INTERNATIONAL, METHODS 67 



grams concentrated H 2 SO 4 for 30 minutes and filled up to 500 

 cubic centimeters. 



3. To determine P 2 O 5 in slag phosphates, the meal, which ap- 

 pears to contain coarse particles, is passed through a two 

 millimeter sieve; the portion which remains behind is slightly 

 crushed. The determination of P 2 O 5 is made in the portion which 

 passes through the sieve, the result being calculated so as to in- 

 clude the portion which remains behind. 



(a) Citric acid soluble P 2 O 5 . 



Five grams of the substance are placed in a 500 cubic centi- 

 meter flask with five cubic centimeters of alcohol to prevent bak- 

 ing and shaken with two per cent, citric acid solution for one half 

 hour at 17. 5 in a rotary apparatus which makes 30-40 revolutions 

 per minute. 



(b) Total P 2 O 5 . 42 



Ten grams of the substance are placed in a 500 cubic centi- 

 meter flask, thoroughly mixed with a few cubic centimeters of 

 water and boiled for 30 minutes with 50 cubic centimeters concen- 

 trated H 2 SO 4 , the flask being frequently shaken. 



B. Analysis of the Solutions. 



i. Molybdate method according to Fresenius and P. Wagner. 



2.. Citrate method. 



3. Free acid. 



(a) Total free acid: The aqueous solution A I is titrated 

 with a solution of NaOH, using methyl orange as an indicator. 



(b) Free phosphoric acid: An alcoholic solution is used for 

 making a gravimetric determination. 



4. Determination of Ferric Oxid and Alumina. 



This determination must be made either according to the meth- 

 od of Eugen Glaser 43 as improved by R. Jones 44 or, in the case 

 of the determination of alumina, according to Henri Lasne. 45 The 

 method adopted must be mentioned. 



42 When a determination of the fine dust is to be made, a sieve of 0.17 

 millimeter mesh must be used. 



43 Zeitschrift fur angewandte Chemie, 1889, 2 : 636 ; Die landwirt- 

 schaftlichen Versuchs-Stationen, 1891, 38 : 284. 



44 Zeitschrift fur angewandte Chemie, 1891, 4 : 3; Zeitschrift fur analyt- 

 ische Chemie, 1891, 30 : 743. 



"Bulletin de la Socie'te' chimique de Paris, 1896, [3], 15 : 146, 23?; 

 Chemiker-Zeitung Repertorium, 1896, 20 : 47, 65. 



