ELISHA MITCHELL SCIEXTIFIC SOCIETY. 4I 



average percentage of analyses, by different authors, is about 1.3. 

 I can find mention of only one other Ilex used as a substitute for 

 tea. The analysis of this by Ryland and Brown is quoted in 

 Blythe's " Composition and Analysis of Foods," p. 343. It is called 

 the Ilex Cassiva, is said to be used as a tea in Virginia, and the per- 

 centage of caffeine is given as .12. This is probably the same thing 

 as the Yopon, the analysis of which is given above, and the "cas- 

 siva " may be a misprint for " cassine." 

 TJnwersity of North Carolina. 



ON THE DETERMINATION OF "TOTAL" TliOS- 

 PHORIC ACID IN FERTILIZERS. 



F. B. DAXCV. 



The writer has been led to make a few comparative experiments 

 on total phosphoric acid in fertilizers mainly by reason of the 

 method adopted by the late convention of Agricultural Chemists in 

 Philadelphia in September last. For a long time it has been my 

 custom, as practiced in the Laboratory of the N. C. Experiment 

 Station, to fuse the fertilizer with a mixture of one-half carbonate 

 of soda and one-half nitrate of potash. I had always found the 

 method most satisfactory and knew of no important objection to it. 

 When, therefore, the Agricultural Chemists decided to use a very 

 diilerent one, I determined to try that method, find out the objec- 

 tions to it and then make as many comparative experiments of that 

 and other methods, with our old " fusion " method, as my limited 

 time would allow. 



The lately adopted method referred to (which I shall call the 

 *' Philadelphia method "j bears the impress of being a theoretical 

 method, so many and so irksome are the practical difficulties to be 

 met with in its pursuit. 



The Philadelphia method is as follows : 



Two grammes of fertilizer are intimately mixed in a capsule with 

 4 -7 c. c. of a nearly saturated solution of magnesium nitrate; dry; 

 ignite gently; if necessary, moisten the residue with nitric acid and 

 ignite again to destroy organic matter; add to the reidue 15—20 c. c. 

 of fuming HCl ; digest at a gentle heat until all phosphates are dis- 

 solved; dilute to 200 c. c. ; mix; pass through a dry filter; take 50 

 6 



