Smith.] 218 [Dee. 21, 
The filtrate from this, after being similarly treated as above, yielded 
62.83 per cent. chromium oxide. 
These results accord with those of Garrett, who analyzed the same ore 
from Texas, Pa., and obtained about 63. per cent. of chromium oxide. 
The ferric oxide that separates out in the tube during the decomposition 
will not contain any chromium whatever, if it is thoroughly washed with 
boiling water. 
In no instance was iron found in the solution containing the chromic 
acid. 
Several tubes containing the pulverized substance, potassium hydrate 
and bromine water, were heated at 125° C., but invariably exploded before 
the decomposition was completed, and therefore no further attempts were 
made to use the alkali to aid in the decomposition. 
All that is necessary to effect the complete decomposition of chromiciron by 
this method is that the substance be exceedingly fine, and that the same be 
exposed with bromine water to a temperature of 180° C., from two to three 
days. The addition of 10-12 drops of bromine hastens the decomposition 
very decidedly. 
In connection with the above, it may be well to mention that the in- 
soluble chromium oxide obtained by the ignition of the corresponding hy- 
drate, may be brought into solution again by digesting it together with 
bromine and sodium hydrate in a beaker. 
Precipitation of Copper with Sodium Carbonate. 
The precipitation of copper from its solutions by sodium hydrate, gives 
a precipitate that is worked with difficulty. Sodium carbonate, on the other 
hand, added to similar solutions, and these boiled, affords a dark brown, 
granular precipitate, that may be readily and completely washed with hot 
“water. 
Mr. Harry G. McCarter, student in the Laboratory of the University, 
made the following analyses, which show that the method yields as accu- 
rate results as could be desired. 
I. .2000 grms. CuSO, + 5H,O —dissolved in water and precipitated with 
sodium carbonate, gave .0630 grm., CuO = 25.15 per cent Cu. 
II. .2000 grms. Cu SO, + 5H,O treated as above, gave .0634 grm. CuO = 
25.30 per cent Cu. 
The theoretical percentage of copper in the salt is 25.25 per cent. 
After the addition of sodium carbonate in slight excess to the copper salt 
solution, the latter was boiled for an hour, until all the carbon dioxide was 
expelled. 
The filtrates from the precipitates in every instance were evaporated, but 
not the slightest trace of copper discovered. 
An excess of acid in the solution from which it is desired to precipitate 
copper by an alkaline carbonate, should be avoided. 
The presence of rather large quantities of alkaline nitrates or sulphates 
will cause the solution of the precipitates first produced by the carbonates. 
Continued boiling will not remedy the matter. From such solutions, how- 
ever, the alkaline hydrates will not fail to precipitate the copper. 
