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<p>[QUOTE=&quot;-jeffB, post: 2886498, member: 27832&quot;]I&#039;m finding it hard to pull myself away from this. <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie11" alt=":rolleyes:" unselectable="on" unselectable="on" /></p><p><br /></p><p>The paper&#039;s author says he expected to see a SG of 10.31 for US 90% coinage, and instead was seeing 10.18 or 10.19. That&#039;s just over a 1% discrepancy.</p><p><br /></p><p>He estimates his own weighing accuracy (without any supporting evidence) at +/- 0.05 g, a hair under 0.5%.</p><p><br /></p><p>The density of water decreases by 0.2% or more as it warms from 10 C (50 F, cold tap water) to 20 C (68 F, &quot;standard room temperature&quot;). Colder water will yield lower SG measurements; warm water will yield higher measurements. The author doesn&#039;t say anything about controlling for this. (This also opens the possibility that the scale itself drifts as its temperature changes.)</p><p><br /></p><p>The author doesn&#039;t say anything about the dimensions of the nylon thread he used for suspending coins. This <i>might</i> be negligible, but I&#039;d expect it to have more of an effect as coins got smaller -- i.e. ASEs and silver dollars would show a higher SG, quarters and dimes would show lower, since nylon is less dense than coin metal.</p><p><br /></p><p>The author doesn&#039;t say anything about the stability over time of his scale. I know that mine shifts predictably over time (I&#039;ll see if I can dig up the post where I talk about it). If he wanted to control for that, he should measure that ASE (which he said read a little <i>high</i> -- see above for large vs. small coins!) <i>twice</i>, once <i>before</i> measuring the suspicious half-dollar and once <i>after</i>, and see if <i>those</i> measurements are consistent.</p><p><br /></p><p>Between all these sources of error, I&#039;m going to say that the author&#039;s measurements are easily within the expected range for true 90% silver.</p><p><br /></p><p>I don&#039;t mean any of this to cast aspersions on the author. Like I said, I admire and want to encourage people who actually Go Forth And Experiment. But again, if your measurements contradict a huge body of existing evidence, <i>you really need to check your measurements</i> before announcing that breakthrough (or scandal).[/QUOTE]</p><p><br /></p>

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