176 LETTER-FILES OF S. W. JOHNSON 



Stoeckhardt's young man analyzed, and that Wolff, v. Gohren, 

 Kiihn, etc., quote as a "mittel. " Haven't the figures here in 

 my Trumbull St. attic, but will publish them by and by. 



I have done a heavy amount of work on P 2 5 estimations 

 during two or three years past, mostly with negative results, 

 don't know as I shall ever get time to write up. Before Carius 

 published, I had satisfied myself that pure H 2 and common 

 air yield NH 4 N0 2 , at temperature from 20 to 100 Centi- 

 grade. I never did believe half of Schonbein's facts, and now 

 that Carius finds that ozone doesn't oxidize nitrogen, I wish 

 old Schonbein were alive again to hear it ! As to P 2 5 , I find 

 that Otto's use of T to keep up Fe 2 3 and A1 2 3 when you 

 ppt. P 2 5 with Mg solution is simply perfect, if you use 

 enough T, enough to give a greenish-yellow solution and 5 to 

 10 grams of T doesn't impair the result seriously, but if you 

 use too little T and have a reddish-yellow solution, you have 

 an imperfect separation of P 2 5 . Ci is of no use, Church 

 Ville, and De Vill to the contrary. 



JnvprieiJ "rose "of 



per/or ale dlin u/ilh 



Jlal filler on bottom. 



Thought I had a method for coming it over the superphos- 

 phates in one coup, viz., to aqueous or acid solution, with Fe ; 

 Al, CaS0 4 , &c. &c, add q. s. (NH 4 ) 2 T, MgS0 4 , NH 4 C1 and 

 NH 3 filter on inverted "rose" of "perforated tin" with flat 

 filter on bottom, wash, without transferring ppt. moisten with 



