Sciencemadness Discussion Board

Na Hexametaphosphate & 31.5% HCl, & TIME

deadrush - 25-3-2026 at 09:16

So for fun I threw some sodium Hexametaphosphate in a 5gal bucket and then about 1/3 of a gallon of hcl. I left it in the basement with a lid placed loosely atop. I stirred by swirling the bucket for about 1min 3-5 times a day for about a week. At first, some (I assume) sodium Hexametaphosphate stuck to the buttom but after vigorous stirring there is nothing stuck anymore. The HCl fumes weren't great but it is stored in a cold (read: average 40F) unfinished basement. I am in no rush. But why after 2 weeks does it look like this? The only change I can discern is a depreciation of hcl fumes.

Thanks

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chloric1 - 25-3-2026 at 09:22

Well if HCl fumes are down then it could mean the sodium hexametaphosphate changed to sodium chloride or it could mean the majority of the HCl simply offgased. Take some of the solid salt, rinse with alcohol and dry then dissolve a few grams in warm distilled water. Sodium chloride is more soluble and should dissolve faster also.

bnull - 26-3-2026 at 01:57

@deadrush: Please convert the image from HEIC to JPG.

Boffis - 26-3-2026 at 03:30

Hi deadrush; what exactly are you trying to achieve? What were you expecting to happen?

I suspect that slowly the polyphosphate ions will be hydrolysed to lower polymers and eventually simple ortho-phosphate ions, which due to the acidity of the HCl will be partly protonated to H2PO4- ad HPO4--. I also suspect that most of the sodium salts present have limited solubility in such strong HCl.