32 FLORIDA GEOLOGICAL SURVEY SIXTH ANNUAL REPORT. 



PROPERTIES OF FULLERS EARTH. 



The action of fullers earth in clarifying oils, and the vary- 

 ing behavior of different fullers earths form an interesting study 

 on which much yet remains to be done. Porter in 1907 reviewed 

 the different explanations of the carifying action that had been 

 given and advanced a new theory to explain this property. Porter 

 believes that the clarifying action is due chiefly to colloidal silica 

 present in the clay, and records a series of very interesting tests 

 and analyses which are believed to support this view.* Porter's 

 theory briefly stated is as follows : ( i ) Fullers earth has for its 

 base a series of hydrous aluminum silicates. (2) These silicates 

 differ in chemical composition. (3) They are, however, similar 

 in that they all possess an amorphous colloidal structure. (4) The 

 colloidal structure is of a rather persistent form; and is not lost 

 on drying at a temperature of 130 degrees Centigrade, or possibly 

 higher. (5) These colloidal silicates possess the power of absorb- 

 ing and, retaining organic coloring matter, thus bleaching oils 

 and fats. 



Among other striking properties of fullers earth is the fact 

 that some earths that serve particularly w^ell in refining mineral 

 oils have not been used successfully for vegetable oils and con- 

 versely those best suited for vegetable oils are not suitable for 

 mineral oils. A recent study bearing on these problems has been 

 issued by the U. S. Bureau of Mines. f At the present time the 

 English fullers earths are being used largely in vegetable oils, while 

 the Amierican fullers earths are used almost entirely for mineral 

 oils. It is stated in this report, however, that the Bureau of Mines 

 believe that the United States has fullers earth far better suited 

 for refining edible oils than any imported, and that to assure the 

 almost universal use of this earth by American refiners there is 

 required only a careful and intelligent control of the preparation 

 of the output and its application to the bleaching of oils. 



Most fullers earth gives more or less of a taste to the edible 

 oils, and formerly the American earth was rejected by refiners of 

 edible oils on this account, but at the present time methods are 

 known for removing taste and odor from the oil. This is accom- 



*Properties and Tests of Fuller's Earth, by John T. Porter. Bull. 315, 

 U. S. Geol. Surve^^ pp. 268-290, 1907. 



tFulIers Earth, by Charles L. Parsons, Pjureau of Mines, Bull. 71, 1913. 



