610 



EXPERIMENT STATION RECORD. 



tion ' are rcportod. Tlie more iiiipoitant of these results are shown in 

 the following tali)le: 



SohiliiHtji of pliOHi)}t(ttin i)i (Hjftrciil rciKjcnts, 



Osso ])li(ispliate 



Soiiiiiic jilHisjihate 



C(i]iriilit(' meal 



Kedomla phosphate 



TlioTiias slag, old 



Thomas slag new 



Iron ]ilic)si)iiatc, dried 



Iron ]ilicjs])liatt', ignited 



Aluniinuni ph(is])hate, dried... 

 Aluiniuum phosphate, ignited. 



Phosphoric acid soluble in — 



It is snggested that Petermann's solution probably gives results 

 more nearly approaching the actual availability of the different phos- 

 phates than any of the other solutions tested, but further experiments 

 on this point are needed. 



A ne^v volumetric method for pure phosphoric acid solution, 

 J. Langer and 0. (IlCtckiMANN {Fluoiti. Post., 27, pp. 369-371 ; ahs. in 

 Chem. Centbl., 1894, II, No. 13, pp. GOD, 6Y>i).— As a result of their tests 

 the authors recomnrend the following method: Phosphoric acid is pre- 

 cipitated by magnesia mixture of known ammonia content and the 

 excess of ammonia titrated with decinornial oxalic acid, using litmus 

 as an indicator. Three molecules of jSTHj correspond to 1 molecule of 

 H3P04,thus: 



H3PO4 + 3 NH, = (XH0.PO4; (xn,);,P04 + i^rg- SO4 = :^H4MgP04 



+ (XH4),S04. 



The magnesia mixture used contains 20 gm. of magnesium sulphate, 

 75 gm. of ammonia solution and 10 gm. of ammonium chlorid to one 

 half liter of water. 



The gravimetric determination of phosphoric acid by means of 

 molybdate of ammonia, H. von Juptner {Oesterr.ZtscJtr. Berg-IIiltt, 

 42, pp. 471-173; ahs. in Chem. Genthl., 1894, II, No. 19, 2^- 813).— The 

 autiior found that additions of considerable amounts of tartaric acid 

 eitlier to the phosphate or molybdic solution did not interfere with 

 the phosphomolybdate precipitation. As high as 100 cc. of tartaric 

 acid per liter of molybdic solution did not interfere with the precipita- 

 tion. Molybdic solution containing tartaric acid had deposited no 

 molybdic acid after standing 12 months at room temperatures. One 

 hundred cubic centimeters of molybdic solution containing 0.2 to O.G 

 gm. tartaric acid remained clear at 30'^ C; containing 1 gm. or more, 



'Fiililing's Laudw. Ztg., 1886, p. 68. The proportions used in this method were 2 

 gm. fine-ground pliospliate, 5 gm. of acid potassium oxalate and 230 cc. of water. 



