﻿26 



INDIANA UNTYEESITY 



was evaporated upon a hot plate to volatilize the hydrochloric acid. 

 The residue which did not volatilize below a temperature of 150° 

 consisted of aqueous perchloric acid whose purity and yield de- 

 pended upon the conditions of the exp-^riment. These samples of 

 perchloric acid Avere anajyzed to determine the free perchloric acid, 

 the sodium perchlorate and the hydrochloric acid. The residues 

 of sodium chloride which were obtained by the first filtration upon 

 the Gooch crucibles, were analyzed to determine the sodium per- 

 chlorate which they contained. 



Methods of Analysis. Free acids Avere determined by titration, 

 using methyl orange as indicator. The end point mth perchloric 

 acid was decisive and satisfactory. Yolhard's method was used for 

 the volumetric determination of the chlorides. The perchlorates in 

 the free perchloric acid were determined by evaporating a meas- 

 ured portion to dr^mess in a platinum dish. The dish was then 

 heated to near redness until the perchlorates were decomposed to 

 chlorides. The end of this decomposition was easily detected, 

 since the perchlorates were easily fusible and the chlorides were 

 infusible at this temperature. The total residue, which consisted 

 essentially of sodium chloride, was calculated to sodium per- 

 chlorate. Of course, this method would give correct results 

 only with samples containing sodium perchlorate and volatile sub- 

 stances such as hydrochloric acid and perchloric acid. For the esti- 

 mation of perchlorate in the presence of chloride, determine the 

 chloriDC in a portion in which the perchlorate has been decomposed 

 into chloride. The difference between the chlorine in this sample 

 and the chlorine in a portion which has not been decomposed rep- 

 resents the perchlorate. This decomposition can be accomplished 

 very easily by the m^^thod of Pittrich and Hollenback". The per- 

 chlorate is fused for several hours with sodium nitrite. The fused 

 mass, after cooling, is dissolved in water and the chlorine is deter- 

 mined by the method of Yolhard. Porcelain dishes are attacked 

 by the fused sodium nitrite, so platinum vessels must be used. The 

 sodium nitrite that was used in this research contained chlorine, 

 so a blank was determined and the proper correction was applied to 

 each analysis. This method gave uniformly accurate results and 

 was satisfactory in every way. 



Materials Used. A commercial preparation of sodium perchlo- 

 rate was used. Its composition was: NaCl, 1.76, 1.86 per cent: 

 NaClO^, 95.38, 95.77 per cent: NaClO;, trace. 



' Dittricli and Hollenback, BericTite dtr Deuischen Chci/dscJien GcseUscliaft, 

 XXVIII, 751 (1905). 



