﻿PREPARATION 0¥ PERCH LORIO ACID 



29 



of perchloric acid was 80.9 per cent of the theoretical. Washing 

 with ten 1 cc. -portions of hydrochloric acid failed to wash the per- 

 chloric acid ont of such a bulky residue. Another experiment 

 showed that ''commercial" hydrochloric acid did not give as good 

 results as the "C. P." acid. This was due, no doubt, to the lower 

 concentration of the " commercial"' acid. The yield of perchloric 

 acid was 88.7 per cent as compared with 96.0 per cent for the ''C. 

 P." acid. Potassium perchlorate cannot be used. 



Summary. — ^These experiments were made to determine the 

 conditions for the preparation of perchloric acid by the action of 

 concentrated hydrochloric acid upon sodium perchlorate. 



The sodium chloride is insoluble in the excess of concentrated 

 hydrochloric acid and can be separated from the perchloric acid 

 and hydrochloric acid by filtering upon an asbestos filter and by 

 washing with concentrated hydrochloric acid. The hydrochloric 

 acid can be volatilized away from the perchloric acid by heating the 

 filtrate. The best conditions are : Use 25 to 30 cc. of concentrated 

 hydrochloric acid for each 20 grams of- sodium perchlorate. Do 

 not add any water to the substances. Filter out the sodium chloride 

 residue and wash with ten 1 cc. portions of concentrated hydro- 

 chloric acid. Heat the filtrate and washings to 135° to volatilize 

 the hydrochloric acid. The yield of perchloric acid is about 95 per 

 cent of the theoretical. Only about 1 per cent of the sodium 

 perchlorate is lost in the sodium chloride residues. The other 4 per 

 cent is in the perchloric acid fis sodium perchlorate. The per- 

 chloric acid is free from chlorides. The process does not work with 

 potassium perchlorate and is unsatisfactory with barium perchlo- 

 rate. 



