Tamerakshar,
Reading your 2 posts in this thread I am unsure if the gold you are dissolving is that left after inquartation and removal of silver by nitric then incinerated or your recovered gold powder after SMB. The only real difference between the 2 in this case is that the finer the gold is (meaning grain size) the easier it will be for it to go into solution.
Gold readily goes into solution with HCl with the addition of an oxidizer and it does not take much. You mentioned that you are careful and do not add H2O to your dried gold and HCl so I guess that you are concerned about the oxygen in the water. Remember that your 29% HCl is still mainly water. You also mention 50 C as a critical temperature or threshold for putting gold into solution with HCl-H2O2. I can assure you that I put gold into solution with HCl-H2O2 all last winter in an unheated lab at a few degrees over freezing, yes heat helps.
Because of your washing of your gold with H2O then double incineration I am willing to believe you have removed your nitrates. So by default I suspect that you are putting your gold into solution by simple aeration by either stirring or boiling, much like people here use an aquarium bubbler to rejuvenate their AP with the addition of nothing more than regular air.
I am not a chemist (maybe they can give some greater detail) but I can share my empirical evidence and observations in my own refining. If I take well washed gold powder from an SMB precipitation and put it in a beaker and add HCl with no additional water, and place it on a hot stir plate at a low temperature setting and a high stir rate the gold powder will dissolve, completely. The action of the stir bar chops in enough air to supply the oxygen to take the gold into solution.
A second case is one I just talked to a chemist about this weekend coincidentally. I had a mixed PGM precipitation that was well washed then covered with HCl to prevent drying of the particulate, I let it set for a few months. When I went to work with this precipitate I noticed the color of the HCl so tested with stannic receiving a positive result. After decanting off the HCl I processed the solution with a standard PGM precipitation. I recovered over 5 grams of ammonium hexachloropalladate from this HCl. After some research (as well as confirmation from a chemist) I found that palladium will go into HCl with exposure to air over time even without agitation.
I hope this helps you and perhaps sinks home the message to others how important it is to always test your solutions even when you have an element that the books will say "does not dissolve in HCl alone". The books are right to a point, but it takes an oxidizer as simple as air over time without agitation and it is no longer just HCl.
P.S. I did not check your knowledge from your past posting history, so I may have just told you information you already know. If that is the case I apologize in advance, but there are others reading that may find the additional information useful. I do not mean this in a bad way, but sometimes post replies are written in greater detail than needed by the individual asking the question so as to benefit others. I wrote all of the above when I could have simply replied by giving a one word answer "air".
Edit: spelling
, first from your politeness and second from your fatal info you mentioned.
