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(table o and 6) or mullite (table 7) other proportions
also occur. The curves plotted in the
correspond-ing diagrams show the molar proportions of reacted
CaO per molecular weight of the other reaction
sub-stance (or in some cases Si02), except the curves
corresponding to mixtures with mica and feldspar
(fig. 7 and 8) which are plotted directly from the
figures of table 4. The points of the curves are
calculated from the average values of the analyses of
two reaction mixtures parallelly heated, the difference
between which does not generally exceed 0,5—1 p.c.
by weight. Only at temperatures above 900° will the
differences between parallel analyses occasionally rise
to somewhat higher values. Even at the highest
temperatures, however, the accuracy is quite
suffi-cient. This holds for heating experiments carried out
with portions of the same reaction mixture (e.g. the
series 800°/5 h.). When comparing the values from
different series, corresponding to different
prepara-tions or preheating treatments (e.g. if comparing
Phoeoo/s h. with Pho80075 h. or VG8OT h. with VL80(m h.)
it is, however, generally not permissible to draw any
conclusions from such small differences as 2—3 per
cent. This being a general experience from work
with powder mixtures, the results have not been
stretched. This should particularly be kept in mind
in regard to results obtained at the high temperatures
(above about 800°). At the highest temperatures
small amounts of liquid phase may play a röle, which
however must be very inconsiderable because of the
fact that none of the reacted mixtures has cohered.
Thus the influence of molten phases ön the reaction
yield in these experiments is minute.
lf we apply earlier results of reaction experiments,
quoted above, to the systems of CaO and kaolin
pre-parations (2 :1) and reaction conditions described in
this paper the following rough picture seems to be
true.
In mixtures containing free A1203 and Si02 the
formation of basic compounds such as 12 CaO • 7 A1203
and 2 CaO • Si02 is favoured at löw reaction
temperatures and short heating times. This is the case
in our experiments with kaolin preparations,
pre-heated at about 900—1 000°. It is, however,
neces-sary to remember that the reactivity of Al2Oa formed
by the decomposition of the meta-kaolin is certainly
considerably increased ön account of the still
imper-fect development of the corundum (a-Al203)
modi-fication, i.e., much lower reaction temperatures than
in the experiments by Jander and others must be
ex-pected. Especially if the preheating time is short
and, therefore, the slow development of a-Al203 and
perhaps also of Si02 very incomplete, a high
reactivity both of A12Qs and Si02 can be expected.
Consequently a longer heating time (5 hours) will
decrease the yield of the basic components in
ques-tion. lf the preparation is kept at 1 200° its
composition and, consequently, its reactivity are entirely
changed, the intermediately formed free oxides having
reacted to mullite.
2 CaO
In mixtures with a molar ratio ———–the
A1203 . 2 Si02
basic aluminate and silicate cannot, however, re-
present stable phases. Thus at higher reaction
temperatures, where the diffusibility is greater and the
chemical exchange consequently facilitated, other
re-actions consuming less CaO, will occur primarily.
When using preparations which are not preheated
above about 800° the highly active meta-kaolin phase
or perhaps the /-A1203 and amorphous Si02 seem
(Jander, Petri) to be able to react directly with
1 CaO to anorthite, consuming only one molecule CaO
per one A1203. 2 Si02 or with 2 CaO to gehlenite, the
latter also being formed in systems of CaO and
silli-manite.
Of course the reaction conditions may be studied
möre closely in mixtures with pholerite than in those
with the other kaolin substances which contain
con-siderable amounts of mica and feldspar. It is evident,
however, that even in the mixtures containing
meta-kaolin from pholerite the picture of the reaction
pro-cesses can only be roughly outlined. It must be
accentuated in this connection that the same
in-dividuality shown by different kaolin minerals in
their physicochemical behaviour may also be expected
with respect to their reactivity in the solid state with
CaO. Thus we may assume that the influence of
thermal treatment ön the reactivity of the dehydrated
substances may to some extent vary from one kaolin
to another and also with the impurities of the
preparations.
(Forts.)
Om metallernas namn.
I en artikel i Teknisk tidskrift 1940, allm. avd. sid.
229—233 redogör doktor Th. Wolff för några av de
vanligaste metallnamnens uppkomst. För namnet
antimon anför författaren emellertid en härledning,,
som icke är hållbar. Det är en folketymologisk
förklaring, som man för övrigt i 1700-talslitteratur ofta
finner i olika variationer. Vanligast av dessa är
kanske den, som återgives i t. e. H. T. Scheffers Chemiske
Föreläsningar, Upsala 1775: "Namnet Antimon
före-gifves af den händelse hafva upkommit, att Basilius
Valentinus börjat nytja detta ämne i medicin och
derigenom hulpit många af sina klosterbröder i grafven,
hvadan medicamentet blifvit ansedt såsom antimoine
eller contra monachum." — Såsom The Oxford
Dic-tionary, Vol. I, part I, p. 370, anmärker, lider denna
folketymologiska härledning av det felet, att ordets
uppkomst förlägges flera århundraden för långt fram
i tiden. Ordet antimon förekommer redan omkring år
1050 hos Constantinus Africanus, vilken i sina skrifter
använder det, som om. det redan då vore allmänt
känt.
Hur ordet antimon uppkommit, vet man icke. The
Oxford Dictionary håller för sannolikt, att det skulle
härstamma från det arabiska ordet uthmud, othmud,
som skulle latiniserats till athimodium, atimodium,
ati-monium, antimonium. Av den tidigare arabiska
formen ithmid förmodas grekerna ha erhållit ordet
stim-mida, som senare skulle ha givit upphov till den
latiniserade formen stibium. I sin utförliga avhandling
om grundämnenas namn (Journ. für prakt. Chemie, Bd
61, S. 510) ställer sig P. Diekgart tveksam inför
antagandet, att antimon skulle ha härletts ur arabiskans
11 jan. 1941
7
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