152 t The Phosphates of America. 



slum sulphocyanate, the liquid is cooled, about one gramme of mag- 

 nesium sulphate is dissolved in it, and it is then titrated with ^ 

 N. permanganate solution, every c.c. of which = .00080 ferric oxide. 

 The number of c.c. used X 2 will represent the amount of iron 

 oxide contained in one gramme of the above phosphates. Two out 

 of the three constituents being thus accurately known, the third, 

 which is the alumina, can easily be determined by difference, as 

 for example : 



Weight of the combined phosphates of iron and alumina. . .058 



Phosphoric anhydride determined in the above 031 



Iron oxide (Fe 2 O 3 ) " " <, 010 



.041 



Oxide of alumina (by difference) 017 



In reporting upon the sample we should therefore state the 

 presence of 



Oxide of iron , 1.00 per cent. 



Oxide of alumina 1.70 " 



Weight of these oxides combined 2.70 " 



instead of the 2.90 per cent, which were obtained by merely divid- 

 ing the combined phosphates by 2. 



The only other method of determining the percentage of iron 

 and alumina which has been used in our laboratory with satis- 

 factory results, was recently adopted at the request of clients, and 

 is generally known as the Glaser method, from its having been 

 first suggested and described by a German chemist of that name 

 (in Ztschr. Angew. Chem., 89, 636). The way in which we carry 

 it out, differs somewhat from the first description by its author, 

 and is as follows : 



Two and a half grammes of the phosphate are dissolved in 10 c.c. 

 hydrochloric acid ; evaporated to dryness ; taken up again with 

 hydrochloric acid, raised to boiling, and washed out into a 250-c.c. 

 flask with as little water as possible. Ten c.c. concentrated sulphuric 

 acid are now added, and the solution is allowed to stand for five min- 

 utes, with frequent shaking. After adding some ninety-five per cent, 

 alcohol, the mixture is cooled, made up to the mark with alcohol, 

 well shaken, and when the contraction in volume has taken place, is 

 again made up to 250 c.c. and mixed. After standing one hour it is 

 filtered, and 200 c.c. (= 2 grammes phosphate) are taken and gently 



