IX, A, 2 Reibling: Natural Cemerit versus Brick 1()5 



It was thought that a study of the physical and chemical 

 properties of the clay might reveal a practicable method of 

 improving the quality of the brick, and finally at the suggestion 

 of the Director of the Bureau of Science a representative sample 

 was forwarded to the Bureau of Science. 



The clay, which is a dirty brown in color and lightly specked 

 with white particles, many of which prove to be grains of coral 

 sand, was first subjected to a chemical examination. The results 

 obtained are recorded in Table II. 



Table II.~— Chemical characteristics of Iwahig clay (dried at 110" C.).* 



ULTIMATE CHEMICAL CONSTITUENTS. 



Constituent. 



Per cent. 



Loss by ignition 



10.70 



Total silica (SiO.) 



42.16 



Soluble silica 



9.40 



Alumina (ALOs) 



24.26 



Ferric oxide (FeiOs) 



13.90 



Calcium oxide (CaO) 



6.40 



Magnesium oxide (MgO) 



0.90 



Sodium oxide (Na20) 



1.41 



Potassium oxide (K2O) 



0.10 



Sulphur trioxide (SO3) 



0.20 



Carbon dioxide (CO2) 





Total fluxes 



22.75 



RATIONAL ANALYSIS. 





Feldspar 



31.38 



Quartz 



21.02 



Clay substance, about 



42.00 



" Analyzed by F. Pena, chemist, Bureau of Science. 



The high content of iron and calcium oxide and the low con- 

 tent of silica indicate that the clay has little or no value for the 

 manufacture of hard-burned ware, such as paving brick. Ex- 

 periments showed that it burned best at a temperature of about 

 1,050° C. Stiff-mud briquettes, burned at this temperature in 

 an oxidizing atmosphere, showed a tensile strength of about 

 230 pounds per square inch and were of an agreeable brick red. 



Except for the few particles of coral, the clay contains very 

 little sand that is visible to the naked eye. It is easily pulverized, 

 and for best results the nodules of coral should be disintegrated 

 or separated from the clay by sifting or elutriation although the 

 clay does not contain more than 1.2 per cent of such material. 



The round ruptured spot near the top of brick 5 and the cracks 

 on the surface of brick 6, as seen in Plate I, fig. 1, show the unde- 

 sirable effects of nodules of calcareous material in the clay. For 



