As a renowned supplier of magnesium hydroxide, Mg(OH)2 , we’re here to explain some of the concepts you will see as you research products and services; especially as it relates to the different types of magnesium materials, and certain grades of magnesium hydroxide. This will become an on going series so be sure to check back often.
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Whether you are a wastewater treatment plant operator, chemist, lab technician, purchasing/procurement specialist, or student, you may come across details that are unfamiliar to you. Hopefully, this helps!
Topics covered in this post:
What is Magnesium Hydroxide?
Magnesium Hydroxide as an Acid Neutralizer
Magnesium Hydroxide as a Natural Fire Retardant
How Magnesium Hydroxide is Made
The History of Magnesium Hydroxide
Useful Terms to Know
Tips and Reminders for Magnesium Hydroxide
What is Magnesium Hydroxide?
First, it is essential to know that magnesium hydroxide is unique and not the same as magnesium metal, magnesium oxide, or other popular magnesium compounds.
By definition, Mg(OH)2 is a slightly alkaline crystalline compound that is frequently utilized within the pharmaceutical industry – especially as a laxative and gastric antacid. It also happens to be a popular additive in cosmetics and hygiene products due to its elemental magnesium content.
For instance, it can keep cosmetic makeup from creating droopy faces and armpits from developing odor-causing bacteria that keeps that kissable cutie at an arm's length.
There is a lot to know about the medicinal values of Mg(OH)2, but for purposes here, we will focus on the technical, municipal, and industrial grades of magnesium hydroxide.
Magnesium Hydroxide as an Acid Neutralizer
Technical grade Mg(OH)2 is used for various commercial and industrial applications. One area that we will focus on is the utilization of magnesium hydroxide for treating municipal and industrial wastewater. Mg(OH)2 provides pH modification and stabilization, odor control, and is an alkalinity source.
Let’s speak geek for a moment:
→ Upon reaction with water, magnesium hydroxide breaks down into a magnesium cation, Mg2+, and two hydroxide anions, 2(OH–).
→ These hydroxide ions are advantageous in applications where an acidic solution needs a raised pH, like wastewater. Free hydrogen ions, H+, contribute to the acidity of a solution and the more there are, the more acidic the solution.
→ By introducing magnesium hydroxide to a solution, each OH– ion attaches to an H+ ion, forming neutral water molecules, H2O. These chemical reactions provide aid to the neutralization process.
Unlike caustic soda and lime, which can also be used for these same applications, magnesium hydroxide is a non-hazardous substance, making it a safer alternative for any industry. We talk more about this in our Transition from Traditional pH Control Methods to Mg(OH)2 with AlkapHix® post.
Magnesium Hydroxide as a Natural Fire Retardant
Magnesium hydroxide can be used as a natural fire retardant. Mg(OH)2 begins to decompose to magnesium oxide, MgO, and water around 340–360°C, resulting in a with-ease reaction with fire, considering that the dullest of fire temperatures is roughly 525°C.
Its unique endothermic decomposition slows ignition by releasing water that dilutes combustible gasses while the formation and accumulation of MgO solids suppresses atmospheric oxygen from reaching; thus, feeding the fire.
How Magnesium Hydroxide is Made
As discussed in a previous post, magnesium hydroxide is produced in one of three ways.
Mining: brucite is the natural source of magnesium hydroxide. The calcining of brucite produces MgO, which is then hydrated to form pure Mg(OH)2.
Precipitation: an aqueous mixture of seawater (brine) and calcium oxide (lime) is used to precipitate magnesium out of seawater. This technique tends to be the most popular method to this day.
Hydration: hydrating magnesium oxide in agitated water creates an exothermic reaction that produces an Mg(OH)2 slurry.
The History of Magnesium Hydroxide
Magnesium is an alkaline earth metal and is the fourth most abundant element on Earth. It was first mined in Magnesia, Greece in its raw forms such as dolomite and magnesite.
Magnesium carbonate made its first grand appearance in the mid-1700s after Joseph Black, a Scottish physicist and chemist with an emphasis in medicine, discovered that this particular alkali could treat minor digestive disorders.
Jumping about 70 years to 1824, mineralogist Archibald Bruce discovered brucite during his chemical analysis of native minerals in his hometown of New Jersey. The significance of this finding meant that there was now a source of magnesium hydroxide that others could soon gain profits off of by selling within the industrial and medicinal sectors.
American inventor John Callen was the first to take advantage of the legal availability of magnesium hydroxide. In 1818, he was granted a patent for the chemical compound Mg(OH)2. This patent would later compel Irish physician, James Murray, to create a solution he called fluid magnesia: a suspension of magnesium sulfate in water that was meant for treating digestive problems. By the 1830s, Murray had a factory in Belfast, Ireland, and was running a successful business across Great Britain.
Since Sir Murray didn’t bother to place a patent on his product beyond Great Britain, some American guy across the pond, aka the Atlantic Ocean, decided to mimic Murray’s success. This American goes by the name of Charles H. Phillips and not only did he start a business and patent his product but also improved upon Murray’s method by replacing the use of magnesium sulfate with magnesium hydroxide. Such suspension of magnesium hydroxide in water came to be known as Milk of Magnesia, due to its milky smoothness and uniformity. To this day, nearly every American has consumed, or is at least familiar with, his laxative product known as Phillips’.
Beginning in 1994, the United States Patent and Trademark Office (USPTO) listed Bayer as the registered owner of both the names and formulation of Milk of Magnesia™ and Phillips’™ Milk of Magnesia.
Useful Terms to Know
pH
A scale used to specify how acidic or basic a water-based solution is. Acidic solutions have a lower pH, whereas basic solutions have a higher pH. At room temperature (25 ºC), pure water is neutral, meaning it is neither basic or acidic, and has a pH of 7.
Alkalinity
The capacity of water to resist changes in pH that would otherwise make it more acidic.
Slurry
A mixture of water and insoluble matter, such as mud or plaster of paris.
Synthetic Magnesium Hydroxide
Man-made magnesium hydroxide which is produced by the precipitation of seawater and lime.
Magnesium Oxide
A white, highly infusible compound used commonly in refractories, cement, insulation, and fertilizers. It is also available in food- and pharmaceutical-grades for hygienics and supplements.
Tips and Reminders for Magnesium Hydroxide
Magnesium hydroxide is not synonymous with other magnesium compounds or materials
Not all magnesium hydroxide products have the same level of reactivity. The production processes is what determines the behavior and magnesium content of the material
There are various grades of magnesium hydroxide, which reflect upon the industrial application. Technical-grade Mg(OH)2 has different chemical and physical properties than food & pharmaceutical grade Mg(OH)2.
Garrison Minerals works hard to stay at the forefront of research and innovation and is excited for our customers and end-users to benefit from that work! We have decades of combined experience and are here to help!
We offer industry, application, and dosing consultations, equipment, and magnesium hydroxide products for nearly every specification.
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Have a question related to this post, or are you ready out magnesium hydroxide for your particular application? Contact Garrison Minerals to let us know how we can help with your Magnesium Hydroxide needs.