COMPOSITION, PROPERTIES, AND TESTS OF PLASTERS 57 



TABLE 10. 

 ANALYSES OF PLASTER OF PARIS. 



1. Theoretical composition of pure plaster of Paris. 



2, 3. Stucco, made' by Ruby Stucco Plaster Co., Ferguson, Oklahoma. 

 2d Rep. Okla. Dep. Geology, p. 128. 



TABLE 11. 

 ANALYSES OF CEMENT PLASTERS. 



1. Florence, Colorado. 



2. Rhoades, Kansas. 



3. Blue Rapids, Kansas, " Crystal Rock " 



brand, Great Western Plaster Co. 



4. Springdale, Kansas, "Roman" brand. 



5. " "Acme" 



6. Blue Rapids, Kansas, "Sunshine" 



finishing plaster, Great Western 

 Plaster Co. 



7. Blue Rapids, Kansas, "Ivory" finishing 



plaster, Blue Valley Plaster Co. 

 8-12. Blue Rapids, Kansas, "Acme" 



cement plasters. 

 13. Okarche, Oklahoma. 

 14. 

 15. Quanak, Texas. 



Weight and Fineness of Plasters. 



Weight and specific gravity. Pure gypsum, before calcination 

 has a specific gravity of 2.30 to 2.33, corresponding to a weight of about 

 143^ Ibs. per cubic foot, while the specific gravity of plaster of Paris is about 

 2.57. The apparent specific gravity of cement plaster in bulk is 1.81.* 

 This would correspond to a weight of about 113 Ibs. per cubic foot if, 

 no allowance were made for air-spaces. According to the results t of 



* Wilder, F. A. Vol. 12, Iowa Geological Survey, p. 139. 

 t Tenth Ann. Rep. Wyoming Agric. and Mech. College. 



