Synthesis and Study of Tetrathioarsenates of d10-Metals
I. Didbaridze1, *, M. Rusia2, K. Rukhaia2
1Chemical LAB, Ivane Javakhishvili Tbilisi State University, Tbilisi, Georgia
2Kutaisi Technical University, Kutaisi, Georgia
To cite this article:
I. Didbaridze, M. Rusia, K. Rukhaia. Synthesis and Study of Tetrathioarsenates of d10-Metals. Earth Sciences. Special Issue: Engineering Seismology: An Interface Between Earthquake Science and Practical Engineering. Vol. 4, No. 5-1, 2015, pp. 84-87. doi: 10.11648/j.earth.s.2015040501.25
Abstract: For the first time in hydrochemical conditions tetrathioarsenates of d10-metals by composition Ag3AsS4 and M3(AsS4)2·H2O, where M-Zn, Cd or Hg and X=(Zn) or 2(Cd, Hg), were synthesized. Their composition, constitution, reaction of dehydration and thermal shock resistance in 20-1000 interval were studied by means of thermal analysis, UR-spectroscopy, X-ray crystal determination and derivatographic research.
Among the inorganic compounds of Arsenic (V) d-metals tetraoxoarsenates are well studied [1-8]. Their search was very intensive in last century and now the all methods of their synthesis are developed in detail. This compounds were obtained by hydrochemical, hydrothermal and solid-phase methods. Among this, it is known method of separation of goal-products from alloys in individual condition. But separation-study of all desirable salts by this method is impossible because of their low thermal stability. Therefore, from abovementioned methods hydrochemical method has advantage, because it does not need favorable conditions to be created and moreover it is easy to obtain chemically pure goal-products.
From inorganic compounds of Arsenic (V), as physiologically active compound, metal tetra okcoarsenates have wide application. It concerns both full and alkali salts of transition metals. As for d-metals tetraoxoarsenates with the general (common) formula M3(AsS4)2∙nH2O, almost completely uninvestigated not only because of revelation of physiologic activity, but also chemical point of view. Therefore, the aim of our research is the study of for d-metals tetraoxoarsenates synthesis and characteristics of their physical-chemical properties.
2. Research Methods and Initial Data
An attempt to obtain and research tetrathioarsenates of d10-metals by modern physic-chemical methods has been made. To produce tetrathioarsenates of d10-metals we use hydrochemical method as one of the easiest to be implemented for obtaining final products in individual state. As initial substances there were used water soluble salts of d10-metals and sodium tetrathioarsenate (V) which was obtained in the following reaction :
3Na2S + As2S3 + 2S + 16H2O→2Na3AsS4·8H2O (1)
Based on many experiments it was established that formation of the product for special purpose runs from the following reactions:
a) Na3AsS4 + 3AgNO3 → Ag3AsS4 + 3NaNO3 (2)
b) 2Na3AsS4+3MX2+nH2O→M3(AsS4)2·2nH2O+6NaX (3)
where M=Zn, Cd and Hg; X=CH3COO, NO3; n=4 or 2.
Reactions were carried out in water solution. Mixing the initial compounds the fine crystalline substances were precipitated immediately.
Based on experiments it was established, that with change of succession and mixing intensity final substances of different composition were formed: when in Na3AsS4·8H2O we gradually added water solutions or d10-metal salt, we obtained mixed salts according to the following reaction:
Na3AsS4+3MX2+nH2O → NaMAsS4·nH2O+2NaX (4)
So, to avoid this process, salts of d10-metals were taken on 5-10 % more than theoretical and the reaction was carried out by adding to the latter the solution of sodium tetrathioarsenate (V).
The composition and structure of synthesized products, except for element analysis has been presented by IR-spectroscopy. X-ray crystal determination and derivatographic research. Charge of starting materials and yield of synthesized products are given in Table 1 and the results of thermal analysis are illustrated in table 2, which shows that all compounds, except silver tetratioarsenates (v), contain water of cristalization.
|Charge os starting materials||Yield of Ag3AsS4|
In the IR-spectra of all samples there appeared bands for ≡ As – S band: of deformative in the region 470 cm-1  valency vibration in the region 430 cm-1 . Presence of water of crystallization observed by week band at 1630 2d (H2O) and rather intensive n(OH) – broad – at 3110 cm-1 and 3530 cm-1 region .
According to the X-ray determination (Tab. 3) the obtained fine-crystal monophase substances don’t contain starting materials as admixture. As it was expected, results of X-ray analysis show similarities of the natural sulphosalts to the synthesized products. The calculations show that they crystallize in a rhombic crystal system. Different results by the character of interflatness distance distribution indicate the different regulation degree of mentioned compounds. That should be exposed by the following summary group: for
Ag3AsS4 –-Pcab; Cd3(AsS4)2·2H2O and
Hg3(AsS4)2·2H2O and Hg3(AsS4)2·2H2O -Pmmn.
Chemical behavior of tetrathioarsenates (V) of d10-metals was studied by heating. For example decomposition of Zn3(AsS4)2·4H2O (Fig.2, b) begins with separation of water of crystallization. This process presents on a DTA curve profound endothermic effects of 60-2300 C interval with maximum of 1000 C interval with maximum of 1000 C. At that time, sample mass decreases by 10 %, that corresponds to separation of 4 mole of water (theoretically – 9.4%). In 230-3500C interval sample loses 8.7% of its own mass, that is probably due to separation of 2 mole sulphur. Next mass decrease takes place in 350-7850C interval, that shows separation of
Zn3(AsS4)2·4H2O Zn3(AsS4)2 3ZnS·As2S3
So decomposition of sample can be presented by the following scheme:
The same processes take place in decomposition of silver (I) and cadmium tetrathioarsenate (V). The other process takes place in decomposition of mercuric(II) tetrathioarsenate (V), which at 800 C presents endothermic effect on DTA curve in 80-2200 C interval at maximum 1700C. In this interval sample mass decreases by 4% (theoretically – 3.4%), due to separation of 2 moles of sulphur. In 320-4000 C interval sample loses 38 % of its mass (theoretically – 38.4 %), which corresponds to 2 mole mercury. Above 4000 C entire decomposition takes place:
|I/I0||d, Å||hkl||I/I0||d, Å||hkl||I/I0||d, Å||hkl||I/I0||d, Å||hkl|
|50||4.439||021||70||3.582||022; 003||80||3.542||022; 003||35||3.044||120|
|40||3.645||022; 003||90||3.344||103; 220||60||3.329||013; 122||20||1.953||113; 222|
|50||3.326||013; 122||90||3.136||031||80||3.096||031||15||1.415||431; 403|
|40||2.388||232||90||2.056||420; 332||50||1.74||404; 432|
|30||2.058||420; 332||60||1.89||422; 340|
|a=9,122 Å b=9,944 Å c=10,68 Å||a=9,050 Å b=9,699 Å c=10,746 Å||a=8,992 Å b=9,632 Å c=10,704 Å||a=7,628 Å b=6,644 Å c=6,372 Å|
Hg3(AsS4)2·2H2O Hg3(AsS4)2 Hg3As2S6 Hg3As2S6full decomposition.
Synthesis of tetrathioarsenate (V), of silver (I). In dilute solution of 3.94 g silver nitrate interacted with 3.00 g of sodium tetrathioarsenate (V) dissolved in 20 ml of water. Black compound precipitated immediately. Next day precipitations were filtered, washed by water and dried by P2O5 in vacuum desiccator to the constant mass. In the same way other tetrathioarsenate (V) were obtained. From the synthesized product tetrathioarsenate (V) of silver (I) and mercury (II) are black substances, zinc is yellow, and cadmium is dark yellow. All the compounds are insoluble in alkalis except zinc tetrathioarsenate (V) and elaborated by acid (HCl, H2SO4) they change arsenic (V) pentasulphide.
As a result of our research, there was established, that d-metals (II) tetra thioarsenates can be easily obtained using hydrochamical method, if the metals soluble salts can be taken for reaction ~10% more, in comparison with theoretical. All synthesized compounds, except silver(I) tetrathioarsenates are crystal hydrates with clearly defined individuality, that is proved not only by results of chemical analysis bus also by the physical-chemical research methods. Synthesized small-crystalline substances are solid compounds with different tints. They are not insoluble in water, alcohol and in other organic solvent. During alkali treatment they are transformed by formation of Arsenic(V) sulphide. Experiment shows that this compound practically don’t react with alkali except copper (II) tetrathioarsenate, which gradually dissolves in much alkali at high temperature.