Separation of Cobalt and Nickel from Manganese By Hydrogen Sulfide in a Solution Containing Pyridine and the Pyridine Salt of Hydrochloric Acid' E. A. OSTROUMOV AND G. S. MASLENIKOVA Institute of Economic Mineralogy, Chemical Analytical Laboratory, Moscow3 U. S. S. R.
separation of cobalt and nickel from manganese chloric acid was added ( 5 ml. of hydrochloric acid, specific of gravity 1.19, were diluted with 20 to 28ml. of waterandneutralized often involves considerable difficulties. l-he with pure pyridine, using methyl red as an indicator). Then the this laboratory had occasion to face this when analyzing assolution was heated to boiling, 5 to 10 of a 20 per cent pyridine solution were added, and hydrogen sulfide was passed, with bolane, a mineral containing about 15 per cent of cobalt, 10 shaking, into the hot solution during 10 to 15 minutes. The COper cent of nickel, and 45 per cent of manganese. The usual balt or nickel sulfide precipitated in crystalline form was filtered method of precipitating sulfides of cobalt and nickel in an off and washed with hydrogen sulfide xater containing a few acetic acid medium (1) does not secure a good separation. drops of pyridine. The nickel sulfide was dissolved in nitric Using the method of Hampe the authors failed to secure a acid, and the nickel was determined by means of dimethylcomplete separation of manganese from nickel and cobalt beglyoxime. Cobalt sulfide was gently heated to the oxide which was dissolved in sulfuric acid; the excess of acid was removed on cause of the strongly pronounced adsorptive capacity of hyan electric plate, and cobalt sulfate was carefully ignited in a drated manganese dioxide. Neither did the use of electrolysis double crucible, and Jveighed. tile filtrates from cobalt and give positive results, owing to t'he formation of very large nickel sulfides, manganese vas precipitated as ammonium manganese phosphate and determined as pyrophosphate. amounts of hydrated manganese dioxide. The impossibility of securing a complete separation of coThe presence of pyridine in the solution favors the formabalt and nickel from manganese by the above methods induced tion cf a crystalline precipitate. The results are given in the authors to search for a new method. Table I. I n another (5) a new method has been proposed for the precipitation of cobalt and nickel in the form of sulfides by hydrogen sulfide from a solution containing pyridine. Cobalt and nickel separate as TABLE I. SEPARATIOS OF C O B A L T ASD N I C K E L a crystalline precipitate, easily filtered and --Taken-Found--. Error washed. It would be very desirable to find conditions for the precipitation of these metals under COO Xi0 MnO COO Xi0 hlnO COO Si0 MnO TThich the manganese would quantitatively reGram Gram Gram Gram Gram Gram 0 0508 ,, . , 0 . 0 6 6 0 0.0506 . . . . 0 0635 -0.0002 , .. . -0 0002 main in the solution. From a heated solution o.0608 0.0660 0.0310 0.0660 +o. OOOY 0.0000 . , 0:0529 0.OG55 . . . . 0 : 0 5 i 7 0 0634 ,... 0 ' O h Z -0 0001 containing manganese, hydrogen sulfide in the ., , o . o m 0.0655 . , .. 0 05.6 0 . 0 6 5 2 .... -0.~003 -0 oon3 presence of pyridine causes the formation of a compact gray-green precipitate of manganese sulfide; however, the precipitation does not take Table I indicates that the results obtained are satisfactory. place quantitatively. As a result of numerous experiments Then the authors determined the amount of manganese adthe authors have been convinced that neither pyridine nor sorbed by cobalt and nickel sulfides n-ith varying amounts ammonium chloride in any amount holds manganese comof cobalt, nickel, and manganese. The volumes of the solupletely in solution. tions were about 200 to 300 ml. The procedure remained unh different result is obtained when a pyridine salt of hychanged; the cobalt and nickel sulfides were gently ignited drochloric acid is added to the solution analyzed. I n this in a porcelain dish, the oxides produced were fused with case when the solution is treated with hydrogen sulfide, manpotassium hyposulfate, and the amounts of manganese ganese is not precipitated a t all. The action of the pyridine adsorbed by the residue of sulfides were determined colorisalt of hydrochloric acid may be accounted for in the following metrically v i t h ammonium persulfate and silver nitrate. manner: (1) The pyridine salts, being added to the solution The results are given in Table 11. containing pyridine, lower the pH value of the solution due to its buffer action, thus creating a medium with a too high acidity for manganese sulfide to precipitate. (2) The exTABLE 11. RIAXGASESEADSORBED istence of complex compounds of pyridine with manganese -Takensalts is very probable. It is likely that complex compounds coo Si0 MnO AInO Adsorbed of manganese with pyridine (or the pyridine salt of hydroGram Gram Gram Gram chloric acid) are formed, which, however, are not very stable 0.0005 0 0005 0.1000 0 00003 0 0003 0 0005 0.1000 0 00005 and the existence of which is limited by a definite p H 1-alue 0.1000 0 0005 0 000.5 0 0ono.i of the solution. 0 0050 0.0050 0.0500 0 00004
THE
, .
,
0 0050 0 0050 0 0500 0.0500 0.0500 0.l000 0.1000 0.1000 0.1000 0 1000 0 1000 0.1000 0.1000 0 1000
Experiment a1 For their experiments the authors have used solutions of metal salts, the titer of which was established by the gravimetric method I n the following experiments on the separation of cobalt and nickel from manganese approximately equal amounts of the metals were taken. T o the neutral or weakly acid solution to be analyzed, m t h a volume of about 200 ml., a solution of the pyridine salt of hydro1
Tranelated into English by A
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S. Brashnina. 695
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n 1000
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0.0500 0 0500 0 0500 0 0500 0 nioo 0 00.50 0 0030 0 0o.io 0 0030 ii 000.3 0.0003 0 .0003 0 0003 n 1000 n 1000 0.1000
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o 00003 0 00000 0 00000 0 0 0 0 0 0
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ISDUSTRIAL AXD ENGISEERING CHEMISTRY
696
VOL. 10, NO 12
The method developed by the authors secures a complete separation of cobalt and nickel from manganese with widely varying proportions of the metals. The adsorption of manganese is so insignificant that a complete separation is achieved by one precipitation.
The method may be applied to various products, such as metals, ores, different catalysts used in organic chemical industry, etc.
Notes
The authors have developed a new method for the separation of cobalt and nickel from manganese, based on the fact that from a hot solution containing a pyridine salt of hydrochloric acid and free pyridine, hydrogen sulfide quantitatively precipitates sulfides of cobalt and nickel in a crystalline state, while all the manganese remains in the filtrate. The sorption of manganese by sulfides of cobalt and nickel is so insignificant that with the most variable proportions of the above metals a complete separation may be secured as a result of a single precipitation.
Cobalt and nickel sulfides sometinies adhere to the wall of the flask, forming a lustrous film; to avoid this, the flask or beakers in which the precipitation of sulfides is carried out should be well washed immediately before this operation. In this way the adhesion of sulfides t o the walls of the flask is considerably diminished. If acid solutions are to be dealt with, they are neutralized with a sodium carbonate solution until the appearance of turbidity, which is subsequently eliminated with the aid of a few drops of dilute hydrochloric acid. It is convenient to use the filtrates obtained after the separation of the iron, aluminum, and chromium from nianganese, cobalt, nickel, etc. by pyridine (2, 4, 5 ) . If the volume is not large, the separation may be carried out after the addition of the pyridine salt and heating. The method has been verified in the analysis of samples I and I1 of asbolane. The results of duplicate tests are given: 14 45, 14 38 11 34, 11 30 34 22, 34 30
xio, %
MnO, %
Literature Cited (1) Bassett, H e n r y , “ T h e o r y of Quantitative Analysis and Its Practical Application,” London, George Routledge & Sons, 1925. (2) Ostroumov, E. -4., Ann. chim. anal. chim. appl., 19, No. 4 (1937); 20, N o . 1 (1938). (3) Ostroumov, E. A., ISD. ENG.CHEY.,Anal. Ed., 10, 693 (1938). (4) Ostroumov, E. A , 2. anal. Chem., 106, 170, 243 (1986). (5) Ostroumov, E. -1..Z a v o d s k a y ~Lab., 4, N o . 11 (1935); 6, No. 1 11937)
11
I
coo, %
Summary
0 1 7 . 0.18 6 19 6 18 48 51, 48 60
RECEIVED March 19. 1938.
A New Catalyst for the Determination of Nitrogen by the Kjeldahl Method H . B. BRADSTREET,‘ United States Rubber Products Company, Passaic, N. J.
T
HE use of catalysts as digestion accelerators in the
Kjeldahl method for total nitrogen has long been known. Numerous investigators have suggested the use of mercuric oxide ( d ) , selenium ( I ) , copper selenite IS), mercuric oxide and and various others, alone and in combination selenium (6, The catalyst herein described consists of equal parts of ferrous sulfate and selenium. A search of the literature failed to show that this combination had ever been used. Its practical value has been demonstrated by a large number of determinations, and its effectiveness is of the order of copper sulfate and selenium. TABLE I. ANALYSISOF PFRECOMPOUNDS Digestion Time CuSOa FeSOi Theoretical Nitrogen Nitrogen Found Acetanilide m-~itrodimeth~.laniljne Chloroacetanilide . initrobenzene
g.
%
70
10.3T
10.33 16.71 8.23 16.62
16.70 8.26 16.67
+
+
%
Se .%fin.
Se Xin.
-0.04 -0.04 -0.03 -0.05
26 33 37 28
20 30 30 23
Difference
anhydrous sodium thiosulfate were added, and the mixture was heated gently for 6 minutes. The flame was withdrawn and the flask allowed to cool somewhat before adding 10 grams of potassium sulfate and 0.5 gram of catalyst (equal parts of ferrous sulfate and selenium). Heating was then continued until the mixture cleared. The contents of the flask were given an hour afterboil. A blank determination was made on the materials used, and the necessary correction applied to the calculations. Distillation was carried out in the usual manner.
To ascertain whether any nitrogen was lost during digestion, several pure compounds were analyzed using ferrous sulfate-selenium as a catalyst. At the same time, check runs were made using copper sulfate-selenium, in order to compare digestion times. Sulfuric-salicylic acid was used in every case as a digestion medium. The digestion times shown in Table I are averages based on duplicate analyses. While the differences in digestion times do not appear to be significant, this may be due in part to inequalities of the burners, in spite of the care used in regulating the heating. However, the efficiency is a t least that of copper sulfateselenium, and the results obtained justify the use of ferrous sulfate-selenium as a catalyst for reducing digestion time.
The possibility of the presence of nitro nitrogen in the samples made it necessary to use sulfuric-salicylic acid as a digestion medium. The following procedure was used : The sample was digested in the cold for 15 minutes with 35 cc. of sulfuric acid containing 1 gram of salicylic acid, 5 grams of 1 Present address: Esso Laboratories, Standard Oil Development Company, Linden, K. J.
Literature Cited (2) Poe anc
RECEIVED February 10, 1938.
