﻿PREPARATION OF PERCHLORIC ACID 



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4. ]3istill a mixture of potassium perchlorate, sulphuric acid, 

 and water^. The distillation should be made under reduced pres- 

 sure to prevent the decomposition of perchloric acid. This is an 

 excellent method and is perhaps best adapted for the preparation 

 of perchloric acid cheaply and in large quantities. A complete 

 description of experiments with this method will be published later. 



5. Perchloric acid is produced in small quantities during the 

 electrolysis of hydrochloric acid solutions. The action of sunlight 

 upon aqueous solutions of chlorine or oxides of chlorine forms 

 some perchloric acid. These devices'', however, have never been 

 suggested as methods for the preparation of perchloric acid. 



6. Treat solid dry sodium perchlorate with an excess of con- 

 centrated hydrochloric acid'^. The mixture is then filtered and the 

 residue of sodium chloride, which is almost insoluble in the excess 

 of hydrochloric acid, is washed with concentrated hydrochloric 

 acid. The filtrate is a mixture of perchloric acid, hydrochloric acid 

 and small amount? of the sodium salts of these acids. Sodium 

 chloride is slightly soluble in the hydrochloric acid solution, so a 

 portion of it is found in the filtrate. By heating this filtrate until 

 white fumes of perchloric acid are evolved, the hydrochloric acid 

 is volatilized and the perchloric acid remains behind. The boiling 

 points of the hydrochloric acid and the perchloric acid with two 

 molecules of water (119° and 203'' respectively) are so far apart 

 that a very satisfactory separation is obtained. 



The object of this research was to determine the best conditions 

 and the proper quantities of reagents to use in order to obtain the 

 best results from this process of Kreider, since the original article 

 gave only a qualitative description of the method. 



Twenty grams of sodium perchlorate (weighed to 1 mg.) was 

 placed in a 100 cc. beaker and treated with the concentrated hydro- 

 chloric acid. The contents of the beaker were filtered upon a Gooch 

 crucible and the residue of sodium chloride w^ashed with ten 1 cc. 

 portions of concentratpd hydrochloric acid. The filtrate, which con- 

 tained the aqueous perchloric acid and the excess of hydrochloric 

 acici together with small amounts of the sodiinn salts of these acids. 



* Vorla/Uder and Schilling-. LieMo's Annalen, CCCX, 369. 

 NatiYGile, Journal fiir praliisclie CLouie, XXVI. 404 (1842). 

 Van Wyk, Zeitsc7iriff fiir aiujrganische Chemic, XXXII. 115; XLVIII, 4. 

 Van Emster, ZeU^clu-ift fiiv anorga ni'^rlte Chciitir. LII. 270. 

 ■'■'Popper, Liehifi's Annalen, CCXXVTI. Ifil : \Millon. Annales dc cliiinie et de 

 physique, (3) VII. 298; Liehic/'st AiDiulen. XT^VI, 281; Stadion, Gilbert's Annalen, 

 LII, 197 and HHU. 



^ Kreiv'ier, An\rrican Journal of 8cicn.cc, (3) XT>IX. 443. Zeitschrift fiir anor- 

 fjanische Chemie, IX, 343. Tread\Yell and Hall, QiiantuaUce Clienvistry, p. 47 

 a904). 



