The Deterioration of Jute Materials. 
9 
superphosphate. Soda ash used either as a dip, dust or spray, proved 
almost as effective. Other treatments were of little or no use. Soaking 
in superphosphate solution hastened deterioration and immersion of the bags 
for half an hour in lime solution proved highly damaging. 
TABLE 5. 
Sample 
Superphosphate 
or 
Super. Mixture. 
Free 
Acidity 
(%H 2 so 4 ). 
Super, 
treatment — 
Per cent, of 
ground 
limestone* 
added. 
Bag 
treatment — 
Upper sides 
sprayed with 
soda ash 
solution. 
Tensile Strength of Sacking 
1 inch wide (lbs.). 
Upper Side. 
Lower Side. 
13 
Nauru Island .... 
1-03 
none 
none 
22 
58 
7 
Christmas Is 
1-19 
none 
none 
32 
66 
10 
Egyptian 
2-30 
none 
none 
30 
52 
2 
Christmas-Egypt 
1-75 
none 
none 
8 
34 
15 
mixture 
do. 
1-75 
none 
0% soln. 
54 
52 
18 
do. 
1*75 
none 
20% soln. 
72 
44 
3 
do. 
2 
none 
21 
44 
16 
do. 
2 
10% soln. 
78 
42 
19 
do. 
2 
20% soln. 
89 
60 
4 
do. 
4 
none 
48 
84 
17 
do. 
4 
10% soln. 
84 
78 
20 
do. 
4 
20% soln. 
120 
79 
* Contains about 60% CaC0 3 . 
Table 5 generally confirmed the results of Table 4 and emphasised that 
damage is most severe on the upper sides of the bags in contact with the 
tarpaulin. In this test 2% ground limestone was insufficient to affoid moie 
than very slight protection but 4% gave considerable protection. The 
variation in the results of the two tests is due to differences in weather 
conditions. The amount of limestone added must, therefore, be adjusted to 
meet the needs of each type of superphosphate* and must be sufficient to 
allow for temperature variations likely to occur during transit. 
(ii) Laboratory Tests. 
The laboratory tests followed two lines of investigation: the protection 
afforded by incorporation of calcium carbonate in the superphosphate and 
the reduction of the proportion of acid used in preparing the superphos- 
phate. 
(a) Incorporation of Calcium Carbonate . — Throughout these tests 
finely divided precipitated calcium carbonate (Merck) was used and the 
required quantities were thoroughly mixed with the superphosphate. 
The first series of tests were run in conjunction with the assessment of 
damage to strips of jute sacking by superphosphate exposed on the roof 
in February, 1942 (p. 5), the superphosphate in this case containing from 
2% to 6% of added calcium carbonate. The tensile strength of the sacking 
is given in Table 6. 
* Experience in a factory in 1943 indicates that more than 5% ground limestone 
may cause setting of the superphosphate. If less than 3% is used, adequate protection 
of the bags may not be accomplished. 
