30 MINERAL WATERS OF THE UNITED STATES. 



alcohol is driven off from the filter and beaker in the air bath, and 

 these two are kept for the determination of potassium and sodium. 

 The contents of the platinum dish are evaporated to dryness, treated 

 with a little sulphuric acid, and finally burned and weighed. This 

 gives the weight of the lithium sulphate, from which is subtracted 

 0.0017 gram to correct for the solubility of the sodium and potassium 

 chlorids in the arnyl alcohol. The residue is finally tested with the 

 spectroscope for the lithium line. (If lithium was found with the 

 spectroscope, but was not present in a large enough quantity to be 

 weighed, it was reported as a trace.) 



The contents of the beaker and filter from which the amyl alcohol 

 has been driven are then used for the determination of potassium and 

 sodium. The contents of the beaker are dissolved in hot water and 

 passed through the filter, which is thoroughly washed. The combined 

 filtrate and washings are transferred to a porcelain dish, treated with 

 platinum chlorid solution, and evaporated nearly to dryness. The 

 residue is treated with 80 per cent alcohol and thoroughly washed on 

 the filter with this medium until all the platinum chlorid has been 

 washed out. The filter paper is dried at the temperature of boiling 

 water and the .residue dissolved in water and passed into a weighed 

 platinum dish, from which the water is evaporated off, the dish and 

 contents being dried at the temperature of boiling water, and finally 

 weighed as potassium platinic chlorid. An addition of 0.0008 gram of 

 potassium chlorid to the weight of this substance found is necessary. 



The weight of the sodium chlorid is found by subtracting the com- 

 bined weights of the lithium chlorid and the potassium chlorid (cor- 

 rected) from the total weight of the three chlorids. 



Of course if the amyl alcohol in the determination of lithium above 

 is not evaporated to exactly 15 cc, the corrections will be different 

 from those mentioned above. 



PHOSPHORIC ACID. 



Another portion of the filtrate mentioned above is treated with 

 about 10 cc of concentrated nitric acid and evaporated in a por- 

 celain dish nearly to dryness to drive off hydrochloric acid. The res- 

 idue is taken up with water and, if necessary, filtered. Ammonia is 

 added to alkalinity and then just enough nitric acid to restore acidity. 

 Some ammonium nitrate is added and the beaker heated in the water 

 bath to 45 to 50 C. Molybdate solution is then added and the solu- 

 tion kept at a temperature of 45 to 50 C. for half an hour. The 

 yellow precipitate formed at this point appears generally only in 

 traces, but in a few cases it must be filtered off and washed with cold 

 water until entirely free of nitric and motybdic acids. The precipi- 

 tate and filter are then transferred to a beaker, a little water added. 



For the discussion of this point see original article by Gooch, loc. cit. 



