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A History of Science, Volume 1, by Henry Smith Williams

 

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A HISTORY OF SCIENCE BY

HENRY SMITH WILLIAMS, M.D., LL.D.

ASSISTED BY

EDWARD H. WILLIAMS, M.D.

IN FIVE VOLUMES

VOLUME IV.

MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES A HISTORY OF SCIENCE BOOK IV

MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES

 

AS regards chronology, the epoch covered in the present volume is

identical with that viewed in the preceding one. But now as

regards subject matter we pass on to those diverse phases of the

physical world which are the field of the chemist, and to those

yet more intricate processes which have to do with living

organisms. So radical are the changes here that we seem to be

entering new worlds; and yet, here as before, there are

intimations of the new discoveries away back in the Greek days.

The solution of the problem of respiration will remind us that

Anaxagoras half guessed the secret; and in those diversified

studies which tell us of the Daltonian atom in its wonderful

transmutations, we shall be reminded again of the Clazomenian

philosopher and his successor Democritus.

 

Yet we should press the analogy much too far were we to intimate

that the Greek of the elder day or any thinker of a more recent

period had penetrated, even in the vaguest way, all of the

mysteries that the nineteenth century has revealed in the fields

of chemistry and biology. At the very most the insight of those

great Greeks and of the wonderful seventeenth-century

philosophers who so often seemed on the verge of our later

discoveries did no more than vaguely anticipate their successors

of this later century. To gain an accurate, really specific

knowledge of the properties of elementary bodies was reserved for

the chemists of a recent epoch. The vague Greek questionings as

to organic evolution were world-wide from the precise inductions

of a Darwin. If the mediaeval Arabian endeavored to dull the

knife of the surgeon with the use of drugs, his results hardly

merit to be termed even an anticipation of modern anaesthesia.

And when we speak of preventive medicine—of bacteriology in all

its phases—we have to do with a marvellous field of which no

previous generation of men had even the slightest inkling.

 

All in all, then, those that lie before us are perhaps the most

wonderful and the most fascinating of all the fields of science.

As the chapters of the preceding book carried us out into a

macrocosm of inconceivable magnitude, our present studies are to

reveal a microcosm of equally inconceivable smallness. As the

studies of the physicist attempted to reveal the very nature of

matter and of energy, we have now to seek the solution of the yet

more inscrutable problems of life and of mind.

 

I. THE PHLOGISTON THEORY IN CHEMISTRY

 

The development of the science of chemistry from the “science” of

alchemy is a striking example of the complete revolution in the

attitude of observers in the field of science. As has been

pointed out in a preceding chapter, the alchemist, having a

preconceived idea of how things should be, made all his

experiments to prove his preconceived theory; while the chemist

reverses this attitude of mind and bases his conceptions on the

results of his laboratory experiments. In short, chemistry is

what alchemy never could be, an inductive science. But this

transition from one point of view to an exactly opposite one was

necessarily a very slow process. Ideas that have held undisputed

sway over the minds of succeeding generations for hundreds of

years cannot be overthrown in a moment, unless the agent of such

an overthrow be so obvious that it cannot be challenged. The

rudimentary chemistry that overthrew alchemy had nothing so

obvious and palpable.

 

The great first step was the substitution of the one principle,

phlogiston, for the three principles, salt, sulphur, and mercury.

We have seen how the experiment of burning or calcining such a

metal as lead “destroyed” the lead as such, leaving an entirely

different substance in its place, and how the original metal

could be restored by the addition of wheat to the calcined

product. To the alchemist this was “mortification” and

“revivification” of the metal. For, as pointed out by

Paracelsus, “anything that could be killed by man could also be

revivified by him, although this was not possible to the things

killed by God.” The burning of such substances as wood, wax,

oil, etc., was also looked upon as the same “killing” process,

and the fact that the alchemist was unable to revivify them was

regarded as simply the lack of skill on his part, and in no wise

affecting the theory itself.

 

But the iconoclastic spirit, if not the acceptance of all the

teachings, of the great Paracelsus had been gradually taking root

among the better class of alchemists, and about the middle of the

seventeenth century Robert Boyle (1626-1691) called attention to

the possibility of making a wrong deduction from the phenomenon

of the calcination of the metals, because of a very important

factor, the action of the air, which was generally overlooked.

And he urged his colleagues of the laboratories to give greater

heed to certain other phenomena that might pass unnoticed in the

ordinary calcinating process. In his work, The Sceptical Chemist,

he showed the reasons for doubting the threefold constitution of

matter; and in his General History of the Air advanced some novel

and carefully studied theories as to the composition of the

atmosphere. This was an important step, and although Boyle is not

directly responsible for the phlogiston theory, it is probable

that his experiments on the atmosphere influenced considerably

the real founders, Becker and Stahl.

 

Boyle gave very definitely his idea of how he thought air might

be composed. “I conjecture that the atmospherical air consists of

three different kinds of corpuscles,” he says; “the first, those

numberless particles which, in the form of vapors or dry

exhalations, ascend from the earth, water, minerals, vegetables,

animals, etc.; in a word, whatever substances are elevated by the

celestial or subterraneal heat, and thence diffused into the

atmosphere. The second may be yet more subtle, and consist of

those exceedingly minute atoms, the magnetical effluvia of the

earth, with other innumerable particles sent out from the bodies

of the celestial luminaries, and causing, by their influence, the

idea of light in us. The third sort is its characteristic and

essential property, I mean permanently elastic parts. Various

hypotheses may be framed relating to the structure of these later

particles of the air. They might be resembled to the springs of

watches, coiled up and endeavoring to restore themselves; to

wool, which, being compressed, has an elastic force; to slender

wires of different substances, consistencies, lengths, and

thickness; in greater curls or less, near to, or remote from each

other, etc., yet all continuing springy, expansible, and

compressible. Lastly, they may also be compared to the thin

shavings of different kinds of wood, various in their lengths,

breadth, and thickness. And this, perhaps, will seem the most

eligible hypothesis, because it, in some measure, illustrates the

production of the elastic particles we are considering. For no

art or curious instruments are required to make these shavings

whose curls are in no wise uniform, but seemingly casual; and

what is more remarkable, bodies that before seemed unelastic, as

beams and blocks, will afford them.”[1]

 

Although this explanation of the composition of the air is most

crude, it had the effect of directing attention to the fact that

the atmosphere is not “mere nothingness,” but a “something” with

a definite composition, and this served as a good foundation for

future investigations. To be sure, Boyle was neither the first

nor the only chemist who had suspected that the air was a mixture

of gases, and not a simple one, and that only certain of these

gases take part in the process of calcination. Jean Rey, a

French physician, and John Mayow, an Englishman, had preformed

experiments which showed conclusively that the air was not a

simple substance; but Boyle’s work was better known, and in its

effect probably more important. But with all Boyle’s explanations

of the composition of air, he still believed that there was an

inexplicable something, a “vital substance,” which he was unable

to fathom, and which later became the basis of Stahl’s phlogiston

theory. Commenting on this mysterious substance, Boyle says:

“The, difficulty we find in keeping flame and fire alive, though

but for a little time, without air, renders it suspicious that

there be dispersed through the rest of the atmosphere some odd

substance, either of a solar, astral, or other foreign nature; on

account of which the air is so necessary to the substance of

flame!” It was this idea that attracted the attention of George

Ernst Stahl (1660-1734), a professor of medicine in the

University of Halle, who later founded his new theory upon it.

Stahl’s theory was a development of an earlier chemist, Johann

Joachim Becker (1635-1682), in whose footsteps he followed and

whose experiments he carried further.

 

In many experiments Stahl had been struck with the fact that

certain substances, while differing widely, from one another in

many respects, were alike in combustibility. From this he argued

that all combustible substances must contain a common principle,

and this principle he named phlogiston. This phlogiston he

believed to be intimately associated in combination with other

substances in nature, and in that condition not perceivable by

the senses; but it was supposed to escape as a substance burned,

and become apparent to the senses as fire or flame. In other

words, phlogiston was something imprisoned in a combustible

structure (itself forming part of the structure), and only

liberated when this structure was destroyed. Fire, or flame, was

FREE phlogiston, while the imprisoned phlogiston was called

COMBINED PHLOGISTON, or combined fire. The peculiar quality of

this strange substance was that it disliked freedom and was

always striving to conceal itself in some combustible substance.

Boyle’s tentative suggestion that heat was simply motion was

apparently not accepted by Stahl, or perhaps it was unknown to

him.

 

According to the phlogistic theory, the part remaining after a

substance was burned was simply the original substance deprived

of phlogiston. To restore the original combustible substance, it

was necessary to heat the residue of the combustion with

something that burned easily, so that the freed phlogiston might

again combine with the ashes. This was explained by the

supposition that the more combustible a substance was the more

phlogiston it contained, and since free phlogiston sought always

to combine with some suitable substance, it was only necessary to

mix the phlogisticating agents, such as charcoal, phosphorus,

oils, fats, etc., with the ashes of the original substance, and

heat the mixture, the phlogiston thus freed uniting at once with

the ashes. This theory fitted very nicely as applied to the

calcined lead revivified by the grains of wheat, although with

some other products of calcination it did not seem to apply at

all.

 

It will be seen from this that the phlogistic theory was a step

towards chemistry and away from alchemy. It led away from the

idea of a “spirit” in metals that could not be seen, felt, or

appreciated by any of the senses, and substituted for it a

principle which, although a falsely conceived one, was still much

more tangible than the “spirit,” since it could be seen and felt

as free phlogiston and weighed and measured as combined

phlogiston. The definiteness of the