38 



Duration of contact. P 2 O 5 soluble. Ca soluble. P 2 O. 5 absorbed, 



One day o. 1385 grs. 0.0309 grs. 0.0165 grs. 



One day 0.1385 grs. 0.0312 grs. 0.0165 grs. 



Four days 0.1360 grs. 0.0278 grs. 0.0190 grs. 



Four days o. 1365 grs. 0.0283 grs. 0.0185 grs. 



Eight days 0.1340 grs. 0.0259 grs. 0.0210 grs. 



Eight days 0.1345 grs. 0.0260 grs. 0.0205 grs. 



The above figures show that absorption of phosphoric acid 

 took place to a limited extent. It occurred to the author that a 

 small amount of calcium carbonate might have been formed in the 

 preparation of the calcium humate, in which case the absorption 

 could not be ascribed to the latter compound. Carbon dioxide 

 was determined in a portion of the preparation therefore, the 

 amount obtained being 0.64 per cent. Calculated to calcium 

 carbonate the one gram of the material contained 0.0142 gram of 

 the material contained 0.0142 gram of the carbonate, which in 

 turn would be sufficient to react with 0.0207 gram of P 2 O 5 form- 

 ing the mono-calcium salt. This salt is decomposed by water with 

 the formation of the di-calcium phosphate which is not soluble in 

 water. The absorption therefore is to be referred to the presence 

 of calcium carbonate. 



The increase of the calcium in solution was due to the for- 

 mation of some of the mono-calcium phosphate from the free 

 phosphoric acid present in the superphosphate solution. 



It is to be inferred from these facts that calcium humate does 

 not take part in the absorption of phosphoric acid from super- 

 phosphate. 



As the majority of the humus compounds found in the soil 

 contain nitrogen, it was thought advisable to include some of 

 these in the present work. The compounds used were soluble 

 and insoluble ammonium humate. 



For the preparation of these 25 grams of humic acid were 

 treated with 500 c.c. or ammonia solution containing 14 3 grams 

 of ammonia, the flask closed, shaken and allowed to stand five 

 days. The insoluble residue was then filtered off and washed 

 until free from ammonia. When dried the product weighed 1 1 

 grams showing that a little more than half of the humic acid had 

 been dissolved by the ammonia. The soluble portion was put 



