Fulcanelli mentions a number of interesting things about the exaltation of gold via cementing/fusion with copper:

"The secret of exaltation, without whose knowledge one cannot succeed, consists in increasing --- in one burst or gradually --- the normal color of pure gold by the sulphur of an imperfect metal, ordinarily copper. The latter gives precious metal its own blood through a sort of chemical transfusion. The gold, overfilled with the tincture, takes on the red color of coral and can thus give to the specific mercury of silver the sulphur which it lacks, owing to the agency of the mineral spirits emanating from the cement during the work. This transmission of the excess sulphur held by the exalted gold takes place gradually under the effect of heat; it takes form 24 to 40 hours according to the skill of the artisan and the volume of the treated matters. It is necessary to pay much attention to the regulation of the heat, which must be constant and strong enough without ever reaching the point of fusion or melting of the alloy. By overheating, one would risk volatilizing the silver and dissipating the sulphur introduced into the gold, since this sulphur has not yet reached a perfect fixity.

Finally, a third manipulation, purposely omitted since an enlightened archemist has no need for so much direction, includes the brushing of the extracted laminae, their fusion and cupellation. Upon being weighed, the pure gold residue will show a more or less perceptible decrease, which varies generally between one-fifth and one-fourth of the alloyed silver. Be that as it may, and in spite of this loss, the process still leaves us with a renumerating profit.

We will point out here, about the process of exaltation, that coralline gold obtained by one or the other of the diverse methods advocated remains capable of transmuting directly, that is, without the help of the later cementation, a certain quantity of the silver: about one-fourth of its weight. Yet, since it is impossible to determine the exact value of the coefficient of auriferous power, one goes around the difficulty by melting the red gold with a triple proportion of silver, (called inquartation) and by submitting the laminated alloy to the beginning operation.

After having said that the exaltation, based in the absorption of a certain portion of the metallic sulphur by the mercury of gold, considerably reinforce the very coloration of the metal, we will give a few indications about the processes used to this end. The processes use the property that solar mercury possesses of strongly retaining a fraction of pure sulphur, when one operates on the metallic mass, so as to dissociate the previously formed alloy. Thus, gold melted with copper, if it comes to be separated from it, never completely abandons a portion of the tincture that it stole from it. So that, by often repeating the same action, gold gradually enriches itself and can then give of its excess tincture to the metal which is closest to it, i.e., silver.

An experienced chemists, points out Naxagoras, knows well enough that if gold is purified up to 24 times or more by the sulphur of antimony, it acquires a remarkable color, brightness, and fineness. There is a loss of metal, contrary to what occurs with copper, because during the purification, the mercury of gold abandons a part of its substance to antimony, and the sulphur becomes overabundant through an imbalance of natural proportions. This renders the process useless and only permits a mere satisfaction of one’s curiosity.

The exaltation of gold is also achieved by first melting it with three times its weight in copper, then decomposing the alloy turned into filings by boiling nitric acid. Although this technique is very laborious and costly, in view of the volume of acid required, it is nevertheless one of the best and one of the surest that we know.

However, if one possesses an energetic reducing agent, and if one knows how to use it during the fusion of the gold and copper itself, the operation will be greatly simplified and one does not need fear a loss of material or excessive labor, in spite of the indispensable repetitions which this method still requires. Finally, the artist, by studying these different methods, will be able to discover better and even more efficient ones. For example, he only has to call upon sulphur directly extracted from lead to incinerate it back to a crude state and to project it little by little into molten gold which will keep its pure parts; unless you prefer to use iron, whose specific sulphur is, of all the metals, the one for which gold manifests the greatest affinity."