Lawrence Scientific School, 59 
after which, in the presence of bases not precipitated by ammo- 
nia, the chromic acid may be precipitated by acetate of lead, or ace- 
tate of barium, and weighed in the form of chromate, provided 
of course, that no sulphuric acid is present. When sulphate and 
chromate of barium are thrown down together, the chromic acid 
of chromium, it is best to oxydize the chromium to chromic 
he as above, and then to precipitate with acetate of lead or 
rium, 
I have stated in a former paper that chromic iron ore may be 
y : : 
aluminum separated by boiling, and the chromic and ace 
acids precipitated by acetate of barium, after which the chromi- 
um may be determined as above. 
In precipitating chromic acid by means of nitrate of suboxyd 
of mercury, hot solutions must not se employed, as a small 
Portion of chromic acid is always reduce 
chromium, The precipitated Sitoniste should be allowed to 
