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INDIANA UNIVERSITY STUDIES 



The test for potassium with perchloric acid (36 per cent alco- 

 hol) gave the following results: 



Gm. KCl. 



Gm. K.O. 



Kind of Test. 



.012415 



.007833 



Very strong. 



.009932 



.006266 



Very strong. 



.007449 



.004699 



Strong. 



.004966 



.003133 



Strong. 



.002483 



.001566 



Fairly strong. 



These data show that perchloric acid in 36 per cent alcohol will 

 remove the potassium so that hydrofluosilicic acid may be used to 

 precipitate sodium. 



The test for sodium with hydrofluosilicic acid is less dehcate 

 than the tests given above; but still one milligram of sodium oxide 

 can be easily detected. 



Gm. NaCl. 



Gm. Na^O. 



Kind of Test. 



.019490 



.010666 



Strong. 



.009745 



.005333 



Strong. 



.005847 



.003199 



Good. 



.003898 



.002133 



Only fair. 



.001949 



.001066 



Weak. 



Summary. 1. Magnesium does not interfere and need not be 

 removed. Magnesium perchlorate is very soluble. Magnesium fluo- 

 sihcate is soluble and is precipitated, even in alcoholic solution, only 

 when large amounts are present. 



2. The test for sodium is delicate but traces of sodium which 

 are present in so many reagents are not detected. This is an ad- 

 vantage over the spectrum test where all substances show sodium. 



3. The tests are simple, and are easily followed and understood 

 by students. 



4. The tests are decisive, and the student has confidence in his 

 work. 



5. Only a short time is required to make a test. 



