SWEDISH METHODS 549 



timeters of the filtrate to the boiling temperature and add am- 

 monium carbonate solution till no more precipitate forms. Cool 

 make up to 100 cubic centimeters and filter. Transfer 50 cubic 

 centimeters of the filtrate to a platinum dish, evaporate and heat 

 the residue, avoiding too high a temperature, till the ammonia 

 salts are expelled. Dissolve the residue in water, filter, and treat 

 the filtrate as described under A. 



469. Swedish Methods. The Swedish chemists determine the 

 potash in mineral salts by the platinum chlorid process, but with 

 certain variations from the processes already given. The manipu- 

 lation is conducted as follows : 38 



Pour about 300 cubic centimeters of hot water over one gram 

 of the sample to be examined in a beaker, and filter after com- 

 plete solution ; add one cubic centimeter of hydrochloric acid, heat 

 nearly to boiling, add dilute barium chlorid solution from a pipette 

 or burette in a very fine stream, stirring slowly and carefully, 

 till all sulfuric acid is completely precipitated, and only a trace 

 of the precipitant is in excess. If the precipitation be conducted 

 in the way given, the barium sulfate will come down in crystal- 

 line condition, and settle rapidly within a few minutes, and al- 

 most immediately after the precipitation is finished may be fil- 

 tered clear. Bring the filtrate and washings from the barium 

 sulfate into a liter flask; fill this to the mark, take out 50 cubic 

 centimeters with a pipette, evaporate the greater portion on a 

 water bath in a porcelain dish, transfer the residue by means of 

 ammonia-free water to a beaker of 50 cubic centimeters capacity, 

 add 10 cubic centimeters of platinic chlorid solution, stir well with 

 a glass rod, evaporate on a water bath to a sirupy condition, allow 

 to cool, and if the residue be too dry, add a few drops of water to 

 allow the sodium platinochlorid to take up crystal water with 

 certainty, stir well, add alcohol after a few minutes, mix care- 

 fully, leave the mixture standing for a while in the beaker cov- 

 ered with a watch-glass, stirring occasionally; finally, decant the 

 solution, which must be of a dark yellow color, through a very 

 small filter, wash the precipitate in the beaker repeatedly with 

 small quantities of alcohol and decant; then transfer the precipi- 

 M Official Swedish Methods, translated for the Author by F. W. Woll. 



