116 JOURNAL OF THE 



To illustrate these results: A given quantity of soluble phos- 

 phoric acid is brought in contact with a moist soil containing 

 5.11 calcium carbonate; after three hours 58.40 per cent, of the 

 phosphoric acid is precipitated. The same quantify of soluble 

 phosphoric acid is next mixed with the same quantity as before 

 of a moist soil containing 4J times as much calcium carbonate. 

 The precipitation now amounts to 93.20 per cent, after three 

 hours have elapsed, due, without much doubt, to the increased 

 amount of lime in the mixture. Next the same quantity of 

 soluble phosphoric acid is mixed with J of the quantity of the 

 soil of the last mixture, and after three hours 71.00 per cent. 

 phosphoric acid is found to be precipitated; and by continuing 

 the action after 48 hours 73.50 per cent, is precipitated, showing 

 that the amount of the soil and the time of contact are also 

 potent factors in the precipitation. 



From these experiments we see that so far as lime soils are 

 concerned the precipitation takes place, and takes place rapidly, 

 when sufficient moisture is present to insure perfect contact. But 

 how is it in regard to other soils — for many localities soils 

 abounding in lime, such as the above experimental soils, are 

 most rare? And indeed many of our soils are sadly deficient 

 in this most useful of ingredients. Does iron and alumina act 

 in the same manner, and does the presence of organic matter or 

 other ingredients alter this action? And to what extent will this 

 action continue after the lapse of time? These and other ques- 

 tions will be discussed in the following investigation. 



It was endeavored as far as possible in the following experi- 

 ments to imitate nature's action on the addition of superphos- 

 phates to the soil, and to retain the best conditions for obtaining 

 strictly accurate analytical results. The disadvantage which one 

 meets with at the first step in pursuing such investigation is the 

 impossibility of having these natural conditions, even in ca>es 

 where extreme care is taken ; at best we can only approximate 

 them. All of the conditions cannot be complied with : the effect 

 of the frost, the rains and snow with the dissolved carbonic acid, 

 the heat of the day and the cold of the nights; the variation 



