78 
FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT 
Hydromica, as the results of the same investigator show, either 
practically disappears at 1150° C. or loses the greater part of its inter¬ 
ference color. Somers states that: “This change of the hydromica on 
heating suggests' that it furnishes some of the flux for the clay, and 
other things being equal, there may be a connection between the degree 
of density at the temperature mentioned and the quantity of hydromica 
.present.” 
Somers further states that: “If it is not fluxed, kaolinite appears 
to retain its shape and at least a part of its original interference color. 
Tourmaline and probably epidote disappear even at 1150° C., but rutile, 
zircon, and probably titanite seem' to be unaffected even at 1300° C.” 
A white Florida clay fired at 1150° C. exhibited the formation of 
sillimanite. Somers believed it to have formed from large flakes of 
kaolinite or the low-grade hydromica. Other similar clays treated in 
the same manner did not develop sillimanite. 
THE CHEMICAL.ANALYSIS OE CLAYS 
There are in common usage two methods of clay analysis. One of 
these.is known as the ultimate analysis and the other as the rational 
analysis. 
The ultimate analysis is the one most frequently used. It is the one 
which considers the various ingredients of a clay as oxides, yet their 
exact condition may be in much more complex forms. Calcium car¬ 
bonate (CaCOs) is thus considered as being broken up into carbon 
dioxide (CO 2 ) and lime (CaO), with the percentage of each given separ¬ 
ately. The sum of these two percentages would, on the other hand, be 
equal to the amount of calcium, carbonate in the clay. The common 
method of expressing the ultimate analysis of a clay is as follows: 
Silica . 
Alumina. 
Ferric Oxide ... 
Ferrous Oxide ., 
Lime . 
Magnesia.. 
Potash . 
Soda. 
Titanic acid 
Sulphur trioxide 
Carbon dioxide 
Water . 
Organic matter 
(Si0 2 ) 
(AI 2 O 3 ) 
(Fe 2 03 ) 
(FeO) 
(CaO) 
(MgO) 
(K 2 0) ^Alkalies 
(Na 2 0) j AIka,les 
(Ti0 2 ) 
(S0 3 ) 
(C0 2 ) 
(H 2 o) 
-Fluxing Impurities. 
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