The Ocala banner. (Ocala, Marion County, Fla.) 1883-194?, 1897-10-01

9iiN"'N hCNt NC NCtcf lhtlicu ny series
of practical experiments, in which
the chemists will use as a starting
poin the analysis he seeks to secure in
the product,
The following analysis Of some of
the best makes of Portland cement
will serve to direct him:
Lime ga ~ ..........' .-..Si II 70 626I
silica ~ q .-...'.........~ .9og6to 24.fo
Alumina (Al q a) ........... ........ ssoto rs
Iron oxide re 0 > tuot essentiaN 200 t. & 90
Magnesia (Mg o. (detTimcntal) ...... o.s- to 2qz
Alkali (Na or Ql.................. o6s to 2oo
Water and carbonic acid. average sac
The best proportions having been
found, the mixing should be thorough,
and then another set of experiments
made on small quantities to deter
mine the temperature and time best
suited for the burning In this pro-
cess care should be exercised in avoid
ing on the one hand the poison of the
mass by over-heating, and on the
other insufficient chemical action
from UNDERWRITING.
In the process of calcination the
limestone parts with its carbonic acid,
becoming thereby 4uick-lime, which
acting upon the clay forms silicate
| and illuminate of lime In this reac-
ton the alumina plays the part of an
| acid in combining with the lime base,
whereas in the original material it was
a base and was in combination with
the silicic acid or silica. 1t is not,
however, necessary that this reaction
should be-from chemical stand
point-cOmplete, since it ia found to
be technically complete, i. Q. pro-
ceeded far enough to secure the highest
efficiency in the product, before that
point is reached. 1t is not quite GER
t:i T'@t "a action is but it i r :h
ably a catalytic one. That is, its pres
ence in some way determines or pro-
notes the necessary changes, while
itself remains unchanged.
The operation of calcination is
very important part of the process,
though after the proper temperature
and duration shall have been estab-
lished by experiment any one Of ordi-
nary intelligence can soon acquire the
requisite technical skill in performing
1T. Another equally important mat
ter is the powdering; for however well
the previous operations may have
been performed, the value Of the pro-
duet still depends upon the thorough
ness with which this is done So inn
p0rtant, indeed, is this consideration
that if a cement is eifted with a sieve
Of 5000 holes in square inch the por-
ton refusing to pass will possess no
virtue whatever, although that pass
ing be ever SO good, and the coarse
portion need only to be reduced to
the proper lincness to be made of the
highest-quality.
AS rule those cementa set most
rapidly that develop their greatest ef-
liciency with a moderate burning.
On the other hand, those requiring the
longest burning TO develop their max
imUm efficiency are slowest in setting.
In some instances the same mate
rails are used for producing either a
strong, slow-setting cement, or more
quickly setting one of less strength,
this variation of the product depend
ing upon the severity of the burning.
The yield of Portland cements
should be about sixty per cent of the
gross materials used. They should set
in half TO two hours and continue to
harden until the maximum is reached.
In setting they combine with water of
crystalization, which, passing from the
liquid to the solid state, causes the
setting.
The natural cements are best bar
relied at once, deteriorating by expos
ure to the air; while it is necessary to
"age" the Portland by the same ex-
posture for some time before barreling
the longer the better, up to about
two years.
1t would he n mistake to consider
the cements that might be produced
in Florida limitations, for, in reality,
they would be no more so than the
corn grown in one field is an imita-
ton OF that grown in another. 1t is
only necessary to observe faithfully
the requirements of the process Of