing to the 
common practice of cutting off the top of the plant. If sufficient 
covering is left as a protection to the core, the tree will live, and can 
be stripped at intervals of several years. The amount of resin that 
can be collected varies very greatly. The yellow resin is not plentiful, 
and an average of about 3 lbs. a tree might be obtained. The red 
variety from the larger trees, ¢.g., preissti, may average 40 lbs. per tree. 
A standard of purity for commercial resin has been suggested 
thus— . , 
not more than 7.5 per cent. woody fibre; 
nor more than 2 per cent. mineral matter. 
The resin has not been exported in any quantity, though exaggerated 
statements have appeared in the press from time to time, especially 
early in the war. The average figures for six years, 1909-1915, are as 
follows :— 
State. Total Export. Average per year. 
New South Wales... af 914 tons $e 152 tons 
South Australia id ye 6,414 ,, si 1,069 ,, 
Western Australia .. e 120 
” tale 2 
In six years 1,831 tons, of a total value of £15,000 (average, £8 per 
ton), went to England; and 4,826 tons, of a value of £35,500 (average, 
£7 6s. per ton), went to Germany. 
In 1913, New South Wales exported 198 tons, valued at £3,237, and 
South Australia 1,082 tons, valued at £5,052. .German imports from 
Australia were, in 1911, 379 tons; 1912, 472 tons; and 1913, 700 tons. 
No doubt it was the exportation from South Australia of over 1,000 
tons, of which the greater part went to Germany in 1913, that gave rise 
to many wild rumours about Germany using it to manufacture explo- 
sives. Inquiries were made both by the British authorities in Eng- 
land and Germany, and also by local authorities in Australia. 
The quantity of resin imported by Germany during the last few 
years preceding the war does not support the. idea of its utilization 
for the manufacture of picric acid for explosives. As early as 1846, 
Stenhouse had shown (Jour. Chem. Soc., 1845-6, p. 10) that by treat- 
ment with nitrie acid, fairly large quantities of picrie acid could be 
produced. He knew that he could get a return of 50 per cent. from | 
a given quantity of resin. Hence acaroid gum became the chief source 
of supply. Later, it was found that phenol was a much better and cheaper 
raw product, so the use of grass tree gum was dropped... The Boer war 
again led to further investigations, but the War Department’s Chemist 
reported unfavorably on it. Since that time, numerous investigations 
have been made; and in June, 1917, the Institute of Science and Industry 
decided to carry out some research work, and appointed a special 
Committee, of which Professor Rennie, of Adelaide University, was 
: “281 
