9 
L. J. IT. Teakle and H. E. Hill. 
lime and then dried before storing for future use. Manufacturers, also, had 
tried out a variety of treatments, including — 
(a) Dipping* 
Bags were dipped in sodium acetate solution in Calcutta prior to 
shipment. Locally they were soaked in water and in solutions such as 
blackboy gum, sugar, bluestone-soda ash mixtures, copper naphthalate and 
sodium silicate and dipped in solutions of sodium acetate, soda ash, milk of 
lime, gypsum, superphosphate, plaster of Paris and “Rot Proof. In 
practice, however, the labour involved in dipping and drying makes the 
process unsuitable. 
(b) Dusting and Spraying. 
The dusts included powdered limestone, lime, soda ash, rock phosphate, 
dicalcium phosphate, plaster of Paris, gypsum; the sprays were solutions 
of soda ash. Sprays and dusts may be used with little expense and, if effec- 
tive, could be adopted as routine practice. 
In 1938, in response to a request for an investigation from the Wheat 
and Wool Growers' Union of Western Australia, the Council for Scientific 
and Industrial Research stated that a thorough investigation into the causes 
of deterioration had been undertaken at the Perth works of the Common- 
wealth Fertilisers and Chemicals Limited and summarised the findings as 
follows : — 
The damage to the bags is apparently caused by slight traces of 
gases of the halogen group, which are always present in superphos- 
phate. Fluorine is believed to be the principal destructive agent. In 
a series of tests carried out on bags stacked in piles, it was found that 
the maximum damage was done in the upper layers, and the upper 
side of the bags invariably suffered more than the lower side. A pro- 
tective treatment has been developed which has given satisfactory results 
in practical tests. This treatment involves immersing the bags in a 
solution of sodium acetate, and costs approximately 9d. per dozen bags 
to apply. It has been found that the damage can be minimised by 
arranging stacks in such a way that free evaporation of moisture and 
corrosive gases can occur on the upper surfaces of the stack. The 
damage usually occurs in the trucks when moist vapour collects under 
the tarpaulin and recondenses during the night-* 
SCOPE OF THE PRESENT INVESTIGATIONS. 
The present investigation considered (1) the nature of the superphos- 
phates; (2) factors likely to be responsible for the damaging effect on 
bags and tarpaulins; (3) measures likely to assist in the protection of the 
bags. 
(1) Nature of the Superphosphates. 
The superphosphates investigated fall into two groups. 
(i) Those manufactured from phosphate rock from Nauru. Ocean and 
Christmas Islands, which are very low in hydrochloric acid but contain 
hydrofluoric acid. 
* Letter of September 23, 1938, Department of Agriculture file No. 837/38. 
