128 
IOWA ACADEMY OF SCIENCES. 
The contents of the watch glass w T ere rinsed into the 
dish and evaporation continued until crystals began to 
appear. Then as the drying continued it was stirred with 
a glass rod until a fine dry powder resulted. This w T as 
moistened with a few drops of concentrated hydrochloric 
acid and then about 20 c.c. dilute hydrochloric acid and 
the same quantity of water were added. The precipitate 
was filtered and determined as silica. 
Analyses by the first method of the same specimen gave 
0.75 per cent and 0.76 per cent silica, and by the second 
gave 0.78 per cent. As the results were similar, and as 
the determinations could be made much more easily and 
quickly by the first method, it was the one usually practiced. 
About two grams of ammonium chloride were added to the 
filtrate from the silica, and at the boiling temperature it 
was treated with a small excess of ammonia to precipitate 
the iron and alumina. The filtrate from these, moderately 
diluted, was heated to boiling and precipitated with a N / 2 
solution of ammonium oxalate, care being taken to avoid an 
excess of the reagent. The oxalate was slowly added from 
a pipette, and with rapid stirring, to prevent as far as pos- 
sible the occlusion of magnesium with trhe calcium oxalate. 
The precipitate was allowed to stand eight to twelve hours 
before filtering. The well washed precipitate of calcium 
oxalate, with a small quantity of magnesium oxalate was 
dissolved in warm, dilute hydrochloric acid and the solution 
was rendered alkaline with ammonia; this precipitates the 
calcium oxalate and leaves the magnesium in solution. 
This amount of magnesium and the main portion from the 
first calcium-magnesium precipitate w 7 ere determined sep- 
arately by precipitating each with disodium phosphate 
and weighed as magnesium pyrophosphate. The carbon 
dioxide was determined by the Bunsen method. After 
the complete analysis was made only the small amount 
of magnesium, that which precipitates with the calcium, 
was determined. 
