martyn111, yes that is very good advice, for small amounts of gold will be lost ( or very difficult to deal with), in solutions of aqua regia heavily contaminated with base metals.
let us say we used Aqua regia on an CPU, dissolving gold copper kovar tin lead or whatever, well if this CPU was not crushed to fine powder (even crushed has its own set of troubles), and all of the metals in it were completely dissolved (metals inside of cpu may be hard for acids to (reach) leach, bubbles of acids may block entry of fresh acid, and not all of the base metals will be dissolved this will leave elemental metals for the gold in solution to plate back to,(which may now be hidden inside the CPU, now you discard this “leached cpu” with some of your gold plated out inside of it
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now we have a dirty solution of gold and base metals, well the gold(ions salts) may latch onto these base metals (ions salts) in solution as we try to precipitate gold, some of our gold will not precipitate normally, well we could shove some more copper out of solution or cement out the little gold with copper, but now we still have a contaminated gold precipitant, yes you may get some gold by using these methods but losses can be much higher and success can be little to none depending on situations.
when eliminating the base metals is such an easy step and your yields and processing will go much smoother and less problems, it can be hard enough for a new guy to learn to recover and process his scrap, and going straight to aqua regia to leach CPU's is setting yourself up for trouble and losses
Once the base metals are removed from the fine gold, the HCl/bleach will dissolve the gold easily, and this solution can be easier to retrieve gold from, (as opposed to aqua regia) as no nitrates to vapor off, and a little excess chlorine is easier to eliminate.