C in a water bath. Molybdic solution was then added, the whole 

 digested for one hour at 65 degrees C, filtered and washed thor- 

 oughly with cold water. The precipitate was dissolved on the 

 filter with ammonia and hot water, knd washed into a beaker to 

 a bulk of not more than 100 c.c. The solution was nearly neu- 

 tralized with hydrochloric acid, cooled, and magnesia mixture 

 added, drop by drop, from a burette, stirring vigorously. After 

 fifteen minutes, 30 c.c. of ammonia (0.96 sp. gr. ) were added, 

 and the whole allowed to stand over night. The precipitate was 

 then collected on a filter, washed with 2.5 per cent ammonia 

 until free from chlorides, dried, ignited to whiteness and 

 weighed. The quantity of P 2 O 5 was calculated from the weight 

 of the Mg 2 P 2 O 7 , using the factor 0.6396. The following results 

 were obtained. 



The results by the two methods agree closely, the difference 

 being within the experimental error usually allowed for such 

 determinations. With the larger quantities of phosphoric acid, 

 the gravimetric method was used as a check on the volumetric. 

 The results in all cases, therefore, are strictly comparable. 



II. Relation Between Phosphoric Acid, and Compounds of Iron, 



and Calcium. 



Recent results obtained by the use of lime in conjunction 

 with phosphates of various kinds, have suggested new possibili- 

 ties with regard to the relation between phosphates of iron and 

 calcium in the soil. Lime has hitherto been regarded, partly as 

 a direct plant food, partly as an amendment in liberating plant 

 food, especially potash, but principally as an agent for improving 



