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Borax Pentahydrate vs. Decahydrate: Key Differences Explained

| Modified on Sep 14, 2024
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Borax, a naturally occurring mineral, is commonly used in a variety of applications, from household cleaning to industrial processes. Two popular forms of borax are borax pentahydrate and borax decahydrate. While they share many similarities, key differences between these two compounds make them suitable for different purposes.

Chemical Composition

The primary difference between borax pentahydrate and borax decahydrate lies in their chemical composition, specifically the amount of water they contain.

  • Borax Pentahydrate: This form of borax contains five molecules of water (hence "penta" meaning five). Its chemical formula is Na2B4O7·5H2O. Due to its lower water content, borax pentahydrate is more concentrated and has a higher boron content by weight compared to borax decahydrate.

  • Borax Decahydrate: This form of borax contains ten molecules of water, with the chemical formula Na2B4O7·10H2O. It is the most common form of borax available and is less concentrated than the pentahydrate form, making it slightly less potent in terms of boron content.

Uses and Applications

Both forms of borax are used in a variety of applications, but their different water content can affect how they are used.

  • Borax Pentahydrate: Due to its higher boron content, borax pentahydrate is often used in industrial processes where a more concentrated form of borax is needed. It is commonly used in manufacturing, metallurgy, and as a flux in welding and soldering. Its lower water content also makes it more suitable for formulations where moisture control is critical.

  • Borax Decahydrate: This more commonly used form of borax is widely available for household and industrial use. It is often used in cleaning products, laundry detergents, and as a fungicide. Its higher water content makes it easier to dissolve in water, which is useful for applications where quick solubility is needed.

Handling and Storage

Both borax pentahydrate and borax decahydrate should be handled with care, as they can be irritating to the skin and eyes. Due to its higher moisture content, borax decahydrate is more prone to clumping and should be stored in a cool, dry place. Borax pentahydrate, on the other hand, is less likely to clump, making it easier to store over time.

Conclusion

When choosing between borax pentahydrate and borax decahydrate, it is important to consider the specific needs of your application. Borax pentahydrate may be the better choice if you require a more concentrated form of borax with higher boron content. However, for general household uses and applications requiring quick dissolution, borax decahydrate is typically more convenient.


0 User Review

Posted by Daniel (Christchurch, Canterbury) on 09/30/2010

Could anybody tell me if borax pentahydrate and borax decahydrate, both being only 5 molecules apart, are both safe to ingest using Ted's recipe?

Replied by Marianne
(Nelson)
07/12/2012

Hello daniel, I am also in NZ, want to know if you found out more info on pentahydrate borax as that is what I've bought from the binn inn. I want to use it for helping me cure my arthritis as well as fungal nails. Looking forward to your reply, many thanks

Replied by Eddy
(Perth, Western Australia)
12/14/2012

The chemical difference is that the Borax Pentahydrate molecule has 5 water molecules attached, and the Borax Decahydrate molecule has 10 water molecules attached.

The practical difference is that the Borax Pentahydrate is around 15% Boron, whereas the Borax Decahydrate molecule is 'bigger' because of the extra water molecules and as a result the ratio of Boron content is less, at about 10% of the total weight.

They are identical substances except for the molecular water content and the resulting different proportions of the element Boron. Since the Pentahydrate is 'stronger' at 15% Boron, you should reduce the doses by around 1/3rd to get to the equivalent Decahydrate doses. That's all.