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may be expected to show
reaction effects similar to
those obtained with
de-composed kaolin, possibly
even with respect to the
capacity of formation of
basic compoimds at löw
reaction temperatures, wich
should appear as maxima
of CaO-consumption ön the
yield curves.
We have therefore
car-ried out two series of
reaction experiments with
mixtures of CaO and
sillimanite in the molecular ratio
CaO 2 8
ai2o3 . Si02 ’ i an T
respectively. The
preheating and other experimental
conditions were identical.
Fig. 9 A, B corresponding
to table 5 show yield curves
of normal type, except that
those corresponding to
preparations preheated at
1 000° actually show a
maximum. This indicates
that the formation of basic
compounds is facilitated
also in these mixtures just
as was the case with the
mixtures of kaolin and CaO,
and, as said, it seems
rea-sonable to connect this
with the decomposition of
sillimanite and its
transition into mullite, which
begins to be noticeable at
about 1 000° in sillimanite
preparations of this kind.
This interpretation of the
results with this reaction
system also seems to be
supported by the fact that
the maximum diminishes
respectively disappears, if
the preheating time at
1000° is prolonged from 1
to 5 hours or if the
preheating is done at such high
temperatures, that the
formation of mullite is very
rapid just as was the case
also in mixtures with
kaolin. The curves Sill iooo/öh.
and table 6 shows that also
with this system the
reaction yield increases if the
heating time is prolonged.
H. Reactions with mullite
(Table 7. Fig. 10).
lf what is said about
reactions with sillimanite is
8 mars 1941
27
Fig. 10.
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