He Barium hydroxide Is a chemical compound of formula Ba (OH) 2 (H 2 OR) X . It is a strong base. It may be anhydrous, monohydrate or octohydrate.
The monohydrate form, also called barite water, is the most common form and commercial use. The structure of the anhydrous and monohydrate compounds is presented in figure 1.
Figure 1: Structure of anhydrous barium hydroxide (Izq.) And monohydrate (Der.)
Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water:
BaO + 9H 2 O → Ba (OH) 2 · 8H 2 OR
It is crystallized as the octahydrate, which is converted into the monohydrate upon heating in air. At 100 ° C under vacuum, the monohydrate will produce BaO and water.
The monohydrate adopts a stratified structure (Figure 2). The Ba 2+ They adopt an octahedral geometry. Each center Ba 2+ Is bound by two water ligands and six hydroxide ligands, which are respectively double and triple bonds to the Ba 2+ neighbors.
In the octahydrate, the Ba 2+ Individual are again eight coordinates but do not share ligands (Barium Hydroxide, S.F.).
Figure 2: crystal structure of barium hydroxide.
Properties of barium hydroxide
Barium hydroxide is white or transparent octahedral crystals. No odor and caustic taste (National Center for Biotechnology Information., 2017). Their appearance is shown in Figure 3 (IndiaMART InterMESH Ltd., S.F.).
Figure 3: appearance of barium hydroxide.
The anhydrous form has a molecular weight of 171.34 g / mol, a density of 2.18 g / ml, a melting point of 407 ° C and a boiling point of 780 ° C (Royal Society of Chemistry, 2015) .
The monohydrate form has a molecular weight of 189.355 g / mol, a density of 3.743 g / ml and a melting point of 300 ° C (Royal Society of Chemistry, 2015).
The octohydrate form has a molecular weight of 315.46 g / mol, a density of 2.18 g / ml and a melting point of 78 ° C (Royal Society of Chemistry, 2015).
The compound is slightly soluble in water and insoluble in acetone. It is a strong base with a pKa of 0.15 and 0.64 for the first and second OH - respectively.
Barium hydroxide reacts similarly to sodium hydroxide (NaOH), but is less soluble in water. Neutralizes acids exothermally to form salts plus water. It can react with aluminum and zinc to form oxides or hydroxides of the metal and generate hydrogen gas.
It may initiate polymerization reactions in polymerizable organic compounds, especially epoxides.
It may generate flammable and / or toxic gases with ammonium , Nitrides, halogenated organic compounds, various metals, peroxides and hydroperoxides. Mixtures with chlorinated gums explode when heated or crushed (BARIUM HYDROXIDE MONOHYDRATE, 2016).
Barium hydroxide decomposes to barium oxide when heated to 800 ° C. The reaction with carbon dioxide produces barium carbonate. Its highly alkaline aqueous solution undergoes acid neutralization reactions. Thus, it forms barium sulfate and barium phosphate with Sulfuric acids And phosphoric, respectively.
H 2 SW 4 + Ba (OH) 2 BaSO 4 + 2H 2 OR
The reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble or less soluble barium salts may result from a double replacement reaction when an aqueous solution of barium hydroxide is mixed with many solutions of other metal salts.
Mixing the solid hydrated barium hydroxide with solid ammonium chloride in a beaker produces an endothermic reaction to produce a liquid, with the evolution of ammonia. The temperature decreases drastically to about -20 ° C (Royal Society of Chemistry, 2017).
Ba (OH) 2 (S) + 2NH 4 Cl (s) → BaCl 2 (Aq) + 2NH 3 (G) + H 2 OR
Figure 4: Endothermic reaction between barium hydroxide and ammonium chloride.
Ba (OH) 2 reacts with carbon dioxide to produce barium carbonate. This is expressed by the following chemical reaction:
Ba (OH) 2 + CO 2 → BaCO 3 + H 2 O.
Reactivity and hazards
Barium hydroxide is classified as a stable, non-combustible compound that reacts rapidly and exothermically with acids, and is incompatible with carbon dioxide and moisture. The compound is toxic and, as a strong base, it is corrosive.
Inhalation, ingestion or skin contact with the material can cause serious injury or death. Contact with molten substance may cause severe burns to the skin and eyes.
Avoid contact with the skin. The effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and / or toxic gases. Fire control wastewater can be corrosive and / or toxic and cause pollution.
Eye contact
If the compound comes into contact with the eyes, contact lenses should be checked and removed. Immediately flush eyes with plenty of water for at least 15 minutes with cold water.
Skin contact
In case of contact with the skin, immediately rinse the affected area for at least 15 minutes with plenty of water or a weak acid, for example vinegar, while removing contaminated clothing and shoes. Cover irritated skin with an emollient.
Wash clothing and shoes before reuse. If contact is severe, wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream.
Inhalation
In case of inhalation, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen.
Ingestion
If the compound is ingested, do not induce vomiting. Loosen tight clothing such as a shirt collar, belt or tie.
In all cases, immediate medical attention should be obtained (Material Safety Data Sheet Barium hydroxide monohydrate, 2013).
Applications
1- Industry
Industrially, barium hydroxide is used as a precursor to other barium compounds. The monohydrate is used to dehydrate and remove sulfate from various products. This application exploits the very low solubility of barium sulfate. This industrial application also applies to laboratory uses.
Barium hydroxide is used as an additive in thermoplastics (such as phenolic resins), scratches and PVC stabilizers to improve the plastic properties. This material is used as a general purpose additive for lubricants and greases.
Other industrial applications of barium hydroxide include sugar manufacture, manufacturing soaps, fat saponification, silicate melting and chemical synthesis of other barium compounds and organic compounds (BARIUM HYDROXIDE, S.F.).
2- Laboratory
Barium hydroxide is used in analytical chemistry for the titration of weak acids, particularly organic acids. It is guaranteed that its transparent aqueous solution is free of carbonate, unlike those of sodium hydroxide and potassium hydroxide, since the barium carbonate is insoluble in water.
This allows the use of indicators such as phenolphthalein or thymolphthalein (with alkaline color changes) without risk of titration errors caused by the presence of carbonate ions, which are much less basic (Mendham, Denney, Barnes, & Thomas, 2000).
Barium hydroxide is occasionally used in organic synthesis as a strong base, for example for the hydrolysis of Esters And nitriles:
Barium hydroxide is also used in the decarboxylation of amino acids that release barium carbonate in the process.
It is also used in the preparation of cyclopentanone, diacetone alcohol and gamma - lactone D - Gulon.
3- Catalyst in the Wittig-Horner reaction
The Wittig-Horner reaction , Also known as the Horner-Wadsworth-Emmons reaction, is a chemical reaction used in organic chemistry to stabilize carbanions of phosphonates with aldehydes (or ketones) to produce predominantly E-alkenes (trans).
The Wittig-Horner sonochemical reaction is catalyzed by activated barium hydroxide and is carried out under solid-liquid interface conditions.
The sonochemical process takes place at room temperature and with a lower catalyst weight and reaction time than the thermal process. Under these conditions, yields similar to those of the thermal process are obtained.
In the work of (J. V. Sinisterra, 1987) the influence on the yield of the sonication time, the weight of the catalyst and the solvent is analyzed. Small amounts of water should be added for the reaction to take place.
The nature of the active site of the catalyst acting in the process is analyzed. An ETC mechanism is proposed for the sleep-chemical process.
4- Other uses
Barium hydroxide has other uses. It is used for a number of purposes, such as:
- The manufacture of alkali.
- The construction of glass.
- Vulcanization of synthetic rubber.
- Inhibitors of corrosion.
- Such as drilling fluids, pesticides and lubricants.
- For the remedy of the boiler.
- To refine vegetable and animal oils.
- For the fresco painting.
- In water softening.
- As an ingredient in homeopathic remedies.
- To clean acid spills.
- It is also used in the sugar industry to prepare beet sugar.
- Construction materials.
- Electrical and electronic products.
- Floor coverings.
References
- BARIUM HYDROXIDE MONOHYDRATE . (2016). Recovered from cameochemicals: cameochemicals.noaa.gov.
- Barium Hydroxide . (S.F.). Retrieved from chemistrylearner: chemistrylearner.com.
- BARIUM HYDROXIDE . (S.F.). Recovered from chemicalland21: chemicalland21.com.
- IndiaMART InterMESH Ltd.. (S.F.). Barium Hydroxide . Retrieved from indiamart: dir.indiamart.com.
- V. Sinisterra, A. F. (1987). Ba (OH) 2 as catalyst in organic reactions. 17. Interfacial solid-liquid Wittig-Horner reaction under sonochemical conditions. The Journal of Organic Chemistry 52 (17) , 3875-3879. Researchgate.net.
- Material Safety Data Sheet Barium hydroxide monohydrate . (2013, May 21). Retrieved from sciencelab: sciencelab.com/msds.
- Mendham, J., Denney, R. C., Barnes, J.D., & Thomas, M.J. (2000). Vogel's Quantitative Chemical Analysis (6th ed.). New York: Prentice Hall.
- National Center for Biotechnology Information. (2017, March 28). PubChem Compound Database; CID = 16211219 . Recovered from PubChem: pubchem.ncbi.nlm.nih.gov.
- Royal Society of Chemistry. (2015). Barium hydroxide . Recovered from chemspider: chemspider.com.
- Royal Society of Chemistry. (2015). Barium hydroxide hydrate (1: 2: 1) . Recovered from chemspider: chemspider.com.
- Royal Society of Chemistry. (2015). Dihydroxybarium hydrate (1: 1) . Recovered from chemspider: chemspider.com.
- Royal Society of Chemistry. (2017). Endothermic solid-solid reactions . Retrieved from: learn-chemistry: rsc.org.