Arsenious Sulphide
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We discussed the step-by-step method for performing an experiment to prepare Arsenious Sulphide sol in this article. To understand the objective, procedure, and materials needed to conduct the experiment, carefully read the content on this page. Try to run the experiment and balance this with your outcome.


Aim

The aim of this experiment- Sulphide Colloidal Solution Preparation, Arsenic sulphide -As2S3 sol.


Theory


Arsenic Sulphide-

The inorganic compound with the formula As2S3  is Arsenic trisulfide. It is a dark yellow solid which is water-insoluble. It also occurs as the mineral orpiment, which has been used as a pigment called King's yellow. It is developed in the field of arsenic compound analysis. It is an intrinsic p-type semiconductor of group V/VI and exhibits phase-change properties that are photo-induced. As4S4, a red-orange solid known as the mineral realgar, is the other principal arsenic sulfide.

In both crystalline and amorphous forms, As2S3 occurs. Both types feature polymeric structures consisting of centres of trigonal pyramidal As(III) connected by centres of sulfide. The centres of the sulfide are double-coordinated with two arsenic atoms. The compound adopts a ruffled sheet structure in the crystalline form. Van der Waals forces consist of the bonding between the sheets. In geological samples, the crystalline form is commonly found. Amorphous As2S3 does not have a structure with layers but is more strongly cross-linked. There is no medium or long-range order, like other lenses, but the first co-ordination sphere is well defined. As2S3  is a strong former glass and has a broad glass-forming shape.

As2S3 (Arsenious sulphide) is a colloid that is lyophobic. It is formed in boiled distilled water due to the hydrolysis of As2O3 (Arsenious oxide). Additional H2S gas is transferred through the solution. The reaction takes place as follows: 

As2O3+ 3H2O · 2As(OH)3 

2As(OH)3 + 3H2S → As2S3 + 6H2O

The particles in the colloidal solution of Arsenious sulphide are surrounded by ions of HS that are formed due to H2S dissociation. H+ ions surround the sulfide ion sheet.


Materials Required

The apparatus and materials required for coagulation of arsenious sulphide sol are as follows:

  1. Beaker 250 mL

  2. Round bottom flask 500 mL

  3. Glass tubing

  4. Conical flask of 250 mL volume

  5. Filter paper

  6. Funnel

  7. Glass rod

  8. Wire gauze

  9. Burner

  10. Tripod stand

  11. Iron stand with clamp

  12. Distilled water

  13. H2S gas

  14. Solid arsenious oxide


Procedure:

  1. Take and clean 250 mL of the conical flask by steaming out the process. 

  2. Add 0.2 g of solid arsenic oxide and distilled water for  100 mL. 

  3. Boil the solution for 10 minutes.

  4. Separate the hot solution with the help of filter paper.

  5. As2O3 using Kipps apparatus pass H2S  through As2O3 as shown below.

  6. The solution's colour shifts to yellow, which is resulting in the As2S3 formation. 

  7. By slowly heating, expelling hydrogen sulfide gas from the sol. 

  8. Mark the filter as 'arsenic sol sulfide.


Precautions: 

  1. Using clean equipment for the experiment affects As2S3  if there are even traces of impurities. 

  2. As2S3 is extremely toxic, so treat it carefully.


Did You Know?

Arsenic groundwater contamination is a form of groundwater pollution that is mostly due to high concentrations of arsenic in deeper groundwater levels that occur naturally. Due to the use of deep tube wells for water supply in the Ganges Delta, it is a high-profile epidemic, causing large numbers of people to have extreme arsenic poisoning. A 2007 study found that arsenic toxicity from drinking water is likely to affect over 137 million people in more than 70 countries. After mass water poisoning in Bangladesh, the problem became a major health issue.


A major issue is arsenic pollution of the groundwater in Bangladesh. Bangladesh had one of the highest child mortality rates in the world prior to the 1970s. These problems have been compounded by inadequate water purification and drainage systems, as well as frequent monsoons and flooding. UNICEF and the World Bank have promoted the use of wells to tap into deeper groundwater as a solution. As a result, millions of wells were installed. Infant death and diarrheal disease have been decreased by fifty percent due to this intervention. With over 8 million wells installed, however, approximately one in five of these wells are now polluted with arsenic above the drinking water level of the government.

FAQ (Frequently Asked Questions)

Question: How will You Prepare a Lyophobic Colloidal Solution?

Answer: Different chemical methods may be used to prepare hydrophilic or lyophobic colloidal solutions, such as the Double Decomposition Technique: We obtain a colloidal solution of arsenic chloride when hydrogen sulphide is passed through a solution of arsenic oxide in distilled water.

Question: Why is Arsenious Sol Charged Negatively?

Answer: The arsenic sulphide sol given in the question bears a negative charge against it. .According to the Hardy-Schulze law, the higher its coagulating strength, the greater the valence of the flocculating ion (ion carrying opposite charge to the sol)." Now, K is the cation in K₂SO₄ and it carries +1 charge on it."

Question: How Does the Chemical Process Prepare Sulphur Sol?

Answer: It is possible to prepare sulphur sols by oxidizing H2S in the solution. By the action of a strong acid, i.e., sulphuric acid, in a concentrated solution of sodium thiosulphate, sulphur sol may also be prepared. Colloidal solutions of elemental sulfur or of compounds high in sulfur are sulfur sols.

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