chemistry

Indium(III) sulfate

Indium(III) sulfate is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Indium(III) sulfate rather than just read about it. In short: Indium(III) sulfate (In2(SO4)3) is a sulfate salt of the metal indium. It is a sesquisulfate, meaning that the sulfate group occurs 1⁠1/2⁠ times as much as the metal.

Key takeaways

Indium(III) sulfate belongs to chemistry; place it in that map before memorising details.
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Connect Indium(III) sulfate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Indium(III) sulfate from memory before moving on to harder problems.

Reference excerpt

Indium(III) sulfate (In2(SO4)3) is a sulfate salt of the metal indium. It is a sesquisulfate, meaning that the sulfate group occurs 1⁠1/2⁠ times as much as the metal. It may be formed by the reaction of indium, its oxide, or its carbonate with sulfuric acid. An excess of strong acid is required, otherwise insoluble basic salts are formed. As a solid indium sulfate can be anhydrous, or take the form of a pentahydrate with five water molecules or a nonahydrate with nine molecules of water. Indium sulfate is used in the production of indium or indium containing substances. Indium sulfate also can be found in basic salts, acidic salts or double salts including indium alum.

Properties In water solution, the indium ion forms a complex with water and sulfate, examples being In(H2O)5(SO4)+ and In(H2O)4(SO4)−2. Indium is unusual in forming a sulfate complex. The effect on the sulfate ion is revealed in the Raman spectrum. The proportion of sulfate complex increases with temperature showing the reaction that forms it is endothermic. The proportion also increases with concentration of the solution and can be over a half. The sulfate complex rapidly exchanges with water at a rate of over 10,000,000 per second, so that NMR cannot detect the difference that results from a complexed and noncomplexed indium ion. An indium sulfate water solution is quite acidic with a 0.14 mol/L solution having a pH of 1.85. If the pH rises above 3.4 then a precipitate will form. The Raman spectrum of the solution shows lines at 650, 1000 and 1125 cm-1 due to a sulfur–oxygen bonds in sulfate bound to indium. A line at 255 cm-1 is due to the indium-oxygen bond to the sulfate. The water attached to the indium atom causes a band at about 400 cm-1. During extraction of indium, a sulfate solution of mixed metals, including indium sulfate, has trivalent metals partitioned into a kerosene solution of di-2-ethylhexyl hydrogen phosphate. Isododecylphosphetanic and diisooctylphosphinic acids can also be used for this function. The kerosene mixture is then backwashed with an acid to recover the metals in a water solution and regenerate the extracting fluid. The heat capacity of anhydrous indium sulfate at standard conditions is 65.73 cal/deg/mole (1.651 J/g/deg). The heat capacity increases smoothly with temperature, indicating no crystal structure transitions.

Production Indium metal reacts with cold concentrated sulfuric acid to produce Indium sulfate and hydrogen gas. If hot concentrated sulfuric acid is used indium will reduce the sulfuric acid to sulfur dioxide. Indium sulfate can also be produced from a reaction of sulfuric acid on indium oxide, indium carbonate, or indium hydroxide.

Reactions When heated to 710 K (437 °C; 818 °F) or above, indium sulfate decomposes by giving off sulfur trioxide vapour, yielding indium oxide.

In2(SO4)3 → In2O3 + 3 SO3↑ Alkalis added to indium sulfate solutions precipitate basic salts. For example, potassium hydroxide produces either a basic sulfate, 2In2O3·SO3·nH2O, or KIn3(OH)6(SO4)2 depending on pH. Sodium pyrophosphate causes a slimy precipitate of indium pyrophosphate, In4(P2O7)3·3H2O. Potassium periodate causes a precipitate of a basic indium periodate, 2InO5·In(OH)3·6H2O. Oxalic acid causes a precipitate of indium oxalate, In2(C2O4)3·10H2O. Alkali oxalates cause a precipitate of the alkali dioxalatoindate to form MIn(C2O4)2·3H2O, where M = Na, K or NH4.

Related compounds

Hydrogen sulfates An acid sulfate, indium hydrogensulfate tetrahydrate with the formula HIn(SO4)2·4H2O crystallises in the orthorhombic system with unit cell dimensions a = 9.997 Å, b = 5.477 Å, c = 18.44 Å, with four of the formula per cell. The density is 2.50 g/cm3. In the acid sulfate, two water molecules are linked to the indium atom and a hydronium ion H5O2 takes care of the proton. This is part of an acid sulfate family that includes Al, Ga, In, Tl(III), Fe(III) and Ti(III). HIn(SO4)2 is made by evaporating an indium sulfate in 40% sulfuric acid solution or cooling indium sulfate in a 60% sulfuric acid solution. As the acid tetrahydrate is heated it gives off water yielding a trihydrate, monohydrate, and an anhydrous form at 370 K (97 °C; 206 °F), 385 K (112 °C; 233 °F) and 482 K (209 °C; 408 °F). Above 505 K (232 °C; 449 °F) it gives out more water and sulfur dioxide yielding the neutral indium sulfate. Indium hydrogensulfate is a proton conductor with conductivity 0.0002 Ω-1cm-1.

Basic sulfates A basic indium sulfate is made by adding ethanol to a water solution of indium sulfate. Crystals can be formed by using a 0.05 molar solution with twice the volume of ethanol, and waiting for several weeks for crystals to form. InOHSO4·(H2O)2 has monoclinic crystals with a=6.06 Å b=7.89 Å c=12.66 Å and β=107.5°. Cell volume is 577.6 Å3. Another basic indium sulfate InOHSO4 with rhombohedral crystals is made by heating an indium sulfate solution at 160 °C (320 °F) or over for about a week in a sealed tube. This insoluble basic salt also forms if indium sulfate solution is diluted below 0.005 molar. So a precipitate forms from diluted solutions as well as from heated solutions.

Anhydrous double sulfates Two different types of anhydrous double indium sulfates have been made. One is from the family MI3MIII(XO4)3, with MI being a large singly positive ion such as K, Rb, Cs, Tl or NH3; MIII is triply charged and can be Al, Ga, In, Tl, V, Cr, Fe, Sc and other rare earths; and X is S or Se. Most of these have a rhombohedral crystal structure. However, triammonium indium trisulfate, (NH4)3In(SO4)3 converts from rhombohedral to monoclinic as the temperature drops below 80 °C (176 °F), and converts back into a rhombohedral form with space group R3c as the temperature rises above 110 °C (230 °F). The low temperature monoclinic form has space group P21/c, a=8.96 Å, b=15.64 Å c=9.13 Å β=108.28° Z=4 The high temperature form is termed "β-". An explanation for this transition is that ammonium (and also thallium) is a non-spherical ion and thus has lower symmetry. However, when it is heated enough, dynamical disorder causing random orientations makes the ions on average spherically symmetric. Alkali metal ions are spherical in shape at all temperatures and form rhombohedral structures. Double sulfates of this form exist of indium with the alkali metals sodium, potassium, rubidium, and cesium. These can be formed by heating a solid mixture of the individual sulfates to 350 °C (662 °F).

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Illustrations

Worked examples

Example 1 — a first encounter with Indium(III) sulfate

Start with the simplest possible case. Write down what Indium(III) sulfate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Indium(III) sulfate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Indium(III) sulfate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Indium(III) sulfate

In research: Indium(III) sulfate appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Indium(III) sulfate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Indium(III) sulfate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Indium compounds, Sulfates, so understanding it makes those chapters shorter.
In everyday life: Look for Indium(III) sulfate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Indium(III) sulfate in 20 minutes

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Frequently asked questions

What is Indium(III) sulfate in simple terms?

Indium(III) sulfate (In2(SO4)3) is a sulfate salt of the metal indium. It is a sesquisulfate, meaning that the sulfate group occurs 1⁠1/2⁠ times as much as the metal.

Why does Indium(III) sulfate matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Indium(III) sulfate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Indium(III) sulfate.