Diana's Tree

Diana's Tree (Latin: Arbor Diana or Dianae), also known as the Philosopher's Tree (Arbor Philosophorum), is a dendritic amalgam of crystallized silver, obtained from mercury in a solution of silver nitrate; so-called by the alchemists, among whom "Diana" stood for silver. The arborescence of this amalgam, which even included fruit-like forms on its branches, led pre-modern chemical philosophers to theorize the existence of life in the kingdom of minerals.

In pre-modern chemistry, the various methods for procuring Diana's Tree were exceedingly time-consuming; for example, the following process, originally described by Nicolas Lemery, required forty days to see results:

"Dissolve an ounce of pure silver in a sufficient quantity of aqua fortis, exceedingly pure, and of a moderate strength, and having put the solution in a jar, dilute it with about twenty ounces of distilled water. Then add two ounces of mercury, and leave the whole at rest. In the course of forty days, there will rise from the mercury a kind of tree, which throwing out branches will represent natural vegetation."

The quickest method, as described by Dutch natural philosopher Wilhelm Homberg (1652-1715), took about a quarter of an hour, and is described as follows. Take four drams of filings of fine silver, with which make an amalgam, without heat, with two drams of quicksilver. Dissolve this amalgam in four ounces of aqua fortis, and pour the solution into three gallons of water. Stir it for a while until mixed, and then keep it in a glass vessel well stopped. To initiate the experiment, take about an ounce of the substance, and put it in a small vial; add to this a quantity the size of a pea of the ordinary amalgam of gold, or silver, which should be as soft as butter. Let the vial rest for two or three minutes. Immediately after this, several small filaments will visibly arise perpendicularly from the little bulb of the amalgam, which will grow and thrust out small branches in the form of a tree. The ball of amalgam will grow hard, like a pellet of white earth, and the little tree will be bright silver in color.

The form of this metallic tree may be varied as desired. The stronger the user makes the first described water, the thicker the tree will be with branches, and sooner formed. Homberg also described how numerous other kinds of trees may be produced by crystallization and "digestion".

There is also Saturn's Tree, which was a deposit of crystallized lead, massed together in the form of a "tree". It is produced by a shaving of zinc in a solution of the lead(II) acetate. In alchemy, "Saturn" was the name used for lead.