CHAPTER I.

IMPROVEMENT OF THE NOTION OF CHEMICAL ANALYSIS, AND RECOGNITION OF IT AS THE SPAGIRIC ART.

THE

HE doctrine of the four elements' is one of the oldest monuments of man's speculative nature; goes back, perhaps, to times anterior to Greek philosophy; and, as the doctrine of Aristotle and Galen, reigned for fifteen hundred years over the Gentile, Christian, and Mohammedan world. In medicine, taught as the doctrine of the four elementary qualities,' of which the human body and all other substances are compounded, it had a very powerful and extensive influence upon medical practice. But this doctrine never led to any attempt actually to analyse bodies into their supposed elements; for composition was inferred from the resemblance of the qualities, not from the separate exhibition of the ingredients; the supposed analysis was, in short, a decomposition of the body into adjectives, not into substances.

This doctrine, therefore, may be considered as a negative state, antecedent to the very beginning of chemistry; and some progress beyond this mere negation was made, as soon as men began to endeavour to compound and decompound substances by the use of fire or mixture, however erroneous might be the opinions and expectations which they combined with their attempts. Alchemy is a step in chemistry, so far as it implies the recognition of the work of the cupel and the retort, as the produce of analysis and synthesis. How perplexed and perverted were the forms in which this recognition was clothed,—how mixed up with mystical follies and extravagancies, we have already seen; and the share which Alchemy had in the formation of any sounder knowledge, is not such as to justify any further notice of that pursuit.

The result of the attempts to analyse bodies by heat, mixture, and the like processes, was the doctrine that the first principles of things are three, not four;

namely, salt, sulphur, and mercury; and that, of these three, all things are compounded. In reality, the doctrine, as thus stated, contained no truth which was of any value; for, though the chemist could extract from most bodies portions which he called salt, and sulphur, and mercury, these names were given, rather to save the hypothesis, than because the substances were really those usually so called: and thus the supposed analyses proved nothing, as Boyle justly urged against them.1

The only real advance in chemical theory, therefore, which we can ascribe to the school of the three principles, as compared with those who held the ancient dogma of the four elements, is, the acknowledgment of the changes produced by the chemist's operations, as being changes which were to be accounted for by the union and separation of substantial elements, or, as they were sometimes called, of hypostatical principles. The workmen of this school acquired, no doubt, a considerable acquaintance with the results of the kinds of processes which they pursued; they applied their knowledge to the preparation of new medicines; and some of them, as Paracelsus and Van Helmont, attained, in this way, to great fame and distinction: but their merits, as regards theoretical chemistry, consist only in a truer conception of the problem, and of the mode of attempting its solution, than their predecessors had entertained.

This step is well marked by a word which, about the time of which we speak, was introduced to denote the chemist's employment. It was called the Spagiric art, (often misspelt Spagyric,) from two Greek words, (onάw, ayelpw,) which mean, to separate parts, and to unite them. These two processes, or, in more modern language, analysis and synthesis, constitute the whole business of the chemist. We are not making a fanciful arrangement, therefore, when we mark the recognition of this object as a step in the progress of chemistry. I now proceed to consider the manner in which the conditions of this analysis and synthesis were further developed.

1 Shaw's Boyle. Skeptical Chymist, pp. 312, 313, &c.

CHAPTER II.

DOCTRINE OF ACID AND ALKALI.-SYLVIUS.

AMONG the results of mixture observed by chemists,

were many instances in which two ingredients, each in itself pungent or destructive, being put together, became mild and inoperative; each counteracting and neutralizing the activity of the other. The notion of such opposition and neutrality is applicable to a very wide range of chemical processes. The person who appears first to have steadily seized and generally applied this notion is Francis de la Boé Sylvius; who was born in 1614, and practised medicine at Amsterdam, with a success and reputation which gave great currency to his opinions on that art.1 His chemical theories were propounded as subordinate to his medical doctrines; and from being thus presented under a most important practical aspect, excited far more attention than mere theoretical opinions on the composition of bodies could have done. Sylvius is spoken of by historians of science, as the founder of the iatro-chemical sect among physicians; that is, the sect which considers the disorders in the human frame as the effects of chemical relations of the fluids, and applies to them modes of cure founded upon this doctrine. We have here to speak, not of his physiological, but of his chemical, views.

The distinction of acid and alkaline bodies (acidum, lixivum) was familiar before the time of Sylvius; but he framed a system, by considering them both as eminently acrid and yet opposite, and by applying this notion to the human frame. Thus the lymph contains an acid, the bile an alkaline salt. These two opposite acrid substances, when they are brought together,

1 Sprengel. Geschichte der Arzneykunde, vol. iv. Thomson's History of Chemistry in the corresponding part is translated from Sprengel. * De Methodo Medendi, Amst. 1679. Lib. ii, cap. 28, sects, 8 and 53. VOL. III. H

neutralize each other (infringunt), and are changed into an intermediate and milder substance.

The progress of this doctrine, as a physiological one, is an important part of the history of medical science in the seventeenth century; but with that we are not here concerned. But as a chemical doctrine, this notion of the opposition of acid and alkali, and of its very general applicability, struck deep root, and has not been eradicated up to our own time. Boyle, indeed, whose disposition led him to suspect all generalities, expressed doubts with regard to this view; and argued that the supposition of acid and alkaline parts in all bodies was precarious, their offices arbitrary, and the notion of them unsettled. Indeed it was not difficult to show, that there was no one certain criterion to which all supposed acids conformed. Yet the general conception of such a combination as that of acid and alkali was supposed to be, served so well to express many chemical facts, that it kept its ground. It is found, for instance, in Lemery's Chemistry, which was one of those in most general use before the introduction of the phlogistic theory. In this work (which was translated into English by Keill, in 1698) we find alkalies defined by their effervescing with acids. They were distinguished as the mineral alkali (soda), the vegetable alkali (potassa), and the volatile alkali (ammonia). Again, in Macquer's Chemistry, which was long the text-book in Europe during the reign of phlogiston, we find acids and alkalies, and their union, in which they rob each other of their characteristic properties, and form neutral salts, stated among the leading principles of the science.5

In truth, the mutual relation of acids to alkalies was the most essential part of the knowledge which chemists possessed concerning them. The importance of this relation arose from its being the first distinct form in which the notion of chemical attraction or affinity appeared. For the acrid or caustic character of acids and alkalies is, in fact, a tendency to alter the bodies they

3 Shaw's Boyle, iii. p 432.

4 Lemery, p. 25.

5 Macquer, p. 19.

touch, and thus to alter themselves; and the neutral character of the compounds is the absence of any such proclivity to change. Acids and alkalies have a strong disposition to unite. They combine, often with vehemence, and produce neutral salts; they exhibit, in short, a prominent example of the chemical attraction, or affinity, by which two ingredients are formed into a compound. The relation of acid and base in a salt is, to this day, one of the main grounds of all theoretical reasonings.

The more distinct development of the notion or such chemical attraction, gradually made its way among the chemists of the latter part of the seventeenth and beginning of the eighteenth century, as we may see in the writings of Boyle, Newton, and their followers. Beecher speaks of this attraction as a magnetism; but I do not know that any writer in particular, can be pointed out as the person who firmly established the general notion of chemical attraction.

But this idea of chemical attraction became both more clear and more extensively applicable, when it assumed the form of the doctrine of elective attractions, in which shape we must now speak of it.

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