Analytical Chemistry in Modern Society
200 Years of Development Frank Greenaway W. H. Bragg's x-ray ionisation spectrometer (1913)
The Science Museum South Kensington London, England
"Analytical chemistry may sound an unromantic pursuit, but if it does, reflect that some techniques of analytical chemistry can help to determine that a loved one in the grip of an obscure disease may yet live, while others may reveal the composition of a remote star. Then this most farreaching science will be seen to touch personal things and universal things." ( 1)
al economics of modern times (Nicolas Oresme's 14th century "De Moneta") devotes considerable space to assaying, and from the Renaissance onward it threw up a considerable literature, far in advance, in its grasp of quantitative considerations, of any other type of chemical study and, indeed, of most other technologies. When the United States of America was founded, one of the marks of its maturity was the establishment of the Mints, and the assayer was always to be found with the prospector as the areas of new mineral wealth were explored. In France before the Revolution scientists were utilised in many ways to examine and direct its technological needs. For example, a team from the Académie Royale des Sciences studied the discrepancies in the assay of silver as between provincial and Parisian mints in 1760, work which led incidentally to new techniques of furnace control (4). Later, despite the profound changes in social organisation after the Revolution, analytical studies were pursued by the same sort of men who had served the Ancien Régime. Descrozilles and Berthollet introduced the first useful titrimetric analysis, testing the efficiency of bleaching solutions with standard indigo, but this was only a culmination of a line of studies in titrimetric methods made necessary by an expanding textile industry all over Western Europe. In one other respect, an analytical technique was the servant of government, namely, by hydrometer testing
To many people analytical chemistry is a modest branch of science-atlarge, an unexciting service provided here and there as necessary but not dominant in industry, research, or social service. This is a gross underestimate of its importance. The material civilisation which we enjoy (or endure) originated in certain acts of our remote ancestors of which the most important was their recognition that substances could be transformed in composition and form to their benefit. From the beginning of a settled "culture of cities", it was found necessary to identify substances and to determine their composition. The assay of the precious metals, the identification of drugs and dyes for commercial purposes, and the detection of fraudulent imitation are only a few of the techniques already well advanced by the time Graeco-Roman civilisation
unified the Mediterranean world. If we are to understand the development of the 20th century world out of the world system of the 18th century, we must recognise the vital role played by analytical chemistry (2). 18th Century Revolutions By the time the great revolutionary movements of the late 18th century began to roll, the main characteristics of analytical chemistry had become clear. It is possible to identify or quantify a chemical species in one or other of four ways: • By isolation of a recognisable species • By comparison with one or more features of a sample of known composition • By inference from-the course of a chemical reaction or series of logically related reactions • By inference from the physical characteristics or behaviour of a specimen. The outstanding example of the first of these was the commercial art of assaying the precious metals. Ever since gold and silver had been utilised (because of their rarity and resistance to corrosion) as the means of reckoning the value of transactions, their constancy for this purpose had been verified by the cupellation assay, the oldest known quantitative chemical process (3), the necessity of which was recognised in many treatises from the 12th century onward. The first important study of nation-
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Report of alcoholic liquors for purposes of customs and excise. By the late 18th century the British Government was so concerned at the important role which alcohol duties had assumed in the national budget that it sought more accurate methods of determination. A long investigation carried out on its behalf by the Royal Society led eventually to the publication of density tables, the acceptance of a standard form of hydrometer, and to new legislation. Industrial Demands It can be maintained that the political revolutions of the late 18th century have been of less importance, socially and philosophically, than the scientific revolutions of the 19th century. The system of matter-theory which came out of the work of Lavoisier and Dalton [and was eventually completed by Mendeleeff (5)] is one of the intellectual triumphs of mankind, establishing as it did that matter and its transformations are ordered and intelligible. It is on this basis that the industrial development of the nations of the West occurred. The first steps had already been taken in the textile industry, but consequent demands on the chemical industry for textile finishing chemicals (soda primarily, and therefore for sulphuric acid for its manufacture) meant that a chemical industry developed in its own right (6). The profitability of this industry depended on optimum use of raw materials and on the maintenance of regular production. Chemical analysis was essential for both these purposes (7), but the demand for skilled men outstripped the supply. One can point to two interesting consequences. The first was the rapid growth of techniques of analysis that could be used by relatively unskilled operatives. It is seen most clearly in volumetric analysis, the rationale of which was based on the chemical arithmetic which, as Humphry Davy so wisely pointed out, was the core of the Daltonian theory. This is an outstanding historical example of the effect of a scientific theory on the economics of an industry. The other consequence was the growth of professionalism in chemistry (8). The need of society for fully trained analysts led to the growth of organisations novel in character and purpose, at the same time that legislators were forced to devise novel forms of law.
Legislative Innovation By the middle of the 19th century, the ambivalent relation between society and the industries it had created had become very clear. The centres of chemicals, iron, and ceramics processing had become intolerably polluted by the effluents of manufactures whose products society increasingly needed and desired. Some British legislation marks the beginning of a new period in world history: the period in which society has been forced to seek a resolution of its conflict with its own
Early hydrometers: ivory, late 17th century; gold-plated brass, mid-18th century technology. The resolution has been achieved in some cases where it has been possible to establish the pattern set by the British Alkali Act of 1863. To simplify: The production of soda had been achieved by processes of the Leblanc type, entailing as a first stage the reaction between sodium chloride and sulphuric acid, yielding the necessary intermediate, sodium sulphate, and the waste by-product, hydrogen chloride gas, a gross atmospheric pollutant. Dispersion by high chimneys was ineffective. So were methods of exposure to water surfaces. Then the Gossage Tower, which greatly multiplied the water area exposed to HCL gas, made effective absorption possible, where applied. Mandatory legislation to prevent discharge thus became possible, but the problem remained:
how to relate legal requirements to practical expediency. Total absorption was impossible. A solution then unique was found. Emission should be limited to a definite ascertainable quantity. This seems simple, but it was the first time a chemically determinable quantity had been made the central factor in a law (other than for matters of revenue). Why was this an innovation? Because it set the criteria for effective legislation in the area of disturbance of public amenity. Supposing always that society wishes to go on receiving the benefits of a manufacturing process or service which is incidentally reducing amenity, then the law must envisage that: • There must exist, prior to the enactment, accessible means of controlling the offensive act. • There must exist known means of measuring the offence and the tolerable limit. • The means of measurement must be universally accessible and independent of the practitioner. These criteria were met in the case of hydrochloric acid emission by the Gossage Tower and by the argentometry devised by Gay-Lussac 30 years previously (9). Not all pollution can be brought under control as was that in this area of the chemical industry, but it is clear from the history of the Alkali Inspectorate set up under the British Alkali Act that analysts armed with authority can advise and promote as well as restrain industry (70). The history of control coupled with advice brings out an important fact: Although the role of chemist-as-analyst within industry seems obvious, in relation to efficient management, he has a further role detached from manufacture—that of accommodating industry to the society which it so constantly outgrows (11). Decision without quantitative expression is powerless. Inspectors and Advisors I place the British Alkali Act before the spread of "food and drugs" legislation because of its close relation with chemical theory. The control of the food and drugs trades which began in the third quarter of the 19th century had at least a treble origin, as indicated below. First, in most advanced countries, traditional methods of marketing were being affected by changes in the size of communities, particularly the capital cities and the great manufacturing centres. Food passed from production
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Part of reconstruction (incorporating original fittings and apparatus) of the (British) Government Chemist's Laboratory (1896)
to consumer through middlemen who might negligently or willfully allow foods to become tainted or adulterated. There was already a long history of protest at adulteration and some history of intervention by chemists ready to warn as analysts and advise as professional consultants. By the mid-century, a body of legislation had grown up which constrained both manufacturer and supplier, the constraints being defined in terms which demanded implicitly or explicitly the growth of a corps of professional analysts at the disposal of, or in full time employment by, public authorities. Secondly, the growing involvement of legislation with science and technique is well illustrated by food and drugs legislation. Prohibitions could not be made without there being some body of accepted knowledge of the constitution of what was wholesome and what was noxious. It needed considerable advance in biology and biochemistry for this to be possible, but the rapid growth of knowledge of nutrition around the mid-century clarified the position. Controversy and conflict of ideas may have characterised the developments of nutrition theory, but the analysis of foodstuffs advanced to a level at which—whatever doubts may have been circulated in the learned societies—the practical analyst had a repertoire of techniques which could stand up in a court of law. Thirdly, less obvious but just as important, was the growing appreciation of what constituted health and sickness. The drama of discovery of the
bacterial origin of many diseases sometimes obscures, to those unfamiliar with the history of medicine, the importance of growth of physiology in the later decades of the 19th century. And it reinforces the claim for the social importance of the analyst that analysis applied to biochemical and physiological studies was contributing to the very knowledge that was strengthening the hand of other analysts in safeguarding the food and the health of citizens. We see, therefore, the analytical chemist making use of new techniques in his own craft, of medical progress, and of progress in biochemistry and physiology promoted by colleagues of like interest. The history of food and drugs legislations is not only a matter of social administration but also an illustration of the permeation of social action by analytical chemistry. Adaptation of New Discoveries
Techniques at the disposal of the analyst at the beginning of the modern chemical era were little more than those available to his cook in the kitchen, but progress in the last quarter of the 18th century was very rapid. It was a period in which instrument making developed both as a trade and as a distinct craft. The gentleman amateur chemist of, say, 1750 could have his equipment made for him by a handyman; in the 1770's he could have it made to order by a specialist; by 1810 he could buy it ready made by specialists who could rely on an established market (12).
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Similarly, there was in 1750 no distinct literature of analytical chemistry, with the notable exception of assaying. However, important works in mineralogical analysis began to appear, and by 1810 a prospective chemist could train himself or be trained in inorganic analysis to a high level, using techniques which would have been intelligible to students 100 years later. This change was not only a matter of trading in the familiar. By 1800 we see a characteristic of analytical chemistry which was to become more and more marked as time went on, namely, the adaptation to routine estimation of discoveries made originally in theoretical pursuits. For example, the radical discoveries in gas chemistry made by Priestley, Cavendish, and Lavoisier were effected in apparatus by which, for the first time, gases could be isolated from the reactants which produced them and also be subjected to chemical manipulation under the same controls as had hitherto been possible only with liquids and solids. Priestley himself established regular procedures for gas testing with rough-and-ready quantitative results. Soon afterward, eudiometers, such as were used by Cavendish and others, became standard laboratory equipment, and the idea of the measurement of gas volume as a parameter in quantitative estimation is exemplified in the (admittedly not very successful) soil-carbonate analysis apparatus of Humphry Davy. An example of a different approach is seen in the work of Kirwan (13). Here, a number of chemical reactions discovered in the decades between 1760 and 1790 were brought together and applied to the successive separation of the products of successive reactions. At each stage a group of substances brought into solution by a given reagent would be separated by filtration from a group indifferent to it. These successive dichotomies resulted in the identification of components by their survival at the end of a chain of separations. The philosophy of this system was to persist as the basis of inorganic analyses until quite recent times, and to form the common basis of celebrated textbooks, running often to many editions, which brought a high degree of unity into the training of analysts in many countries (14). One result of this development was that chemists came to speak a common language of technique throughout the world, as is fairly obvious on inspection of the technical literature. What is less obvious is that since the technique had a common origin in the basic needs of society, analytical chemistry produced a hidden (and as yet unacknowledged) force for inter-
