Читать книгу The Fontana History of Chemistry - William Brock J. - Страница 16

Iatrochemistry came to fruition in the work of a Flemish nobleman, Joan-Baptista van Helmont (1577–1644). Present-day Belgium was then under Spanish control. In 1625, as a consequence of Helmont’s controversial advocation of ‘weapon salve’ treatment in which a weapon, and not a wound, was treated, he was denounced as a heretic by the Spanish Inquisition and spent the remainder of his life, like Galileo, under house arrest. As with Paracelsus, it was van Helmont’s posthumous writings that brought his name to fame and exerted a considerable influence upon seventeenth-century natural philosophers like Boyle and Newton. This influence was firmly established after 1648 with the posthumous publication of his Ortus Medicinae, which was issued in English in 1662 as Oriatricke or Physick Refined. Helmont, who claimed to have witnessed a successful transmutation of a base metal into gold, was a disciple of Paracelsus and an iatrochemist. However, like any good disciple, he modified, interpreted and disagreed with his master’s doctrines considerably.

After studying several areas of natural philosophy, he chose medicine and chemistry for his career, calling himself a ‘philosopher by fire’. He was strongly anti-Aristotelian, one facet of which was that he refused to accept the four-element theory. But neither was he able to accept Paracelsus’ tria prima. To simplify a rather complex philosophy, we can say that according to van Helmont there were two first beginnings of bodies: water and an active, organizing principle, or ‘ferment’, which moulded the various forms and properties of substances. This return to a unitary theory of matter was influenced by his interpretation of Genesis, for water, together with the heavens and the earth, had been formed on the first day.

In more detail, he imagined that there were two ultimate elements, air and water. Air was, however, purely a physical medium, which did not participate in transmutations, whereas water could be moulded into the rich variety of substances found on the earth. Van Helmont did not consider fire to be a material element, but a transforming agent. As for earth, from his experimental observations, he believed that this was created by the action of ferments upon water.

The first beginnings of bodies, and of corporeal causes, are two, and no more. They are surely the element water, from which bodies are fashioned, and the ferment.

As we have already seen in the introduction, the justification for this belief was an interesting, quantitative growth experiment with a young willow tree. Additional supporting evidence came from the fact that fish were nourished ‘solely’ by water, that seashells were found on dry land, and that solid bodies could be transformed into ‘savoury waters’, that is, into solution. In the latter case, Helmont took a weighed amount of sand, and fused it with excess alkali to form water-glass, which liquefied on standing in air. Here was a palpable demonstration of the reconversion of earth back into water. More remarkably, this ‘water’ could be reconverted back to ‘earth’ by treatment with acid, when the silica sand recovered was found to have the same weight as the starting material.

There are a number of interesting features about these experiments and Helmont’s reasoning. Their most important feature is not that Helmont misinterpreted his observations because he ignored the role of air, but that they were quantitative. The experiments were also controlled. In the willow tree experiment, Helmont covered the vessel so as to prevent dust contamination, which might have affected the result. Similarly, he dried the earth beforehand and used only distilled water. He clearly had thought about the experiment and possible objections that might be raised against his conclusions because of the way the experiment had been designed. All this was the hallmark of the experimental method that was to lead to the transformation of chemistry. In addition, it is noticeable that he implicitly assumed that matter was conserved in any changes it underwent. When metals were dissolved in acids they were not destroyed, but were recoverable weight for weight. Helmont also postulated the existence of an alcahest, or universal solvent, which had the property of turning things back into water. Much time and effort was spent by contemporary chemists, including Robert Boyle, in trying to identify this mysterious solvent.

There is a further item of interest to be found in Helmont’s writings. Since air could not be turned into water, he accepted it as a separate element. However, his keen interest was awakened by the ‘air-like’ substances that were frequently evolved during chemical reactions. Helmont identified these fuliginous effluvia as ‘gases’, from a Greek word for ‘chaos’ that Paracelsus had ascribed to air in another connection. Where did these uncontrollable, dangerous materials fit in Helmont’s ontology?

Gases were simply water, not air, for any matter carried into the atmosphere was turned into gas by the cold and ‘death’ of its ferments. A gas was chaos because it bore no form. A gas might also condense to a vapour and fall as rain under the influence of blas, a term that did not stay in chemical language, and which Helmont coined to refer to a kind of ‘gravitational’, astral influence or power that caused motion and change throughout the universe.

In a typical gas experiment, Helmont heated 62 lb (28 kg) of charcoal in air and was left with 1 lb (2.2 kg) of ash, the rest having disappeared as ‘spiritus sylvester’ or wild spirit. When charcoal was heated in a sealed vessel, combustion would either not occur, or would occur with violence as the spirit escaped from the exploding vessel. This disruptive experience led to Helmont’s definition of gas:

This spirit, hitherto unknown, which can neither be retained in vessels nor reduced to a visible body … I call by the new name gas.

Although Helmont implied by this a distinction between gas and air, and even between different gases, these were features to which commentators paid scant attention. The reason for this is that, in the absence of any suitable apparatus to collect and study such aerial emissions, it was impossible to distinguish between them chemically. Helmont himself had to be content with classifying gases from their obvious physical properties: for example, the wild and unrestrainable gas (spiritus sylvester) obtained from charcoal; gases from fermentations; vegetable juices; from the action of vinegar on the shells of certain sea creatures; intestinal putrefactions; from mines, mineral waters and from certain caverns like the Grotto del Cane near Naples, which allowed men to breathe but extinguished the life of a dog.

In striking contrast to his French contemporary. René Descartes, who claimed that, apart from the existence of a human soul, life was a mechanistic process, Helmont refused to separate soul from matter itself. Matter became spiritualized and nature pantheistic. Such a spiritualization of matter proved especially attractive to various religious groups during the Puritan revolution in England. The writings of Paracelsus and Helmont circulated widely during the 1650s and 1660s, partly because they could be used as weapons in the power struggles between physicians and pharmacists, but also because religious ideology was in a state of flux. The Neoplatonic, unmechanical, vitalistic and almost anti-rational aspects of both Paracelsianism and Helmontianism appealed to many because they emphasized the significance of personal illumination against pure reason. This appealed to the Puritan conscience precisely because it could justify religious and political revolution for the sake of one’s ideals.

But along with the ideology went the ‘positive’ science of Helmont: gases, quantification and measurement, and iatrochemistry. Once the Commonwealth was achieved, the concept of personal illumination had to be played down (as Libavius had foreseen) in order to prevent anarchy. In the 1660s, therefore, Helmontianism came under attack. Whereas in the 1640s it had been argued by some that Oxford and Cambridge Universities ought to be reformed under Paracelsian and Helmontian lines, by the mid 1660s this was out of the question and the mechanical philosophy of Descartes, Boyle and Newton was to be triumphantly advocated by the new Royal Society. Nevertheless, echoes of Helmontianism remained in the works of Boyle and Newton.