538 ^y. a. nelson — Appalachian bauxite deposits 



23ered with rubber stoppers containing capillar}' tubes, and allowed to 

 stand in the laboratory. 



Within two days a residue appeared in flasks niunber 1, number 4, 

 and number 7. After four days residues appeared in number 2, num- 

 ber 3, and number 5, and after a week in number 6, number 8, and 

 number 9. From then on no marked change appeared to occur in any 

 of the samples. After standing for 814 months, they were filtered, 

 residue washed thoroughly with cold water (residue consisting of organic 

 matter and alumina with a faint trace of iron), and alumina determined 

 in this residue. 



Weight of Weigbt of Weight of Per cent of 



Sample numl>er bentonite tannic acid Al,03 precipitated AI2O3 precipitated 



1 25 grams 5 grams .0038 gram .07 



2 25 grams 2 . 5 grams . 0034 gram .VI 



3 25 grams 0.5 grams .0036 gram .07 



4 10 grams 5 . grams . 0034 gram ' . 17 



5 10 grams 2.5 grams .0012 gram .06 



6 10 grams 0.5 grams .0010 gram .05 



7 5 grams 5.0 grams .0028 gram .28 • 



8 5 grams 2.5 grams .0011 gram .11 



9 5 grams 0.5 grams .0010 gram .10 



Assuming that bentonite is 20 per cent alumina. 



Xow, if we arrange these with reference to the ratio of tannic acid to 

 alumina (weights) in sample treated, we notice as follows : 



Weight of tannic 

 acid divided by 

 weiglit of alumina Precipitated A1^03 



Sample number ratio (percent) 



7 5.0 times as much tannic acid as alumina .28 



4 2.5 times as much tannic acid as alumina .17 



8 2.5 times as much tannic acid as alumina .11 



5 1.25 times as much tannic acid as alumina .06 



1 1.0 times as much tannic acid as alumina .07 



2 .5 times as much tannic acid as alumina .07 



9 .5 times as much tannic acid as alumina .10 



3 .1 times as much tannic acid as alumina .07 



6 .1 times as much tannic acid as alumina .05 



From this it appears that the greater the ratio of tannic acid to 

 alumina present, tlie greater the precipitated alumina. The relative 

 concentration of the solution seems to be of minor importance. A pre- 

 liminary test was made with a sample containing sulphuric acid soluble 

 matter from .5 gram bentonite plus 1 gram of tannic acid. Thirty days 



