What Is Sulfur? Key Properties and Popular Applications

What is sulfur? (Photo: Internet Collection)

What is Sulfur?

Sulfur (also spelled sulphur) is a chemical element found in the periodic table, denoted by the symbol S and the atomic number 16. It is a familiar, non-metallic, odorless substance with a distinctive taste, and it has various medicinal applications. In its native state, sulfur exists as a lemon-yellow crystalline solid. It is deemed an essential element for life and is present in two amino acids.

Where is Sulfur Found?

In its natural state, sulfur is commonly found in pure form and in minerals like sulfide and sulfate.

Pure sulfur is present in regions with hot springs and volcanic activity, particularly along the Pacific Ring of Fire.

• Atomic Number: 16
• Position: Belongs to Group VIA, Period 3 in the periodic table of chemical elements.
• Electronic Configuration: 1s22s22p63s23p4, with 6 outermost layers.
• Physical Properties of Sulfur

Sulfur exhibits the following physical properties:

Study the physical characteristics of sulfur. (Photo: Internet Collection)

State: Sulfur is typically a brittle solid at room temperature, exhibiting a pale yellow color. It primarily exists in the form of ring-shaped S8 molecules, although other shapes also occur. Removing an atom from the ring yields S7, which imparts the characteristic yellow color. Additionally, sulfur can exist amor-phously, known as plastic sulfur.

Crystals: Sulfur exhibits complex crystal formations, depending on various conditions. Its morphologies can result in different crystal structures, with rhombohedral and monoclinic S8 being the most extensively studied forms.

Odor: Sulfur’s distinct odor resembles that of rotten eggs due to the presence of hydrogen sulfide (H2S). Pure sulfur, however, is odorless. When burnt, it produces a blue flame and emits sulfur dioxide, recognized for its suffocating smell.

Solubility: While sulfur is insoluble in water, it dissolves in carbon disulfide and other non-polar solvents.

Oxidation States: Sulfur displays multiple oxidation states, including -2, -1 (in iron pyrite), +2, +4, and +6. It readily forms stable compounds with nearly all elements, except for the noble gases.

Melting: Molten sulfur typically exhibits viscosity, a notable characteristic of this nonmetal. Its viscosity increases with temperature due to the formation of polymer chains. However, within a certain temperature range, the viscosity decreases again as the energy required to break the polymer chain is reached.

Sulfur’s Shape

Sulfur is known to have two allotropic forms, namely hexagonal sulfur (Sα) and monoclinic sulfur (Sβ). These forms differ in their crystal structures and certain physical properties, while sharing similar chemical properties. The interconversion between Sα and Sβ occurs based on temperature conditions. Refer to the table below for an in-depth understanding of this reversible transformation:

Impact of Temperature on Sulfur’s Physical Properties

Sulfur’s physical properties undergo significant changes at various temperatures, as detailed below:

• Below 113 degrees: Sα and Sβ both exist as yellow solids, with eight atoms forming a covalently bonded ring in each molecule.
• At 119 degrees: Both Sα and Sβ transform into a mobile yellow liquid.
• At 187 degrees: The liquid sulfur becomes viscous and takes on a reddish-brown hue.
• At 445 degrees: Sulfur begins to boil, leading to the breakdown of sulfur molecules into numerous small evaporating molecules.

For instance, at 1400 degrees Celsius, sulfur vapors form S2 molecules, while at 1700 degrees Celsius, sulfur exists as individual S atoms.

Chemical Properties of Sulfur

Sulfur’s notable chemical properties involve its ability to exhibit various oxidation states, including -2, 0, +4, and +6, alongside reducing properties. Let’s delve into this property through sulfur’s interactions with metals, hydrogen, and nonmetals.

Reactions with Metals and Hydrogen

Sulfur reacts with hydrogen at elevated temperatures, resulting in the production of hydrogen sulfide gas, and with metals to form sulfide salts.

Reaction with Hydrogen

Upon passing H2 into a test tube containing boiling sulfur, sulfur readily reacts with hydrogen, producing a gas with a distinct rotten egg odor, identified as hydrogen sulfide.

Reaction equation:  H2 + S → H2S (temperature condition: 350 degrees)

Interaction with Metals

Sulfur’s reaction with metals represents a characteristic chemical property. When heated, sulfur readily reacts with various metals, giving rise to a diverse range of compounds.

For example:

1. A mixture of iron powder and sulfur, when gently heated, results in an exothermic reaction described by the equation: Fe + S → FeS (at certain temperature conditions).
2. Sulfur also reacts vigorously with zinc and aluminum, often accompanied by a flash. Thin copper filaments can combust in sulfur, forming black CuS.

An intriguing observation is that mercury reacts with sulfur at room temperature, yielding HgS according to the equation: Hg + S → HgS. This reaction highlights sulfur’s oxidizing properties, which oxidize Fe(0) and Hg(0) to Fe(+2) and Hg(+02), respectively, as well as oxidizing H(0) to H(1).

Effect on Nonmetals

Under normal conditions, sulfur displays heightened reactivity with several non-metallic elements, including fluorine, oxygen, chlorine, and others, with the exception of iodine and nitrogen. When sulfur undergoes combustion in the presence of air, it yields sulfur(IV) oxide with a characteristic blue flame.

• S + O2 → SO2 (temperature)
• S + 3F2 → SF6 (temperature)

Throughout these reactions, sulfur demonstrates its reducing properties, reducing O(0) to O(-2) and F(0) to F(-1).

How to Prepare Sulfur

This section outlines two common methods for preparing sulfur: one in the laboratory and the other in the industry.

In the Laboratory

Sulfur is prepared in the laboratory by reacting a sulfite salt (a salt of a weak acid) with a stronger acid, usually sulfuric acid solution, with sodium sulfite according to the following steps:

1. Gradually pour the sulfuric acid solution into the flask containing sodium sulfite and close the lid as follows: H2SO4 + Na2SO3 → Na2SO4 + SO2 + H2O (heating required). Keep the receiver upright as SO2 is heavier than air.
2. Heat the flask over the flame of an alcohol lamp using an asbestos grid to prevent the flame from concentrating in one area and shattering the flask during heating.
3. Collect sulfur dioxide gas using the air transfer method, employing cotton soaked in sodium hydroxide solution (NaOH) to contain the released SO2 gas.

Note:

• Avoid using cotton soaked in ammonia gas (NH3) as it is a volatile gas that could render the gas collection process ineffective.
• Allow the sulfite salt to react with hydrochloric acid to prevent acid volatilization and mixing with SO2, which could affect the accuracy of the results.

In Industry

Sulfur is typically prepared in the industry using the following common methods:

1. Sulfur burning: S + O2 (temperature) → SO2
2. Burning H2S in excess oxygen: 2H2S + 3O2 → 2H2O + 2SO2
3. Metal reacting with H2SO4 (hot thickening): Cu + 2H2SO4 → CuSO4 + SO2 + 2H2O
4. Burning iron pyrite ore (FeS2): 4FeS2 + 11O2 → 2Fe2O3 + 8SO2

Significant Applications of Sulfur in Industry and Daily Life

Sulfur is a fundamental element with various practical applications, playing a crucial role in the global economy.

Industrial Uses of Sulfur

In industry, about 90% of sulfur is extracted through its primary derivative, sulfuric acid (H2SO4), a crucial industrial raw material. The consumption of sulfuric acid serves as a key indicator of a country’s industrial development. The United States produces more sulfur each year than any other industrial chemical.

Sulfur finds application in numerous industrial products, including batteries, detergents, rubber vulcanization, fungicides, and phosphate fertilizers. Specifically, it is utilized to whiten paper, act as a preservative in wine, and aid in the drying of fruits. Its flammable nature also makes it an essential component in matches, gunpowder, explosives, and fireworks.

Sulfur’s Role in Skincare

Throughout history, sulfur has been recognized for its use in promoting skin health and treating acne. However, there is a lack of definitive studies detailing its mechanism in acne treatment.

Experimental evidence suggests that sulfur possesses strong anti-inflammatory and antibacterial properties, making it effective in reducing acne lesions.

Application of Sulfur in Agriculture

In addition to its vital role in industry, sulfur serves as a crucial raw material in the production of chemical fertilizers, pesticides, and fungicides within the realm of agriculture.

Sulfur’s Role in Medicine

Sulfur has found applications in the medical field as well. Magnesium sulfate, for instance, is used as a laxative and in the treatment of various skin disorders due to its potent anti-inflammatory and antibacterial properties.

For instance, sulfur cream, lotion, ointment, or soap is used in the treatment of acne, while sulfur ointment is employed to address seborrheic dermatitis and scabies, among other conditions.

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Is Sulfur Toxic? Detrimental Effects of Sulfur on the Environment and Human Health

Is sulfur poisonous? (Photo: Internet Collection)

Is Sulfur Toxic?

Sulfur, when used in large amounts, can be a toxic chemical element. While sulfur dioxide is relatively safe in small quantities, high concentrations can lead to the production of sulfurous acid, which can harm the lungs, eyes, and other organs.

The Detrimental Effects of Sulfur

Industrial sulfur is a toxic chemical that is prohibited in food processing and preservation. Unfortunately, due to profitability concerns, the misuse of industrial sulfur is prevalent in the preservation and drying of medicinal herbs, leading to adverse impacts on human health, the environment, and various forms of life.

Acid rain – one of the adverse impacts of sulfur. (Photo: Internet Collection)

Impact on Human Health

According to the World Health Organization’s (WHO) recommendations, the sulfur dioxide (SO2) content in foods should not exceed 20mg per 1kg. However, in Vietnam, the usage of sulfur surpasses the permissible levels by many folds, leading to severe health implications. The impact of sulfur on human health occurs through both ingestion and inhalation, resulting in various health issues:

• Headache: Inhaling sulfur compounds can lead to headaches, depending on the concentration of the fumes.
• Nasal congestion: Sulfur dioxide emissions cause irritation and can result in nasal congestion, affecting breathing.
• Shortness of breath: Sulfur dioxide can disrupt the alkaline balance in the blood, leading to breathing difficulties and constriction of the airways.
• Bronchitis: Inhalation of sulfur compounds can lead to the development of bronchitis and other respiratory illnesses.
• Blood poisoning: High levels of sulfur can disrupt the blood’s pH balance, leading to blood poisoning.
• Fatality: Exposure to high concentrations of sulfur can paralyze vital organs, potentially resulting in death.

It is crucial to avoid direct contact with sulfur and to thoroughly wash sulfur-containing foods before consumption.

Impact on Aquatic Life

Industrial sulfur contamination in water sources can have devastating effects on aquatic life, causing mass deaths of fish, shrimp, crabs, clams, and other marine organisms. Consuming these contaminated organisms can also pose a significant risk of indirect sulfur poisoning to humans.

Impact on the Environment

Burning sulfur at high temperatures can significantly harm the living environment, leading to gas pollution, climate change, acid rain, and the greenhouse effect.

• Environmental Pollution: Sulfur dioxide (SO2) is a major environmental pollutant.
• Acid Rain: The oxidation of SO2 and its subsequent reaction with water form sulfuric acid, resulting in acid rain that can damage plants when exposed to environments with SO2 levels ranging from 1-2 ppm over several hours.
• Ozone Layer Depletion: SO2 can react with ozone (O3) to form sulfur trioxide (SO3) and oxygen (O2), contributing to the destruction of the ozone layer.
• Water Pollution: Hydrogen sulfide (H2S), a gas formed during organic matter decomposition, is a common cause of water pollution, particularly in well water. H2S with a concentration of about 1.0 PPM exhibits corrosive properties, leading to the degradation of metals, concrete, and other materials. This substance can also cause discoloration and physical property changes in limestone and marble, contributing to the deterioration of architecture, iron, steel, fabrics, and paper.

Precautions for Using and Storing Sulfur

Due to its toxic nature, it is essential to handle sulfur with caution, considering the following factors to prevent direct harm to health and the environment.

Precautions When Using Sulfur

When dealing with sulfur compounds, such as carbon disulfide, carbonyl sulfide, hydrogen sulfide, and sulfur dioxide, it is important to handle them carefully.

When using sulfur-based medication, pay close attention to the dosage, duration of use, and follow the instructions of a medical professional.

How to Store and Preserve Sulfur

Store sulfur chemicals in a cool, dry place away from direct sunlight.

For sulfur-based medications, store them at room temperature, avoiding moisture and direct sunlight. Avoid storing sulfur in bathrooms or freezers. Properly dispose of expired medications by consulting your pharmacist or local waste disposal company, and avoid flushing sulfur pills down the toilet or drain.

Some Common Sulfur Compounds

In this section, we’ll explore several common sulfur compounds and their isotopes.

Explore common sulfur compounds. (Photo: Internet Collection)

• Hydrogen Sulfide: The primary sulfur compound, with a distinctive rotten egg odor. When dissolved in water, it becomes acidic and reacts with various metals to form metal sulfides. Iron sulfides, notably pyrite, are particularly common.
• Ethyl and Methyl Mercaptan: Other sulfur compounds, such as ethyl and methyl mercaptan, emit unpleasant odors and are used as gas odorants to detect leaks.
• Polymerized Sulfur Nitride: Derived from sulfur tetranitride S4N4, a compound exhibiting metallic properties despite the absence of any metal atoms. It displays unique optical and electrical properties, and the polymer can be created from sulfur tetranitride S4N4.

Additionally, some other important sulfur compounds include:

Certain inorganic compounds:

• Sulfide (S2-)
• Sulfite (SO32-), salts of sulfuric acid, H2SO3, and corresponding sulfites, pyrosulfite ion, metabisulfite (S2O52−).
• Sulfate (SO42-) and salts of sulfuric acid.
• Thiosulfate (sometimes referred to as thiosulfite or “hyposulfite”) (S2O32−), such as sodium thiosulfate.
• Sodium dithionite, Na2S2O4, derived from hyposulfuric acid/dithionine.
• Sodium Dithionate (Na2S2O6)
• Polythionic Acid (H2SnO6)
• Peroxymonosulfuric acid (H2SO5) and peroxydisulfuric acid (H2S2O8)
• Sodium polysulfide (Na2Sx)
• Sulfur hexafluoride, SF6
• Sulfur tetranitride, S4N4

Several organic compounds:

• Dimethyl Sulfoniopropionate (DMSP; (CH3)2S+CH2CH2COO-)
• Thiol (or mercaptan)
• Thiolate
• Sulfoxide
• Sulfone
• Lawesson’s Reagent
• Naphthalene-1,8-diyl 1,3,2,4-dithiadiphosphate 2,4-disulfide
• Isotopes: Sulfur has 18 isotopes, of which 4 are stable: S32 (95.02%), S33 (0.75%), S34 (4.21%), and S36 (0.02%).

Understanding what sulfur is, its potential toxicity, and its various properties is crucial. This comprehensive guide aims to provide a detailed and clear insight into sulfur. We hope this article aids in your learning journey. Visit our website for more intriguing elements in chemistry!