1895.] 



PUBLIC DOCUMENT — No. 33. 



307 



was diluted with 25 cubic centimeters of water, appearing 

 then as a thick, blaolv fluid. To this fluid were added 60 

 grams of flouts. The resulting superpliosphate, after drying 

 in the air for twenty-four hours, weighed 102 grams. The 

 tannic acid reaction was quite strong. 



Experiment IV. — To 30 grams of 50° B. acid were added 

 25 cubic centimeters of water and 70 grams of floats. The 

 dry supcrpliospliate weighed 101.5 grams. 



Experiment V. — To 30 grams of 50° B. acid were added 

 9 grams of Philadelpliia tankage, which resulted in a medium 

 tliick paste. Twenty cubic centimeters of water and 48.5 

 grams of floats were afterwards added. The dry superphos- 

 l)hate weighed 88 grams, and gave no tannic acid reaction. 



Experiment VI, — To 30 grams of 40° B. acid 9 grams 

 of Philadelphia tankage were added, resulting in a medium 

 thick paste. This paste was diluted with 20 cubic centi- 

 meters of water, and 50 grams of floats were put in. 

 Seventy-nine grams of superphosphate were obtained, which 

 gave a strong tannic acid reaction. 



These several products were analyzed : — 



It would appear that 9 grams of leather were all that 

 could be added to 30 grams of sulphuric acid without getting 

 the tannic-acid reaction. AVhen, as in Experiment III., 12 

 grams of leather were added, the reaction for tannic acid was 

 quite marked, and the nitrogen in the superphosphate had a 

 digestibility of but 54 per cent. Experiment VI. indicates 

 that 40° B. sulphuric acid was not quite strong enough to 



