140 B. B. Biggs — Separation of Iron, Manganese, etc. 



w 



eight of CaO 



Weight of CaO 







taken. 



found. 



Error. 





grm. 



grm. 



grm. 



(35.) 



0-1136 



0-1131 



0-0005 — 



(36.) 



0-1138 



0-1135 



0-0003 — 



(37.) 



0-1136 



0-1136 



o-oooo 



(38.) 



0-1139 



0-1137 



0-0002 — 



(39.) 



0-1136 



0-1 132 



0-0004 — 



(40.) 



0-1138 



0-1133 



0-0005 — 



The solutions 300 cc - contained approximately 5 grams of 

 the chloride, 5 grams of the acetate and 10 grams of the bro- 

 mide of ammonium. The inference is that their influence in 

 restraining the oxalate precipitation is slight. 



Summary : In precipitating iron as basic acetate it is proba- 

 bly better to avoid a great excess of the acetate. A conside- 

 rable excess need not however interfere with the separation. 

 While an acetate solution favors the reduction of iron, with 

 care this reduction may be avoided. The precipitate should 

 not be digested too vigorously nor too long. 



In neutralizing the solution, preparatory to the acetate sepa- 

 ration, a slight precipitate of manganese, due to oxidation, is 

 almost always formed. This influences more or less markedly 

 the completeness of a single separation. It cannot be wholly 

 avoided, though the effect of the presence of ammonium salts, 

 in holding manganese salts in solution, is probably beneficial. 

 While the manganese remains in solution oxidation cannot 

 take place. 



In precipitating manganese from an ammoniacal solution by 

 means of bromine the presence of acetates is desirable. The 

 oxidation is more rapid, hence more complete than in a solu- 

 tion free from acetates. Bromine water should be added to 

 the hot ammoniacal solution. If the solution be cold the oxi- 

 dation is slow and in the end often incomplete. The addition 

 of bromine to the solution already made ammoniacal seems 

 preferable to a reversal of this order as it insures a more uni- 

 form oxidation. 



Where either the calcium or the manganese is in excess of 

 0*02 grams two precipitations are necessary. 



In conclusion it may be said that, in the hands of a careful 

 analyst, both methods are, according to present standards accu- 

 rate. 



Chemical Laboratory, Trinity College, 

 Hartford, Nov., 1891. 



