Matthew Steel 175 



E. — Ferric chlorid: 5 gm. of FeClg were dissolved in dist. water 



in a 500 cc. flask and made up to volume, 

 F. — Sodium dum: 20 gm. of sodium alum were dissolved in 



dist. water and made up to a liter. 

 G. — Standard blank soL: 25 gm. of sodium phosphate, 15 gm. of 



potassium chlorid, 1 1 gm. of calcium chlorid, and 1 1 gm. 



of magnesium chlorid, were mixed with 800 cc. of dist. 



water and just enough hydrochloric acid to effect sol. 



The mixture was then made up to i 1. 



2. Standardization of THE KMnO^ SGL. The potassium per- 

 manganate used for all of this work was an old, approximately 

 n/40, sol., which had been made up over a year previously. A portion 

 of this sample was filtered and diluted to n/40 strength for use. The 

 diluted permanganate sol. was standardized against a n/40 sol. of 

 oxalic acid, and against weighed portions of sodium Oxalate. 



A. Standardising with oxalic acid. In preparing the n/40 oxalic 

 acid sol., 0.7878 gm. of oxalic acid were dissolved in 500 cc. of water. 



(a) 20 cc. of the n/40 oxaHc acid required 20.80 cc. of the KMnOi. 

 (&) 20 " " " " " " " 20.75 " 



\c) 20 " " " " " " " 20.80 " 



« II « 



B. Standardising with sodium Oxalate. In standardizing the per- 

 manganate sol. with sodium Oxalate, the conditions outlined in the 

 "U. S. Bur. of Standards' Circular No. 40" (7) were followed. 



(a) 0.0335 g"i- of sodium Oxalate required 20.80 cc. of the KMnO.4. 

 \h) " " " " " " 20.85 " " " 



(c) " " " " " " 20.80 " " " 



The average of the six tests equals 20.8. A " blank " on the reagents 

 used in the above tests indicated absence of all oxidizable substances. 

 Therefore, i cc. of the KMnO^ sol. had a value of 1.93 mg. of FeaOg. 



3. ESTIMATION OF THE IRON IN THE STANDARD FeCl^ SOL. 



The iron was determined in the Standard sol. first by the Mixer and 

 DuBois (8) modification of the Zimmerman-Rheinhardt method, 

 and second, by Jones and Jeffrey's (9) modification of the Zimmer- 

 man-Rheinhardt method. The following results were obtained : 



