The mystery of Aqua Regia as a more effective gold dissolvent than the modern one. Perhaps because of the strange ancient work with salts.
These operations are nowadays hardly performed. To tell the truth, the suppositions behind all that ancient chemistry were rather foolish: it will be enough to read the appalling theory about acids to understand the scientific imagination of the age.
So we cannot define these pages as chemistry, and sadly here, Nicolas Lemery tries to give a rationale too. Still, it remains the fact that his Aqua Regia is more effective in its main purpose: to dissolve metallic gold. As we will see, also his Fulminating Gold did act in a slightly different way than the modern one.
We know that molecular purity was unwanted and not searched. Back in the seventeenth century, they have the myth of salts’ “penetrability”, which is rather alchemical. In their mind, salt became penetrable when volatilized. We know where this concept could get to. Alcahest is not so far.
Nevertheless, it is a fact that Aqua Regia is not an alchemical dissolvent. Our dissolvent is Alcahest, which reduces our metals to their seeds. In poor words: Alcahest, that’s to say, Secret Fire reduces metal in another Secret Fire. We look for nothing less in our work; a simple gold dissolution is pretty useless. I said “quiet”, since, in alchemical works, imagination is the King.
You have already encountered countless operations to operate on salts to obtain Aqua Regia according to Lemery, that’s was in my articles Lemery & Aqua Regia First Step/ Sal Armoniac , Lemery & the Spirits of Salt Armoniac , Lemery & the Spirits of Common Salts with Wine and Lemery, Saltpeter & the Blood of Salamander . Here we will discover the goal, that’s to say, where these works did intend to arrive: Aqua Regia and Fulminating Gold.
I decided to maintain the chaotic connection system of Lemery, so I started translating from Fulminating Gold chapters and Aqua Regia’s ( Fulminating Gold is a product of Aqua Regia). Nicolas Lemery “Cours de la Chymie” Paris, 1675. My translation from the original french:
“Page 39: Fulminating Gold, called the Golden Saffron.
Take the quantity you like of gold filings, put it into a vial, and pour in little by three or four as much weight as the gold of Aqua Regia. Place the flask on warm sand till the gold is all dissolved in half an hour. Pour your solution into a glass vessel where you have previously put five or six as much volumes as the gold solution of common water; then, little by little, pour on this mix some volatile Spirit of Salt Armoniac or oil of Tartar made by failure (1), you will cause the gold to precipitate at the bottom of the glass. Let it rest for a long time in order not to lose anything; then pour by inclination the exceeding water, and wash your powder with warm water till the water is strongly insipid, then make it dry on a paper at very slow heat because the fire tends to run very easily. The powder flew out with a great noise.
Fulminating gold induces sweating and pushes out the nasty moisture by transpiration. It may be useful against Verole ( pox) at the dosage of two to six grains in a tablet or an opiate. it stops the vomit and the action of mercury.
One uses filings of gold to obtain an easier dissolution. One has to pour the Aqua Regia little to prevent the matter from going out of the flask. This effervescence is consequent to the dramatic breaking of gold by Aqua Regia since when Aqua Regia doesn’t find any body to act on anymore and has divided the gold into as particles as possible; the eruption will stop. Even if the gold remains in the Aqua Regia, this is not perceptible because we cannot see any change compared to what it was before; so much of the water is clear and transparent.
One can use some oil Tartar to make the gold precipitate and some Spirit of Salt Armoniac because both liquors contain a salt Alkali, so when mixing it with acids, they have to ferment. Inside this fermentation, the parts of Aqua Regia keep in suspension. The particles of gold are getting weaker and lacking the power to retain them, and the particles precipitate by their weight.
Maybe someone will have a hard time understanding how the volatile Spirit of Salt Armoniac could weaken the Aqua Regia, the same Aqua Regia composed of Salt Armoniac. Still, he has to consider that the strength of Aqua Regia is not dependent on the volatile salt armoniac but on the marine salt, which is in great quantity tied up with the Aqua Forte/Strong Water; since the marine salt or the rock salt may well substitute the salt Armoniac to make the Aqua Regia (2), as we will point when talking of this water composition. It remains to me to examine how the dissolvents abandon the bodies they have dissolved before to assault another. For example: why does the Aqua Regia leave the gold packed to deliver the salt Alkali? This question is one of the most difficult to be answered in the whole of physics. The following are some of the most sensible things one can say about it.
I ( Lemery) suppose that when the Aqua Regia has operated on gold and consequently has dissolved it, the points composing its force are attached to gold particles.”
The state of the art of seventeenth-century chemistry does provide this theory by which acids could dissolve and penetrate because they had sharp “ points” to enter and force the pores of other substances.
I can easily explain, with the same theory, the action of a powder composed of three parts of Nitre, two parts of Salt Tartar, and one part of Sulphur. This powder being in a spoon, the quantity about a drachm weighs, it bursts like a cannonball. The fixed salt of Tartar in this powder serves the same purpose as gold in the other, that’s to say that it retains the Spirits of Nitre and Sulphur joined together; in fact, they cannot stand out with great violence, but after having broken their chains, and it this process to cause the noise.
The Fulminating Gold taken orally provokes sweating because the heat from the body gets it to volatilize and discharge from the pores. If it finds open pores, it produces just inappreciable sweating. Someone thinks that the gold doesn’t contribute to sweating and that the Spirit of Nitre alone, being prevented by the body heat from leaving, does all the action. Nevertheless, I believe that the Spirits of Nitre are more likely to take some parts of gold with which they are tied up. And by this explication, one can understand how such a little quantity of Spirit can make to sweat; We have already mentioned that gold keeps mercury from violence because it amalgamates with it, but Fulminating Gold does it better since being volatile, it does meet mercury sooner.
Page 311: Aqua Regia.
This water is called Regia or royal because it dissolves gold. It is also called “Stygia”, or Chrisulca.
The Vessels into which to make the royal water, or aqua regia, must be very wide because, during the dissolving phase, the volatile Spirits tend to rarefy so impetuously to cause the vessels to break if they don’t have enough room. In the case of a large quantity of Aqua Regia to be prepared, one has to promptly remove the vessel from fire as soon as the dissolution starts.”One can also make Aqua Regia with equal parts of saltpeter and Rock Salt, mixing these salts with as much threefold Bole in powder and performing a distillation in the same way we have already mentioned to extract the Spirit of Nitre.
It is very difficult to understand how the Aqua Regia dissolves gold, which is a very firm and stable metal and cannot dissolve less hard silver. Some chemists eager to solve this difficulty have said that metallic gold does contain more Sulphur than Mercurius, demands a sulfurous dissolvent as Aqua Regia seems to be since it is composed by the volatile sulfurous salts constituting salt Armoniac: but this explication denies itself because if the gold contained more Sulphur than the Silver, consequently it would be less heavy since Sulphur is one of the lighter chemical principles.”
On chemical principles, see Glaser 2, Active three Principles. Here Lemery is losing himself in a chemical superstition of his age: the belief that an oily generic substance and a generic milky one did compose all metals. The oily was called Sulphur, and the milky one Mercurius. Of course, not only is this theory false but the alchemical Sulphur and Mercurius are the same substance, just in different stages (3).
“If besides we examine the composition of the gold dissolvent, it will not difficult to contradict this opinion, since we can easily see that as soon as the Spirit of Nitre begins to penetrate the Salt Armoniac, the acid salt ties up with it and leaves the volatile salts, which found itself without a body keeping it fixed, rises dramatically; but as these salts, which are alkalis, meet in their way some acid of Spirit of Nitre which penetrate them, the usual great effervescence of a salt alkali running into acid is being made. This being passed, our Aqua Regia does remain the vessel; this is just an acid, marine salt dissolved in the Spirit of Nitre, the volatile salts being exalted or destroyed by the acid. Evidence of this thinking is that we can make the Aqua Regia either with marine salt, which has no volatiles inside or with salt armoniac, as we have said.
But these considerations cannot make this phenomenon clear, I think (Lemery), to give a rationale that if the Aqua Regia cannot dissolve the silver because, in the Spirits of Nitre, the addition of salt causes the points to be too much large to affect the silver’s pores. And consequently, they are not allowed to enter, while they can penetrate the gold, which pores are larger. If, on the contrary, the Spirits of Nitre can dissolve the silver is because its points are as subtle as to enter the little pores of his metal. These little pores can enter the larger pores of gold, but they are too little and folded to have an action on this body. So one needs a more sharp knife, still being of a suitable size and the power to cut the gold’s pores.
I know that you may object that the gold, being heavier than silver, must have smaller dimension pores, as the weight of a body must only consist of a great nearness of the parts, but it is very easy to have a closer look into that with a good microscope. In this case, one can see that gold’s pores are larger than silvers, but they are considerably less in number, and this can explain why gold is heavier than silver. Since they are larger but far from each other, we can see a very compact mass which makes all of them weigh. The silver’s pores are very close to each other and in large quantity, so there is less mass around them, and silver has less weight. I will use a familiar example to make myself clear.
If I take two bowls of the same size and volume, one packed with balls of caliber and the other with filings of lead, the first will be heavier despite the major space among the balls. For the same reason, gold is more malleable than silver and can be cut more quickly, since if the pores of a body are larger it is easier for a knife to enter. And for the same reason, a hammer can dilate the gold more easily.”
You can find a modern comprehensive essay to perform ancient methods to get Aqua Regia at Aqua Regia & Fulminating Gold by Phantom Play.
- See Lemery and the Fixed Salt of Tartar Called Oil by Failure ;
- For the reasons Lemery prefers Rock Salt to marine salt see Lemery and the Spirits of Common Salt with Wine ;
- See also Stuart Chevalier, a Virgin’s Marriages ;