IV] WATERS 45 



by calculating the amount of sodium necessary to combine with the excess of acids 

 (hydrochloric, sulphuric, and bicarbonic) over the calcium and magnesium. 



Take a quantity, usually 1-5 liters, of the water suflficient to yield not more than 

 1 gram of barium sulphate and not more than 0.5 gram of mixed chlorids. Acidify 

 with hydrochloric acid, evaporate to dryness in a platinum dish and remove silica 

 by 2 evaporations as under 40, using not more than 2 cc. of hydrochloric acid (1 to 1) 

 for the final solution. Combine the filtrate and washings from the silica determi- 

 nations, and concentrate to about 150-200 cc. Heat to boiling and precipitate with 

 alight excess of 10% barium chlorid solution, added very slowly and with constant 

 stirring. Cover and allow to stand on the steam bath about 12 hours. Filter, wash 

 thoroughly the precipitate of barium sulphate with hot water, dry, ignite over a 

 Bunsen burner, and weigh. 



If the content of sulphate in the sample is unusually large proceed as far as the 

 concentration of the silica filtrates as directed above. Add 50 cc. of concentrated 

 hydrochloric acid, heat to boiling and precipitate with barium chlorid solution as 

 before. Evaporate to dryness, wash the precipitate repeatedly by decantation and 

 filter. Complete the washing of the precipitate; ignite and weigh. Calculate to 

 the sulphuric acid ion. Designate the filtrate as E. 



49 



SODroM, POTASSIUM AND LITHIUM.— OFFICIAL. 



Evaporate to dryness £', under 48, in a platinum dish and ignite the residue to faint 

 redness to remove all traces of ammonium salts. Dissolve the residue in the dish 

 in about 200 cc. of water and precipitate with milk of lime or a solution of barium 

 hydroxid. Boil, allow to stand 30 minutes, and filter off the insoluble magnesium 

 hydroxid. Thoroughly wash the precipitate with hot water and combine the filtrate 

 and washings. If the precipitate of magnesium is large, it is advisable to dissolve 

 in a small amount of hydrochloric acid, evaporate to dryness, take up with water, 

 and precipitate as before. Concentrate the 2 filtrates and washings to 200-250 cc. 

 Add ammonium hj'droxid and sufficient ammonium carbonate solution to precipi- 

 tate the calcium and barium. Allow to stand on a steam bath 1-2 hours. Filter off 

 the supernatant liquid, dissolve the precipitate in hydrochloric acid, reprecipitate as 

 above, and wash thoroughly with hot water. Evaporate the combined filtrates and 

 washings to dryness and drive off the ammonium salts by gentle heat. Treat the 

 residue with water; filter through a small filter, using as little wash water as possible; 

 evaporate to a small volume and again precipitate with 1 or 2 drops of ammonium 

 hydroxid and 2 or 3 drops of ammonium carbonate and oxalate. If any precipitate 

 appears (which is usually not the case) filter and repeat the process. Evaporate the 

 filtrate to dryness and drive off all ammonium salts by heating in platinum to faint 

 redness. Treat the residue with a little water; filter into a small platinum dish; 

 add a few drops of hydrochloric acid and evaporate to dryness. Dry in an oven, 

 heat to faint redness, cool in a desiccator, and weigh the combined chlorids of potas- 

 sium, sodium, and lithium. Repeat the heating to constant weight, (i). Dissolve 

 the mixed chlorids in hot water; filter, and wash. Return the filter paper and residue 

 to the dish, dry, ignite, and weigh, {y). The difference between (x) and {y) is the 

 weight of the mixed chlorids. 



The determination of lithium is then made according to the method of Gooch.* 

 Transfer the combined chlorids to a 50-100 cc. Erlenmeyer flask and evaporate the 

 solution nearly, but not quite, to dryness. Add about 30 cc. of redistilled amyl 

 alcohol. Connect the flask, the stopper of which carries a thermometer, using a 

 condenser if desired, to avoid the escape of the irritating vapor of the amyl alcohol, 

 and boil until the temperature rises approximately to the boiling point of amyl alco- 



