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A comment on Apple gold. Parent comment

Re:Apple gold by sp332 on Saturday March 07, 2015 @06:42PM (#9163623)
Archimedes' trick only works if you know the ratio of materials inside ahead of time. Otherwise it could be e.g. some gold + some copper and have the same density as silver.
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Re:Apple gold by Dylan16807 on Saturday March 07, 2015 @10:26PM (#9164380)
If you know it's 18k then all you have to do is weigh it to know how much gold there is. Then measuring volume can tell you the density of the rest of the alloy.
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Re:Apple gold by sukilot on Sunday March 08, 2015 @05:00PM (#9167234)
Only if the entire mass is 18k gold. Not if the entire mass is 18k gold plus other Try your approach on two cases: 0% gold, with 100% unknown alloy, and 100% watch components.

Like how foods made with "100% fruit" still have other ingredients.

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