Tutton\u27s salts, (NH4hM(S04h\u27 6H20, in which M represents one, two or three different metal ions in the structure have been obtained previously. Because of similar properties of the transition . elements we started to study the system (NH4hS04-H20-MS04 (M= Mn, Fe, Co, Ni, Cu, Zn or mixtures of these elements) and we isolated the crystals (NH4hM(S04)2. 6H20 where M represents mixtures of Ni, Zn; Co, Ni, Zn; Co, Ni, Cu, Zn; Fe, Co, Ni, Cu, Zn; Mn, Fe, Co, Ni, Cu, Zn. The products were characterized by chemical analysis. X-ray powder photographs of the products confirmed that they have structures similar to those of other Tutton\u27s salts. The thermal decomposition of the salts was studied in air and in an argon atmosphere and the final products were identified by X-ray powder photographs

A. Rahten

D. Gantar

J. Slivnik

English

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CROATICA CHEMICA ACTACCA-1581CCACAA 58 (3) 289-294 (1985)YU ISSN 0011-1643UDC 548.312.6Original Scientific PaperStudy of Tutton's Sa1ts (NH4)lM(S04)1· 6H10 with Mixed MetalIons in the StructureJ. Slivnik*, A. Rahten, and D. Gantar»Jožef Stefan« Institute, P.O.B. 199, 61001 Ljubljana, YugoslaviaReceived .Tanuary 28, 1985Tutton's salts, (NH4hM(S04h' 6H20, in which M representsone, two or three different metal ions in the structure have beenobtained previously. Because of similar properties of the transition .elements we started to study the system (NH4hS04-H20-MS04(M= Mn, Fe, Co, Ni, Cu, Zn or mixtures of these elements) andwe isolated the crystals (NH4hM(S04)2. 6H20 where M representsmixtures of Ni, Zn; Co, Ni, Zn; Co, Ni, Cu, Zn; Fe, Co, Ni, Cu,Zn; Mn, Fe, Co, Ni, Cu, Zn. The products were characterized bychemical analysis. X-ray powder photographs of the productsconfirmed that they have structures similar to those of otherTutton's salts. The thermal decomposition of the salts was studiedin air and in an argon atmosphere and the final products wereidentified by X-ray powder photographs,INTRODUCTIONThe hydrated double sulphates (Tutton's salts), (NH1)2M(S04h'6H20, whereM is Mn or a transition element, were widely investigated in the sixtiesl-6•The structures of the compounds were established by X-ray diffraction ana-lysis which showed that the general packing of the ions and the hydrogenbonded network is essentially identical in all Tutton's salts. The central metalion is surround ed by six water molecules and each water molecule forms twohydrogen bonds. These range in length from 2.72 to 2.82 A. The ammoniumion is also hydrogen-bonded to the oxygen atoms of the sulphate groups;three are normal but one is bifurcated.Soviet workers have studied the solubility of two or three differentTutton's salts and determined the equilibria between aqueous and solid solut-ions/-". In our laboratory Tutton's salts with two to six different metal ionswere prepared and investigated.RESULTS AND DISCUSSIONAqueous solutions of mixed metal sulphates in equi-molar ratios togetherwith ammonium sulphate (50% excess) were mixed and crystals of the for-mula (NH4)2M(S04h. 6H20 were isolated, where M = Ni, Zn; Co, Ni, Zn; Co,Ni, Cu, Zn; Fe, Co, Ni, Cu, Zn; or Mn, Fe, Co, Ni, Cu, Zn. The chemicalanalyses are given in Table I and shows the fraction of the metal ions whichcrystalized when the solids were harvested.* Died in 1983.r290 J. SLIVNIK ET AL.TABLE IChemical Analysis of (NH4hM(S04h . 6H20*..• OQ) o Z ;:s I:: O ~~ ~ U N ens -:. '" '" ~;;-- ;;-- ;;-- '" ;;--M = Ni, Zn 9.0 8.7 6.2 49.3 26.8M = Co, Ni, Zn 9.1 2.7 6.9 4.7 49.7 26.9M = CO, Ni, Cu, Zn 9.0 2.4 6.1 1.9 4.2 49.3 27.1M = Fe, Co, Ni, Cu, Zn 9.1 0.87 2.2 5.9 1.6 3.7 49.3 27.3M = Mn, Fe, Co, Ni, Cu, Zn 9.1 0.32 0.72 2.1 5.8 1.5 3.5 49.4 27.6*H20 is calculated as a difference to 100.On the basis of chemical analysis the mol ar ratios of the componentswere calculated and are given in Table II.TABLE IICalculated Molar Ratio of NH4: M : S04 : H20 (M = 1)(NH4hM(804h . 6H20 NH4 Mn Fe Co Ni Cu Zn 804 H20M = Ni, Zn 2.05 0.61 0.39 2.11 6.12M = Co, Ni, Zn 2.14 0.20 0.50 0.30 2.19 6.32M = Co, Ni, Cu, Zn 2.08 0.17 0.44 0.12 0.27 2.15 6.30M = Fe, Co, Ni, Cu, Zn 2.14 0.06 0.16 0.43 0.11 0.24 2.17 6.44M = Mn, Fe, Co, Ni,Cu, Zn 2.19 0.03 0.06 0.15 0.43 0.10 0.23 2.23 6.67In the syntheses described, incorporation of a new metal ion in thestructure inevitably changes the mol ar ratio of the metals, but the ratiobetween any two metals is nearly constant (deviations can be attributed toanalytical error).The X-ray powder photographs of the compounds isolated are identical.It is evident that one metal can be replaced by another without significanteffect on the structure.Thermal decomposition studies show that decomposition occurs in thesame way irrespective of the number of metals in the structure. The de-compositions were investigated in an inert argon atmosphere and in air. Cha-racteristic TG, DTG and DTA curves of (NH4hM(S04h'6H20 (M = Mn, Fe,Co, Ni, Cu, Zn) are shown in Figures 1 and 2.Thermal decomposition of (NH4hM(S04h' 6H20 in an argon atmosphere(Figure 1) begins at 25 "C. In the first step the sample loses 26.0% of itsweight, which corresponds to the loss of water. This step is accompanied bya strong DTA endothermic effect at 165°C and DTG effect at the same tem-perature. In the temperature interval between 220 and 500°C a further34.4010 weight loss occurs, corresponding to formation of metal sulphates. TheDTA curve exhibits two exothermic peaks at 270 and 350°C and two endo-thermic peaks at 410 and 454°C. In this temperature region ammonium sul-o20~*~tIl 40tIlo~+-'-<=o">• .-< 60'"380TUTTON'S SALTS 291DTGr------...... ,-----', r--V-" I ,,(\ I -6H20 \ I \ :, \ I \ I \ II I J \ I\ I I \ I \J'\1'\ I I \ I\ I I ti ''\ I -(NH4)ZS04. \ I v\ \ I .' \ -------\ V I II .".j \ I '"\\ ! \i \I \I .,I . I'I \. i\ I \;, I\ I\ I\ .. I\ ..J Ir>; '-/. '-. ...•., ---TGMOOTA T OTG10}V .!. 0,5 mg/mino 200 400 600 800 1000T (DC)Figure 1. TG, DTG and DTA curves of (NH4)2M(S04h' 6H20 (M= Mn, Fe, Co, Ni,Cu, Zn)Atmosphere: argon - 5 l/hSample weight: 100,00mgCrucible: ptHeating rate: 8DC/minTG range: 100mgDTG range: 20 mg/minDTA range: 200 ~\VRef. substance: a-A1203phate is decomposedv-P. The exothermic peaks can be explained by partialoxidation of certain metals (Mn, Fe).In the last step between 500 and 900 DC the sample loses 19.6010 of itsweight and the total weight loss for the three steps is 80.0010. The decompositionof metal sulphates is accompanied by an endothermic DTA peak and a DTGminimum at 850 DC. Thermal decomposition can be described in terms of theequations:200°C5000C(NH4hM(S04h ) MS04 + 2NH3+ H20 + S03890°CMS04 ) MO + S02 +1/202Thermal decomposition in an atmosphere of air (Figure 2) is differentfrom that in the second step. In the first step the sample loses 26.3010 of itsweight. In the temperature interval between 215 and 500 DC, where a further32.8% weight-loss occurs, a mixture of metal sulphates is formed; however,292O20~.....'-" 40v>v>o.--<+-' 60 --'=o">'~'"380J. SLIVNIK ET AL.DTG'./'\ I"'" .•.••- "" ,/ - - - - - - - -... \ (\ ( -6 H 2 O \ I \ I\ I \ I \ I\ I ,( \ I\ \, \ I \J~\ (" \("' \ I !\.r> \. -(NH4)2S04\ \ ( .t \j \ yI --------. \ I ,IV \~. V v. -. _\ V .'i !· I\ .· I\ .· I\ .· I\ '. I\ .\J<,<,<, TG<, -, MO\M203\ M304DTA T DTG\10 yV 1. 0,5 mg/min f\\j \\,, DTAO 200 400 600 800 1000Figure 2. TG, DTG and DTA curves of (NH4hM(S04h . 6H20 (M = Mn, Fe, Co, Ni,Cu, Zn)Atmosphere: air - 5 I/hSample weight: 100,00mgCrucible: PtHeating rate: 8°C/minTG range: 100 mgDTG range: 20 mg/minDTA range: 200 !-tVRef. substance: a-A1203Fe2+ and Mn2+ are oxidized to their higher valences.l1-14 The DTA curveexhibits exothermic effects at 260, 331 and 432 -c and the minimum of theDTG curve is at 420 "C. Between 500 and 925 -c the sample loses 21.0 ofits weight and this step is accompanied by peaks in the DTA and DTG curvesat 883 "C, The observed total weight loss for the three steps of decompositionis 80.1010 and the final product is a solid solution of metal(2+) and (3+) oxides.Thermal decomposition is described in terms of the equations:21500(NH4hM(S04h . 6H20-----'» (NH4hM(S04h + 6H2050000(NH2hM(S04)2 ) MS04 + 2NH3+ S03 + H20M2(S04laMS04 MOM2(S04la----+) Fe20s + S02 + 1/202Mn304In thermal decomposition studies of (NR4hM(S04h' 6R20 in argon andin air atmospheres the DTG and TG curves show completion of the decom-92500TUTTON'S SALTS 293position at 900-950 -c, whereas the DTA curve does not stabilize even at1000°C. This can be explained by the phase changes which occur in the com-pound during the heating process.The study of the synthesis of (NH4hM(S04h· 6H20 with mixed metalsprovides evidence that several metals can be incorporated into the structureat the same time. The X-ray diffraction patterns show that the salts are solidsolutions with structures similar to those of Tutton's salts. The X-ray powderphotographs of all starting materials were recorded and compared with thoseof solids solutions. Their d spacings are distinctly different from d spacingsof isolated Tutton's salts.Studies on Tutton's salts containing mixed metals in ratios which, onthermal decomposition, yield solid solutions suitable for the preparation offerrites are in progress.EXPERIMENTALSt art i n 9 mat eri a I s: The same volumes of 1 M solutions of metalsulphates and a 50% excess of 1 M solution of (NH4hS04 were mixed and themixture was acidified with sulphuric acid to prevent hydrolysis. After isothermalevaporation, crystals appeared. They were separated from solution after threehours and dried in air.C h e m i c ala n a I y s i s: Ammonium was determined by a direct method!".A solution of the ammonium salt was treated with a solution of sodium hydroxideand the mixture distilled. Ammonia was quantitatively expelled and was absorbedin an excess of standard acid. The excess of acid was back-titrated in the presenceof methyl red.The sulphate ion was determined by an indirect complexometric trtration-" afteraddition of concentrated ammonia solution and a buffer solution (pH 10) usingEriochrome Black T as indicator.Metals were determined by the atomic absorption spectroscopy'? in the flamesair-acetylene (Zn) and N20-acetylene (Mn, Fe, Co, Ni, Cu) on a Varian AA5Instrument.The solids were transferred to Pyrex capillaries and X-ray powder photo-graphs were taken with a Debye-Scherrer type camera and CuKa or FeKa radiation.Thermal analysis was studied on a Mettler TA 1 Thermoanalyzer.Acknowledgement. - We are indebted to Miss B. Sedej and Mrs. M. Špenkofor chemical analysis. The work was financed through the Research Communityof Slovenia.REFERENCE S1. H. M o n t g o m e r y and E. C. L i n gaf e 1ter, Acta Cryst. 17 (1964) 1295.2. H. M o n t g o m e r y ibid. 17 (1964) 1478.3. H. M o n t g o m e r y and E. C. L i n gaf e lt e r, ibid., 20 (1966) 659.4. H. M o n t g o m e r y and E. C. L i n gaf e 1ter, ibid., 20 (1966) 728.5. H. M o n t g o m e r y, R. V. C h a s t a i n, J. J. Na t t, A. M. W i tko w-s k a, and E. C. L i n gaf e 1ter, ibid., 22 (1967) 775.6 H. M o n t g o m e r y, R. V. C h a s t a i n, and E. C. L i n gaf e 1ter, ibid.,20 (1966) 731.7. 1. V. Iva n ova, M. 1. O z e r ova, Ž. Neorg. Him. 8 (1964) 1983.8. R. A. Ave r i n a, V. G. Š e v čuk, Ž. Neorg. Him. 1 (1968) 267.9. R. K i you r a and K. Ura n o, Ind. Eng. Chem. Process. Des. Develop. 9 (4)(1970) 489.10. W. D. HaI ste a d, J. AppL Chem. 20 (1970) 129.11. M. S. R. S w amy, T. P. Pra sad, and B. R. S a n t, J. Therm. AnaL 15(1979) 307.12. A. B r i s t o t i, J. 1. K u n na t h, and P. J. Vic car o, J. Inorg. NucL Chem.37 (1975) 1149.13. A. H. Ka m e l, A. M. A b d u Il ah, J. AppL Chem. BiotechnoL 22 (1972) 599.294 3". SLIVNIK ET AL.14. J. S 1 i V n i k and A. R a h t e n, unpublished work.15. A. I. Vo g e 1, A Textbook of Quantitative Inorg. AnaL, Longmans, London,1961.16. G. Seh war zen b a c h and H. F 1ase h k a, Complexometric Titrations, Me-thuen, London, 1969.17. Analytical Methods for Flame Spectroscopy, Varian Techtron, Australia, 1972.POVZETEKTuttonove soliJ. Slivnik, A. Rahten in D. GantarTuttonove soli (NH4)2M(S04h' 6H20, kjer M predstavlja enega, dva ali trirazlične kovinske ione v strukturi, so bile že izolirane. Z ozirom na podobne last-nosti elementov prehoda smo začeli raziskovati sistem (NH4hS04-H20-MS04(M = Mn, Fe, Co, Ni, Cu, Zn in zmesi teh elementov). Izolirali smo kristale(NH4)2M(S04)2. 6H20, kjer M predstavlja zmes Ni, Zn; Co, Ni, Zn; Co, Ni, Cu, Zn;Fe, Co, Ni, Cu, Zn ali Mn, Fe, Co, Ni, Cu, Zn. Produkte smo karakterizirali s kemij-sko analizo. Rentgenski praškovni posnetki spojin so potrdili, da imajo le-te struk-turo podobno Tuttonovim solem. Studirali smo tudi termične razkroje spojin v atmo-sferi zraka in argona in končne produkte opredelili z rentgenskimi praškovnimiposnetki.

Study of Tutton\u27s Salts (NH4)M(SO4)2 · 6H2O with Mixed Metal Ions in the Structure

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