Heinrich Caro and the Creation of Modern Chemical Industry

It was Heinrich Caro’s fate that he passed from childhood to adolescence during a turbulent period of European history, one smouldering with social unrest. It was his good fortune that he grew to manhood during a period of European enlightenment, in which industrialising nations were poised to engage in the most challenging enterprise of modern times, that for which scientific ideas became the basis of industrial power. It is our good fortune that he has left extensive records of those early years, even if often in the form of reminiscences that were shaped by later events. They are important because the social background and the political and economic climate in which he grew up were significant to his later choice of career, and moulded his outlook, which, as we shall see, certainly irritated his less-admiring colleagues.

In October 1852, Heinrich Caro gained entry to Berlin’s Königliches Gewerbeinstitut, the leading trade school of Prussia. Two years earlier the school had introduced a chemistry course, one that catered for young men intending to pursue careers in local industries. The emphasis was on chemical technology, analysis, and laboratory work.¹ Caro also enrolled in a chemistry course at the University of Berlin. By this time, however, Caro’s parents were in poor financial shape. Heinrich was too proud to request assistance from wealthier family members, but was fortunate to receive a scholarship from the Seydlitz foundation. This came about in part because of Heinrich’s mathematical capabilities, demonstrated during one of the first lectures he attended at the Gewerbeinstitut. The lecturer, college director Nikolaus Druckenmüller, was so impressed with his student’s performance that he immediately arranged for the stipend, and continued to encourage Heinrich Caro throughout his time at the college.²

In this and the next two chapters we follow Heinrich Caro’s first foray into synthetic dyes and their various applications at Roberts, Dale & Co., the firm he worked with for seven years in Manchester. Certain of Caro’s activities arose from the need to investigate novel reactions as a response to the patent monopolies of the main English rival, Simpson, Maule & Nicholson of London. The enterprise in Manchester was aided by a number of German chemists and colourists, many of whom would later make substantial contributions to the German dye industry. Though not all the new products and processes were successful, they did enhance Caro’s familiarity with both academic and industrial coal-tar chemistry. Moreover, his assistance to English and Scottish dye-users during the 1860s as they experimented with coal-tar products brought about a further merging of calico printing technology with the practice of chemistry. Caro’s perseverance, his own experiments in dyeing and printing, and his travels to factories and agents in Britain and on continental Europe contributed to the widespread acceptance by dyers and printers of aniline dyes. On this he also built his own reputation. It was while working in England that he acquired the skills for inventing, manufacturing and marketing synthetic dyes that he would later exploit to such great advantage in Germany.

Making profits from new chemical processes in the 1860s provided tough challenges that engendered both friendships and jealousies. With success came profit-sharing arrangements and new status. Failure, however, led to confrontations, clashes, and rivalries. Disgruntled employees sought out new opportunities and partnerships elsewhere. Outside of the factory walls there were drama and combat in the marketplace, discreet dealings with agents and customers, gentle persuasions in order to gain acceptance of new products, and conflicts in the courtroom. We find all these aspects of business life at Roberts, Dale & Co., including widely different attitudes towards its chief inventor, Heinrich Caro. Scheming colleagues revealed their distrust of him, while agents for chemical products barely concealed their admiration. Here, in Manchester, we have a further foretaste of Caro’s later life at BASF.

The development of new dyes, as the previous two chapters have demonstrated, brought together industrial and academic chemists to engage in highly novel synthetic studies. Since the academics were particularly important as consultants, solving problems that might make dye manufacture more profitable, and as expert witnesses in cases of patent litigation, it was in their interests to undertake in-depth studies on processes and products.

At the close of the 19th century, the German synthetic dye industry was the undisputed world leader. It had become a symbol not just of Germany’s industrial prowess but also of its mastery of organic chemistry. This was recognised at home and abroad, particularly in England, where the dye industry was founded. During the 20th century there were moments of acute interest in how this had occurred, most particularly at the outbreak of World War I, when Britain found itself without a strategic dye industry— whose intermediates and processes were the sources of modern explosives and poison gas—and in the aftermath of World War II when, especially in the United States, new paradigms of technological revolutions were invoked. The latter was to be the stimulus for the classic study, John J. Beer’s The Emergence of the German Dye Industry, published in 1959.² Beer’s volume reviewed the history of the German synthetic dye industry prior to the formation of I. G. Farbenindustrie in 1925, and though it remains the most readable introduction to the subject, it does not address many important aspects of the key relationships between chemistry and technology, and of corporate structure and innovation. Beer readily admitted an important lacuna, namely the precise nature of the connections between academic chemists and the dye firms, particularly royalties and contractual arrangements.³

With these words, the British chemist Raphael Meldola, in his 1886 lecture before the Society of Arts in London, commenced a review of the influence of the German dye industry on industrial progress. That influence was hardly more tellingly invoked than by its impact on British chemists, particularly those with industrial experience, such as Meldola, who invented an important colorant, Meldola’s blue, similar to Caro’s methylene blue, when employed at Brooke, Simpson & Spiller of London. Meldola and others were not slow in recognising the weaknesses of the British dye-making firms, whose decline had started in the mid-1860s, around the time when Caro and other Germans returned to their homeland. It was a few years later, in the aftermath of the Franco-Prussian war of 1870–71, that German hegemony in dye manufacture became anchored in mastery of aromatic organic chemistry to an extent that was not to be achieved elsewhere. This at first took place through academic-industrial research alliances of the sort exemplified by the alizarin work of Caro, Graebe, and Liebermann during 1869–70, and formalised by Caro and Baeyer from 1874. The endeavour was soon woven into the fabric of factory life by the assignment of chemists to laboratories that were increasingly given over to research and development tasks.

The emergence of the synthetic dyestuff industry during the second half of the 19th century is often presented as a tale of poorly exploited British inventiveness, followed by smooth and unhindered German successes. According to this standard story, the British failed because they neglected appropriate education and legislation, were incompetent, and preferred to invest in profitable heavy manufacturing and colonial enterprises.³ The Germans succeeded because of their mastery of the use of formal knowledge, the introduction in 1877 of a comprehensive patent system, the inauguration of dedicated industrial research laboratories, and the application of business strategies based increasingly upon the monopoly power of “conventions,” or cartels, and “communities of interests.”⁴ Such clear-cut conclusions are invariably supported by the accounts of participants. The Germans used the situation to promote increased funding for education and research. On the British side the conclusions were often meant as warnings of the failure to invest in scientific education and basic research. This was the message of Raphael Meldola’s 1886 lecture before the Society of Arts in London in which he advised his audience that a survey of British dye users had revealed that over 80 per cent of the colorants they employed were “Made in Germany.”

What made Heinrich Caro such a successful and prolific inventor? This is the principal question that we tried to answer as we followed his career, especially during the 1870s and early 1880s. Because of Caro’s artistic inclinations, we might with considerable justification describe this as his second most fertile period, when, as development chemist and then research director at BASF, he became the most important inventor of synthetic dyestuffs in the 19th century. Despite the surviving personal journals, diaries, and correspondence, and even self-congratulatory accounts, this is, however, one part of Caro’s life for which source material is thin, at least from his own perspective. Accordingly, other approaches to verisimilitude must be sought out. There is, fortunately, an important insight into Caro’s working style at that time. This derives from a retrospective and somewhat one-sided account written by his main professional rival at BASF, Carl Andreas Glaser, who joined the firm in 1869.

The two decades that Caro spent in retirement provided little of interest in the way of new dyes and processes to BASF, despite his agreement to undertake research for the firm. He developed a novel process for the synthesis of rhodamine dyes, which, though patented, appears not to have been adopted. He also synthesized the only compound that carries his name, Caro’s acid (persulphuric acid), through which he became known to generations of chemistry graduates, though probably few of them were aware of his industrial career. Nevertheless, Caro did make other contributions to the firm in the form of documentation, notes, and reports that were invaluable in patent litigation. Until 1898, he remained active on the consultative committee of the Verein zur Wahrung der Interessen der chemischen Industrie Deutschlands. As a pioneer in the development of synthetic dyes, he wrote the first comprehensive history of the industry, presented to the Deutsche Chemische Gesellschaft in 1891.²

Myth and history are sometimes almost inextricably bound together, especially when the myth has been created from actual events to draw lessons and provide examples. There is no doubt that during the early years of the 20th century, Heinrich Caro’s career and achievements in relation to the overwhelming success of the German dye industry reached almost mythical proportions, particularly in England, where chemists and industrialists sought out reasons for the decline of the British synthetic dye industry. Responses ranged from Meldola’s claim that England lost the dye industry when Caro returned to Germany to the collective belief that the genius of men like Caro had masterminded the rise of the German dye industry. British chemists turned the German model of dye-making to their own contemporary ends, which of course only served to magnify Caro’s contribution. At a more mundane level, reasons for failure were sought in education, legislation, research, and the duty on industrial alcohol. Certainly there were elements of truth in these claims, apart from the duty on alcohol, all of which have been perpetuated to the present day.