Pe ee eee ee ea eee 
W. R. Nichols on the Chromites of Magnesium. 19 
TV. 2:0244 grm. of chrome alum and 0:2500 grm. of Epsom 
salt were taken, so that the mixture contained 2 equivalents of 
chromic oxyd for 1 equivalent of magnesia, A trace of mag- 
nesium was detected in the filtrate from the ammonia precipi- 
tate, and 0:0337 grm. of MgO was obtained from the soda 
precipitate. 0°1167 grm of Gr, O, was thrown down on boil- 
ing the filtrate from the sone precipitate. 
V. 2:3967 grm. of chrome alum and 0°3005 grm, of Epsom 
salt were taken, so that the mixture contained 1:97 equivalent 
of Cr,O, for 1 " equivalent of MgO. No magnesium was de- 
tected i in the filtrate from the paiocaa precipitate, 0°0250 
grm. of Cr,O, was thrown down on boiling the filtrate from 
the sa precipit ate 
VI. 1:0120 grm. of chrome alum and 0:5000 grm. of Epsom 
salt were taken, so that the magnesia should be in large excess, 
the proportion ‘of magnesia to chromic oxyd in this case being 
as2to 1. 00077 grm. of MgO was obtained in the filtrate 
from the ammonia precipitate, and 0-0765 grm. of MgO in the 
soda precipitate. No chromium was found in the filtrate from 
the ammonia precipitate, while 0°1508 grm. was obtained from 
the soda precipitate. The results ae be tabulated as eens 
und 
Taken. in the ae precipitate. (eMg0, 0720 ). 
VI 2M¢O 0°0809 0°:0765 33°66 
( -) Or Os 0°1549 0°1508 66°34 65°66 
0°2358 02273 10000 —*100°00 
The soda precipitates, after having been ignited and a 
were decomposed by fusion with carbonate of sodium a 
trate of potassium in the usual way.* The ee fa 
then determined as chromate of lead, and the magnesium in the 
ei resorted to in each case, in order to complete a 
mposition. The yellow color of the fused mass and of the _ 
solutions obtained after these second fusions, —— clearly 
‘enough that, whatever the tial os composition of me 
powder may be, a certain proportion of cheamigi is always 
* Fresenius. Quantitative Analysis, p. ee 
