Pechblende

To identify the material used centuries ago by alchemists we are conduced to research natural compounds able to produce the Philosopher's Stone identified as being necessarily a fluoride of the last Superheavy element I named Trinitium (Tn). This research took into account modern knowledge , history of science and old alchemy books. The result is that pechblende, uranium oxide, is the true matter of alchemists. We may consider other way to reach that result : let suppose that mercury (Z = 80) found in cinnabar is the material used by alchemists. It results that its chemical treatment (or for mad guys its philosophical treatment) will have to modify the isotopic ratio in order to obtain a mercury enriched with neutrons ! for example. Because if you do not act on the nucleus of mercury we know that mercury does not have the nuclear reactivity of the Philosopher's Stone. But experience demonstrates us that when the nucleus of an atome, Z, is enriched with neutrons, its spontaneously transmutes itself in the element Z + 1 more stable. This fact is well established, so my hypothesis of neutron enrichment, for the purpose of the demonstration, is not irrealistic. A strong neutron enrichment of a mercury atom will necessarily produce the elements (Z+1), (Z+2), (Z+3),.... and finally we will have the last natural element, uranium (Z = 92) that will give, if it exists a neutron excess, one of the transuranium element until it disintegrates itself as science knows.
The problem is that it does not exist any natural source of neutrons able to produce this set of nuclear reactions from mercury. Consequently, to optimize the conditions of making the Philosopher's Stone, it is obvious that we have to choose a compound of uranium as the first material of alchemists in order to produce Trinitium, the active element of the Philosopher's Stone, which owns outstanding properties, among them the property of transmutation of mercury (Z=80) into gold (Z=79). Uranium is the good choice considering what we know about the Philosopher's Stone : a density higher than gold density, and an energy source because any transmutation requires an energy source. Uranium is also well distributed in nature, it is frequently associated with gold ores and, the very important fact, uranium is an energy source... How could you produce the Philosopher's Stone without energy source ? It is a lie to say the contrary.
Other fact in direct relation with alchemy books is that uranyl salt are of a yellow color, like sulphur. The black Uranium oxide, named pechblende looks like pitch whih was a very common substance, but pechblende was also very common in some silver mines, Joachimstahl for example, where it was discarded because it was useless.
I examined the case of cinnabar used by some monkey alchemists. It is not necessary to repeat the demonstration in the case of the choice of stibine, antimony sulfide, we will also reach uranium, so as it is said in old alchemy books, It exists one and only one mineral required by the Art.

Despite it is quite evident why old alchemists used Pechblende, as the basic material to prepare the Philosopher's Stone, it is still interesting to know more about that mineral.
Klaproth is the chemist and mineralogist who first has beeen able to identify the mineral pechblende, let see what he tells us in 1789:

The ancient philosophers, who considered our globe as the center of the material universe; and the sun , on the contrary, merely as a planet, destinated, like the others, to a periodical circumvolution around the earth, flattered themselves that they had discovered a great mystery of Nature, in the agreement of the seven celestial bodies, which they assumed for planets, with the seven metals known in those time...
... But as the above number of metals has long been increased by later researches; and as the discovery of new planets has not kept pace with that of metals, the metals newly found out have been deprived of the honour of receiving their names from planets, like the olden ores. They, therefore, must be satisfied with the name given them accidentally, and , in most instances, by the common miners....
... The particular fossil by the decomposition of which I have discovered this new metallic substance is the black, or pitch-blende (pseudo galene of many) as it has been hitherto called. In the mean time, I shall continue to use that appelation, till, in the progress of this essay, the necessity of giving it a new name will be conspicious. This fossil is found at Joachimsthal in Bohemia, and at Johann Georgenstadt, in the metalliferous mountains of Saxony.
Only a few writers appear to have been formerly acquainted with this mineral. Wallerius and Brünich mention indeed, under the head Argentiferous Ores of Zinc, the pitch-blende, and a black pitch-ore (Pecherz); but it does not appear that they meant by it or even known the above fossil from Joachimsthal and Johann Georgenstadt.
Werner, to whom its fracture, hardness, and gravity, sufficiently indicated that it could not be a blende, has transferred it from the class of zinc ores to that of the ores of iron calling it Eisen-pecherz.
A subsequent conjoncture of his that this fossil might perhaps contain the metallic radical of tungsten, or wolfram, was thought to be supported by actual experiments made at Schemnitz....
The varieties of this fossil, that have hitherto occured, may be divided into two sorts. The first of them is found in brownish-black, massive, and, for the most part, outwardly flat, reniform pieces. It is resplendent both externally and internally; wholly opake, and of an imperfect conchoïdal fracture. It is brittle, admits of being easily comminuted by trituration, and affords then a black powder, tending to the greenish. Its specific gravity upon an average is 7.500.
To this sort belong;, in particular, the pitchblendes dug at Joachimsthal, in the mines, or galleries; Süchsischer Edelleustalln, and Hobe Tanne; where they are accompanied by brown-red ponderous spar.
The second variety, to which belong the greatest part of pitchblende that occurs at Johann Georgenstadt, is greyish black, and exhibits avrious degradations, from the glittering to the dull or dim. At that place it is obtained in the mine Geor Wasfort, in larger or small masses between strata or shistose mica (glimmerschiefer); which is nearly in a state of decay. It is usually accompanied by a metallic earth (oxyde), of a yellow reddish, and light brown colour; and besides, also frequently by the "green mica" (torbernite), as it is called, crystallized in small quadrangular tables. Sometimes it is observed to be invested by compact galena (Bleyschweif), or having this latter disseminated in its substance in delicate veins and points. It has also been met with there in the mine Neujahrsmaaffen, between alternate strats of the fibrous brown iron stone.

Klaproth Martin Henry is an interesting person. He born on december 1,in 1743. He is a self learnig chemist and mineralogist and has been recognized by all as a very bright scientist ! he had a very good friend, Herschel, who discovered Uranus in 1781; both were very interested by astrology, and we may note above that Klaproth begins his paper talking about the relation of planets with metals. klaproth also identified Titane and Tellure.
Zinc is known in Europe since VI century, in the XVI century zinc was known as a metal and is mentioned by Agricola and the monk alchemist Basile Valentin.
Klaproth isolated Tellurium in 1798 and named it Tellurium.
Klaproth named Titanium in 1795.
The question is to know why Herschel named the planet Uranus and why Klaproth named the element extracted from pechblende, Urane (that becomes later Uranium). In my opinion, I think we must note that in 1780 Europe science was making a lot of discoveries, chemistry really born at that time. Alchemy was still a recognized science, in 1763 Kerdanek de Pornic published his alchemy treatise about the Philosopher's Stone, ... Klaproth was 20 y.o., and since Klaproth was a self learning chemist and mineralogist, he was necessarily interested by alchemy. So the name of Urane given to the element contained in pechblende is not the product of hazard :
- Uranus was hiden to the sight during centuries like the matter of alchemists.
- Pechblende was a rare mineral known by very few searchers. Only the true scientists were able to find it : in the mines.
Pechblende had been found as compact samples in silver and gold deposits : Joachimsthal in Bohemia; Johann-Georgenstadt, Annaberg, Schneeberg, Marienberg, in Saxonia, or in tin deposits : Tolearn, Tincroft in Cornwall.
People knew that the matter of alchemists is a mineral, but nobody knew which mineral. Therefore, like Basile Valentin, Klaproth learnt chemistry and mineralogy in order to find the true matter of alchemists : all his description of the mineral has a strange smell of alchemy writings. Uranium ... comes from Ouranos , the sky of philosophers; the common symbol is a snake making a circle. What is above is like what is below .... establishing the relation between the planet Uranus and the element Uranium contained in pechblende. Herschel was searching planets, ... Klaproth was searching the matter of alchemists so when Herschel discovered the planet, he probably named it after a lot of talks with Klaproth who surely, at that time, had discovered the properties of the mineral pechblende.

Here is the picture of a sample of pechblende from a well known mine.

Here is the picture of the same sample of pechblende reduced to small pieces with a hammer.

You will note the different look of the mineral. In that case it is very hard,
Let see what Klaproth tells us about the chemical analysis of pechblende.

To examine the relations of pitchblende to the fixed alcalis in the dry way. I tritured 1/2 ounce of it with one of carbonate pot-ashes, and urged the fire to the fusion of the mixture in the crucible. The mass poured out of the vessel was black-grey, compact, hard, and of a lamellar fracture. When ground, boiled with water, and filtered, the powder of the fossil remained on the paper with its former black colour, and also nearly with its original weight.

We learn that pechblende is unattacked by fusion with potassium carbonate, in the conditions described by Klaproth, that is true.

Dilute sulfuric acid was incapable of effecting a true solution; it only extracted from it a faint greenish tincture. Even concentrated sulfuric acid did not entirely dissolve this fossil : for , after 1/2 ounce of pitchblende had been digested with one ounce of that acid, in a retort, the liquor being again distilled of to dryness, and the residue softened with water, its undissolved part still weighted 3 drachms; (1 ounce = 8 dracms, so we have 25 %) in solution) and likewise the black colour which is still preserved shewed that no perfect solution had taken place . The fluid that had passed over was sulphureous acid; and the solution filtered off from the residue had a green colour.

This is a remarquable description of a chemical test that demonstrates the level of chemistry knowledge of people in 1789 : it was established that the gas escape was SO2, that is to say the product of combustion of sulfur. So for chemists this gas resulted from sulfuric acid decomposition.
Klaproth noted that pechblende does not dissolve completely with sulfuric acid. The green solution indicated U(IV).
Next Klaproth attacks pechblende with nitric acid :

Half an ounce of the grey-black, dull pitchblende, was digested, in a low heat, with moderately strong nitric acid. It was attacked by the acid, with an evolution of red nitrous vapors. I affufed by degrees, more of the acid till the disappearance of the black colour of the fossil shewed that its decomposition was accomplished. The solution when again diluted with water, was of a bright-wine yellow, variegrated with the greenish. It left on the paper a white-grey residue weighting 16 grains upon dessication. This took fire when heated in an earthen pot, and burned with a sulphureous flame : losing thereby 5 1/2 grains. The remaining 10 1/2 grains consisted of silex from which nitromuriatic acid still extracted some portions of iron.

It is the typical reaction of pechblende with nitric acid. Production of red vapors has the same intensity than during the attack of copper with nitric acid. The residue of sulphur is characteristics of attack of sulfide ores; I experimented the case with galene, and I got a yellow colored residue.
Klaproth repeats the experiment with other sample of pechblende.

One half ounce of the blacker sort of pitchblende treated in the same manner with nitric acid, coagulated upon solution, to a bright-green gelatinous consistence, in which some light grey-yellow prticles lay dispersed. By dilution with water, and filtration, is left 26 grains of a reddish-grey residue, 6 grains of which were sulphur, and the remainder an earthy matter impregnated with iron.

It is a typical fact of pechblende attack with nitric acid.
Klaproth tells us more about the different kinds of minerals found with pechblende :

In the pit Geor Wagsfort, at Johann Georgenstadt, the metal uranium likewise occurs in the form of a metallic oxide, of an earthy appearance. This is the earthy fossi, already mentioned at the beginning of this essay which there accompanies the compact uraninite ore unfder various stades of colour, passing from the pale sulphur yellow into the brick red, as also into the brown yellow. The light yellow and reddish varieties are the purest; since when dissolved in nitric acid, and treated with potassium prussiate, then immediately precipitate of a brown red colour. The darker varieties, on the other hand contain more or less of iron. This earthy oxyde of uranium has formerly been taken for an ochre of iron. It has likewise been considerated as the product arising from a previous decay of shistose mica, which forms the gangue, containing this fossil in the mine just mentionned.

You wil note that the reddish varieties correspond to the Red Earth of old alchemists, it is a kind of gummite.
The chemical test to detect uranium, with potassium ferrocianide gives a red precipitate. It may be used with paper chromatography, eluent is MIBK or ethyl acetate, uranium follows the eluent, sensitivity of the test is 30 ppm.

You may get uranium associated with element such as cobalt and copper in the case of the mineral presented above :

The problem of the First Matter of true old alchemists was sometimes difficult because it depends on the quality of the uranium mineral, but as you surely know it : chemistry of uranium is old basic chemistry.