14 UNIVERSITY OF COLORADO 



then filtered off. The filtrate is placed in a flask, corked, and placed 

 under running water to cool. When quite cold add 20 cc. of 

 ammonia and 5 cc. of sodium phosphate solution, shake and let 

 stand alternately until all the magnesium phosphate is precipitated. 

 Filter, wash with cold dilute ammonia, burn, and weigh. 



Alumina. — Weigh out in a No. 3 RB casserole £ gram of slag 

 and treat as in silica, but, on filtering, do not add nitric acid to the 

 filtrate. This will give you a check on your silica determination. 



Wash the filter paper carefully with dilute HC1, and then 

 with water before removing. Then, to the filtrate, add ammonia 

 until the solution becomes dark red in color, but contains no 

 precipitate. Now add 3 cc. of HC1 and 2 grams of phosphate of 

 sodium (dissolved in water and filtered), constantly stirring, then 

 add 10 grams of hyposulphite of sodium in solution and 15 cc. of 

 acetic acid. Heat to boiling and boil for 15 minutes, filter rapidly, 

 wash with hot water, burn in a porcelain crucible,* and weigh as 

 A1P0 4 , which, multiplied by .41847, gives the weight of A1 2 3 . 



The student should now begin to study how to weigh these all 

 out, start them together, run them along together, and cut the 

 mechanical operations down as much as possible. Try to have all 

 filtrations come at the same time, etc., etc. 



The chemist is now ready to make his report to the metal- 

 lurgist, and since these elements must be reported as oxides, the 

 following table will be useful: 



CONVERSION TABLE. 



Fe x 1.29 = FeO 

 Fe x 1.43 = Fe 2 3 

 Mn x 1.29 = MnO 

 Zn x 1.25 = ZnO 

 Cuxl.25 = CuO 

 Pb x 1.08 = PbO 



S x 2.50 = S0 3 

 As x 1.32 = As 2 3 

 Sb x 1.27 = Sb 2 4 



S x 7.47 = PbS 



* It is necessary, in burning off the ppt., to raise the heat very carefully, until all the carbon 

 is burned off, otherwise the A1P0 4 may fuse. (Wohler 1.) 



