DIFFICULTIES OF THE GLASER-ALCOHOL METHOD 235 



centimeters of sulfuric acid of 1.84 specific gravity added. The 

 flask is allowed to stand for about five minutes and meanwhile 

 shaken a few times. About 100 cubic centimeters of 95 per cent, 

 alcohol are added and then the flask is filled with alcohol to the 

 mark and well shaken. A certain degree of concentration takes 

 place, and this is compensated for by lifting the stopper and filling 

 .again with alcohol to the mark and shaking a second time. After 

 allowing to stand for half an hour the contents of the flask are fil- 

 tered, and loo cubic centimeters of the filtrate, equal to four-tenths 

 gram of the substance, evaporated in a platinum dish until the 

 alcohol is driven off. The alcohol-free residue is heated to boil- 

 ing in a beaker with about 50 cubic centimeters of water. Am- 

 monia is added to alkaline reaction, but in order to avoid strong 

 effervescence it is not added during the boiling. The excess of 

 ammonia is evaporated, the flask allowed to cool, the contents 

 filtered, precipitate and filter washed with warm water, dried, 

 ignited and the phosphates of iron and alumina weighed. Half 

 of the weight of the precipitate represents the weight of Fe 2 O 3 

 -)-Al 2 O 3 . The estimation, as before indicated, should be carried 

 on without delay, the whole time required not exceeding from 

 one and a half to two hours. 



207. Difficulties of the Glaser-Alcohol Method. The objections 

 on the part of English chemists to the method of freeing dis- 

 solved phosphate from lime by means of alcohol preparatory to 

 the separation of iron and alumina are as follows : 92 



1. To working upon a solution representing as little as 0.4 

 gram of phosphate. 



2. To employing nitro-hydrochloric acid as the solvent for the 

 raw phosphate and consequently to including in the oxids of 

 iron and alumina any iron previously present as pyrite. 



3. To the plan of dividing the phosphates of iron and alumina 

 found by two to obtain the oxids of iron and alumina, instead of 

 determining the phosphoric acid in the precipitates and deducting 

 its weight from the total. 



4. Should the phosphate under examination contain magnesia, 

 the phosphates of iron and alumina obtained in the foregoing 



91 Shepherd, Chemical News, 1891, 63 : 251. 



