. 
CONSTITUENTS OF THE SAP OF THE SILKY OAK. 195 
that it was necessary to cut the log into short pieces before the 
sap wouldrun, The sap is thus obtained without much difficulty, 
but he thinks that the spring is the best time to procure it. The 
present sample was obtained during the month of February last. 
It will be noted that the method adopted by Mr. Pope to obtain 
this sap, is that by which the aborigines of the dry Western Dis- 
trict of this Colony used to obtain a liquid from the roots of the 
“Mallee” trees to allay their thirst. The following extract will 
explain this :—‘ Looking as if they understood me, they therefore 
_ hastened to resume their work, and then I discovered that they 
dug up the roots for the sake of drinking the sap. It appeared 
that they first cut these into billets, and strip the bark and rind 
off, sometimes chewing it, then holding up the billet and applying 
one end to the mouth the juice drops out. We now understood 
for what purpose those short clubs, which we had seen the day 
before, had been cut.” 
| The Organic Acid. 
When received, the sap had a specific gravity of 1-0036 at 15:5°C. 
It was strongly acid to test paper, and had rather an unpleasant 
smell, indicating by its odour the presence of butyric acid. The 
determination of the acid was at once proceeded with. The total 
acidity determined by standard soda, 1 ce. = ‘0088 butyric acid, 
using phenol-phthalein as indicator, and after air had been drawn 
through the sap to remove CO, if present, was as follows :—10cc. 
of the original sap required 1:9 cc. of soda solution, or 100 ce. 
required 19 cc.; 50 cc. were then distilled almost to dryness, a 
small quantity of water added, and the remainder of the 50 ce. 
distilled over ; 10 ce. of this distillate required 1-4 cc. of soda 
Solution or 100 ce, required 14 cc., equal to 1232 gram. of butyric 
acid, so that by far the greater portion of the total acidity was 
due to this volatile acid, as it is not considered that the whole | 
* the acid was obtained by this distillation. After the distilla- 
tion.of the 50 cc. had been thus carried out, a small quantity 
1 Mitchell—Three Expeditions, p. 197. 
