122 JOURNAL OF THE 



Thinking that the wetting itself might have some effect on the 

 acid phosphate, a parallel line of experiments were carried on to 

 ascertain if any change was due to this cause alone The same 

 quantity (1 grm.) of acid phosphate was used as in the above 

 experiment with the result as indicated in Table VII. 



"We see from this table that the change due to the mere wet- 

 ting of the acid phosphate may be said to be practically nothing, 

 and, therefore, that the change in the content of the different 

 forms of phosphoric acid when the superphosphate is applied to 

 moist soils is due entirely to the action of the soil upon them. 



In order better to compare the results I insert a graphic chart 

 (Chart I) representing the variation of soluble phoshoric acid 

 clue to the action of moisture alone on the acid phosphate, and 

 to the action of the four varieties of moist soil, for the whole 

 period of 27 weeks. (See page 121). 



The first noticeable effect is the immediate precipitation of a 

 portion of the soluble phosphoric acid in all the soils, except the 

 one containing a large quantity of organic matter, varying in 

 amount in the various soils according to their composition, even 

 to the extent of changing while in the course of analysis. Tiiat 

 further on the precipitation proceeds gradually, increasing as 

 time goes on. It will be noticed in soil 1 for the 4th week and 

 soil 3 for the 5th week and 6th week a variation from this 

 gradual increase occurs. I am inclined to think that some out- 

 side influence, such as the fumes of the laboratory or incomplete 

 washing, may have caused this variation, though oscillation simi- 

 lar to this has been noticed in the reversion of superphosphates 

 by Phillips,* and also Post,f quoted by Phillips. It is to be 

 regretted that duplicate determinations could not have been made 

 in order to settle this point. 



It is plainly noticeable that the greatest precipitation occurs 

 from contact with the soil containing the largest amount of iron 

 and alumina, and the smallest precipitation with the soil with 

 least iron and alumina. For example, in soil 3, where the cou- 



*Journal Mitchell Soc, I, p. 57 

 fChem. Indus., '82, p. 217. 



