84 
FLORIDA GEOLOGICAL SURVEY-I5TH ANNUAL REPORT 
Titanium —Titanium is often regarded as an uncommon constituent 
of clays but in reality it is of frequent occurrence. Rutile and ilmenite are 
the most important sources of titanium dioxide in clays. Unfortunately 
tests for titanium are rarely made in a chemical analysis. It exerts a 
blue and yellow coloring effect and Ries 1 has shown that it lowers the 
refractoriness of clay. Veatch 2 states that titanium was shown in the 
analysis of some Georgia clays, but when those clays were examined 
microscopically no titanium minerals could be identified with certainty. 
Water —This includes the mechanically combined water or moisture 
and the chemically combined water. The mechanically combined water is 
that held in the spaces between the clay particles by capillary action and 
can be driven off by heating the clay to the boiling point of water. The 
loss of this water causes the clay to shrink to a certain extent. This 
shrinkage, known as air shrinkage, ceases when the clay particles have 
all come in contact. The chemically combined water exists in combina¬ 
tion with other elements and can only be driven off at a temperature 
ranging from 400° to 600° C. 
Organic Matter —Organic matter, usually in the form of vegetable 
particles, occurs in many clays. It is a strong coloring agent in the un¬ 
burned state and imparts to the clay a gray, blue, brown or black color. 
The same clays may, on burning, be red, buff, cream, or white, depending 
upon the other coloring agents. In such cases the carbonaceous matter 
has masked the other substances like iron in the raw state. 
Carbon may interfere with the proper oxidation of iron and expul¬ 
sion of sulphur when present. Clays with a high content of organic mat¬ 
ter are of common occurrence in Florida. 
It has been shown by the experiments of Orton and Griffin 3 that 
between 800° and 900° C. is the best temperature interval for burning 
off the carbon, as below this the oxidation of it does not proceed as 
rapidly, and above this there is danger of vitrification beginning and 
the oxidation being stopped. All the moisture should first be driven out 
of the clay, then the heat raised as rapidly as possible to a temperature 
between 800° and 900° C. and held there until the ware no longer shows 
a black core denoting ferrous iron. 
1 Ries, H., Clays, Their Occurrence, Properties and Uses, p. 104, 1908. 
2 Veatch, Otto, Clay Deposits of Georgia, Georgia Geol. Survey, Bull. 18, p. 
48, 1909. 
3 Second Report of Committee on Technical Investigation, National Brick 
Makers’ Association, Indianapolis, 1905. 
