The Breakthrough of Gerhardt's Reform

By this time, the Gerhardt-Laurent reform had begun to make headway in the chemical world. Although most French chemists, including all the influential ones, continued publicly to oppose Gerhardt and Laurent, they did begin to receive some private sympathy. As early as 1846 Thenard was treating Gerhardt kindly again, and Dumas began quietly to support Laurent in 1847. In Great Britain and the United States a few disciples began to appear.^[50]

It was Williamson's publications on etherification and the water type in 1850-1851 that marked the critical break for the type theory and for its French partisans. His novel syntheses of asymmetric ethers (such as methyl ethyl ether) provided the first compelling experimental support for Laurent's and Gerhardt's conceptions of the relative constitutions of those theoretically most central substances alcohol, ether, and acetic acid. More indirectly, he argued for the truth of the entire new French system, including the atomic weight reform. "In your formulas," Williamson wrote Gerhardt, "I see the future."^[51]

On the heels of this work, and taking advantage of the recent research of Holmann, Wurtz, and others, from 1851 Gerhardt developed his modified type theory. In this theory, four inorganic substances (water, ammonia, hydrogen, and hydrogen chloride) served as models for large series of organic derivatives. Ethers, acids, acid anhydrides, aldehydes, and ketones were all schematically derived from water by replacement of one or both hydrogen atoms; similarly, amines and amides were related to ammonia through substitution of hydrogen by radicals, alkyl derivatives were derived from the "hydrogen type," and chlorides from the "hydrogen chloride type."^[52]

In 1852 Gerhardt succeeded in producing asymmetric organic acid anhydrides, providing another compelling argument in favor of the view that organic acids must be seen as analogous to water, but containing no water per se even in their hydrated forms. In brief, the dualists assumed organic acid formulas twice as large as Gerhardt's and Laurent's so that every acid could be formulated to have two replaceable hydrogens, namely, the hydrogens of the associated water molecule. Extract the water molecule, the dualists argued, and you produce the acid anhydride. What Gerhardt succeeded in doing, in a complete analogy to Williamson's asymmetric ethers, was to create structurally asymmetric or mixed acid anhydrides, such as acetic-benzoic anhydride. The dualists could write acceptable formulas representing the new reaction, but such an equation predicted two products, a mixture of acetic anhydride and benzoic anhydride. The actual production of a single asymmetric product could only be accounted for by the smaller, non-dualistic formulas for the acids. Another way to put the matter is that the only way to force monobasic acids such as acetic and benzoic acids to form anhydrides is to join two molecules, since the water that must be removed requires two hydrogen atoms from two molecules; the production of asymmetric anhydrides made it inescapably clear that two different molecules must be involved. Thus, there is no pre-formed water in acids, merely replaceable hydrogen atoms.

Gerhardt knew immediately that he had a winner. He was so excited that his letter announcing the discovery to his student Gustave Chancel is barely legible. In May and June 1852 he read two major papers on acid anhydrides to the Académie.^[53] The discovery was received with a great deal more immediate acclaim than Williamson's had been, despite the fact that Williamson had predicted Gerhardt's reaction the previous year and that Gerhardt's theoretical argument was identical to Williamson's (Gerhardt did not mention the Englishman's name). Indeed, Williamson's work seems to have been little known, or at least little noticed, on the European continent until 1853.

Even Gerhardt's most implacable adversaries were impressed. After his second memoir was read to the Académie, he wrote Chancel, "You

could not imagine how everyone has changed toward me: Regnault shook my hand, Dumas nearly hugged me, even Fremy paid me the sweetest compliments . . . What a success!" Dumas wrote a somewhat restrained but strongly favorable report on Gerhardt's paper for the Académie. Thenard became an enthusiastic advocate for Gerhardt's career.^[54] The following year Gerhardt published a large review article, carefully crafted to be "academic" in tone, although, he thought, "terribly revolutionary."^[55]

For once, others agreed with Gerhardt. Chancel congratulated Gerhardt, predicting a "great sensation" in Germany and England, along with many new converts—perhaps even Liebig himself. Indeed, Liebig soon wrote Gerhardt, praising the discovery as "one of the most brilliant of recent times," the (Williamsonian) theoretical argument being "as simple as it is elegant." "It is very strange," he concluded, "that these two theories, although completely opposed, are now unified into a single one which explains all the phenomena in the two senses."^[56] Liebig was but echoing the words in Gerhardt's letter to him two years earlier, urging their reconciliation. In October 1853 Gerhardt visited Giessen and was treated very warmly by Liebig.^[57]

As Chancel predicted, during the next two or three years the Gerhardtian system began to attract converts, especially in Germany—a story that is explored in greater detail in chapter 6. A few Russian and a few more English and American disciples began to appear. In France, Malaguti, Quesneville, Cahours, Pelouze, and Gerhardt's students Chancel and Chiozza had adopted elements of the reform even before the acid anhydride work.

Important for this turning of the tide was not only Gerhardt's acid anhydride work, but also his massive and magisterial Traité de chimie organique . It was begun in 1851, and by August of the following year, Gerhardt had written close to 600 printed pages worth of manuscript for the first volume, but with no publisher in prospect. It was reading this manuscript in 1851-1852 and conversing with its author that converted Kekulé to Gerhardt's views. On 28 November 1852, Gerhardt wrote Chancel: "Grreat news! I have sold my organic chemistry to Didot for the trifling sum of ten thousand francs." Gerhardt related that Didot had inquired whether Gerhardt might be willing to complete the last unfinished edition of Berzelius' text. He had replied that the book was already out of date, even though the last volume had only appeared two years earlier, but coincidentally, he had the manuscript of a text himself. They agreed on publishing Gerhardt's manuscript under the title "Traité de chimie organique de Berzelius entièrement refondu et enrichi des descouvertes récentes par C. Gerhardt," with the spine reading "C. Gerhardt: Traité de chimie

organique de Berzelius." Gerhardt added that Laurent had joked that if Berzelius had known this would happen, he would have died a week earlier.^[58]

The book was published in fascicles starting in June 1853 and was exceedingly and justly popular. Liebig himself heartily praised the work and told Gerhardt on a visit to Giessen in 1854 that the book would have ten times as many German readers as French.^[59] Gerhardt worked on it at a furious pace; by February 1856 he finished the manuscript, and the final fascicle appeared in print by May.^[60] In five years, he had written a four-volume work of nearly 4000 printed pages. The book provided a detailed description of the entire science of organic chemistry of his day, along with a defense of his ideas. Ironically, however, all but the last volume utilized the older chemical equivalents, for Gerhardt had for once adopted the pragmatic strategy of presenting the material in the most acceptable possible form.^[61]

In his preface, dated June 1853, Gerhardt advertised his avoidance of all molecular speculation as a fruitful methodology that he had been employing for the past ten years (since the Précis ). He justified his return to the older Liebig-Gmelin equivalents as a way of showing the world how irrational they are. He would trust to time, he said, the consummation of the reform that his colleagues had not yet generally adopted. But at the end of the preface, he hinted that the time may now have arrived, following the work of Williamson, Hofmann, Frank-land, Wurtz, and others, to begin building more than just a conventional system of chemical theory.^[62]

Finally, Gerhardt had achieved the career success he had been seeking, though unfortunately not in Paris. In 1855, through Thenard's influence, Gerhardt was offered and accepted two professorships at his hometown university, Strasbourg. In April 1856 he was named Corresponding Member of the Académie, a cherished honor. However, in August of the same year, soon after the publication of the final theoretical volume of his Traité and just when it appeared Gerhardt might finally be able to enjoy the acclaim and financial security he had long wanted, he died of a sudden fever.