Heroes of Science: Chemists

CHAPTER II.

ESTABLISHMENT OF CHEMISTRY AS A SCIENCE--PERIOD OF BLACK, PRIESTLEY AND LAVOISIER.

Introduction of accurate measurements into chemistry--Black's researches on alkalis and on fixed air--His conception of heat--Priestley's experiments on airs--His discovery of oxygen--Lavoisier, the founder of the science of chemistry--He clearly establishes a connection between composition and properties of bodies 30

CHAPTER III.

ESTABLISHMENT OF GENERAL PRINCIPLES OF CHEMICAL SCIENCE--PERIOD OF DALTON.

Dalton's training in physical science--He revives and renders quantitative the atomic theory--The term "atom" is applied by him to elements and compounds alike--His rules for chemical synthesis 106

CHAPTER IV.. Establishment of General Principles of Chemical Science

ESTABLISHMENT OF GENERAL PRINCIPLES OF CHEMICAL SCIENCE (continued)--PERIOD OF DAVY AND BERZELIUS.

Electro-chemistry--The dualistic theory developed by Berzelius--Davy's work on acids, alkalis, and salts--He proves chlorine to be an element--His discovery of the safety-lamp 155

CHAPTER V.. The Work of Graham.

THE WORK OF GRAHAM.

Graham traces the movements of molecules--He distinguishes between colloids and cystalloids--Dialysis 232

CHAPTER VI.

RISE AND PROGRESS OF ORGANIC CHEMISTRY--PERIOD OF LIEBIG AND DUMAS.

The barrier between inorganic and organic chemistry begins to be broken down--Woehler prepares urea--Dumas opposes the dualistic system of Berzelius--Liebig's conception of compound radicles--His work in animal and agricultural chemistry 252

CHAPTER VII.. Modern Chemistry.

MODERN CHEMISTRY.

The relations between composition and properties of bodies are developed and rendered more definite--Physical methods are more largely made use of in chemistry--Spectroscopic analysis 294

CHAPTER VIII.. Summary and Conclusion 316

SUMMARY AND CONCLUSION 316

HEROES OF SCIENCE.

INTRODUCTORY.

As we trace the development of any branch of natural knowledge we find that there has been a gradual progress from vague and fanciful to accurate and definite views of Nature. We find that as man's conceptions of natural phenomena become more accurate they also for a time become more limited, but that this limitation is necessary in order that facts may be correctly classified, and so there may be laid the basis for generalizations which, being definite, shall also be capable of expansion.

At first Nature is strange; she is full of wonderful and fearful appearances. Man is overwhelmed by the sudden and apparently irregular outbreaks of storms, by the capricious freaks of thunder and lightning, by the awful and unannounced devastations of the volcano or the earthquake; he believes himself to be surrounded by an invisible array of beings more powerful than himself, but, like himself, changeable in their moods and easily provoked to anger. After a time he begins to find that it is possible to trace points of connection between some of the appearances which had so overpowered or perplexed him.

The huntsman observes that certain kinds of plants always grow where the game which he pursues is chiefly to be found; from the appearance of the sky at morning and evening the fisherman is able to tell whether there will follow weather suitable for him to set out in his fishing-boat; the tiller of the ground begins to feel sure that if he sow the seed in the well-dug soil and water it in proper seasons he will certainly reap the harvest in due time. And thus man comes to believe that natural events follow each other in a fixed order; there arises a conscious reference on his part of certain effects to certain definite causes. Accurate knowledge has begun.

As knowledge of natural appearances advances there comes a time when men devote themselves chiefly to a careful study of some one class of facts; they try to consider that part of Nature with which they are mostly concerned as separate from all other parts of Nature. Thus the various branches of natural knowledge begin to have each a distinct existence. These branches get more and more subdivided, each division is more accurately studied, and so a great number of facts is accumulated in many classes. Then we usually find that a master mind arises, who shows the connection which exists between the different parts of each division of natural knowledge, who takes a wide, far-reaching view of the whole range of the province of knowledge which he studies, and who, at the same time, is able to hold in his vision all the important details of each branch of which that province is composed.

And thus we again get wide views of Nature. But these are very different from the vague, dim and hesitating notions in which natural knowledge had its beginnings. In this later time men see that Nature is both simple and complex; that she is more wonderful than their fathers dreamed, but that through all the complexity there runs a definite purpose; that the apparently separate facts are bound together by definite laws, and that to discover this purpose and these laws is possible for man.

As we trace this progress in the various branches of natural knowledge we are struck with the fact that each important advance is generally accomplished by one or two leading men; we find that it becomes possible to group the history of each period round a few central figures; and we also learn that the character of the work done by each of these men of note is dependent on the nature and training of the individual man.

It will be my endeavour in the following pages to give an account of the advance of chemical science, grouping the facts in each stage of progress round the figures of one or two men who were prominent in that period.

For the purposes of this book it will be necessary that I should sketch only the most important periods in the story of chemical progress, and that in each of these I should fill in the prominent points alone.

I shall therefore select three periods in the progress of this science, and try to give an account of the main work done in each of these. And the periods will be:--

I. The period wherein, chiefly by the work of Black, Priestley and Lavoisier, the aim of chemical science was defined and the essential characters of the phenomena to be studied were clearly stated.

II. The period during which, chiefly by the labours of Dalton, Berzelius and Davy, the great central propositions of the science were laid down and were developed into a definite theory. As belonging in great extent to this period, although chronologically later, I shall also consider the work of Graham.

III. The period when, chiefly owing to advances made in organic chemistry, broader and more far-reaching systems of classification were introduced, and the propositions laid down in the preceding period were modified and strengthened. The workers in this period were very numerous; I shall chiefly consider these two--Liebig and Dumas.

I shall conclude with a brief sketch of some of the important advances of chemical science in more recent times, and a summary of the characteristics of each of the three periods.

CHAPTER I.. Alchemy: and the Dawn of Chemistry.

ALCHEMY: AND THE DAWN OF CHEMISTRY.

Early chemistry was not a science. The ancient chemists dealt chiefly with what we should now call chemical manufactures; they made glass, cleaned leather, dyed cloth purple and other colours, extracted metals from their ores, and made alloys of metals. No well-founded explanations of these processes could be expected either from men who simply used the recipes of their predecessors, or from philosophers who studied natural science, not by the help of accurate experiments, but by the unaided light of their own minds.

At somewhat later times chemistry assumed a very important place in the general schemes propounded by philosophers.

Change is vividly impressed on all man's surroundings: the endeavour to find some resting-place amidst the chaos of circumstances, some unchanging substance beneath the ever-changing appearances of things, has always held a prominent place with those who study the phenomena of the world which surrounds them. In the third and fourth centuries of our era much attention was given to the art which professed to explain the changes of Nature. Religion, philosophy, and what we should now call natural science, were at that time closely intermingled; the scheme of things which then, and for several centuries after that time, exerted a powerful influence over the minds of many thinkers was largely based on the conception of a fundamental unity underlying and regulating the observed dissimilarities of the universe.

Thus, in the Emerald Table of Hermes, which was held in much repute in the Middle Ages, we read--

"True, without error, certain and most true: that which is above is as that which is below, and that which is below is as that which is above, for performing the miracles of the One Thing; and as all things were from one, by the mediation of one, so all things arose from this one thing by adaptation: the father of it is the Sun, the mother of it is the Moon, the wind carried it in its belly, the nurse of it is the Earth. This is the father of all perfection, the consummation of the whole world."

And again, in a later writing we have laid down the basis of the art of alchemy in the proposition that "there abides in nature a certain pure matter, which, being discovered and brought by art to perfection, converts to itself proportionally all imperfect bodies that it touches."

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