93 



MAKING AND STANDARDIZING PERMANGANATE SOLUTION. 



l)i.-olve 2.82 grains of pure crystallized potassium permanganate in distilled water 

 by MM- aid of lu-at; cool and dilute to 1 liter and preserve in stoppered flask. Stand- 

 ardize this solution l>y titration with metallic iron solution as directed in the second 

 American edition "f Kresenius's Quantitative Chemical Analysis, pages 268-269. 



A copy "f the method as outlined above, together with the ash sample, was sent to 

 eiuhi cliemi-is \vh.. had signified their intention of cooperating in this work. The 

 result- received from five analysts are given in the tabulated statement which follows: 



n-nrk on ash sample. 



t im-lii(l'<l in average. 

 COMMBMTI il ANALYSTS. 



J. A. I.e I'lcrc found thai ii u.i- necessary to redigest tin- asli residue with hydro- 

 chlorie . id in order to remove all of the iron present. In Method C some organic 

 mailer M- nied to interfere with the end point of permanganate titration. 



Andrew .1 Patten used an approximately hundredth-normal solution of perman- 

 te -"lut ion, thi.- heiirj preferred mi account of the small amount of iron present. 



M. >hedd found objection to the determination of iron by Method B in that it 

 a 1'iii'j time to di--ol\ e the oxids in the sulphuric acid solution, and at this point 

 intended tin- fusion of the oxids with potassium hydrogen sulphate. 



The referee i- of the opinion that a weaker solution of permanganate is preferable 

 t-i the on,- recommended. 



Th- -Mined by the two method- airree very closely and indicate 



b'lt little ehoi.-e in method of procedure. 



The variation-* obtained between the various chemists in the results reported may 

 be due 1,1 the method of standardixiiig the permanganate solution. The referee has 

 u-ed for t hi- purpose a solution made from iron of a known composition furnished 

 by the I'.un-a'i of ^tandard-, \Va-hington, I>. <'. The personal equation must also 

 enter int., cooperative .'"rk of thi* nature to a greater or less extent. 



>MMI:\I>ATI<)\S. 



In view of the f.iet that the two methods gave results agreeing within 0.01 of a per 

 cent, the referee feels justified in rccommciH 1 i ng the one which involves the least 

 manipulation. The following is therefore recommended as an official method for the 

 separation of iron and aluminum in inorganic plant constituents: 



an aliquot part of solution A corresponding to 0.2 to 0.5 gram of ash for the deter- 

 mination. After removing the phosphoric acid, place the filtrate from the precipitate 

 of phoBphomolybdate, consisting of the nitric acid solution of molybdic acid, ferric oxid, 

 alumina, lime.' and magnesia, in a beaker and cautiously neutralize with ammonia, 

 care being taken that the temperature does not rise above 40 C., and that the alkali 

 is added only in slight excess; allow to stand in a warm place until the precipitate 

 completely settles. Filter the clear supernatant fluid, wash the precipitate a couple 



