HOT SPEINGS, ARKANSAS. 25 



amount of phosphoric acid ion in the water can be calculated/ For the 

 determination of fluorine the same method was used as described by 

 Gooch and Whitfield. - b For the determination of barium and stron- 

 tium a combination of Gooch and Whitfield's method along with another 

 was employed. They are briefly as follows: 



Fluorine. — A large quantity of water was evaporated to dryness 

 and filtered off from the residue which was washed on the filter. The 

 filter and contents were dried, the contents placed aside and the filter 

 burned and the ash added to the contents. The whole was now trans- 

 ferred to a flask, which was so arranged as to allow a current of air to 

 pass through any liquid that might be in the bottom, and from there 

 into an attached u-tube, partly filled with dilute ammonia. Concen- 

 trated sulphuric acid was added to the contents of the flask, and a 

 current of dry air passed through the liquid, and from there into the 

 U-tube. The flask was heated to 150° C. If any considerable amount 

 of fluorine had been present it should have been volatilized as silican 

 tetra fluoride and then decomposed by the dilute ammonia in the u-tube, 

 depositing silica in so doing. No silica appeared at this point in the 

 spring examined. The contents of the u-tube was removed and treated 

 with zinc oxide dissolved in ammonia, evaporated till ammonia ceased 

 to come off and filtered. The filtrate was treated with calcium chloride, 

 followed by sodium carbonate in boiling solution, filtered and washed. 

 The residue was ignited and extracted w 7 ith acetic acid. Operating 

 in this way no residue of calcium fluoride was found. 



Barium and strontium. — The residue left in the flask from the 

 above determination was transferred to platium, treated with enough 

 hydrofluoric acid to volatilize all silica and with some sulphuric acid 

 and evaporated to dryness. This treatment was repeated. The residue 

 was fused with sodium carbonate, treated with water and a few drops 

 of alcohol, filtered, and w-ashed. The contents of the filter was digested 

 with hot dilute acetic acid to dissolve barium, strontium, magnesium, 

 and calcium carbonates and filtered. The filtrate was then nearly 

 neutralized with ammonia and about fifty times the weight of the com- 

 bined sulphates in ammonium sulphate was added, which ammonium 

 sulphate was dissolved in four times its weight of water. The whole- 

 was allowed to stand over night. In case barium or strontium were 

 present they would be precipitated here as the sulphates. Onty a 

 slight nomveighable opalescence appeared, however, in the spring 

 examined. For the sake of completeness, and to be able to test the 

 final residue with the spectroscope, the process was carried on just as 

 in an actual determination. The precipitated sulphates were Altered and 

 washed with a concentrated solution of ammonium sulphate, till no 

 more calcium was present in the wash water, as shown by the ammo- 

 nium oxalate test. The filter was ignited and the residue evaporated to 

 dryness with a drop or two of sulphuric acid. The combined sul- 

 phates so obtained from a very large quantity of water did not weigh 

 over 0.5 milligram, and most of this was calcium sulphate. The 

 extremely small residue was fused with sodium carbonate, treated with 

 a very small quantity of water, and filtered on a very small filter paper, 

 washing only once. Dilute hydrochloric acid was now passed through 



a Bul. 46 (revised edition), U. S. Department of Agriculture, Division of Chemistry. 

 1899. 



b Bul. 47, Y . S. Geological Survey. 



