8 
L. J. H. Teakle and H. E. Hill. 
These tests further confirmed that hydrochloric acid was the most 
damaging substance although it is possible that all of these agents may take 
part in the damage which occurs in the vapour phase. No explanation of the 
effect of the sodium fluosilicate in 5 per cent, sulphuric acid is offered. 
(3) Measures Likely to Assist in the Protection of the Bags. 
This section of the investigation concerned treatment of the bags and 
treatment of the superphosphate, and materials were studied firstly in 
stacking tests (in which bags containing different superphosphates were 
stacked in the open under tarpaulins to simulate railway conditions) and 
secondly in the laboratory. 
(i) Stacking Tests. 
Stacking tests were designed by manufacturers and carried out at two 
metropolitan factories. Both bags and superphosphates were subjected to 
treatment and, after being stacked for about a month, the bags were tested 
in the laboratory. The results of two separate tests are given in Tables 4 
and 5 respectively. 
TABLE 4. 
Super 
Super 
Bag Treatment. 
Tensile Strength of 
Sacking 1 inch wide. 
Mixture. 
Treatment. 
Upper 
side. 
Lower 
side. 
Xmas-Egypt 
2% CaC0 3 
None 
lbs. 
94 
lbs. 
118 
None 
Lime dust ... 
86 
122 
Soda-ash solution, J hour 
72 
100 
Soda-ash dust 
70 
125 
}f 
55 * • • 
Soda-ash spray, 30 gm/bag 
56 
90 
Limestone dust 
25 
72 
55 
5% phos. 
None 
24 
76 
rock 
None 
Dicalcium phosphate dust 
23 
86 
55 
55 • • • 
Phosphate rock dust 
18 
76 
None 
18 
75 
55 • • • 
Rot proof solution, £ hour 
18 
82 
55 
55 * ■ ■ 
Gypsum solution, 48 hours 
14 
105 
None 
12 
62 
Lime solution, 48 hours* 
12 
46 
Immersed in water, 48 hours ... 
10 
96 
55 
55 • • • 
Gypsum dust 
10 
40 
55 
55 • • • 
Super solution, ^ hour ... 
8 
64 
* Bag appeared completely rotted in patches. 
In Table 4 the treatments are arranged in order of increasing deteri- 
oration of the fabric on the upper sides of the bags as they lay in the stack. 
From the results given, it is obvious that mildly alkaline substances, either 
mixed with the superphosphate or impregnated in the bags, are protective, 
the best effect being obtained by mixing 2% ground limestone with the 
