40 
IOWA ACADEMY OF SCIENCES. 
of the copper or by Traube’s theory which is backed up by 
almost convincing evidenced 
Stannous chloride will reduce sulphuric acid with formation 
of hydrogen sulphide and free sulphur, an analogous reaction 
in which the assumption of “nascent” hydrogen is inadmissible. 
3Movitz Traube, loc. c/it. andBer., 18, 1877, etc. 
CLAYS OF THE INDIANOLA BRICK, TILE AND POT- 
TERY WORKS 
L. A. YOUTZ, INDIANOLA. 
Analyses of several clays from a brickyard at Indianola have 
recently been made by me to go into a report of the Geological 
Survey of Warren county. Though it has been said that a 
knowledge of the constituents of a clay, determined by a purely 
chemical analysis, is of very little value to a practical brick- 
maker, yet in comparing the analyses of these clays and those 
from other vicinities, it seems that points of great value to the 
manufacturer are made plain, and points that can be derived 
from no other source. So I wish to give a few ideas which 
came to me as I made the comparison, as points, of local inter- 
est at least, were, it seems to me, clearly brought out. 
In order to get an intelligent idea of the value of this clay 
for brick and tile it may be helpful to give a short outline of 
some of the qualities of clay for the various kinds of brick. 
The quality and character of brick depends, of course, pri- 
marily upon the kinds of earth used; the mechanical mixing, 
drying and burning being important items, however. 
The varieties of clay most frequently used for common 
bricks are three. The so-called blue clays, hydrated aluminum 
silicates, combined with small quantities of iron, calcium, mag- 
nesium and alkalis; sandy clays or loams, and marls which con- 
tain a large proportion of lime and magnesium. In addition to 
these are the clays for special kinds of brick, as fire-brick, 
pottery, terra cotta, etc. Hydrated silicate of aluminum is 
infusible even at the most intense furnace heat, but if these be 
mixed with alkalis, or alkali earths, it becomes fusible, and in 
