User:Syncategoremata/al-Majriti and the principle of the conservation of mass

Overview
The claim appears on various pages on Wikipedia that al-Majriti "was the first to prove the principle of the conservation of mass — credit for which was claimed 900 years later by Lavoisier". This claim is false.

Source
Although the quote above originally comes from, when it appears on Wikipedia it usually comes via.

The full quote from is: "Abu al-Qasim Salamah Ibn Ahmad al-Majriti (950–1007), the Andalusian from Majrit (today's Madrid), was the first to prove the principle of conservation of mass — credit for which was claimed 900 years later by Lavoisier. His relevant experiment is described in his work, Rutbah al-Hakim, in the following terms:"


 * "I took clean, shining mercury and I put it in an egg-shaped utensil made of glass, and I introduced it into another utensil similar to kitchen utensils. I let it warm under such a low fire as I could put my hand on the outer surface of the instrument. The heating continued for forty days, and when I opened the instrument I found the mercury (which weighed a quarter of a pound) had been transformed into a red powder without any change in the overall weight. [Emphasis in Kettani.]"

"The red powder was, of course, mercury oxide (HgO). Compare this experiment with that of Lavoisier."

In a later section, I compare this experiment with that of Lavoisier (his "famous mercury experiment") and show that there is no comparison.

A better source
Compare this with the treatment in : "One observation is of particular interest to chemists as in it occurs the first definite description of a substance which was destined, in the hands of Priestley and Lavoisier, to play an historic rôle—mercuric oxide:"


 * "I took natural quivering mercury, free from impurity, and placed it in a glass vessel shaped like an egg. This I put inside another vessel like a cooking-pot, and set the whole apparatus over an extremely gentle fire. The outer pot was then in such a degree of heat that I could bear my hand upon it. I heated the apparatus day and night for forty days, after which I opened it. I found that the mercury (the original weight of which was ¼lb.) had been completely converted into a red powder, soft to the touch, the weight remaining as it was originally."

"That no gain in weight was observed is not surprising, as some of the mercury would probably have been lost by volatilization, while the increase in weight of mercury on oxidation is only about 8 per cent. The fact, however, that the author attempted to carry out the experiment quantitatively is in itself important, as indicating that he paid attention to a fundamental chemical rule not universally observed until centuries later."

Holmyard notes the interesting point in this text: that al-Majriti took an interest in the quantitative aspects of alchemy, at a time when this was quite rare. His discussion also clarifies that al-Majriti's experiment has no relation to Lavoisier's "famous mercury experiment": as I will show in the next section, the one performed by al-Majriti does not provide any evidence for the law of the conservation of mass.

A comparison of the two experiments
There are three problems with Kettani's claim:
 * 1) al-Majriti probably performed a completely different experiment from Lavoisier;
 * 2) if he performed a similar experiment, he got the wrong result;
 * 3) even if he had performed exactly the same experiment (and had gotten the correct result), it is still a further step from there to the law of the conservation of mass, and it is a step that contemporaries of Lavoisier's failed to take.

I will describe Lavoisier's "famous mercury experiment" and then treat these three problems in order.

Lavoisier's famous mercury experiment
As documented by, Lavoisier initially reported his "famous mercury experiment" in his On Respiration of 1777 , giving full details of the apparatus and technique in his later Elements of Chemistry.

Probably a completely different experiment
The main problem with calcining mercury is that it is extremely volatile; so if it is heated in the open air, it evaporates before any great amount is calcined. Unfortunately it is even harder to calcine any quantity of mercury in a sealed vessel. For one thing it takes a large volume of air to fully calcine mercury (thousands of times the mercury's volume), which means you need a huge, hermetically sealed vessel to calcine any quantity of mercury, and for another the vessel will tend to burst from the pressure of the heated air and mercury fumes.

So in the 17th century mercury was calcined in a special matrass known as "Boyle's hell", with a flat base and an extremely tall thin neck, open to the air at the top via an extremely small opening. With this sort of apparatus and over a long period of time, mercury can be calcined without any great loss of volume of the mercury. We might then assume that al-Majriti used some apparatus such as this—as Holmyard seems to suggest above, with his mention of some mercury being "lost by volatilization".

If that were the case, the experiment is entirely different from Lavoisier's and would lead

Or else a wrong result
Alternatively we might assume that al-Majriti managed to perform the experiment in a sealed vessel. To fully calcine 115 grams of mercury (a quarter of a pound) requires all the oxygen from some 70 litres of air, which implies that the experiment would have needed a hermetically sealed glass vessel at least 50 cm in internal diameter. The vessel would also need to be strong enough to withstand the pressures generated by the experiment, which might be why he "put [it] inside another vessel like a cooking-pot", so as to reinforce it.

But as Holmyard notes in the extract quoted above, mercury increases in weight by about 8% when it is calcined, which is not the result found by al-Majriti. Without understanding the increase in weight, and without any knowledge of the consumption of air during the experiment, al-Majriti would still have no reason or basis for postulating a conservation law: he would presumably have thought that the change was a purely mechanical one, heat having changed the mercury from one qualitative form to another.

But what if, despite a silence in the sources, al-Majriti had actually performed exactly the same experiment as Lavoisier. Wouldn't he then have been inexorably led to the law of the conservation of matter? No.

And still a missing step
There is no suggestion that al-Majriti understood the role of air in the calcination of mercury. In the Renaissance mercury oxide was customarily known as "mercury precipitate per se"; that is, converted to a solid without the addition of any other substance.

Summary of Kettani's claim
Kettani's claim is both bad science, as he gives no indication of understanding the chemistry involved, and also bad history of science, as he seems to have no understanding of the developments that lead up to the statement of laws such as the conservation of mass.

Full background

 * I'm gathering more material here to add to various articles, such as the one on phlogiston theory.

When a metal is calcined, that is, heated in air to form its oxide, it increases in weight by some small proportion, usually at most 10%. It had been known since antiquity that lead increases in weight if kept in a damp location such as a cellar and from the the 16th century (if not earlier) an increasing number of different metals were found to increase in weight when they were calcined. Then in 1677, the Royal Society made a "firm declaration" that all metals increase in weight on calcination, though the chemical processes involved were not at all understood. It is now known that this increase in weight is due to the oxygen that combines with the metal to form the oxide.

van Helmont
Jan Baptist van Helmont — TBC

Boyle
In his New Experiments to make Fire and Flame Stable and Ponderable of 1673, Robert Boyle attempted to discover whether metal would still increase in weight if it were converted into its calx in a sealed container. He found that there was indeed an increase in weight, and he believed that this was caused by the accumulation in the calx of "igneous particles" that, despite having a considerable weight, were sufficiently small to have passed through the walls of the glass container. Despite performing his experiments in sealed containers, there was still sufficient air inside the container to form some of the oxide and thus increase the weight of his samples. Also, since he had to break open the container after it had cooled—so as to remove the sample for weighing—there was a further opportunity for it to react with the air to form more oxide.

Hales
Stephen Hales — TBC

Priestley
Joseph Priestley — TBC

Lavoisier
Lavoisier repeated these experiments some one hundred years later, but instead of following Boyle's process, he weighed the entire container, with the sample sealed inside, both before and after calcination. The result, as we would now expect, is that the entire system showed no change in weight despite the (partial) calcination of the sample.

TBC

The principle of the conservation of mass
It should be noted that the general principle of conservation of mass has had a very long history; see the relevant section of the conservation of mass article for some background. Thus al-Majriti would in all likelihood have agreed to some version of the principle, as would most scientists since ancient times.

Lavoisier is usually credited with the 'discovery' of the principle as he was one of the first modern chemists who stated the principle explicitly : "We may lay it down as an incontestable axiom, that, in all the operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of the elements remain precisely the same: and nothing takes place beyond changes and modifications in the combination of these elements. Upon this principle, the whole art of performing chemical experiments depends: We must always suppose an exact equality between the elements of the body examined, and those of the products of its analysis."

Notice that in its modern form as presented here, the principle involves not just a conservation of mass (or 'quantity', as Lavoisier puts it) but also a conservation of the types (or 'quality') of substance conserved.

Al-Majriti's experiment in context
Given this context it can be seen why al-Majriti's experiment was not comparable to those carried out by Lavoisier and would not have led him to formulate any such principle as that of the conservation of mass.

The experiments that led Lavoisier to this principle were ones where he could show that the weight of the air that was consumed in forming a calx matched the change in weight of the calx, and that the same amount of air was released again if the calx was reduced to the metal. In al-Majriti's account, he says that the entire ¼lb of mercury was converted into a calx. The amount of oxygen that would be consumed by this would be "prodigious", perhaps as much as 1000 times the volume of the mercury. Thus he could not have been performing this experiment in a sealed container, as Boyle and Lavoisier did in some of their experiments.

So al-Majriti's experiment must have been carried out in an open container. At this point we can see what an extremely skilful technician he must have been: almost any attempt to heat mercury in an open vessel will just evaporate the mercury before any amount of it has been calcined. Yet al-Majriri heated it for forty days and yet seems to have lost less than 8% of his original sample. Al-Majriti probably interpreted this result as meaning that the change of mercury into its oxide was a qualitative change rather than that some kind of compound had been formed. That is, the heating caused the mercury to convert to another form (like the change that occurs when a substance melts, for example) and thus he would have expected to have found no change in weight.

It was only because Lavoisier was aware that the calx weighed more than the original sample and because he knew of Hales's experiments on gases, that he was led to consider what happened when calces were formed and then reduced back again.

Just to note that even if al-Majriti had performed the exact same experiments as Lavoisier, there is no necessity that he would have come to the same conclusion, that of the principle of the conservation of mass. We can see this by considering that at the same time Lavoisier was re-formulating chemistry into a recognisably modern form, Joseph Priestley was performing very similar experiments (and had available reports both of Lavoisier's experiments and of his conclusions) and yet Priestley never agreed to this new analysis of the results, and remained a believer in phlogiston to the end of his life. Thus without any explicit claim of al-Majriti's of the principle of the conservation of mass—which we do not have in any way, shape or form—it is simply an unfounded assertion to claim that he was the "first to prove" anything of the sort.