Grasselly, Gyula

English

Grasselly Gyula

University of Szeged

ANALYTICAL METHODS OF MANGANESE ORES III. Contribution to the determination of N a 2 0 and K 2 0 in manganese ores by G Y . GRASSELLY József A t t i l a Univers i ty , Ins t i tu te fo r Minera logy a n d P e t r o g r a p h y The determination of alkali content may be of interest and necessary, whether natural manganese ores or artificial oxides are studied. On the one hand, various natural manganese compounds may contain alkali metals, such as potassium contained in cryptomelane, but alkali metals as adsorbed cations may be contained in various manganoxihydrates, particularly in those preci-pitated in colloidal state. On the other hand, alkali, especially potassium, may be present in various artificial manganese dioxides in dependence on the pro-duction technique adopted. In rap id methods of silicate analysis the a lkal i content is usually de te rmined by f l ame-pho tome t ry . L. SHAPIRO and W . W. BRANNOCK [1956] de te rmined the a lka l i metals w i t h o u t p re l iminary separa t ion , using l i th ium sulphate as in te rna l s t anda rd . J . P . RILEY [1958] removed the in te r fe r ing Fe, Al, Ti ions by means of an anion exchanger Amber l i t e I R A — 4 0 0 in its c i t ra te f o rm , where a m m o n i u m sulphate was added as b u f f e r to bo th the sample solutions a n d the s t a n d a r d solutions. In the book of selected papers compi led by A. A. SMALES and L. R. WAGER [1960], E. A. VINCENT has proposed separa t ion of in te r fe r ing ions by a m m o n i u m h y d r o x i d e and a m m o n i u m carbona te . This me thod was app l i ed by M. WEIBEL {[1961], too, in his r ap id process of rock analysis. In view of the rather ample choice of methods available the only question we faced concerned the choice of the basic approach which would yield reliable results in a comparatively simple way in the analysis of manganese ores, i.e. in presence of considerable amounts of manganese. E X P E R I M E N T A L The determinations were carried out by means of Zeiss Flammenphoto-meter Modell III „A". Comparing the different methods for determination of N a 2 0 and K 2 0 , we found simple and, at the same time, reliable, the method proposed by V I N C E N T and W E I B E L . Slightly modified (chiefly as far as the attacking and, in certain respect, the measuring techniques are concerned), it yields accurate results even at considerable manganese, contents, as demonstrated; by the analyses to be shown later in this paper. 13 I . D i s s o l u t i o n of t h e s a m p l e 1. 0,5 g of finely powdered manganese ore is weighed into a 250 ml beaker, 25 ml of 1:1 hydrochloric acid and a few drops of 30% hydrogen hyperoxide is added to the sample. The beaker is covered and slightly heated over a water bath. If after the cessation of effervescence some undissolved brownish-blackish grains are still visible at the bottom of the beaker, a few drops of hydrogen hyperoxide are added to the solution. 2. As the sample is completely dissolved and dark grains are no longer visible at the bottom of the beaker, the solution is brought to boil, and after a few minutes of boiling it is thoroughly washed into a platinum dish of suitable size, together with the possible insoluble residue. Afterwards, it is almost comp-letely evaporated on a water bath. 3. 1 ml of 60°/o perchloric acid and 15 ml of 40% hydrofluoric acid is poured into the platinum dish (to dissolve the insoluble, silicate-bearing residue) and the hydrofluoric acid is expelled over a water bath. In case of considerable amounts of insoluble residue this latter operation is repeated by adding 15 ml of hydrofluoric acid. 4. After the removal of hydrofluoric acid the residue is moistened merely by perchloric acid. The platinum dish is put on a sand bath and most of per-chloric acid is removed by careful heating. Once it is done, the dish is taken off from the sand bath, but do not allow to become completely dry. J. After the second removal of perchloric acid, 1 ml of perchloric acid is poured into the platinum dish and some hot water is added to it, in order to dissolve the residue. Complete dissolution of the residue is achieved by washing thoroughly the contents of the platinum dish into a 100 ml beaker repeating this operation several times, taking care that, the volume of the solution should not exceed 60—70 ml. The solution is then boiled for a short time. 6. After cooling the solution is transferred into a 100-ml graduated flask and filled up to the mark with ion-free water. The alkali content is determined in aliquot parts taken from this solution by flame photometry. The volume of the aliquot parts taken depends on the alkali content to be expected. I I . R e a g e n t s a n d s o l u t i o n s 1. Stock solutions A. Stock solution of NaCl: 0,9430 g of NaCl dried at 105 °C and 0,7920 g of KC1 dried at 105 °C are weighed. Having been dissolved, they are poured into a calibrated 1000 ml measuring flask filled up to the mark with ion-free water: 1 ml of solution = 0,5 mg N a 2 0 + 0,5 mg K 2 0 . The solution is stored in a plastic vessel. B. Ammoniacal-ammonium carbonate solution: 2 g of ammonium carbo-nate is dissolved in 100 ml of ammonium hydroxide diluted 1 : 9. Each time a fresh solution has to be prepared. C. Blank test solution. Cj. Concentrated: 1 ml of perchloric acid is poured.into a 100 ml measur-ing flask and diluted by ion-free water up to the mark. 14 . C2. Diluted: 10 ml of concentrated blank test solution f C J ( = 0,1 ml of perchloric acid) is brought into a 100 ml measuring flask, diluted by water to 50—60 ml, added to it 5 ml of ammoniacal ammonium carbonate solution (B} and filled up with ion-free water up to the mark. 2. Preparation of the standard solutions a) 1, 2, 4, 6, 8, 10 ml volumes of stock solution A are successively intro-duced into 100 ml graduated flasks (0,5, 1, 2, 3, 4, 5 mg N a 2 0 and K 2 0 , re-spectively). b) 10 ml of concentrated blank test solution (C,) is poured into each flask,, being diluted to 50—60 ml. c) The flasks are charged with 5 ml of ammonia-ammonium carbonate solution each, shaken up, and filled up to the mark with ion-free water. After-wards, they are thoroughly shaken up once more, and the solution with preci-pitate is poured over into a plastic bottle (dry) provided with a well-sealing, cover, where it is let stay for one day. I I I . D e t e r m i n a t i o n of N a , 0 a n d K 2 0 1. Volumes corresponding to the alkali content expected are taken with a. pipette or burette from 100-ml sample stock solution obtained following the: attack, and each is poured-into a 100 ml measuring flask. Since in the above standard N a + K solution series the extreme values of the alkali concentration are 0,5 mg/100 ml and 5,00 mg/100 ml N a 2 0 or K 20, . respectively, it is advisable to take such aliquot parts from the stock solution that their alkali content should fall within these two limits. . 2. To the aliquot parts of stock solution poured into the flask and filled up to 50—60 ml with water add 5 ml of ammoniacal ammonium carbonate solution, mixed well, and filled up to the mark with ion-free water, then after repeated mixing the solution with the precipitate is poured over into a dry plastic bottle provided with a well-sealing cover, where it is let stay for one day, just as was the case with the standard solutions. 3. Using N a filter, the members of the standard solution and afterwards the sample solutions are atomized, one by one, into the flame. The atomization of the standard solutions and of the sample solutions is repeated alternately a t least three times. In the further course of the analytical process the mean values; of galvanometer readings are taken and then plotted. After the atomization of the individual samples it is the diluted blank test solution (C2J that will be atomized and the values of the corresponding: readings are discounted from those of both the calibrational series and the samples analysed. From the plastic bottle the clear solution above the precipitate is atomized. The precipitate itself need not be filtrated previously, we must merely take care that the precipitate should not be stirred up to avoid precipitate particles: entering the atomizer. 4. After the determination of N a 2 0 , filter K is introduced and the K 2 0 content is determined in just the same way as previously and galvanometer readings proportional to K concentrations are taken. IS 5. The readings obtained for the members of the standard series are plotted un form of a calibration curve. Superimposing on the latter the galvanometer readings of the individual samples, we can determine the N a a O and/or K a O •content. I V . P r e c i s i o n a n d a c c u r a c y of d e t e r m i n a t i o n Following the above-outlined working process, we made first parallel de-terminations of the alkali content of a granite sample, then having attacked the same rock sample in one and the same way and having prepared the stock ^solution, we added different amounts of manganese td the solution to be atom-ized, before filling it up, and we performed the determination of the alkali content of this solution, too. The results are shown in Table 1. T A B L E 1. N a > 0 a n d K s O conten t s of a s t a n d a r d rock sample as o b t a i n e d b y pa ra l l e l measurement s of the o r ig ina l sample a n d as d e t e r m i n e d in presence of d i f f e r e n t a m o u n t s of manganese N a a O % as de te rmined K 2 O «/a as d e t e r m i n e d in the or ig inal sample in the same, bu t in' presence of M n in the or iginal sample in the same, bu t in presence of M n M n a d d e d m g / 1 0 0 ml 4,00 4,00 3,99 3,99 3,92 3,92 3,98 3,98 3,82 4,17 3,82 3,90 4,00 4,00 4,00 4,00 4,00 3,98 3,98 3,84 3,84 3,84 3,84 3,82 3.79 3.80 3,90 3 ,90 ' 3,92 3,90 3,89 3,86 3,85 3,40 3,40 3,40 3,40 3,40 3,40 3,56 3,56 3,52 3,48 3,47 3,40 3,54 3,54 3,52 3,52 3,50 3,60 3,60 3.51 3.52 3.51 3,55 3.52 3,55 3,48 3,38 3,45 3,40 3.45 3.46 3,45 3,45 0,53 1,07 2,14 5,35 10,71 21,42 42,84 x = 3,9 50/o s = + 0 , 0 8 2 2 J ? = 0 , 0 2 3 7 C = 2 , 0 8 £ = 0,60 x = 3,90°/o s= + 0 , 0 7 4 3 $« = 0,0162 C = 1,90 £ = 0,41 x = 3,443/o s = + 0 , 0 6 6 6 J* = 0,0164 C = 1,93 £ = 0,559 jc = 3,50°/o s= + 0 , 0 5 6 7 ; ; = 0 ,0123 C = 1,62 £ = - 0 , 3 5 3 The terminology of the parameters characterizing the accuracy of deter-mination is the same as that applied in the author's first paper on manganese •ore analysis [GRASSELLY, 1 9 6 2 ] , viz.: x = mean; 5 = standard deviation; s - = standard error; C — relative deviation, and E = relative error. In one of their paper F A I R B A I R N et al. [1951] have dealt with the precision and accuracy of different methods of rock analysis, relying on analyses from various laboratories. A similar comparative study of 16 parallel silicate analyses is reported by G . C S A J A G H Y [ 1 9 5 9 ] . Here we have used only the data concern-ing alkali content in the references quoted. A comparison of F A I R B A I R N ' S and CSAJAGHY'S data concerning the accuracy of alkali determinations to those •obtained by us in presence of considerable amounts of manganese indicates that the present analytical process provides reliable, accurate results even at high .manganese contents and that it can certainly be applied successfully for the determination of the alkali content of manganese ores. 16 T A B L E 2 Precision of the de t e rmina t ion of Na-^O a n d K » 0 I n r o c k s In rocks in presence of manganese a s c h e c k e d b y t h e d a t a o f F A I R B A I R N C S A J Á G H Y the au thor N a s O N a s O K Î O K2O N a î O KÜO X 3,26 5,51 3,21 4,42 3,90 3,50 i 0,284 0,549 0,173 0,218 0,082 0,056 ST 0,06 0,11 0,043 0,054 0,016 0,012 C 8,71 9,96 5,39 4,93 1,90 1,62 E 1,81 2,07 1,35 1,23 0,41 0,35 C O N C L U S I O N S Manganese ores can be advan tageous ly analysed fo r N a 2 0 and K » 0 by using, w i th slight modi f i ca t ion , the me thod proposed by VINCENT and WEIBEL which essentially consists in separa t ing the in te r fe r ing ions by ammoniaca l a m m o n i u m ca rbona te solution and de termin-ing subsequent ly the a lkal i content by f l a m e p h o t o m e t r y di rect ly f r o m the solution wi thou t f i l te r ing the prec ip i ta te . The manganese ores (ei ther oxides or carbonates) are dissolved by hydrochlor ic acid add ing to it a f e w d rops of hydrogen hyperox ide or , p rov ided some insoluble silicate residue is present , the a t t ack by hydroch lo r i c acid is fo l lowed by an a t tack by h y d r o f l u o r i c acid — perchlor ic acid. T h e present ana ly t ica l process yields accura te results even in presence of considerable amoun t s of manganese . A n d since the de te rmina t ion of the alkal i con ten t does not require to r emove the d is turb ing ions by means of exchangers or to f i l ter the prec ip i ta te , it can be p e r f o r m e d in a simple w a y a n d re la t ive ly quickly , if only the ac tua l ly necessary opera t ions are considered (in f ac t , the prec ip i ta te is let s tay fo r a n igh t ) . In case of serial measurements , on one d a y the dissolution of the samples and the p r e p a r a t i o n of the solutions are p e r f o r m e d , and on the fo l lowing d a y we m a y proceed to measure the alkal i content of the solutions p repa red the d a y before . The author is greatly indebted to Miss M. BARANYI , his assistant in labo-ratory, whose thorough performing of the serial measurements is highly app-reciated. R E F E R E N C E S •CSAJÁGHY, G. [1959]: Szi l ikátelemzéseink megbízha tósága . — Ann . R e p o r t of the H u n g . Geol . Inst , of 1955 and 1956. pp . 21—28. "FAIRBAIRN, H . W . , S C H L E C H T , W . G . , STEVENS, R . E . , D E N N E N , W . H . , A H R E N S , L . H . , CHAYES, F . [1951]: A Coope ra t i ve Inves t iga t ion of Precis ion and Accuracy in Chemical , Spect rochemical and Moda l Analysis of Silicate Rocks. — U . S. Geol . Survey Bull. 980. GRASSELLY, GY. [1962]: Ana ly t ica l Me thods of Manganese Ores I. — Acta Miner . Pe t r . U n i v . Szegediensis, T o m . XV. pp . 7—18. TULEY, J . P . [1958]: T h e R a p i d Analysis of Silicate Rocks and Minerals . — Ana l . Ch im. Ac ta . 19. pp . 413—428. SHAPIRO, LEONARD, BRANNOCK, W. W. [1956]: R a p i d Analysis of Silicate Rocks. — U. S. Geol . Survey Bull. 1036—C. pp . 19—56. SMALES, A. A., WAGER, L. R . [ I960] : Me thods in Geochemis t ry . Interscience Publishers , L o n -don, C h a p t e r 3. VINCENT, E. A. : Analysis by Grav ime t r i c and Volumetr ic Methods . F l ame pho tome t ry , Co lo r ime t ry and Re la ted Techniques, p p . 33—80. WEIBEL, M. [1961]: Die Schnel lmethoden der Gesteinsanalyse. — Schweiz. Miner . Pe t r . Mi t t . 41. pp . 285—294. 2 ACTA MINERALOGICA—PETROGRAPHICA 17 

Analytical methods of manganese ores : III. : Contribution to the determination of NA2O and K2O in manganese ores

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Analytical methods of manganese ores : III. : Contribution to the determination of NA2O and K2O in manganese ores

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