706 EXPERIMENT STATION HKCORD. 



The authors on this basis propose the following; sclieme f(tr rleterniining these 

 acids ill the presence of each otlier : (a) Ilypopliosphates and phosphites or 

 hypophosphites — titration with many! nitrate is followed by the oxidation with 

 standard potassium permanganate solution, (b) Pliosphites and hypophos- 

 phites — the acids are oxidized with either standard potassium permanganate or 

 iodiu and the total phosphate produced by oxidizing with nitric acid is deter- 

 mined, (c) Hypophosphates, phosphites, and hypophosphites — the hypophos- 

 l)hate is estimated with uranyl nitrate and the remaining acids identified as 

 described in (b). (d) I'hosphates, hypophosi)hates, phosphites and hypoplios- 

 phites — the total jiliosphorus is estimated as phosphates after oxidizing with 

 nitx'ic acid. The; remaining acids are oxidized in another portion with standard 

 potassium permanganate solution. In still another portion of the solution the 

 phosphites and hypophosphites are oxidized with iodin soltition, while the fourth 

 liortion serves for titration with uranyl nitrate solution. In calculating the 

 results, if x, y, z, and t x'epresent the (piantities of the respective acids, 

 21+2k~n n-2k k+2m-21-n ,, 21+n-2m , , ,„ -or. 



^=^a ' ^'^ a^T' ^^ a; ' 2a4 ' '"^ ai^l/HgPO^, 



ao=l/H,,P03, ag^l/HaPOg, a4=l/H3P02, m=2g,/Mg2P207 (gi=weight of magnesium 

 pyrophosphate obtained), n=5g2/KMn04 (g2=weight of permanganate required), 

 k=g3/2I (g3=weight of iodin required), and l=qS/P205(S= cubic centimeters of uranyl 

 nitrate solution used; 1 cc. =q gm. of phosphoric oxid). 



In making the potassium permanganate oxidation, an approximately deci- 

 normal solution of the salt is slightly acidified with sulphuric acid, a few cubic 

 centimeters of decinormal potassium permanganate added, and the mixture 

 heated to S0° or 90° C. If a red color remains this is to be removed by titrat- 

 ing with acid solution, then adding potassium permanganate, repeating the 

 titration with oxalic acid, adding the potassium permanganate in decreasing 

 amounts until the oxidation is complete. In oxidizing the iodin a 10 per cent 

 solution of hydrochloric acid and a known volume of twentieth-normal iodin 

 solution is taken for a measured amount of the original liquid, and the mixture 

 heated for from 2 to 3 hours on the water bath in a closed flask. After allowing 

 it to stand for several hours, the excess of iodin is finally titrated with thiosul- 

 phate in the presence of sodium ])icarbonate. 



Analysis of double superphosphates, O. Foester (Chem. Ztg., 33 (1909), 

 No. 75, pp. 685, 686; abs. in Ztsclir. Analyt. Chcm., ',9 {1910), No. 1, pp. 61, 

 62). — It has been shown that the method of preparing the double superphos- 

 phate solution has some influence on the results for water soluble phosphoric 

 acid. The experiment stations at Berlin and Breslau recommend the following 

 procedure : 



Twenty gm. of the well-mixed but not powdered double superphosphate is 

 placed in a mortar, rubbed up with the least possible amount of water, and the 

 aqueous portion poured into a liter flask. This operation is repeated several 

 times, w'hen the residue is also placed in the flask which is finally filled to the 

 mark with w^ater. The solution is allowed to stand for 24 hours (shaking oc- 

 casionally in the interval). After filtering the solution 25 cc. of the filtrate is 

 taken and to it are added 10 cc. of fuming nitric acid, boiled for 10 minutes, 

 neutralized exactly with ammonia (using an indicator), and after cooling, 

 precipitated with 50 cc. of Maercker's ammonium citrate solution and 25 cc. of 

 magnesium mixture. The mixture is stirred 30 minutes in the stirring 

 apparatus. 



For determining the moisture in double superphosphates 5 gm. of the sub- 

 stance is dried for 6 hours at 100° C. 



The reduction of nitric nitrogen to ammonia and a new method for doter- 

 mining' nitrates, M. E. Pozzi-Escot (Ann. CJiim. Anahjt., IJf (1909), No. 12, 



