ELISHA MITCHELL SCIENTIFIC SOCIETY. 53 



sulphur to form 4.61 per ceut. ferric oxide (F^^Og). Analysis of the 

 ash shows 5.51 per ceut. Fe.Oy, allowing a sulphur of .90 percent, 

 for other combinations, after all the iron needed by the sulphur to 

 form FeSo is taken up. 



Other analys-es tend to prove the combination of Sulphur with 

 Iron, for it is noticeable in every analysis that for a high percentage 

 of SulphuTjthere exists a corresponding high per cent, of Ash, which 

 would not apt to be the case were the Sulphur present in organic 

 compounds. , 



H. B. BATTLE. 



Laboratory N. C. Ag. Expt. Station, 

 Raleigh, Feb. IStJi, 1886. 



ON THE EFFECT OF USING DIFFERENT 

 AMOUNTS OF ACID PHOSPHATE IN 

 THE DETERMINATION OF SOL- 

 UBLE PHOSPHORIC ACID. 



H. B. BATTLE. 



The Association of Official Agricultural Chemists adopted the fol- 

 lowing method for the determination of Water Soluble Phosphoric 

 Acid: " Bring 2 grms. on a filter; add a little waier, let it run out 

 before adding more water, and repeat this treatmenr cautiously un- 

 til no phosphate is likely to precipitate in the filter. (The washings 

 may show turbidity after passing the filter). When the substance 

 is nearly washed, it is transferred to a mortar and rubbtd with a 

 rubber-tipped pestle to a homogenous pas^e (but not further pulver- 

 ized), then returned to the filter and washed wiih water until the 

 washings no longer react acid will deliccite test paper. Mix the 

 washings. Take an aliquot — determine phosphoric acid. &;c." 



I have observed that the amount of substance taken affects the 

 result as obtained by the above method. 



The substance experimented on was a finely ground acid phos- 

 phate, passing a 60 mesh sieve, and of high grade. 2 grms. was 



