50 The Philippine Journal of Science 1922 
Following a suggestion by Gibbs,’ that the development of 
the tuba invertase from a zymogen may require air, various 
experiments were tried with inert oils, such as kerosene, instead 
of toluene. Since these were found to have little inhibitory effect 
on the fermentation, it seems that the main action of toluene 
is as an antiseptic, and that inversion of tuba takes place only 
very slowly unless assisted by yeast or bacteria. 
LARGE-SCALE COLLECTION OF TUBA 
Due to the high price of toluene at the time of experimentation 
little beyond laboratory-scale work has been done with toluene. 
As mentioned above, a very light liming of the tuquil, not suffi- 
cient to interfere with the edibility of the product, checks the 
yeast but does not prevent inversion. A heavier liming, as 
advised by Gibbs,’® necessitates subsequent removal of lime 
from the tuba. In March, 1920, an experiment was conducted 
to test the effectiveness of heavy liming. The tuba was collected 
in Pampanga and transported to Manila for removal of the lime 
and boiling to sugar. 
TABLE 2.—Collection data on limed tuba. 
Group. | 
A B Cc D 
Bee0r tale coo See days_- 65 45 30 2 
Number of palms ---.-.------ 84 31 55 90 
Duration of experiment _-.-........-.-....-...-... days-_. 16 18 9 9 
Average daily yield per palm _--___._..-_._---..--_- cc. 630 173 581 500 
Sucriseon 5s es eae per cent_- 9.0 10.1 9.1 10.7 
Alkalinity (as CaO) _____- do 1.38 1.4 14 1.3 
United 2202s ae per cent sucrose__ pg Pe 14.9 14, 2 
Preservative——Due to the tendency of lime to sink to the 
bottom of the tuquil and allow the top layers of tuba to become 
acid, it was found necessary to use very heavy liming or else 
collect twice a day. A thick lime cream was made of density 
50° Baumé, containing about 600 grams of lime (calculated as 
calcium oxide) and 25 grams of sodium bisulphite per liter. A 
liter of this mixture was poured into each tuquil and poured out 
again, about 200 cubic centimeters adhering to the tuquil. The 
tuquil was then placed horizontally and allowed to dry. The 
liming was done at a central place to which the used tuquils 
° Op. cit, 124. * Loc. cit. 
