Summary for kauri butanol method Discussion
Kauri butanol method questions here center on whether the Kauri-Butanol (KB) test can really measure the cleaning strength of isopropanol (IPA) on metal parts, and where to obtain the standard solution. William Brohinsky says the test is probably not suitable for a definitive answer about IPA, because Kauri dissolves completely in butanol and closely related alcohols such as 1-propanol and 2-propanol. He explains that the KB number is based on how much another solvent must be added to standard butanol before Kauri precipitates, but IPA typically gives very high KB values, often above the range where the test is considered valid. He also cautions that KB does not predict how well a solvent will clean a specific material; for example, high-KB solvents may dissolve oils well but not sugars, while water behaves the opposite way. His practical advice is to go back to the source of the recommendation or consult a chemistry department for better guidance.
Q. We use Isopropanol as a cleaning solution on metallic parts. We need to come up with a method to test the effectiveness of the IPA we use. The Kauri butanol value is used to check the solvency of solvents but it is very difficult to find details about this method.
We got the ASTM paper and we have to find a supplier for the Kauri butanol solution. Any ideas or details about this method and how to get the standard KB solution would be most appreciated.
Thank you very much,
Marie Sautrot
surface treatment – Farnborough, Hampshire, England
2004
A. I’m sorry to say that you probably will not be able to use the Kauri-Butanol test for a definitive answer about the strength of your IPA.
Kauri dissolves completely in Butanol and closely-related alcohols. This includes 1-propanol and 2-propanol (isopropyl alcohol).
The premise of the KB test is that Kauri will precipitate from Butanol if the Butanol is sufficiently diluted with another solvent which does not dissolve Kauri as well. Solvents like water take very little to precipitate Kauri from the standard solution. Others, like acetone
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, can dissolve Kauri fairly well, if not as well as butanol: where .5 mL of water will precipitate Kauri (earning a Kb of 6.5), about 18.7mL of acetone is required before Kauri precipitates (for a KB of 76.2). 2-propanol (IPA) requires upwards of 150mL to precipitate Kauri, making KB values over 500. Generally, KB is considered valid with maximum numbers under 200.
Additionally, the KB number is not indicative of the ability of any solvent to dissolve any particular material. For instance, high-KB-number solvents like trichlorethylene (KB 129) dissolve oils very well, but won’t touch sugars. Water, (KB 6.5) dissolves sugar very well and won’t have much affect (alone) on oils.
If the Kauri-Butanol test was recommended to you by someone, I recommend returning to them for further information and verification of the usefulness of this test on IPA: alternatively, a call to the nearest college with a good chemistry program may be considerably more helpful.
William Brohinsky
– Hanover, Connecticut, USA
May 24, 2013