Ancient proceedings from Ammonium chloride and Saltpeter to obtain Aqua Regia through Hydrochloric Acid and Nitric Acid 3:1 often leads to Fulminating Gold.
Labors of Hercules were so exhausting ( and still are today) that Aqua Regia had the air of being a too good to be true shortcut to “open” or dissolve crude matter metallic gold into Mercurius/Secret Fire. Aqua Regia in latin means the water of the king. Indeed Aqua is an allegory for universal solvent and king for metallic gold. Actually Aqua Regia cannot in any way be employed in Alchemy as the legendary Alkahest. The Spit of the Moon. For the chemical solution of metallic gold in Aqua Regia does not really bring to the exterior what is hidden inside gold. Here I don’t mean the splitting of the Au2 molecule in mono-atomic Au, for I would rather interested in gold electronic cloud, since this seems to be full of Secret Fire. Which is our matter as well as our cooking tool. Subject, Subjectum Artis, as well as function. I don’t mean to be tedious, but only Spirit/Mercurius, that’s to say a more handy Secret Fire coming out of laboratory work, can be our solvent. Since very few alchemists did know about Secret Fire, the many tried to get to seeds of matter through matter ultimate units. Although metallic gold finely dividing takes its part in salts volatilization to get Alkahest/Universal Solvent.
In all ages the obsession to get universal solvent was directly proportionate to the obsession of getting it fast and easy. And Aqua Regia, the faster way to dissolve metallic gold, composed by legendary Sal Ammoniacum and Saltpeter, appeared to a great number of researchers as the ultimate secret shrouded in mystery and finally unveiled. I read on “ The Alchemic Gold” by K.K Doblerer that an eighteenth century alchemist was hired by a countess of Wuttemberg ( I guess I remember right, for I have lost the book) to have a try with Aqua Regia. In a summer afternoon, during their garden reading, the countess and her nephew could witness the bursting apart of the poor alchemist along with the wooden tower he was in. The nephew, in a later letter, described the amazing laboratory housing taking off, apparently not being so concerned about the man fate.
In 2005, at phantomplay.com (now expired), I found this very exhaustive presentation of Aqua Regia preparation from Ammonium chloride and Saltpeter ( Potassium Nitrate) ending to fulminating gold, which I thought to post here, not before having communicate them my appreciation as well as special thanks. Well done, phantom!
Heating the Ammonium Chloride and Potassium Nitrate mixture first causes some of the Ammonium Chloride to sublime. This is then followed by a formation of a yellow substance which distills from the mixture.
The vapor which is distilled is condensed in another test tube in a beaker of crushed ice. The vapor appears to be Nitric Acid with no indication Chlorine. Some sublimated Ammonium Chloride or Ammonium Salt appears in the glass connection tube and on the wall of the test tube.
Continued heating of the test tube containing the salt mixture caused the test tube to melt and form a blow hole at the heated area. The vapors are a mixture of Ammonium Chloride and Nitric Acid. Further experiments were done with Pyrex test tubes.
The distillate from the condensation test tube was placed in an evaporation dish. It is a light yellow fuming liquid which appears to be Nitric Acid. There does not appear to be any odor of free Chlorine gas.
The yellow solution of Gold dissolved in the Aqua Regia was added to Tin dissolved in Hydrochloric Acid. The formation of a purple precipitate (Purple of Cassius) is a positive test that gold was in solution.
A few drops of Aqua Regia were placed in a test tube and heated with a pellet of Potassium Hydroxide. A strip of damp red litmus paper was placed on the tube which turned blue indicating the vapors of a base. There was also the smell of Ammonia. Both these test are positive that an Ammonium Salt is present in the Aqua Regia.
The solution in the test tube above was heated to insure complete expulsion of Ammonia. This solution was allowed to cool and acidified with dilute Nitric Acid to neutralize the Potassium Hydroxide. A few drops of a solution of 2% Silver Nitrate was added to the test tube with the formation of a curd white precipitate (left). This precipitate was washed with distilled water and allowed to settle (center). The water was pipetted off, and to the damp precipitate, a few drops of concentrated Ammonium Hydroxide were added (right). The precipitate dissolved, proving the presence of Chlorine.
Potassium and Sodium are elements which are difficult to analyze by wet analytical methods because their salts are mostly soluble. The presence of these elements can be detected by saturating a piece of asbestos with the unknown solution and placing it into a flame. Potassium colors the flame violet (left). The sample was taken from the distilled Aqua Regia showing the presence of Potassium in the acid.
Because Sodium is a common contaminant and it imparts a yellow – orange color to the flame in extremely low concentrations, it is often difficult to see the presence of other elements that would impart color to the flame. In this case it is useful to use a Bunsen spectroscope to determine the presence of other elements.