238 AGRICULTURAL ANALYSIS 



washed with hot water. The phosphoric acid is separated by 

 40 cubic centimeters of molybdate solution, and the precipi- 

 tate washed three or four times with a one per cent, nitric acid 

 solution. 



To the filtrate are added 50 cubic centimeters of a half- 

 saturated ammonium chlorid solution, ammonia is added in 

 slight excess to produce precipitation and the mixture boiled for 

 a few minutes. After filtering, the precipitate is washed with hot 

 water three or four times, dissolved in two cubic centimeters of 

 nitric acid, and the filter washed with hot water. Again, 50 

 cubic centimeters of half-saturated ammonium chlorid solution 

 are added and the precipitate thrown down once more by ammo- 

 nia in slight excess. The precipitate is washed with hot water 

 and finally ignited and weighed as iron and aluminum oxids. 



According to Crispo, the original Glaser method, with its 

 various modifications, is not to be considered reliable, and the 

 choice lies between the molybdate method as usually practiced, 

 and his own for the accurate estimation of iron and alumina. 

 Manganese disturbs the accuracy of the results unless the direc- 

 tions given are carefully followed. Manganese phosphate is 

 soluble at all temperatures below 50. If then the mixture of 

 the phosphates be allowed to cool before filtering, the iron and 

 aluminum salts are not contaminated with manganese. This 

 method of Crispo is somewhat tedious, but it is claimed that these 

 variations render it exact in respect of the determination of iron 

 and alumina. 



210. Variation of the Alcohol Method. Chatard conducts the 

 Glaser-Jones process as follows : 96 The distillation flask contain- 

 ing the alcoholic filtrate is connected with its condenser and 

 heated on a water bath until no more alcohol comes over. This 

 distillate, if mixed with a little sodium carbonate and redistilled 

 over quicklime, can be used over and over again, so that the ex- 

 pense for alcohol is really very slight, while in the use of the 

 Glaser method, with its large amount of sulfuric acid, all the 

 alcohol is lost. 



When the distillation is ended the residue in the flask is 



"Transactions of the American Institute of Mining Engineers, 1892-93, 

 21 : 169. 



