[Qwebec]

Greetings,

I am looking to learn what is the commonly accepted procedure to create a solution containing the smallest possible gold clusters.

I write you these line, extremely wary of the responses I will get, having googled the previous answers, which were inflammatory and wherein none had any meat or substance to their rebuke. I hope the kids with their flippant answers will not comment.

Also, I have been forwarded a Patent from England which gives the following procedure, and claims cluster sizes of one atom only. I guess that's not even a cluster anymore. The patent contains apparently some errors with regards to the chemistry. Can anyone point them out to me please?

I sincerely thank anyone taking the time to actually offer more than a cursory answer, telling me specifically where and what is wrong with the chemistry of this patent, and I hope the people who can only offer a flippant dismissal in an attempt to show wit and conformity will abstain from boring me and maybe their peers. Adult responses only, please.

Thank you again for your time,

Duncan

ps: here's the procedure:

(1) 50 mg gold (99.99% pure) were dispersed in 200 ml aqua regia to provide clusters of gold atoms.

(2) 60 ml concentrated hydrochloric acid were added to the dispersion and the mixture was brought to boil, and continued boiling until the volume was reduced to approximately 10-15 ml. 60 ml concentrated HCl were added, and the sample brought to boil and checked for evolution of NOCl fumes. The process was repeated until no further fumes evolved, thus indicating that the nitric acid had been removed and the gold had been converted completely to the gold chloride.

(3) The volume of the dispersion was reduced by careful heating until the salt was just dry. "Just dry" as used herein means that all of the liquid had been boiled off, but the solid residue had not been "baked" or scorched.

(4) The just dry salts were again dispersed in aqua regia and steps (2) and (3) were repeated. This treatment provides gold chloride clusters of greater than 11 atoms.

(5) 150 ml 6M hydrochloric acid were added to the just dry salts and boiled again to evaporate off the liquid to just dry salts. This step was repeated four times. This

procedure leads to a greater degree of sub-division to provide smaller clusters of gold chloride. At the end of this procedure an orangish-red salt of gold chloride is obtained. The salt will analyze as substantially pure Au2Cl6.

(6) Sodium chloride is added in an amount whereby the sodium is present at a ratio 20 moles sodium per mole of gold. The solution is then diluted with deionized water to a volume of 400 ml. The presence of the aqueous sodium chloride provides the salt Na2Au2Cl8. The presence of water is essential to break apart the diatoms of gold.

(7) The aqueous sodium chloride solution is very gently boiled to a just dry salt, and thereafter the salts were taken up alternatively in 200 ml deionized water and 300 ml 6M hydrochloric acid until no further change in color is evidenced. The 6M hydrochloric acid is used in the last treatment.

( After the last treatment with 6M hydrochloric acid, and subsequent boildown, the just dry salt is diluted with 400 ml deionized water to provide a monoatomic gold salt solution of NaAuCl2'XH2O. The pH is approximately 1.0.

(9) The pH is adjusted very slowly with dilute sodium hydroxide solution, while constantly stirring, until the pH of the solution remains constant at 7.0 for a period of more than twelve hours. This adjustment may take several days. Care must be taken not to exceed pH 7.0 during the neutralization.

(10) After the pH is stabilized at pH 7.0, the solution is gently boiled down to 10 ml and 10 ml concentrated nitric acid is added to provide a sodium-gold nitrate. As is apparent, the nitrate is an oxidizer and removes the chloride. The product obtained should be white crystals. If a black or brown precipitate forms, this is an indication that there is still Na2Au2Cl8 present. If present, it is then necessary to restart the process at step (1).

(11) If white crystals are obtained, the solution is boiled to obtain just dry crystals. It is important not to overheat, i.e., bake.

(12) 5 ml concentrated nitric acid are added to the crystals and again boiled to where the solution goes to just dry. Again it is essential not to overheat or bake. Steps (11) and (12) provide a complete conversion of the product to a sodium-gold nitrate. No chlorides are present.

(13) 10 ml deionized water are added and again boiled to just dry salts. This step is repeated once. This step eliminates any excess nitric acid which may be present.

(14) Thereafter, the just dry material is diluted to 80 ml with deionized water. The solution will have a pH of approximately 1. This step causes the nitrate to dissociate to obtain NaAu in water with a small amount of HNO3 remaining .

(15) The pH is adjusted very slowly with dilute sodium hydroxide to 7.0 + 0.2. This will eliminate all free acid, leaving only NaAu in water.

(16) The NaAu hydrolyzes with the water and dissociates to form HAu. The product will be a white precipitate in water. The Au atoms have water at the surface which creates a voluminous cotton-like product.

(17) The white precipitate is decanted off from any dark gray solids and filtered through a 0.45 micron cellulose nitrate filter paper. Any dark gray solids of sodium auride should be redissolved and again processed starting at step (1).

(18) The filtered white precipitate on the filter paper is vacuum dried at 120C for two hours. The dry solid should be light grey in color which is HAuXH2O and is easily removed from the filter paper.

(19) The monoatomic gold is placed in a porcelain ignition boat and annealed at 300C under an inert gas to remove hydrogen and to form a very chemically and thermally stable white gold monomer.

(20) After cooling, the ignited white gold can be cleaned of remaining traces of sodium by digesting with dilute nitric acid for approximately one hour.

(21) The insoluble white gold is filtered on 0.45 micron paper and vacuum dried at 120C for two hours. The white powder product obtained from the filtration and drying is pure G-ORME.

The G-ORME made according to this invention will exhibit the special properties described in the "General Description" of this application, including catalytic activity, special magnetic properties, resistance to sintering at high temperatures, and resistance to aqua regia and cyanide attack.



 

[Arkcon]

(15) The pH is adjusted very slowly with dilute sodium hydroxide to 7.0 + 0.2. This will eliminate all free acid, leaving only NaAu in water.

(16) The NaAu hydrolyzes with the water and dissociates to form HAu. The product will be a white precipitate in water. The Au atoms have water at the surface which creates a voluminous cotton-like product.

Sorry, these two steps here, in particular, are a little difficult for me to understand.  I don't see how NaAu is actually a stable compound, and I don't really see sodium-gold alloy having the properties described, in water, and formed from NaOH neutralization.  Furthermore, HAu sounds very weird to me, and again, doesn't seem to have the properties I'd associate with a transition metal hydride.  Its very possible these repeated manipulations may produce nano-sized gold clusters, which could very likely have interesting catalytic properties, but some of the descriptions seem way out there.

I'm sorry you've caught a bunch of jokers so far, but I think I'm voicing valid (if uninformed) concerns.  Patents are often a little obtuse on purpose -- they're written to cover all economic bases for legal reasons, not for ease of peer-review like journal articles.  But stiill, this procedure leaves my head spinning.

[discodermolide]

( After the last treatment with 6M hydrochloric acid, and subsequent boildown, the just dry salt is diluted with 400 ml deionized water to provide a monoatomic gold salt solution of NaAuCl2'XH2O. The pH is approximately 1.0.
(18) The filtered white precipitate on the filter paper is vacuum dried at 120C for two hours. The dry solid should be light grey in color which is HAuXH2O and is easily removed from the filter paper.

(19) The monoatomic gold is placed in a porcelain ignition boat and annealed at 300C under an inert gas to remove hydrogen and to form a very chemically and thermally stable white gold monomer.
[/quote]


A couple of things, point 8 infers that "monoatomic gold" is NaAuCl₂XH₂O
Point 19 suggests that it is HAuXH₂O. It can't be both.
It also seems to me that there must be a horrible mixture of salts present, If that last purification step is sufficient to remove then I doubt.
Is this the only procedure in the patent? What is the patent number, by that I mean is it a GB, a USA, or a European patent?
What is claimed?