A PRELIMINARY REPORT ON CLAYS OE FLORIDA 
85 
Sulphur —The determination of sulphur is rarely made in the analy¬ 
sis of a clay unless it is being considered for the manufacture of Port¬ 
land cement. It sometimes occurs, however, in clays and when present 
is usually in the form of sulphate or sulphide. Orton and Staley 1 con¬ 
cluded, from a series of experiments carried on by them, that sulphur 
retained in the clay during the period of burning, regardless of its form 
or cause of retention, is not likely to cause any physical disturbance 
until a fairly complete degree of vitrification is reached, but when a dense 
vitrified state is reached it soon becomes less dense, on account of the 
formation of multitudes of minute vesicles in the viscous body, and 
finally the body becomes spongy and worthless. They further conclude: 
“That in clays of low sulphur content, and of favorable structure for 
oxidation, the amount of sulphur left in the clay at vitrification is very 
small. Hence the period of good structure is long, the vesicular struc¬ 
ture develops slowly, and the clay is said to stand overfiring well. 
“In some clays of high sulphur content or of dense structure un¬ 
favorable for oxidation, or of high content of iron and carbon, the escape 
of sulphur is prevented, the clay has a narrow period of usefulness, or 
none at all, and the vesicular structure becomes enormously exag¬ 
gerated.” 
Soluble Salts —'Soluble salts is a term applied to those 'compounds 
readily soluble in water which are found in practically all clays to a 
greater or less degree. Upon being dried the moisture in the clay carries 
these compounds to the surface where it leaves them, upon evaporation, 
as an efflorescence. This effloresence or white coating may also occur 
in the burned product after exposure to moisture. 
The term “effloresence” and “scum” have hitherto been used inter¬ 
changeably to describe the accumulation of the salts (coating) upon the 
surface where they have been brought in solution and deposited upon 
the evaporation of the water. Parmelee 2 suggests that the usage of the 
term effloresence be limited only to include those surface deposits of 
salts that accumulate on raw clays in their original beds or in storage 
bins; all those surface deposits which occur in the drying of the ware, 
iThird Report of Committee on Technical Investigation, National Brick 
Makers’ Association, Indianapolis, 1908. 
2 Parmelee, C. W., Soluble Salts and Clay Wares, an address before the Indiana- 
Illinois Division of the American Face Brick Association. Chicago, April 11, 1922. 
