ISDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1926
597
The Bismuthate Method for Manganese' By Bart Park MICHIGAN COLLEGE OF MINBU,HOUGHTON, MICH.
K THE bisinuthate method for manganese originally proposed by Schneider2 and modified by Reddrop and Ramage,3 the manganese was oxidized in a solution containing nitric acid. This procedure has been adopted by Ibbotson and BriarleyJ4 Blum15Blair,O Brinton,' Demorist,8 KinderJ9 and later by Cunningham and Coltman."J Nitric acid has certain inherent defects as a medium for this oxidation: (1) The oxides of nitrogen must be removed. ( 2 ) The permanganic acid is not so stable in nitric acid as might be desired. (3) The temperature during oxidation must be kept low. (4) Nitric acid has a tendency t o react with ferrous iron.
The purpose of this study is to show that sulfuric acid, which has none of these defects, may be substituted for nitric acid with no loss in accuracy. Procedure
After it was established that the oxidation proceeds in sulfuric acid, experiments were made to determine the conditions, if any, under which it is quantitative. A solution of pure manganous sulfate was prepared from the oxalate as proposed by Coltman.*l Measured volumes of this solution were acidified with sulfuric acid, approximately 0.5 gram of sodium bismuthate was added to each portion, and after shaking for 1 minute the solution was filtered through asbestos and glass wool with the aid of suction. The permanganic acid was washed from the flask and filter by means of 3 per cent sulfuric acid. A weighed amount of ferrous ammonium sulfate was added and the excess determined by titration with dilute permanganate solution (1 cc. = 0.0002 gram Mn). The titrations, unless otherwise noted, were made immediately after the filtrations.
T e m e a~. ture 15
25 35 40 45
Table I1 Other conditions constant KMnOl found c.c~. . 51.79 51.77 51.74 51. 80
51.s5 51.80
50 60
51.60
51.50
70
It is evident from Table I1 that the degree of oxidation is independent of the temperature over a wide range and that the solution need only be cooled to below 50" C. Effect of Standing after Filtration Table 111 Temperature, 20' t o 25" C. KMnO4 found Time of standing cc. 1 minute 50.4 1 hour 50.3 2 hours 50.2 4 hours 50.0
Permanganic acid is quite stable in dilute sulfuric acid a t ordinary temperatures. Effect of Varying Concentrations of Manganese Table IV Concentration Mn Mg./cc. 0.50 0.25 0.20
KhlnOd found
0.14 0.12 0.10
246.0
cc.
240.0
244.0 245.5
0.17
245.5
246.5 246.5
Results
E f e c t of Varying Concentration of Acid
Degree of Oxidation in Sulfuric and Nitric Acids
2.1 2.9 3.8
4.3 6.0
50.80
50.75 50.80 50.55 50.30
Table I shows that the maximum yield of permanganic acid is obtained in concentrations of sulfuric acid between two and four times normal. Received November 27, 1925. Dinglers polyfcch. J . , 869, 224 (1888). J . Chcm. SOC.(London), 67, 268 (1895). 4 Chcm. News, 84, 247 (1901). 5 J . A m . Chcm. SOC.,84, 1379 (1912). 8 I b i d . , 46, 793 (1904). 7 THIS JOURNAL, 8, 237 (1911). 8 Ibid., 4, 19 (1912). Stahl u . Eiscn, $7, 197 (1917). 10 THIS J O U R N A L , 16, 58 (1924). 11 I b r d . , 16, 606 (1924). 2
Acidity, 3 N.
When the concentration of manganese is between 0.1 and 0.2 mg. per cc. the degree of oxidation is practically constant. Oxidation is incomplete for concentrations of manganese above 0.2 mg. per cc.
Table I Weight of manganese, 0.01 gram Volume during oxidation, 75 cc. Temperature, 25' C. Weight of ferrous ammonium sulfate, 0.4 gram KLfnO4 found Normality of &SO4 cc. 1.2 50.00 1.7 50.19
1
Effect of Varying Temperature
Table V Manganese added, 0.02067 gram Fe(NH4SOl)z.6H20, 0.7500 gram Volume during Mn found oxidation --h70rmalit)-Gram CC. HiSOi HSOI 150 2.9 0.02052 0.02053 250 2.9 ... 0.02054 350 2.9 ... 1.8 3.2 0.02061 100 0.9 3.2 0.02057 200 3.2 0.02052 100 0.02052 ... 3.2 200 4.8 0,02054 100
.
...
... ...
KMnO4 found CC.
102.66
102.75 102.78
102.63 102.90 102.69 102.68 102.78
Table V shows that the oxidation proceeds to the same degree in sulfuric acid of proper concentration as in nitric acid. The weights of manganese found were calculated from the sodium oxalate value of the permanganate. The discrepancies between the weights added and the weights found disappear if manganous sulfate is used for the standardization. Determination of Manganese in Iron Ores The oxidation in sulfuric acid solution is particularly adapted to the determination of manganese in iron ores. The following method is both rapid and accurate:
598
I X D CSTRIAL A S D ENGISEERI-YG C H E M I S T R Y
Treat 0.5 to 3 grams of ore in an Erlenmeyer flask with sufficient hydrochloric acid to effect solution. Add 10 cc. of concentrated sulfuric acid and evaporate rapidly over a bare flame t o copious fumes of sulfur trioxide. If the heating is continued until the interior of the flask is clear and the fumes appear only at the mouth, all the chlorides will be removed. If organic matter is present in the ore it may be completely removed by adding a little nitric acid prior to the fuming. This makes a preliminary oxidation with bismuthate unnecessary. After the flask has cooled estimate the amount of acid present and add enough more to bring the volume up t o 6 or 8 cc. Then add 90 to 100 cc. of water and heat to dissolve the sulfates, cool
Vo1. 18, Xo. 6
t o below 50” C., and add a slight excess of sodium bismuthate; 0.5 gram is sufficient for ores containing up to 2 per cent of manganese. Agitate the solution for 1 minute and filter through glass wool and asbestos. Rinse out the flask with several small portions of 3 per cent sulfuric acid and wash the filter until all the permanganic acid has been removed. One hundred to 150 cc. are usually enough wash solution. Water may be used to wash out the permanganic acid, but in this case a larger volume is
required. Transfer the filtrate to a beaker, add a weighed excess of ferrous ammonium sulfate, and titrate with dilute standard permanganate solution.
Calculations for the Regeneration of Nitrating Acids‘ By H. V. Hansen? 959-8CrI”
ST.,BROOKLYS, h-.I‘.
N THE manufacture of nitrocellulose it is the practice to fortifying acids upon the amount of used acid, and none will regenerate the used nitrating acids. The regeneration be given. as usual works practice has shown that in a properly is usually accomplished by mixing a fixed amount of used designed nitrating system the amounts of the fortifying acids acid with two fortifying acids in amounts dependent upon the which readjust the composition of the used acid, for practical composition of the used acid, which has been determined need, also readjust the amount of acid. It is an analytical practice to evaluate the acids involved analytically. The purpose of this paper is to give methods for the calculation of the “butt-up”-the amounts of the for- in the regeneration by their composition-e. g.,the fortifying tifying acids which can regenerate a given amount of used nitric acid as the acid which in 100 kg. contains 60 kg. HN03 and 35 kg. HzS04. The commercial value of this acid is acid. Redpath,3 Clement and RiviBre,4 F ~ w l e r ,and ~ Young6 given thereby, but the value of the acid as an appliance to the have lsresented methods for the calculation of this problem. regeneration of a used acid in a given nitrating system is only s e c o n d a r i l y exNone of these methods or pressed. In this case the modifications thereof have acid must be evaluated by found general use as they Quick, accurate methods are given for calculating the effects it produces upon are laborious to adapt to t h e amounts of two fortifying acids which will rethe composition of the used variation of the composition generate a given a m o u n t of used acid. The methods acid when it is applied unof the fortifying acids. This are easily adjusted t o variations in the composition of d e r s u c h conditions that disadvantage has been elimit h e fortifying acid and altered specification for t h e the used acid is regenerated. n a t e d f r o m the methods nitrating acid. They are simple, and i t is easy t o For t h e nitrating system given herein. give instructions for their use in routine work. A used in the following as an convenient check of t h e calculations practically elimiGeneral Considerations e x a m p l e , the above-mennates erroneous results. tioned fortifying nitric acid The purpose of regenerais evaluated as the acid of tion is to correct the effects which 100 kg., when applied of the nitration upon the nitrating acid, whi‘ch are to decrease the amount of acid and under the conditions for regeneration, produce the -effect of 0.0004 upon the fraction of “ 0 3 and the effect of the fraction of “Os and to increase the fraction of &Sod. I n usual works practice the regeneration is accomplished -0.00025 upon the fraction of &So4 in the used acid. by applying a fortifying nitric acid and a fortifying sulfuric The used acid must be evaluated as an acid acquiring effects for regeneration. acid to the used acid as admixtures. The fortifying nitric upon the fractions of HN03 and acid produces a positive effect upon the fraction of HNO, The specified mixed acid is not involved in the regeneration, in the used acid, a negative effect upon the fraction of &Sod; but is the product of the regeneration. The evaluation of the acids for the regeneration will be used the fortifying sulfuric acid produces opposite effects. It is easily comprehended that inside certain limits any combina- in the following mathematical discussion of the calculations intion of effects upon the fractions of ” 0 3 and HzSO~in the volved in the regeneration. The quantities required in the disused acid can be produced by means of these fortifying acids, cussion, together with their numerical values for the given thus making it possible to adjust the composition of the quantities in the nitrating system used as an example, are given below. used acid. So far no consideration has been given to the effect of the Nomenclature 1 Received July 14, 1925. Revised manuscript received February 18, U , Jl, N, and S denote amounts of used, specified mixed, 1928. fortifying nitric, and fortifying sulfuric acid, respectively. Published with permission of the du Pont Viscoloid Company, with n and s denote fractions of nitric and sulfuric acid, respecwhom the author was previously employed. tively, in the acids referred to by the subscripts. The a Worden, “Nitrocellulose Industry,” 1911, Vol. I, p. 138; “Technology of Cellulose Esters,” Vol. I , Pt. 2,p. 1490. symbols for the effects have been derived similarly. 4 Caoutchouc b gutfa-percha, 9, 6244, 6329 (1912). U (100,000) = kg. charge of used acid 5 J . SOC.Chem. I n d . , 38, 34T (1919); 40, 166T (1921). nu = fraction of HNOa in used acid r l b i d . , 99, 315T (1920).
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