W ~ H L E RAND THE VITAL FORCE I. HARTMAN Fats Research Laboratory, Deparhent of Scientific and Industrial Research, Wellington, New Zealand
SOME years ago McKiel relegated Wohler's part in overthrowing the vitalistic theory as well as his "synthesis" of urea into the realm of chemical legend and his views have been accepted in some quarters. Recently, CampaigneZ after examining the evidence arrived at the conclusion that Wohler in preparing urea from ammonium cyanate in 1828 actually sounded the death knell of vitalism. Not the least of Campaigne's merits in reopening the case rests in the inducement to study relevant texts, especially Wohler's paper about the artificial formation of urea.3 This merit is in my eyes not diminished by the fact that for reasons given below I cannot endorse his conclusion. In assessing Wohler's part in the overthrow of the vitalistic theory, his own appraisal of the implications arising from his discovery in 1828 seems to be of considerable importance. I submit that the study of the original paper leaves the reader with rather mixed feelings as to Wohler's stand with regard to vitalism. His only remark in this connection is contained in a sentence quoted by Campaigne in the German original and in the English translation. However, this translation is not correct. Campaigne quotes: " . . . this research has given the unexpected result, that urea i s produced by the combining of cyanic acid with ammonia, an especially remarkable fact, inasmuch as it offers an example of the artificial production of an organic, and, indeed, a so-called animal substance from inorganic (nonorganic) materials." (Italics are mine.) I n reality the italicized passage should run as follows: ". . . that by the combining of cyanic acid with ammonia urea is produced, a fact remarkable also, inasmuch as . , . ." It seems clear that in the sentence quoted emphasis is laid on the formation of urea instead of a salt, which would be expected from an interaction between base and acid, and that the production of an organic material from an inorganic source is mentioned only on second thought. The main body of the paper is devoted to analytical considerations, and in the concluding paragraph there is a reference to the analogy between the urea-ammonium cyanate system and such compounds as fulminic and cyanic acids. Thus the main purpose of the paper appears to he the description of another instance of isomerism first observed by Wohler and Liebig a few years earlier. On the basis of this paper only, there would be little reason to attribute to Wohler any intent to question the vitalistic theory. However, in reporting his discovery to his master Berzelius, Wohler indicated clearly that he gave this matter considerable thought. The relevant paragraph in his letter to Berzelius, referred to by MCKIF, D., Nalwe, 153, 608-10 (1944). CAMPNGNE, E.,J. CAEM. EDUC.,32,403 (1955). WOHLER,F., Ann. P h ~ s i k . 12,253-7 , (1828).
VOLUME 34, NO. 3, MARCH, 1957
both McKie and Campaigne, but interpreted in a different way, is worth translating in full: Can this artificial formation of urea be regarded as an exsmplp of forming an organic substance from inorganic msterials? J t is remarkable that in order to produce ryanic acid (and also ammonia) one must yet have always an organic substance to begin with, and a natural philosopher would say that the organic part has not disappeared either from the animal charcoal or from the cyanogen compounds made from it, and, therefow, one roulrl always produce from it again an organic hody."
Campaigne is of t,he opinion that by "natural philosopher" Wohler meant not himself but a diehard vitalist. To my mind this passage implies that Wohler, while not identifying himself with his natural philosopher, did not oppose his views. These various conflicting statements being a matter of interpretation rather than of fact, I submit that both McKie and Campaigne have failed to consider two aspects which could throw some light on the subject: Wohler's limitation as theorist, and his relations with Bereelius. On the first point Wohler himself comments in a letter to Liehig as follow^:^ . . . as a thinker I am painfully slow. No one is less meant to be a. critic than I. As you well knor., t.he capacity for philosophical thinking is entirely lacking in my make-up, as a.ell as thitt for mathemstioii. Only for observation there is, I think, an adequate provision in my hrain, possihly also linked up with a kind of instinct for antiripating artoal relationships.
He is, after all, the author of the often quoted sentence: "Probieren geht iiber Studieren" (experiment is superior to speculation). Accordingly, his previously mentioned communication to Berzelius gives me the impression that not being sure what to make out of his discovery, he approached Berzelius, as on previous occasions, hoping for guidance. McKie is of the opinion that Berzelius did not sense any refutation of vita1ist.i~ belief in Wohler's discovery and letter. I am not so sure. Berzelius' jibe4 about the artificial creation in the laboratory of a baby ("if only so small") as the next step in his disciple's scientific career seems to indicate that he suspected in Wohler some tendency towards heresy, and as a convinced vitalist was quick to bring it into ridicule. Then in a more serious vein he complimented Wohler on his discovery, hut referred only to the part which pertained to isomerism. The reply of the revered master must have stifled in Wohler any inclination to venture further into the field of the vitalistic theory. And so "a man of quiet and peaceful mind, and free from self assertion, Wohler pursued the even tenor of his way, taking but little part in the controversies of his time."= It was not his fault
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WALLACE,O., Editor, "Briefwechsel swischen J. Bereelius and F. Wbhler," Leipzig, 1901, Vol. I, 208. A. W., Ber., 15, 3127-90 (1882). HOFMANN, FINDLAY, A,, "A Hundred Years of Chemi~try,"Duekwort,h, London, 1937, 337-8.
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that his more determined French contemporaries carried the matter further and used his discovery as one of the arguments in combating vitalism. Hofmann's claims' regarding Wohler's part in the overthrow of vitalism, rightly criticized by McKie, are thus not based on fact, and can only be regarded as exaggeration, perhaps not unnatural in an obituary. A more sober appraisal of Wohler's discovery was given in 1869 by another of his famous compatriots, Ladenburg?
urea, a known product of animal life, was formed upon the evaporatianaf asolution of its ammonia salt. It is true that the prohlem was not completely solved by this discovery. The synthesis from the elements was not yet possible, hut still the most essential thing had been accomplished. From inorganic compounds (amongst which many a t that time classed cyanic acid) a substance had been prepared which had hitherto been found in the animal organism only. In spite of this, the revolution of ideas proceeded but slowly; it was still believed that the vital force ~ o u l dnot be dispensed with, and some decades afterwards scimtific discussions took place as to its existence.
W6hler had discovered cyanic acid in 1822 and was occupied with its investigation when he made the observation in 1828 that
If this mas so, then Wohler's preparation of urea did not of the vital force more than priestlev's discovery of oxygen disposed of the phlogiston theory. According to his own testimony Wohler lacked the speculative genius of a Lavoisier.
LADENBURG,A,, translated by L. Dobbin, "Lectures on the History of the Development of Chemistry since the ~i~~ of Lavoi~ier." J a m ~ aThin, Edinburgh, 1905, 116.
JOURNAL OF CHEMICAL EDUCATION
