QUALITATIVE ANALYSIS OF UNKNOWN ORGANIC COMPOUND THROUGH PHYSICAL PROPERTIES ANALYSIS, ELEMENT ANALYSIS AND FUNCTIONAL GROUP ANALYSIS

By

I Kadek Irvan Adistha Putra

Chemistry Education Departement, Faculty of Mathematics and Natural Science,

Ganesha University of Education

Jalan Udayana Singaraja-Bali

Email: irvan.adistha@gmail.com

Abstract

The objectives of this experimental research are (1) to determine the physical properties of the unknown organic sample, (2) to analyze the elements contained in unknown organic sample, (3) to analyze the functional group contained in unknown organic sampled and (4) to determine the derivative compound contained in unknown organic sample. The subject of this experiment is unknown sample which was prepared by laboratory staff. The object of this experiment is the unknown sample of organic compound, especially the structure of organic compounds. From the analysis of physical properties, it is obtained the boiling point of the unknown sample of organic compound, 111^oC. Data from the element analysis show that only carbon and hydrogen contained in this unknown organic sample. It has unsaturated bonding and positive as aromatic compound. It does not have any derivative compound. All of the data obtained direct the unknown sample into Toluene, which has similar properties with the unknown sample. Therefore, the unknown sample is toluene.

Keyword: Qualitative analysis, unknown organic compound, toluene

INTRODUCTION

The qualitative analysis of organic compound is series of procedural analysis in order to determine the identity of organic compound, especially name, constituent and structure of organic compound. According to Suja and Nurlita (2004), there are four important steps that must be done to identify the unknown organic compounds, namely (1) physical properties determination, (2) qualitative analysis of elements, (3) determination of functional groups, and (4) making of derivative of the compound.

First analysis that must be conducted is the physical properties analysis. The physical properties analysis cover the iden-tification of melting points, identification of boiling points and identification of refractive index. Both of them are important in determination of organic compounds. They are present the physical properties of organic compounds.

The second analysis is the analysis of the constituent element of the organic compounds. There are analysis of carbon, analysis of hydrogen, analysis of nitrogen, analysis sulfur and analysis of Halogen. If the constituent elements is known it can be considered the possible formula of the unknown organic compounds.

The third analysis is analysis of contained functional group. There are analysis of unsaturated bond, analysis of aromatic compounds, analysis of phenolate group, analysis of ketones and aldehyde groups, analysis of hydroxyl group and analysis of ether group. If the contained functional group known, the structure of unknown organic compounds can be more specified. Then it can be proven by making the derivatives as the last step.

Generally, organic compounds is already compound is already contained element of carbon and hydrogen. Therefore, test for carbon and hydrogen is not necessary. But, in order to make more valid data, test of carbon and hydrogen is conducted. To identify the existence of carbon and hydrogen in organic compound, addition of Cupper (II) oxide (CuO) can be done. Then, it is continued by CO₂ and H₂O test. The existence of H₂O can turn the silica gels into blue. CO₂ gas is flowed into lime water. The CO₂ gas will make the solution become turbid. The reactions occur is as follows

C_xH_y + CuO  à  Cu_(s) + H₂O_(g) + CO_2(g)

Oxygen can be identified by Ferox reagent. Ferox reagent is mixture of KCNS and FeCl₃ in methanol. The change of red color in ferox paper into brighter red indicates the existence of oxygen.

Additional elements are usually detected by Lassaigne's test. In this test, organic compounds fused with sodium metal to convert the elements into water-soluble sodium salt. And then the extract was used to test additional elements in organic compounds, namely nitrogen, sulfur and halogen.

As written before, the functional group analysis is important. Baeyer test is used to detect saturated compounds. It uses an alkaline solution of KMnO₄, if the sample contains a double bond then the reaction will occur as follows:

 

When an organic compound containing unsaturated bonds or double bonds (-C = C-), then the solution of KMnO₄ color fading.

Bromine test is also used to detect unsaturated bonds. If the sample to be tested contains a double bond (-C = C-), then the brown color of bromine disappears. The reaction is as follows:

 

Aliphatic or aromatic compounds is tested by using smoke test. If smoke is formed, the unknown organic compounds is belong to aromatic compounds.

Hydroxyl group test performed with the 2 test fiber-ammonium-nitrate and acetyl chloride test. Test fiber-ammonium-nitrate reagent solution using fiber-ammonium-nitrate to test for the presence of hydroxyl groups on organic compounds. Test will be positive when there is a red color to the mixture. Acetyl chloride test is a test that uses acetyl chloride reagent to produce a gas that will be tested further with NH₄OH solution. Test will be positive if the smoke is formed when gas approximated with NH₄OH solution.

Phenolic group test is the test to determine whether there is the presence of phenol groups in organic compounds. Tests were conducted using the test ferrichloride FeCl₃ reagent. Test will be positive if the mixture of FeCl₃ with organic substances dissolved in alcohol change color to purple, blue, green, or red wine.

Aldehyde test can be done with a test Fehling and Tollens test. Fehling tests using a mixture of Fehling's solution A and Fehling B as a reagent to test the existence of un-aldehyde. This test will be positive if after mixed Fehling and organic matter is heated in a water bath to form a brick red precipitate that Cu₂O. Tollens test is also a test to test for aldehydes using the Tollens reagent mixture of AgNO₃, NaOH, and NH₄OH. This test will be positive if the Tollens reagent mixtures and organic substances to form a silver mirror on the wall of the reaction tube.

Ketone group test performed with 2 test which tests DNP (2,4-dinitrofenil hid-resin) and iodoform test. Tests using the reagent 2,4-DNP hydrazine dinitrophenyl to test the un-organic substances. Test will be positive if a precipitate is formed after download DNP reagent mix and organic substances in dilute HCl. Iodoform test uses a solution of iodine in the KI as a reagent. The test will be positive if the color fades and iodine iodoform yellow precipitate formed.

Carboxyl group test can be done with the 2 test of Na-bicarbonate and the formation of esters. Na-bicarbonate test is a test used to test for the presence of carboxyl groups with sodium bicarbonate reagent. This test will be positive if the bubbles are formed when the addition of a solution of sodium bicarbonate. This can be supported by the following equation.

CH₃COOH + NaHCO₃ → CH₃COONa (aq) + H₂CO₃ (aq) H₂CO₃ → H₂O (g) + CO₂ (g)

Ester group test is done by using a saturated solution of reagent hydroxylamine hydrochloride, KOH, a solution of FeCl₃ and HCl solution. This test will be positive if the color changes to red wine.

Ether group test performed using a mixture of reagent cupriacetate and benzydine hydrochloride. This test will be positive if the filter paper changes color changed to blue.

Nitro group test performed using nitrite solvent and reagent NaOH. This test aims to determine whether classified nitro-alkane primary or secondary nitroalkane. Will be classified as primary nitroalkane when after the addition of NaOH reagent turns red and the primary would fall if there is no change in color after the addition of reagents

MATERIALS, EQUIPMENT AND METHODS

     This experiment was conducted three times at Organic Chemistry Laboratory of Chemistry Education Department, Faculty of Mathematics and Natural Sciences, Ganesha Education University on 2^nd of September 2013, 9^th of September 2013 and 16^th of September 2013.

Materials:

The sample used was liquid samples. This experiment was conducted in some steps, namely (1) determining the boiling point (2) element analysis (3) determining the functional group (4) determining the derivatives compound. On the first and second step, the materials used namely oil, unknown liquid sample which is colorless, dry copper oxide powder, silica gel, solid potassium thiocyanate (KSCN), solid iron (III) chloride (FeCl₃), toluene, sodium, ethanol, aquades, acetic acid solution, Pb-acetate solution, sodium nitrorupsid solution, Mohr salt solution (FeSO₄), sodium hydroxide (NaOH) solution, concentrated sulfuric acid (H₂SO₄), concentrated nitric acid (HNO₃), silver nitrate (AgNO₃)solution, ammonium hydroxide (NH₄OH) solution, and limestone. Then, for the third and fourth step, it needed some materials namely, unknown liquid sample, aquades, Baeyer solution (KMnO₄ solution), carbon tetrachloride (CCl₄) solution, and bromine (Br₂) solution.

Equipment:

Some equipment used to support this experiment namely beaker glasses 100 mL, beaker glass 500 mL, graduated cylinder10 mL, graduated cylinder 25 mL, Erlenmeyer flask 100 mL, Thiele tube, thermometer, capillary pipe, test tubes, small test tube, a non-Pyrex test tube, a test tube rack, spatula, drop pipette, watch glass, funnel, glass flowing, test tube holder, and spirits burner.  

Methods:

            The methods used in this experiment exactly follows the practicum manual proposed by Nurlita and Suja (2004). Firstly,  in the determination of boiling point, one tip of capillary pipe was melted until covered. While, 0.25-0.5 mL ofliquid unknown sample was poured into small test tube. Then , the capillary pipe which has been melted (covered tip of capillary pipe was on the top) was entered into the small test tube which already contains liquid unknown sample. After that , the small test tube was bounded to the tip of thermometer. This set of equipment was entered into steam bath of oil (Thiele tube which contains oil). Last , the boiling point of this liquid unknown sample was record.

Next ,it was done analysis of the elemnt. Fisrt, detection of carbon and hydrogen. The sample was mixed with dry powder of copper oxide (CuO).  This mixture then was poured into test tube and dried. The test tubes was heated until all the substance changed into CO₂ and H₂O.  Gas of CO₂ was tested by flowing the gas produced,  then flowing the lime water with the gas diverter (when contains CO₂, it raised the turbidity). Water (H₂O) was tested by flowing the gas through silica gel CuSO₄ anhydrate (when the silica gel changed become blue, there was H₂O).

Second, it was caaried out the detection of oxygen. The sample was dissolved in toluene as solvent. On the other hand, the filter paper (which already given ferox reagent) was prepared and dried. Then, the sample was dropped on the ferox paper (when the ferox paper turn into red color, it means that the sample contains oxygen).

Third, detection of nitrogen, sulfur and halogen that it should be started by making extraction of sodium. The sample was placed in the test tube. Then, a piece of sodium metal (which already dried by filter paper) was added into the test tube. This incandescent sample was heated to get perfect reaction. In this process, ethanol was added to remove the excess of sodium. The mixture was heated until produced red color. After that, the mixture was dissolved in distilled water (breaking the test tube). Last, the solution was filtered to get the filtrate (lassaigne filtrate).

In the detection of sulfur, sodium extraction (± 2 mL) was pickled by acetic acid and heated (it was tested by litmus paper to know its acidity). While , filter paper was added to the solution of Pb-acetate 10% and then filter paper was approximated to the test tube (gasses testing). Then, the change on the filter paper was observed (black color indicated the existence of sulfur). Last, sodiumnitropusid solution was dropped on the rest of filtrate on the test tube (black color indicated the existence of sulfur).

In the detection of nitrogen, sodium extraction (± 2 mL) was added into FeSO₄ solution (Mohr salt). Then, it was heated until boiled. Then, it was cooled and acidified by H₂SO₄ solution until the precipitate was soluble. Last, the change was observed and recorded (when it appeared blue-green or blue passion color, it indicated the existence of nitrogen).

In the detection of halogen, extraction of sodium (± 2 mL) was acidified by using concentrated HNO₃ and then it was boiled. Then, it was cooled and added by 1 mL l of AgNO₃ solution.  The white or yellowed precipitate indicated the existence of halogen.

Then, it was done detection of unsaturated compound. This experiment was conducted by using Baeyer test and Bromine test. In Baeyer test, Baeyer solution (solution of alkaline KMnO₄) was added drop by drop into the sample in water while shaken. When the color of KMnO₄ was faded, it indicated positive of unsaturated bond. In the test of bromine, sample was dissolved in CCl₄ and added solution of 5% Br₂ in CCl₄ drop by drop while shaken. When the brown color turned into colorless, it indicated positive of unsaturated bond.

Detection of aromatic compound was started by placing the sample on the spatula, and then it was heated on the spirtus. The existence of smokes indicated the aromatic compound. The detection of functional group that contain oxygen is not conducted because the sample is already known that is not contain oxygen. The making of derivative compounds is also not conducted.

RESULT AND DISCUSSION

            In this experiment, the sample used was liquid samples. So, it was started by determining the boiling point of the sample. It used Thiele equipment. From the observation, it can be determined that the boiling point of the sample is 111⁰ C.

The results for the element analysis and functional group can be seen as the following tables:

Table 1. Observation Result of Element Analysis of Unknown Organic Sample

Element	Observation	Identification
Carbon	Carbon dioxide gas was produced	Positive toward carbon
Hydrogen	Water vapor was produced	Positive toward hydrogen
Oxygen	No red color was produced on the ferox paper after the sample was added.	Negative toward oxygen
Nitrogen	No green suspension was produced	Negative toward nitrogen
Sulfur	No black color was formed on filter paper containing Pb(CH3COOH)210%	Negative toward sulfur
Halogen	No white precipitate was formed	Negative toward halogen

Table 2. Result of Functional Group

Functional Group	Observation	Identification
Unsaturated bond	a)   In Baeyer test, addition of sample solution turned the violet color KMnO4 to become faded. b)  Addition of sample solution turned solution to colorless (Bromine test)	Positive
Aromatic  compound	in the smoke test, black smoke was formed by using smoke test	Positive

Since the result from the element analysis yield that the unknown organic substance only contain carbon and hydrogen, therefore it was only detected the unsaturated compound and the aromatic compound.

The test for functional group that contain oxygen is not conducted because the sample is already known not contain oxygen. Therefore, it is not possible for the sample to contain functional group that contain oxygen.Based on the experiment it is obtained data, namely the boiling point of the unknown sample of organic compounds is 111^oC, the constituent element are only carbon and hydrogen. The unknown sample of organic compounds also detected to has unsaturated bonds and aromatic rings. By using the data it can be identified the possible structure of the compound.

The unknown organic compound must has aromatic ring, because the aromatic ring test resulted in positive. Then, by considering the only constituent element are carbon and hydrogen, and the boiling point is 111^oC, the most possible structure for this unknown organic compound is Toluene.

Morrison and Boyd (1989) report that Toluene has the same characteristics as the writers reported. The toluene only has carbon and hydrogen, and the boiling point is ±111^oC. Jespersen, Brady and Hyslop (2012) strengthen the Morrison explanation by providing some additional information. Wade (2010) also stated that toluene has the same characteristics as the writers reported.   Therefore, by considering the three textbooks, it can be stated the unknown organic compound is toluene.  

The general structure of toluene is as follows.

CONCLUSION

Based on the explanation above, it can be concluded that the unknown organic compound is toluene which has boiling point ±111^oC.

ACKNOWLEDGEMENT

            Writer want to say thanks to Mr.I Nyoman Tika, as the lecturer, who always give the writer guidance, Mrs. Dewi Wirmandiyanthi, as the assistant lecturer, who assist writer in doing the practicum and Mr. Ketut Lasia as the laboratory staff who provide writer equipment and materials for practicum. Thanks also for writers group and all of writer’s beloved friends.

REFERENCES.

Jespersen, N. D., Brady, J. E., & Hyslop, A. (2012). Chemistry: The Molecular Nature of Matter. Hoboken: John Wiley & Sons, Inc

Morrison and Boyd. 1983. Organic Chemistry Fourth Edition. Singapore: Allyn and Bacon Inc.

Nurlita, F., & Suja, I. W. (2004). Buku Ajar: Praktikum Kimia Organic. Singaraja: IKIP Negeri Singaraja.

Wade Jr, L.G. (2010). Organic Chemistry. Upper Saddle River: Pearson Eduation, Inc.

CHEMISTRY OF SULFUR

BY:

I KADEK IRVAN ADISTHA PUTRA 

I KOMANG ADI WIRANATA 

CHEMISTRY EDUCATION DEPARTMENT

FACULTY OF MATHEMATICS AND NATURAL SCIENCES

GANESHA UNIVERSITY OF EDUCATION

2012

            Sulfur is well known by the peoples because it is used in people’s daily life. For matches, gunpowder, detergents, fireworks, batteries are some of sulfur usefulness. Not only its usefulness, but also it is needed to know or make the others   know, the danger of sulfur itself. The usefulness and the danger are absolutely related into the science of matter, chemistry. In chemistry term, sulfur can be analyzed in the periodic table of the elements. Sulfur is placed at group VI A, and at the third period. Started from periodic table, it can be known all about sulfur including its properties and its allotropes, ways in producing sulfur, the kind of sulfur compounds and ways in producing or preparing sulfur compounds. So, this essay is going to tell or explain sulfur including its histories, its properties, allotropes, compounds and ways in producing sulfur compounds.

Sulfur was firstly known in China, in a natural form that the chinese had called “brimstone” or shiliuhuang that was found in Hanzhong (Freshney, 2007). By the third century, chinese discovered that sulfur can be extracted from pyrite. A Song Dynasty of military treatise of 1044 AD described different formulas of chinese gunpowder, which is a mixture of potassium nitrate (KNO₃), carbon, sulfur. Early, alchemist gave sulfur its own alchemical symbol which was a triangle at the top of a cross. In the late 1770s, Antoine Lavoisier helped convince the scientific community that sulfur was an element and not a compound. In 1867, sulfur was discovered in underground deposits in Louissiana and Texas. The overlying layer of earth was quicksand, prohibiting ordinary mining operation. Therefore, the Frasch process was utilized to produce sulfur.

In modern era, its specifically known the properties of sulfur and its allotropes. Sulfur is classified into group VIA in periodic table or it is called chalcogen group. Sulfur is also classified into non-metallic group. Sulfur has melting point at 388,36 K or 115,21^o C. The melting point of S₈ is actually a decomposition point. Just after melting rings with an average of 13.8 sulfur atoms are formed and at higher temperature still larger rings form. The in the high viscosity region there are giant macromolecules that are probably chains with radical ends. At higher temperature, highly colored S₃ and S₄ molecules are present to the extent 1-3 % at the boiling point.. Then, sulfur also has boiling point at 717,8 K or 444,6^o C. Sulfur is normally seen in lemon yellow colour. The density of sulfur is 2,08 gr/cm³ (alpha), 1,96 gr/cm³ (beta) and 1,92 gr/cm³ (gama).

Sulfur has allotropes. At least, twenty four  sulfur allotropes has been identified. Two of the most common sulfur allotropes are Orthorhombic sulfur (α-S₈) and Cyclohexasulfur or Rhombohedral sulfur (S₆). The most stable allotrope form in room temperature is Orthorhombic sulfur (α-S₈). Eight sulfur atoms bond covalently crown like rings. The Cyclohexasulfur or Rhombohedral sulfur is the densest of the sulfur allotropes and forms air sensitive orange red crystals containing chair shape, six membered rings. The structure of Orthorhombic sulfur (α-S₈) and Cyclohexasulfur are shown in figure below.

(a)

(b)

 

	Figure 1. The structure of Orthorhombic (a) and Cyclohexasulfur (b). The picture of (a) is taken from Garry L Miessller et al., “Inorganic Chemistry”. The picture of (b) is taken from Bodie E. Douglas et al., “Structure and Chemistry of Crystaline Solid”.

 

Sulfur occurs widely in nature as the element, as H₂S and SO₂, in metal sulfide ores, and as sulfates [e.g., gypsum and anhydrite (CaSO₄), magnesium sulfate and so on](Cotton et al., 1995). Freshney (2007) mention sulfur can be found in pure form (near hot springs and in volcanic regions) and in ores like cinnabar (HgS), galena (PbS), alunite, barite (BaSO₄), sphalerite (ZnS), and stibnite (Sb₂S₃). The main concern is the existence of sulfur as element. Sulfur as element is found in Orthorhombic sulfur structure (α-S₈). Related with sulfur usefulness, it is made a system or prototype to produce sulfur from natural sulfur resources.

In 1904, Frasch was successful to develop a method to extract sulfur from natural sulfur resources. This method is known as Frasch method. In this process, metal pipe with diameters of 15 cm which is consisted of two smaller concentric pipes inside is buried until reach the sulfur layer. Extremely hot water vapor is pumped into the sulfur layer through the pipe until the sulfur melt. Then, high pressure air is pumped into the sulfur layer through small pipe until sulfur foam is formed and the sulfur foam is pumped up into surface. On the surface, liquid sulfur is gathered in together in large vessel and let them freeze, produce solid sulfur with purity of 99,5%. The frasch method is shown in picture below.

	Figure 2. The pump in Frasch method. The picture is taken from C. Chambers et al., “Modern Inorganic Chemistry”.

 

Sulfur has oxides, especially sulfur dioxide. The dioxides are commonly produced by burning elements in the air. So, sulfur dioxides is produced when sulfur is burned in the air. Sulfur dioxide is a gas with a pungent smell (Cotton et al., 1995). The molecule is angular. Sulfur dioxide has lone pairs and can act as base according to Lewis acid-base theory. The other sulfur oxides is sulfur trioxide. Sulfur trioxide is obtained by reaction of sulfur dioxide with O₂, a reaction that is thermodynamically very favorable but extremely slow in the absence of a catalyst such as platinum sponge, V₂O₅, on NO (Cotton et al., 1995). The sulfur trioxide molecule, in the gas phase, has a planar, triangular structure involving both p-p an p-d S-O bonding and forms polymers in the solid state.

The other compound of sulfur is Sulfuric Acid. Sulfuric Acid, H₂SO₄, corrosive, oily, colorless liquid, with a specific gravity of 1.85. It is formed from hydrogen, sulfur, and oxygen. Sulfuric acid melts at 10.36°C (50.6°F), boils at 340°C (644°F), and is soluble in all proportions in water. When sulfuric acid is mixed with water, considerable heat is released. Unless the mixture is well stirred, the added water may be heated beyond its boiling point and the sudden formation of steam may blow the acid out of its container. The concentrated acid destroys skin and flesh, and can cause blindness if it gets into the eyes. The best treatment is to flush away the acid with large amounts of water. Despite the dangers created by careless handling, sulfuric acid has been commercially important for many years.

Sulfuric acid is a strong acid, that is, in aqueous solution it is largely changed to hydrogen ions (H⁺) and sulfate ions (SO₄^2-). Each molecule gives two H⁺ ions, thus sulfuric acid is dibasic. Dilute solutions of sulfuric acid show all the behavior characteristics of acids. They taste sour, conduct electricity, neutralize alkalies, and corrode active metals with formation of hydrogen gas. From sulfuric acid one can prepare both normal salts containing the sulfate group, SO₄, and acid salts containing the hydrogen sulfate group, HSO_4.

There are two major processes (lead chamber and contact) for production of H₂SO₄, and it is available commercially in a number of grades and concentrations. The lead chamber process, the older of the two processes, is used to produce much of the acid used to make fertilizers; it produces a relatively dilute acid (62%-78% H₂SO₄). The contact process produces a purer, more concentrated acid but requires purer raw materials and the use of expensive catalysts. In both processes sulfur dioxide is oxidized and dissolved in water. There are four steps to the contact process which starts with elemental sulfur.

1.      Step 1: The Burner. Pure sulfur is burned in air to give sulfur dioxide (SO₂), which is familiar to as rotten egg gas. This reaction happens at about 1000⁰C. The air used for the burning must be dust free as the presence of dust in the second part of the process will cause damage to the catalyst.

S_(g) + O_2(g)à SO_2(g)

2.      Step 2: The Converter. The sulfur dioxide is passed into a tower made of stacked vertical beds of catalyst material, usually vanadium oxide (V₂O₅) but sometimes platinum. Here the sulfur dioxide reacts with oxygen once again to give sulfur trioxide. The purpose of the catalyst is to reduce the temperature needed for the reaction to occur. This is used because the reaction of SO₂ with O₂is more productive at the lower temperature of 300⁰C.Sulfur Trioxide cannot be immediately converted into Sulfuric acid by absorbing water, as happens in acid rain. If allowed to absorb water the SO₃ becomes a fine mist that is very difficult to collect.

SO_2(g) + ½ O_2(g)à SO_3(g)

3.      Step 3: Absorption of sulfur trioxide. In order to produce sulfuric acid in liquid form, the sulfur trioxide gas from the converter is bubbled through very high purity liquid H₂SO₄. This is a very efficient process that results in virtually complete absorption of the SO₃ gas. The resulting liquid chemical is called oleum and has the formula H₂S₂O₇.

SO_3(g) + H₂SO_4(l)à H₂S₂O_7(l)

4.      Step 4: Hydration of the oleum. Finally the oleum is converted into highly concentrated H₂SO₄ by the addition of dilute H₂S₂O₇ and water. This reaction gives off a lot of heat and so the resulting acid needs to be cooled before it is sent to storage.

H₂S₂O_7(l) + H₂O_(l)à  H₂SO_4(aq)

The other well-known of the sulfur compound is hydrogen sulfide (H₂S). Hydrogen sulfide is colorless gas, and known as rotten egg smell gas. In chemistry terms, it can be said complete, if the structure and the chemical properties of hydrogen sulfide is explained. When the sulfur and the other chalcogenides make a bond with hydrogen, they form compounds with analogous formulas that may represented as H₂Y where Y, in this term is sulfur. The hydrogen chalconides molecules are angular, since there are four groups of electrons on each central chalcogens. As one of the chalcogen, the sulfur molecule is angular too. Snyder (1966) mention the properties of Hydrogen sulfide such as melting point, boiling point heat of fusion, heat of vaporization critical temperature dipole moment and dielectric constant. The melting point of hydrogen sulfide is 190 K and the boiling point of hydrogen sulfide is 213 K. Heat of fusion and heat of vaporization of hydrogen sulfide in a row is 0,568 kcal/mole and 4,46 kcal/mole. The dipole moment of hydrogen sulfide is 0,931 debyes, and the dielectric constant of hydrogen sulfide at 212 K is 8,0.

As said before, Hydrogen sulfide is colorless gas, and known as rotten egg odor gas. Hydrogen sulfide itself is a poisonus gas and its more poisonus than carbon monoxide, but its bad odor allows it to be detected at low concentrations. In nature, hydrogen sulfide is released into the air during volcanic eruption and by the decomposition of organic matter in the absence of air that’s rotten eggs smell of hydrogen sulfide. Hydrogen sulfide is difficult to dissolve in water and its solution become turbid because hydrogen sulfide is oxidized produce sulfur. In laboratory, hydrogen sulfide is used as strong reductor. The reaction is shown below.

H₂S + ½ O₂ à H₂O + SO₂

H₂S + SO₂ à 2 H₂O + 3S

Brady (1990), mention that hydrogen sulfide can be prepared in laboratory by reacting a metal sulfide with a strong monoxidizing acid, for example, HCl.

FeS_(s) + 2H⁺_(aq) à Fe²⁺_(aq) + H₂S_(g)

Another method, generally used when one wants to generate the H₂S in an aqueous solution, is the hydrolysis of an organic compound called thioacetamide.

Thioacetamide_(aq) + 2H₂O à H₂S_(aq) + NH₄⁺_(aq) + acetate ion_(aq)

The advantage of this reaction is that it avoids the release of significant amounts of toxic H₂S into the atmosphere. Qualitatively, hydrogen sulfide can be analyzed with paper which is tear-stained by salt solution of Pb²⁺ and produce black spot, because PbS is formed.

H₂S_(g) + Pb²⁺_(aq) à PbS + 2H⁺_(aq)

The last sulfur compound that will be explained is sodium thiosulfate (Na₂S₂O₃). Sodium thiosulfate is formed in reaction of sodium sulfites solutions and sulfur. The reaction is shown below.

S_(aq) + Na₂SO­_3(aq) à Na₂S₂O_3(aq)

The sodium thiosulfate has characteristic as reductor and used in iodometric analysis, according reaction:

2Na₂S₂O₃ + I₂ à Na₂S₄O₆ + 2 NaI

Specifically, the thiosulfates ion has the structure SSO₃^2-, and may be considered to be derived from sulfate by replacement of an atom by an S atom.

Based on the explanation above, it can be concluded that sulfur is common element that has several advantage and disadvantage for human being. Sulfur has allotropes. Sulfur exists in nature in pure element and in compound form. Some of sulfur compounds are sulfur dioxide, sulfuric acid, hydrogen sulfide and sodium thiosulfate. Every sulfur compound has their own properties, structure and process to prepare or making it. After knowing all about sulfur that is explained in this essay, the peoples understanding and its used is expected to be improve at the future.

REFERENCES

Brady, James E. 1990. General Chemistry Principles and Structure. Canada:Jhon Wiley and Sons, Inc.

Cotton, F. Albert., Wilkinson, Geoffrey., Gaus, Paul.L. 1995. Basic Inorganic Chemistry. Singapore: John Willey & Sons Pte. Ltd

Freshney, Paul Alan. 2007. PA Freshney Periodic Table v3.3.

Petrucci Hill, Ralph., Hill Jhon. 2002. General Chemistry An Integrated Approach. New Jersey:Prentice-Hall, Inc.

Snyder, Milton K. 1966. Chemistry Structure and Relations. USA: Holt, Rinehart and Winston, Inc.

Siregar, Manimpan., Sudria, Ida Bagus Nyoman. 2000. Buku Ajar Kimia Anorganik I. Singaraja : STKIP Negeri Singaraja