Ok, lets turn this around, lets do a more relative and unreliable method of determining what acid you might have.
wikipedia wrote:at a rate of 1.36 g of citric acid to every 0.91 grams of fumaric acid to add sourness, similar to the way malic acid is used
Fumaric acid has a fruit-like taste.
according to this, fumaric is not as sour as citric, and tastes slightly fruity. But I don't see how this could be of any use to you unless you had both citric and fumaric acids to compare it with.
Who knows, you might even have citrate or fumarate salts.
^ in this case you might not want to be eating whatever powder came in the package with the chinese lettering.
The easiest and most reliable way to solve your problem is doing what infundibulum posted, and sharing a link to where you obtained the stuff.
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If you want to be really cool, you should titrate it, plot equivalents vs pH, and post the titration curve on the forum. Now that may sound unreasonable, or even unfathomable, but it would be cool and maybe we would all learn something
Expect nothing, Receive everything.
"Experiment and extrapolation is the only means the organic chemists (humans) currrently have - in contrast to "God" (and possibly R. B. Woodward). "
He alone sees truly who sees the Absolute the same in every creature...seeing the same Absolute everywhere, he does not harm himself or others. - The Bhagavad Gita
"The most beautiful thing we can experience, is the mysterious. The source of all true art and science."