38 KANSAS ACADEMY OF SCIENCE. 
THE CHEMICAL COMPOSITION OF CEMENT PLASTER. 
BY E. H. S, BAILEY, LAWRENCE. 
Read before the Academy October 28, 1897. 
There has been found, scattered over quite large areas in some of the central 
states, especially Kansas, Indian Territory, and Texas, an earthy material, which 
consists practically of gypsum sand, and which has been utilized for the manu- 
facture of a material which has been called ‘‘cement plaster.’’ This material is 
of light color, and when dry frequently as fine as dust, and is evidently of recent 
origin, deposited from water. There are often watercourses in the vicinity of 
the deposits; and springs of water strongly impregnated with calcium sulfate often 
flow from the beds. These beds cover an area of from ten to twenty acres, and 
vary in thickness from two to ten feet. One peculiarity of the location is that 
they are usually on only one side of a stream. 
This material, to which we have assigned the name ‘‘gypsite,’’ upon being 
examined with a microscope, is seen to consist of numerous crystals of gypsum, 
associated, however, with much material that seems to be amorphous in struc- 
ture. As it can be readily broken up with a plow and harrow, and can be handled 
like ordinary dirt, being loaded upon wagons with a grader, it has been found 
very economical to use it for the manufacture of plaster. All expense of 
quarrying and grinding is thus avoided. Of course many claims are made for 
the superior quality of the product over the ordinary plaster of Paris, made 
from rock, but practical use of the material will solve the reasonableness of such 
claims. We have had special opportunities to examine a large number of sam- 
ples of the original crude material, and of the manufactured product, in connec- 
tion with some work for a report of the University Geological Survey. 
COMPOSITION OF THE RAW MATERIAL, 
The gypsite varies greatly in composition, even in the same area. This is 
due to various mixtures of clay on the one hand and of sand on the other. An 
expert can, by the appearance of the material, select the different grades, and 
mix them in such a proportion as to produce a product of the right composition. 
As an example of this, the following analyses may be quoted, all taken from 
material from the same bed. but sampled at different times by different persons. 
For convenience the constituents only are given here; but something will be said 
of the probable combinations farther on. 
GyPpsITE BeEps. 
CONSTITUENTS. 
No. & No. 2. No.3 
Silica and insoluble residue.............. 18.69 12.29 10.23 
Tronand alummum oxids.: >: .2...2-55oe8 al 2.27 L.2 
C@alciumtoxideees. 0. ta 2 eee eee 26.11 29.69 30.78 
IMamnesininm oxi) oy. sicher .43 .78 .49 
Suliuricanh yard. Asc. esa. eee ee ooeed 34.87 34.56 
Warpon dioxzid (eale.)).....c. po epee aan 3.15 | (det.) 3.52 | (cale.) 5.67 
BVVarber 24> fon ee. Ne ie eee ee 15.29 16.07 176 
MD OGAIS Sy ows cokes Ae ee 98.75 99.49 99.91 
It will be noticed that the proportion of insoluble material varies considera- 
bly, and the water increases as this diminishes. 
