Harold said:
It makes no sense putting any of it in a filter, not even when it's completely washed and rinsed. Keep it in the same container (one that resists heat---- a beaker, for example) so it can be washed and rinsed well, then dried by direct application of heat.
I've done what you're saying many times on many different materials but I assume you're talking about gold powder. I've found it to work well for heavy, quick settling materials. For a small amount of gold powder, it works well, but, for a large amount, I prefer a filter.
Here's my reasoning. Rinsing is dilution. If you are able to remove 90% of the liquid each rinse, after 3 rinses you will have removed 99.9% of it = [1-(.1 x .1 x .1)](100). When you add water and decant, you probably leave 4 or 5 times as much liquid in the powder itself as you would in a filter, unless you set it so it can drip for awhile. Therefore, it will take many more rinses than it would in a filter, for the same effectiveness. Also, it is slower (clean gold powder filters very quickly), since each time, you have to add the water, stir everything up, rinse down the inside of the container, let it settle, and pour it off. It's also more labor intensive than filtering and it's hard to do it 12 times without pouring off at least one speck of gold.
On the plus side, you can dry it in the original container. There's no filter paper to catch small gold particles. That's a pretty big advantage. If your goal is to get every teeny-weeny bit, the first time, this is the way to go. That wasn't my goal.
A trick. When using a vacuum filter, you can dry it in the filter by putting a 60 watt light bulb above it and then sucking the heat from the bulb through the gold. It's very fast. In short order, both the gold and paper will be dry. Most of the gold will end up falling off the paper - the paper is still worth saving, though. Don't put the bulb too close, or the paper will char after the gold dries and you'll have a mess - keep it maybe 3" - 5" away. For large Buchner filters, we used an infra red or regular bulb in a large reflector.
I might mention that, in a regular filter funnel, 5 small rinses are more effective, and faster, than 2 or 3 large rinses. Just barely cover the gold. Check the pH of the rinse water after a few rinses - pH paper is fine. When it's about 6, you are finished. Hot rinse water is more effective than cold.
