ll, t. Chem. 22 (1998) 2 j
THE WISWESSER-LOSCHMIDT CONNECTION *
Alfr d d r, M l , WI
W ll ph W r ( 4 8 [ . ] r d t d fr h h Un v r t th .S. n h tr n 6 nd r v d n h n r r .S . fr th t n t t t n n 4. pl d b r l , th r j n d r C p n , th t nn Ar n l, th C p r Un n, W ll n r d t , th U.S. Ar t rt tr , nd f n ll b th A r lt r l r h S rv f th U.S. .A., n nt r t d thr h t h v r d r r n pl f n h l tr t r d r pt n , h d v l p d th W r n t t n (W , h h d p bl th n l l n d p t n f v r l l , n tt r h pl t d. r h r n z
r 2. Josef Loschmidt
t n n th 80 h d ll n f W r rd n th r p t r . h Aldr h Ch l C p n v n f f r d t t l n W . W r l rn d b t th h l r f f h dt ( 82 8 [ . 2] fr M r tz K hn p p r n th Journal of Chemical Education (1), h h b d n h rd An hütz p p r (2 nd r pr nt ( f h dt 86 v l (4 . f lt th t h h d d r t r d v r , l b l v n th t th h t b r h t th f r r nn r f th W nd h nt d th rld t n b t t. r I. W ll . W r 22 Bull. Hist. Chem. 22 (1998)
He submitted a manuscript to the present author (A.B.) he had been invited, and then at chemical society meet- for the Aldrichimica Acta, which at the time was being ings and in chemistry departments, and finally by pub- distributed to over 200,000 scientists worldwide. Al- lishing several papers (7). All of these lectures and pa- though the initial response was one of reluctance, I be- pers were based on Wiswesser's seminal paper in the came enthusiastic about the subject after reading Aldrichimica Acta (5). I have been greatly helped in Loschmidt's book (3) and some letters, in particular one these efforts by Professor Christian R. Noe, formerly at by Wiswesser to Linus Pulling (see Ref. 16), and col- Loschmidt's alma mater, the Technical University in laborated to expand the paper, which appeared in Vienna, and now at the J.W. Goethe University in Frank- Aldrichimica Acta in 1989 (5). furt. Wiswesser described Loschmidt's chemical firsts: Our papers have been attacked quite sharply by two 1. The first correct cyclic structure of benzene and historians of chemistry, Professors A.J. Rocke (8) and of many aromatic chemicals, 121 in all. G.P. Schiemenz (9). Rocke presents three main argu- 2. The first representation of the allyl moiety. ments: 3. The first representation of the vinyl moiety and (1) "Loschmidt clearly believed that the most prob- of many others. able structure for benzene (Schema 182) was a 4. The first representation of cyclopropane, 21 formula constructed from multiple fused years before it was made by Freund. cyclopropyl rings, using only single bonds. (8)" 5. The first picture book of molecules, containing graphic displays with atomic domains, rather than abstract bond lines. 6. The first double- and triple-bond marks (within the overlaps). 7. The first realistic displays of atomic sizes and bond distances (largest overlap with triple bonds). S h 82 8. The first set of diagrams with correct C = 12, N = 14, O = 16 formulas. However, all of Loschmidt's more than 100 aro- 9. The first textbook use of atomic-group symbols. matic compounds are based on Schema 185 as the basic 10. The first use of the valence prime marks on benzene structure. these and atomic symbols ("Valenz" was intro- duced by Wichelhaus in 1868, 7 years later). 11. The first LINE-FORMULA NOTATIONS ("ra- tional formulas"). 12. The first revelations of hexavalent and tetrava- lent sulfur. S h 8 The article also outlined Loschmidt's life and work, based largely on the biography Richard Anschütz pub- lished with the 1913 reprint. Wiswesser also prepared (2 "... Kekulé himself did not recognize Loschmidt indices of Loschmidt and Anschütz citations, by author as a predecessor for the benzene structure be- and subject. He translated Loschmidt's chemical names cause he cited Loschmidt's benzene proposal into English and collated structures with page numbers. in his first paper on the subject. If Kekulé had On the occasion of our last meeting in Reading, consciously taken the idea for benzene from this PA, Wiswesser gave me a great deal of his material on obscure source, or regarded the Loschmidt Loschmidt, even copies of the original plates, which he structure as similar to his own, the last thing he had hand-colored Expressing concern about his own would have wanted to do was to draw attention failing health, he urged me to continue his work on to it. (8)" Loschmidt. I remember his pleasure upon receiving the Kekulé did not "cite" Loschmidt's proposal. All Acta containing his article, just a few days before he he said in one footnote in French (10) and one in Ger- died. man (11) was, "I prefer my structure to those of Since then, I have been trying to continue his work, Loschmidt and Crum Brown." Aside from these deni- by giving many lectures, first at the Boston American 0grating 0 footnotes - not citations - and one brief abstract Chemical Society meeting in April 1990 (6), to which (12), there were no references to Loschmidt's book in Bull. Hist. Chem. 22 (1998) 23
the entire 19th century. Rocke points to the Dictionary This misunderstanding that Loschmidt's benzene of Scientific Biography, where more space is devoted to structures might symbolize a monocyclic formula was Loschmidt than to Kekulé. Loschmidt was indeed well already discussed by E. Rey in 1965, who aptly com- known in the 19th century, but as a physicist, not a chem- mented that one must lnterpret the circular symbol as what it really means and not as what it could be, ist. Not until Anschütz's first paper (2) was Loschmidt and hence not as a circular array of six carbon atoms. recognized as a highly competent chemist. The argument also holds true for all of Loschmidt's (3) "Even if Loschmidt had suggested a cyclical formulae (by the way, there were not 386!) which benzene structure in 1861, I would argue for its may have some superficial resemblance with mod- insignificance, because no empirical evidence em molecular models. To date molecular modeling could then be adduced to support the idea. (8)" back to I861 is just anachronistic. This is the kind of argument that can be made Schiemenz's English summary of his longest paper states against much purely theoretical work. (9c): Schiemenz criticized Wiswesser inter alia for claim- ing that Loschmidt was the first to consider a 6-carbon In 1989, W. J. Wiswesser claimed that the correct, monocyclic structure for benzene, and also for stating monocyclic structure of benzene was not conceived that Loschmidt's book of 1861 was practically unknown in 1865 by A. Kekulé, but already in 1861 by J. and that he was "a shy and self-effacing man." Loschmidt. It is shown that this view is neither cor- rect nor new. As a symbol for the benzene nucleus "Die Idee einer monocyclischen Anordnung der sechs C 6 , Loschmidt used a circle which Wiswesser be- C-Atome des Benzols kommt nach allem bei lieved to stand for a cyclic array of the six carbon Loschmidt auch nicht andeutungsweise vor. (9a, 9c)" atoms. In fact, this circle represents, in the two-di- (" h r th r n h dt b v n th mensionality of the printed page, a sphere. Similar, l ht t h nt f n l rr n nt f th 6 but smaller 'circles' ( . . spheres) represent hydro- rb n t n b nz n ."( gen, carbon, nitrogen, oxygen and sulfur atoms. Their sizes are chosen so that the volumes of the corre- But consider the following structures to represent aro- sponding spheres reflect the respective atomic matic compounds aniline, benezenesulfonic acid, ben- weights (72 for C 6). This meaning soon passed into zoic acid, and cinnamic acid. oblivion. As a consequence, gradually a misinter- pretation developed which culminated in Wiswesser's view which recently has been popularized by C.R Noe and A. Bader. The most telling indication that Loschmidt thought of a monocyclic structure is in his Schema 229 for p-phe- nylenediamine (13): Aniline nz n lf n A d S h n d r Anbl d S h z t d Mö l h t v n r n M d f t n n. ["Just looking at Schema 229 shows the possibility of isomeric modi- fications."]
S h 22
C nn A d Schiemenz counters (9d):
Auch eine Anmerkung h dt zum In a letter to Chemistry and Industry, Schiemenz wrote 'Semibenzidam'='Azophenylamin' (9b): (Phenylendiamin), Schema 229, gehört hierher: 'Schon der Anblick des Schema zeigt die Möglichkeit 24 Bull. Hist. Chem. 22 (1998)
von isomeren Modificationen' (Loschmidt (1861), wir Isomerie im engern Shine nennen. Solche 34). Entgegen der Auffassung von Noe and Bader Isomerie findet statt zwischen Milchsäure und (Chemistry in Britain 29 (1993) 402, Corrigendum: Paramilchsäure, zwischen Alphatoluolsäure und S.573; vlg, dies., in Wotiz (1993), 233) einer Inter- Betatoluolsäure. Die anderen Arten der Isomerie pretation als o-, m-, p- Positionsisomerie noch nicht im weiteren Sinne sind: erstens jene Fälle, wo zwei zugänglich (Anschütz (1913), I32), kann diese Substanzen denselben Kern und dieselben Aufsatz- Bemerkung nur im Sinne einer Konstitutionsisomerie Atome haben, wo aber die letzteren zu anderen verstanden werden (vgl. Loschmidt (1861): Isomerie, Aufsatzelementen gruppiert sind. So haben S.8-1I). Mithin muß bereits Loschmidt, der anderswo Nitrotoluol und Benzaminsäure [i.e., aminobenzoic N-N- und auch 0-0-Bindungen hat (Schema acid] nicht nur dieselbe Zusammenstellung C 7NH7O 2 , 176,178), an die Atomverknüpfung des Phenylhydrazins sondern auch denselben Kern C 7VIII und dieselben gedacht haben. Aufsatzatome NH 7 O 2 ." [Emphasis added] Thus, Schiemenz dismisses this argument by claiming Schiemenz points out that Loschmidt did think of six- that Loschmidt must have been thinking of an isomer atom monocycles such as his Schema 237, 1,4- like phenylhydrazine (which had not yet been made). diphenylpiperazine, and claims that this is "unambigu- However, in his discussion on isomerism, Loschmidt ous proof that he did not think of such an array for [the distinguished between isomers " n rn S nn ," like C6 nuclei]. (15)" Yet, in fact, Loschmidt came even o-, m-, and p-isomers, and isomers " t r n S nn ," closer to Kekulé's cyclohexatriene structure in his like phenylenediamine and phenylhydrazine. The former Schema 239 for the 1,3,5-triazine derived from aniline you can predict just by looking at them, but not the lat- and 2,4,6-trichloro-1,3,5-triazine ter (14):
Figure 3. Letter from Kekulé to E. Erlenmeyer I Bull. Hist. Chem. 22 (1998) 2
tained by the comparative study of physical proper- ties of the existing compound and certainly not by th ofreactions chemical t d ... But even when we have succeeded in this, different rational formulae ( 'Umsetzungsformeln will still be appropriate. [Em- phasis added]
As . . W d rd tr d n h 2 C p l t r Schema 237 (18): He [Kekulé] was, in truth, too much under the influ- ence of the theoretical and physical chemists of the time, who were inordinately opposed to the idea of fixed chemical structure—so much so that, until 1886, the infant r ht d r t h n Ch h n G ll h ft, born in 1868, would only print struc- tural formulae using dotted-and-dashed lines; the use of solid lines to represent the nearest neighbor rela- tionships would have imputed too much reality to an hypothesis which leading theorists of the day simply th r th n b n n b pr f th t h dt would not accept. d d n t th n f b nz n x rb n n l , t Schiemenz (19) h l d th t h dt 86 b t th t h t h v n d r d h tr t r b ll n n ft r t p bl t n. A l r b t d d n t n h t d th th t th n l n f fr K lé l tt r, h nd Erl n r n f t (20 . d bl b nd , h n , h d n t l v th t " n S d d r n K pp h r v d t br fl ( 2 . p n . (16)" f r An hütz p bl t n f 2 (2 nd ( , Sh rtl ft r h dt b pp r d n n h v r, th r r nl thr r f r n t t: t br f r 4, 862, K lé r t l tt r t E l Erl n r nd d p r n f tn t ( 0, n K l p p r [ . ], n h h h ll d d t " h dt C nf n nd K pp r v ( 2 . If nd d S h nz ( f r ln ( ." Wh ld K lé h v h n h rr t n rt n th t h dt b d l d r pt n f r h dt tr t r ? n 86 , n n, h t h v b rr d fr t th t K lé t t d th t nn t r t f r l f n t b th r n t t t b t th t nl l (2 . t t n, nd n d r d h dt tr t r "f r S h nz f lt W r f r d r b n l f nf n ( : h dt " h nd lf ff n n." ld Which of the different rational formulae one wants n " h b r f th I p r l A d f to use for specific cases is essentially a question of S n , f nd r f th Ch l h l S t , appropriateness. Based on the observations already n t t t d r t r nd, t n t , d n f th f lt f given, there can be no doubt that one may use differ- ph l ph f th Un v r t f nn b h nd ent rational formulae for the same substance. At the lf ff n n ? (22 " Alth h th nd d b same time, one must also, of course, keep in mind d ff lt t nd r t nd, n h n h dt p r that the rational formulae are only formulae of reac- n ll r t b t th t v r l t . r nz Exn r, tions ( ' Umsetzungsformeln') and not formulae of con- h dt r pr f r f ph t th stitution ( C n t t t n f r ln , and that they do not in any way describe the constitution, i.e., the po- Un v r t f nn , h d n n h dt ll f r sition of the atoms in the compounds. This should n r b h dt h d b n t d nt nd be clearly stressed, because oddly enough some fr nd f Exn r f th r t th Un v r t f r . At chemists still believe that by the study of chemical th 00th nn v r r f h dt b rth, Exn r r t reactions, one can derive with rt nt the constitu- th t h dt h d " r r dn f h rt nd d tion of compounds, and thus depict the positions of t t t ll th t j l , h ld nj th n the atoms in the chemical formula. That the latter is t f f th r j t h h n. (2 " not possible warrants no special proof ... Yet a basic Al x nd r r, th r ndf th r f th b l l r t task of natural science must of necessity be to dis- Er n S hröd n r, d r b d h n f l tt pt cover the constitution of matter or in other words, Ch h St d n the position of atoms; this, however, can only be at- t br n th t th tt nt n f nt t d r n tr p t En l nd (24 : 26 Bull. Hist. Chem. 22 (1998)
th h tr nd ph , h v b n p bl h d n En l h b l n (28 . It W r r n t n f h dt r r bl n ht nt h l tr t r h h p r d th r n d nt r t n nd r t r nd r t nd n nd ppr t n f th Chemische Studien, l n t n n th S p .
r 4. C r t v St p r . r t d t r h A tr n p t l rv d r Onl n , th th t n nv ll (2 n r t v t p [ . 4] h n n f h dt n h d r t nt r t nd v t v r f v r bl rr t r t tr t r , th t f nn d. h r v . h t p bl t n [Ch h St d n] l f r tt n. It nn t b d n d th t t th r p t r f th f r t d v r [ . ] h d th tr h t bl f r th t, b h l t r d d n th t r f t d, n f h dt n f r t . n t dr tt nt n t t, v n th h h h d n d W r t ? Of th t lv "f pp rt n t . f r t ," . , " h f r t rr t l tr t r f b nz n nd f n r t h l , 2 n ll," h dt b t fr nd, d ltz nn, d, h t f n v r t t nt. h dt th f r t "... v r h r h dt x v d t pr t n d r n l x rb n r n , b t h d d n t v nt d h b n ppr t d h h ld nd n h t t d th th d bl b nd . K lé h ld h v b n. (26 ... j t ld n t t nd t, l h x tr n f 86 pp r d t b n pr v nt, h n p pl t l d b t h nd h r t .(26b " b t th p zzl b t t n t r t n t ll t b d h rd An hütz t n d h h dt d d dr d (2 . W r rr t n d r b n n t p nt t h n r f 86 t th t f th h dt th r f r t nd n nd n h p p r th, Benzolfest n 8 0 h h l br t d th 2 th nn v r ...th t t n b f 86 r ll th t rp r f th rr t b nz n tr t r . An hütz b l v d f th nt r n r n h tr ." th t h dt l n "...b f th nd nd n d t h h n nt r l p rt f h h r E E E CES A O ES t r. h d v r f Chemische Studien ... h ld, nn t d nd f r tt n r , h l ft t h n (2 "— h p p r pr nt d th p t r n t th A r nd, l l , t dd, t h rd An hütz nd n Ch l S t t n n S n r n n W ll W r. Apr l, , IS 00 . A h h p nt n h dt r n t n h t . M. K hn, . Ch . Ed ., 1945, 22, 8 . 2. . An hütz, r. t h. Ch . G ., 1912, 4 , . t p t th Un v r t f nn n n , . . An hütz, Ed., "K n t t t n r ln d r , t h h n ll n n h t p d tr b t Or n h n Ch n r ph h r r t ll n , t h dt, h h d d d 00 r rl r n l , O t ld Kl r d r x t n W n h ft n," . 8 . A n th l t r r r M x r tz, C rl 0, pz , . pr nt d b th Aldr h Ch l j r , nd S r rb rt nd , ll r n ll fr C ., C t. . 8 . O E: All b nt r f r nn , nd Ern t El l, Alb rt E h n r, Chr n t tr t r l b l d "S h " r t n fr t n nd Günt r S h nz. h p p r , h h d lt th b l t. Bull. Hist. Chem. 22 (1998) 2
4. J. Loschmidt, Chemishe Studien I, Carl Gerold's Sohn, personal collection), Loschmidt provided "amazingly Vienna, 1861. Reprinted by the Aldrich Chemical Co., perceptive graphical visualizations" in 1861 of increas- Cat. No. Z18576-0. ingly tighter, overlapping bonding in ethane (Schema 5. W. J. Wiswesser, "Johann Josef Loschmidt (1821-1895): 9), ethylene (Schema 56, 57), and acetylene (Schema a forgotten genius. Benzene rings and much more in 59). Photocopies of this letter are available on request 1861," Aldrichimica Acta, 8 , 22 [I], 17. from either the author or the editor of the Bulletin. 6. C. R. Noe, A. Bader, and W, J. Wiswesser, "Loschmidt, 17. A. Kekulé, Lehrbuch der organischen Chemie, F. Enke, not Kekulé, published first benzene ring diagrams" pre- Erlangen, 1861, p. 157. sented at the symposium on the Kekulé's Benzolfest, 18. R. B. Woodward, unpublished manuscript, courtesy of 100 years later, 199th American Chemical Society Na- R. Hoffmann and the Chemical Heritage Foundation. tional Meeting, Boston, April 22, 1990, HIST 008. 19. Ref. 9c, pp. 42-43. 7. (a) A. Bader, "Josef Loschmidt, the Father of Molecu- 20. "Knowing" and "understanding" are not always the lar Modeling," Royal Institution Proceedings, 2, 64, same. In the heat of discussion during the Boston Ameri- 197; (b) C. R. Noe and A. Bader, "Josef Loschmidt," can Chemical Society meeting (6), I suggested that in J. H. Wotiz, Ed., The Kekulé. Riddle, Cache River Kekulé may have plagiarized Loschmidt. I no longer Press, Vienna, Illinois, 62595, 1993, Ch. 16; (c) C. R. think so. Kekulé 'knew' Loschmidt's book but did not Noe and A. Bader, "Facts are Better than Dreams," 'understand' it as Anschütz and Wiswesser did. Chem. Br., , 29, 126; (d) A. Bader, "Out of the Loschmidt's Schema 185 for benzene may have led to Shadow," Chem. Ind. (London), , 367; (e) A. Bader, Kekulé's snake dream, but we can never know for cer- Adventures of a Chemist Collector, Weidenfeld & tain whether he even had that dream. The first six-car- Nicolson, London, 1995, Ch. 16; (f) A. Bader, "A bon monocyclic benzene structure was Loschmidt's; the Chemist Turns Detective," Chem. Br., 6, 32, 41; (g) first cyclohexatriene Kekulé's. Most recently E. A. Bader, "Loschmidt's Graphic Formulae of 1861: Heilbronner and K. Hafner have reviewed this contro- Forerunners of Modern Structural Formulae," in W. versy ("Bemerkungen zu Loschmidts Benzolformel," Fleischhacker and T. Schönfeld, Ed., Pioneering Ideas Chemie Unserer Zeit, 8, 32, 34). The authors ap- for the Physical and Chemical Sciences, Plenum, New prove particularly of Schiemenz' (Ref. 9c) York, 1997; (h) A. Bader, "Richard Anschütz, Archibald "ausgezeichneten und akribisch recherchierten Scott Couper, and Josef Loschmidt", Ref. 7g. Richtigstellung" [Schiemenz' excellent and meticulously 8. A. J. Rocke, "Waking up to the Facts?" Chem. Br., , researched correction] and of Hafner's "August Kekulé, 29, 401-403. dem Baumeister der Chemie zum I50 Geburtstag," 9. G. P. Schiemenz, (a) "Good-bye, Kekulé. Joseph Justus von Liebig Verlag, Darmstadt, 1980. There (p. Loschmidt und die Monocyclische Struktur des Ben- 76) Hafner wrote, "...again Kekulé succeeded brilliantly. zols," Naturwissenschaftliche Rundschau, , 46 [3], His irresistible desire for clarity and his unusual power 85; (b) "Further out of the Shadow," Chem. Ind. (Lon- of imagination again helped. Basically the benzene for- don), , 522; (c) "Joseph Loschmidt und die Ben- mula is a logical conclusion from structural history. zol-Formel. Ober die Entstehung einer Legende," Today it seems obvious, but over a hundred years ago it Sudhoffs Archiv, 4 [1], 41; (d) Ref. 9c, p. 57, foot- was an extraordinary mental leap, comparable to the in- note 120; (e) "Spheres from Dalton to Loschmidt. In- tellectual effort once necessary before man could ex- sights into the Ways of Thinking of a Genius," in W. change sled runners for the wheel. The idea that a hy- Fleischhacker and T. Schönfeld, Ed., Pioneering Ideas drocarbon might have a circular structure was totally for the Physical and Chemical Sciences, Plenum, New foreign to chemists of that time. The circle was the sym- York, 1997. bol for the indivisible, the atom." [emphasis added]. But 10. A. Kekulé, "Sur la constitution des substances 13 years earlier Ferdinand Kirchhof ("Joseph Loschmidt aromatiques," Bull. Soc. Chim. Fr., 86 [2], 3, 100. und die Benzolformel," Chem. Appar., 6 , 91(2), 48) 11. A. Kekulé, "Untersuchungen über aromatische had written, "The idea that a compound might have a Verbindungen,"Ann. Chem. Pharm., 866, , [2], 134. circular structure was totally foreign to chemists of that 12. Liebig's Jahresbericht, 86 , 1, 335. [ See Ref. 3, p. time. The circle was the symbol for the indivisible, the I00.] atom, and the merit of having depicted the nucleus 13. Ref. 3, p. 68. as a circle belongs unquestionably to Loschmidt." [em- 14. Ref. 3, p. 15, phasis added]. 15. Ref. 9b; Ref. 9c, p. 47. 21. Recently, F. W. Lichtenthaler ("Emil Fischer's Proof of 16. I want to thank William F. Reynolds for pointing out the Configuration of Sugars: A Centennial Tribute," that Loschmidt was probably reluctant to accept a ben- Angew. Chem. Int. Ed. Engl., 2, 31, 1541) has sug- zene structure with double bonds, of which he was well gested that Adolf Baeyer, Hugo Schiff, and Rudolph aware, since this seemed inconsistent with the known Fittig were the first to depict sugars correctly, around chemistry of benzene. As Wiswesser pointed out in a 1870. Anschütz pointed out that Loschmidt was the letter to Linus Pauling (August 2, 1987, copy in author's 28 ll. t. Ch . 22 ( 8
first—nine years earlier—to show the correct structures 28. W. Fleischhacker and T. Schönfeld, Ed., Pioneering of mannitol and other sugars (Ref. 3, pp. 119-120, foot- Ideas for the Physical and Chemical Sciences, Plenum notes 63, 66, 69, 70 and 72), But are Baeyer, Schiff, Press, New York, 1997; see also Ref. 7g, h, 9e. and Fittig likely to have known this? 29. For a clear discussion of Kekulé's benzene formulae, 22. Ref. 9c, p. 57. see G. P. Schiemenz' "Where did Kekulé Find 'his' Ben- 23. F. Exner, "Zur Érinnerung an Josef Loschmidt," zene Formula?" Ref. 7b, Ch. 9. Naturwissenschaften, 2 , 9, Heft 11, March 18. 24. A. Bauer, Oesterreichische Chemiker-Zeitung, , ABOUT THE AUTHOR XVI, No. 18, 241, September 15. 25. Jean Jacques has kindly pointed out that this was Jo- r. Alfr d d r, 2 6 rth Sh p rd Av n , M l seph Liouville (1809-1882), but his review of , WI 2 , rn d h h. . nd r . Chemische Studien appears not to have been published. r t rv rd Un v r t n 0. f nd d th 26. L. Boltzmann, "Zur Érinnerung an Josef Loschmidt," Aldr h Ch l C p n n M l n nd a eulogy presented to the Imperial Academy of Sciences th f nd r f S Aldr h n . r. in Vienna on October 29, 1895 and published by the d r, n 4, nt n t p r v r l h n executive committee for the erection of the Loschmidt t r t n h tr , rt, nd th h t r f rt nd h monument, Vienna 1899; (a) p. 14; (b) p. 16. 27. Ref. 3, p. 109. tr .
AU U GE I E
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CO E E CE O IS O Y A E I AGE O SCIE CE I O MA IO SYS EMS O t b r 2 2 , 8 tt b r h, A