Earth Sciences
Volume 4, Issue 5-1, September 2015, Pages: 84-87

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

Email address:

(M. Rusia)

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.

Keywords: Tetrathioarsenate, IR-spectra, X-ray Crystal Determination


1. Introduction

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 [1]:

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.

Table 1. Charge of starting materials and yield of synthesized products

  Charge os starting materials Yield of Ag3AsS4
Na3AsS4·8H2O MX2·H2O and M3(AsS4)2·nH2O
g mole M X Y g mole n g mole %
1 3000 0.0072 Ag NO3 - 3.94 0.0232 - 3.88 0.0067 98.45
2 3000 0.0072 Zn CH3COO 2 2.50 0.0114 4 2.43 0.0036 94.34
3 3000 0.0072 Cd CH3COO 2 3.05 0.0115 2 2.81 0.0036 93.67
4 3000 0.0027 Hg NO3 1 3.93 0.0115 2 3.63 0.0036 95.56

Table 2. Results of chemical analysis

Found, % Compound Calculated
M As S H2O M As S H2O
61.36 14.29 24.35 - Ag3AsS4 61.48 14.23 24.29 -
29.028 22.13 37.75 10.84 Zn3(AsS4)2·4H2O 29.11 22.25 37.96 10.68
43.42 19.08 32.58 42.92 Cd3(AsS4)2·2H2O 43.28 19.25 32.85 4.62
57.22 14.66 25.04 3.08 Hg3(AsS4)2·2H2O 57.65 14.37 24.53 3.45

In the IR-spectra of all samples there appeared bands for As – S band: of deformative in the region 470 cm-1 [2] valency vibration in the region 430 cm-1 [3]. 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 [3].

Figure 1. IR spectra of synthesized compounds:Ag3As3(a);Zn3(AsS4)∙4H2O (b); Cd3(AsS4)@∙2H2O (c); Hg3(AsS4)2∙2H2O

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

Zn3(AsS4)2·4H2O-Pbnm;

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:

Table 3. Experimental x-ray diffraction parameters for synthesized products

Ag3AsS4 Zn3(AsS4)2·4H2O Cd3(AsS4)2·2H2O Hg3(AsS4)2·2H2O
I/I0 d, Å hkl I/I0 d, Å hkl I/I0 d, Å hkl I/I0 d, Å hkl
20 7.50 011 30 7.68 011 20 5.644 111 20 7.628 100
20 6.67 110 20 6.65 110 20 5.352 002 10 4.457 011
25 5.717 111 15 5.91 111 30 4.811 020 20 3.814 200; 111
30 5.340 002 50 4.44 102 50 4.496 200 100 3.351 210
90 4.972 020 30 4.23 120 40 3.972 121 95 3.322 020
100 4.561 200 30 4.00 121 30 3.779 211 40 3.186 002
50 4.439 021 70 3.582 022; 003 80 3.542 022; 003 35 3.044 120
100 4.320 120 80 3.458 202 80 3.461 202 40 2.921 211; 021
100 4.065 210; 121 90 3.363 013 80 3.366 103 65 2.095 103
40 3.645 022; 003 90 3.344 103; 220 60 3.329 013; 122 20 1.953 113; 222
40 3.515 202 80 3.186 212 100 3.186 212; 220 50 1.753 411
30 3.427 103 100 3.162 221 80 3.132 221 15 1.446 430
50 3.326 013; 122 90 3.136 031 80 3.096 031 15 1.415 431; 403
50 3.271 212; 221 35 2.936 301 25 2.931 130 20 1.366 341
30 3.157 031 35 2.758 311; 123 25 2.850 310 20 1.330 050
30 3.038 300; 130 35 2.678 302 40 2.429 223      
40 2.865 301 30 2.50 321 50 2.058 224; 323      
60 2.831 311 20 2.28 322; 141 40 1.933        
60 2.614 302 35 2.22 330 40 1.898 403; 422      
100 2.574 320 20 2.14 331 50 1.877 340      
50 2.415 223 75 2.08 323; 402 45 1.76 342      
40 2.388 232 90 2.056 420; 332 50 1.74 404; 432      
40 2.085 224; 323 50 1.940 430            
30 2.058 420; 332 60 1.89 422; 340            
50 1.970 314; 304 75 1.758 432            
40 1.930 403; 340                  
30 1.858 431                  
40 1.730 404                  
20 1.713 334                  
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.

Figure 2. Thermogravigrams of Synthesized Compounds:Ag3AsS4 (a); Zn3(AsS4)2·4H2O (b); Cd3(AsS4)2·2H2O (e);Hg3(AsS4)2·2H2O (d)

3. Conclusion

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.


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