METHOD OF KREIDER 583 



liquid and in breaking up the mass of salt. Otherwise the per- 

 chlorate seems to solidify with a certain amount of water and its 

 removal from the dish, without moistening and reheating, is im- 

 possible. 



After triturating the residue, easily accomplished in a porce- 

 lain mortar, an excess of the strongest hydrochloric acid is added 

 to the dry salt, preferably in a tall beaker, where there is less 

 surface for the escape of hydrochloric acid and from which the 

 acid can be decanted without disturbing the precipitated chlorid. 

 If the salt has been reduced to a very fine powder, by stirring 

 energetically for a minute, the hydrochloric acid will set free the 

 perchloric acid and precipitate the sodium as chlorid, which in a 

 few minutes settles, leaving a clear solution of the perchloric 

 acid with the excess of hydrochloric acid. The clear superna- 

 tant liquid is then decanted upon a gooch, through which it may 

 be rapidly drawn with the aid of suction, and the residue re- 

 treated with the strongest hydrochloric acid, settled, and again 

 decanted, the salt being finally brought upon the filter, where it 

 is washed with a little strong hydrochloric acid. A large plati- 

 num cone will be found more convenient than the crucible, be- 

 cause of its greater capacity and filtering surface. When the 

 filter will not hold all the sodium chlorid, the latter, after wash- 

 ing, may be removed by water or by mechanical means, with 

 precautions not to disturb the felt, which is then ready for the 

 remainder. Of course, if water is used, the felt had better be 

 washed with a little strong hydrochloric acid before receiving 

 another portion of the salt. This residue will be found to con- 

 tain only an inconsiderable amount of perchlorate, when tested 

 by first heating to expel the free acid and then treating the dry 

 and powdered residue with 97 per cent, alcohol, which dissolves 

 the perchlorate of sodium, but has little soluble effect on the 

 chlorid. 



The filtrate, containing the perchloric acid with the excess of 

 hydrochloric acid and the small per cent, of sodium chlorid which 

 is soluble in the latter, is then evaporated over the steam-bath 

 till all hydrochloric acid is expelled and the heavy white fumes 

 of perchloric acid appear, when it is ready for use in potassium 



