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Physics/Salt vs Baking Soda

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Question
Dear Dr. Nelson,

Hope all is well. I wanted to know whether baking soda or rock salt (specifically Himalayan Pink Salt) rank higher on Moh's scale of Mineral Hardness.  Baking soda seems to have a hardness of 2.5, while rock salt has a hardness of 2.0. Can you please confirm that this is true. The reason for this question has to do with which would be less abrasive for teeth brushing. I read that tooth enamel has a hardness of 5 and dentin has a hardness of 2.5. Not sure if these numbers are correct because I pulled them from google.

Thank you very much for your time,
Alex

Answer
It's 2-2.5 depending on the type of rock salt. You're thinking of the powdered forms, perhaps, and not the solid crystals?  In the case you're asking for, it doesn't really matter.  Water solubility and chemical compatibility with the enamel are the keys.  You should probably ask a chemist, a biochemist, or a dentist... this isn't really a physics question now.

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Dr. Stephen O. Nelson

Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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