4 
L. J. H. Teakle and H. E. Hill. 
From the tests on new material it became obvious that the humidity of 
the air above the superphosphate affected the tensile strength. Whereas 
the normal tensile strength of twine may be taken as 35 lbs., six strings 
under examination in bottles averaged more than 40 lbs., the difference 
being due to the fact that the humidity above the superphosphate was 
greater than that of the atmosphere. The string absorbs moisture and 
increases in tensile strength; drying decreases the tensile strength. Owing 
to this variability, conclusions can only be based on major differences. 
On the other hand, experimental conditions were severe and it is thought 
that differences of practical importance are so magnified that the observed 
effects on the twine are highly significant. 
In tests on damaged material, the extent of the damage affects the 
accuracy of measurement. Jute materials damaged by superphosphate are 
discoloured brownish or reddish; the fibres become brittle and, in cases of 
severe damage, are furry in appearance and powder in the fingers. Under 
these conditions they cannot be bent or tied and tests were therefore made 
by means of a straight-out pull. In consequence, the resultant figures may 
be somewhat higher than could be expected from bags being handled in 
transport. Where the tensile strength for twine is less than 5 lbs. the 
destruction may be regarded as practically complete; a tensile strength of 
20 lbs. indicates severe damage. 
Tests on damaged jute materials followed three main lines of investiga- 
tion — (i) tests on superphosphate bags returned from the country; (ii) 
laboratory tests to determine the action of superphosphates from rocks of 
different sources on jute materials; (iii) determination of relationship be- 
tween temperature and severity of damage. 
(i) Tests on Superphosphate Bags Returned from the Country. 
In order to obtain information regarding the damage to superphosphate 
bags during the 1942 despatch, arrangements were made in February for 
the collection of representative bags by district officers of the Department 
of Agriculture. These were obtained subsequent to the hottest part of the 
weather and also subsequent to the initiation of control measures by the 
manufacturers. 
It is well established that, in railway trucks, damage is always most 
severe on the upper sides of bags in contact with the tarpaulins. Maximum 
temperatures develop at these points and there will be a tendency for volatile 
substances to be liberated and concentrate where temperatures are highest. 
Whether condensation during the cooler night periods is a factor is not 
known; in the later laboratory tests (p. 9) no condensation occurred and 
the action was very severe. 
Standard strips were selected to represent varying positions of the bags 
in the trucks and, where information was available, the upper and lower 
sides of the bag. Examination of the bags showed that deterioration was 
not uniform— some parts were relatively strong and other parts almost 
rotten. 
Tests of tensile strength showed that three specimens of the eleven bags 
containing superphosphate were seriously damaged. These were despatched 
