| One of the general methods used in the opening out
of Chrome ore and Chrome refractory products for
analysis is fusion with Na20a. Aluminium Oxide in these
materials is estimated from water extract 1, 2, 3, · 4, after
filtering and precipitating the aluminia by boiling the
filtrate with NH,Cl. The well washed precipitate is
ignited, SiOa separated by Potassium bisulphate fusion,
after which Al203 is determined in the usual way. It has
been found, however, that either complete solution of
AlaOs is uncertain or some sodium aluminate hydrohses
during boiling, so that some of it remains unaccounted for
if the water insoluble residue left! after· NatOa fusion is
not looked for it. Probably, on this account, in the
A. S. T. M. standard methods5 , the entire peroxide fusion
is treated with Hydrochloric acid and AlsOa determined
from the filtrate after separating the SiOa. The present
investigation was, therefore, undertaken to determine
whether the residue as stated above, contains any alumina
and if it does, the method under . consideration would
give accurate results only, when the constituent was
looked for both in the filtrate as weir as in the residue. |
