308 AGRICULTURAL EXPERIMENT STATION. [Jan. 



thoroughly disintegrate the 9 grams of leather, for the tan- 

 nic acid in the superphosphate was easily recognized, and 

 the nitrogen was but 60 per cent, digestible. When 9 grams 

 of the Philadelphia tankage were dissolved in 30 grams of 

 50° B. acid, no tannic acid could be recognized, and 70 per 

 cent, of the total nitrogen was digestible. This is probably 

 the average percentage of organic nitrogen that would be 

 found digestible in mixed fertilizer, as offered for sale in our 

 markets. Such a result is quite encouraging. It would 

 seem from the analysis of IV. that the leather had not seri- 

 ously interfered with the action of the sulphuric acid upon 

 the floats. We have in the four experiments above cited 

 added rather too much phosphate rock and water, and in the 

 two following experiments less were added. 



Experinent VII. — To 30 grams of 50° B. acid 9 grams 

 of Philadelphia tankage were added, and then 12 cubic cen- 

 timeters of water. To the thick fluid resulting 41 grams of 

 floats were added. After standing twenty-four hours the 

 material could be easily handled, and weighed 71.5 grams. 



Experiment VIII. — To 30 grams of 50° B. acid 9 grams 

 of Philadelphia tankage were added, producing a thick, 

 pasty mass. Without the addition of water 28 grams of 

 floats were stirred in, and after twenty-four hours the mass 

 weighed 63 grams. The phosphate was quite black in color 

 and sticky. It needed at least 5 to 7 grams more floats 

 before it could be easily handled. It was plain that the sul- 

 phuric acid was not all neutralized. If no water were added 

 to dilute the thick, pasty mass, it would be very difiicult to 

 work in the floats should large quantities be mixed. 



Analyses. 



