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I soaked and washed white Darice decorative sand in distilled water. I added food-grade citric acid to different distilled water, then I sprinkled in a few grains of the sand. The sand bubbled and dissolved.

AFAIK, citric acid should not dissolve quartz sand. Either

  1. the sand is not quartz, or
  2. the internet is wrong that citric acid cannot dissolve quartz sand.

If 2, then an equation would be appreciated.

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    $\begingroup$ It is (1).$\mathstrut$ $\endgroup$
    – Ivan Neretin
    Commented Feb 2, 2023 at 6:23
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    $\begingroup$ It would be great if you listed the composition of this decorative sand. This will help in writing of a possible reaction equation between the "sand" and citric acid. $\endgroup$
    – Exeplone
    Commented Feb 2, 2023 at 6:48
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    $\begingroup$ Bright white decorative sand is usually molten limestone or marble. $\endgroup$
    – fraxinus
    Commented Feb 2, 2023 at 17:33
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    $\begingroup$ Did I say molten? It's crushed and ground, of course. $\endgroup$
    – fraxinus
    Commented Feb 2, 2023 at 20:12

1 Answer 1

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Your sand dissolves in citric acid because it is carbonate sand.

Not all sand is formed by quartz, even if it is usually implied in context of masonry or fish-keeping. There are sometimes used explicit respective expressions for "quartz sand" in some languages.

The term sand does not describe what the material is, but how the material looks like. It means solid, water insoluble "stoney" material, consisting of loose particles with the particular range of granularity $\pu{0.05 - 2 mm}$ (credit to David S).

Quoting the Wikipedia:

Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt.

Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.

There are beaches with bright, near white sand formed from shells. It is based on calcite/aragonite $\ce{CaCO3}$, soluble in acids while releasing gaseous carbon dioxide.

$$\ce{CaCO3(s) + 2 H+(aq) -> Ca^2+(aq) + H2O(l) + CO2(g)}$$

There are beaches and deserts with dark, near black sand formed from various volcanic rocks.

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    $\begingroup$ Sand is also used to define particle size. Gravel or Stones is above 2mm in size, Sand is 2mm - 0.05mm, Silt is 0.05mm - 0.002mm, and Clay is below 0.002mm. $\endgroup$
    – David S
    Commented Feb 2, 2023 at 17:38
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    $\begingroup$ Well, that is what is said in the quote and respective links. Thanks for the explicit values. $\endgroup$
    – Poutnik
    Commented Feb 2, 2023 at 17:43

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