ORGANON 25:1989/1993 AUTEURS ET PROBLÈMES
Stefan Z am ecki (Poland)
M E N D E L E E V ’S F IR S T P E R IO D IC T A B L E IN IT S M E T H O D O L O G IC A L A S P E C T
Introductory note
M ost historians o f chem istry agree that the periodic table and the peri odic law were discovered by Dm itri Ivanovich M endeleev (1 8 3 4 -1 9 0 7 ), which is said to have happened in Sainkt Petersburg on 17 F ebruary 1869. Som e historians go as far as to regard the em inent R ussian chem ist as the sole discoverer, while the others, notably A. E. B eguyer de C hancourtois, J. A. R. N ew lands, W. Odling, G. D. H inrichs and J. L. M eyer, w ere m erely precursors of the periodic table and the periodic law. The form er position is taken m ainly by W estern historians, notably by J. W. van Spronsen, the author o f several interesting studies on the history o f classification o f e le m en ts.1 T he other m ore radical view is voiced m ainly by Soviet historians am ong w hom we should m ention R. B. D obrotin, B. M. K edrov, A. A. M akarenia, D. N. Trifonov.2 At any rate, even those who say the discovery of the periodic law was the jo b o f several men nam e M endeleev as one of the discoverers. I know o f no one who w ould question M endeleev the title o f “discoverer,” in 19th or 20th-century historical studies.
The fact that no historian challenges M endeleev’s title to “discov ery ” is proof o f the wide acclaim the R ussian chem ist got for his w ork, but it certainly does not decide the question o f whether M endeleev was at all the
discoverer o f the periodic table and the periodic law in chemistry. The answer
o f course depends on how you interpret the terms “discoverer,” “periodic tab le” and periodic law .” But as there is no exact definition o f the term “d isco verer” or related term s (such as “scientific discovery,” say), it is difficult to draw any positive know ledge from propositions such as “A is the d iscov erer,” w here A stands for som e person. W hile the value o f such propositions is
debatable, the word itself does have a positive ring in colloquial language, and that tends to boost the prestige of a researcher referred to as “discoverer.”
But let us not dwell on the sem antic im plications o f the term “d is coverer” or related ones and let us go back to the title question w ithout saying for the tim e being w hether or not M endeleev was the discoverer of the periodic table and the periodic law in chem istry. N eedless to say, the replies m ay differ depending on the m eaning o f the term s.
In this article, I take for granted a num ber of established facts from the history o f chemistry, such as the one that M endeleev and other 19th-century chemists did publish studies speaking of the classification of chemical elements.
’’Chem ical elem ent” in their works stood for natural products with the sam e general features, specifically products w hich could no longer be decom posed by chem ical m ethods yet w ere capable o f entering w hat were called “chem ical” reactions (synthesis, analysis, replacem ent). But som e 19th-century chem ists did not rule out the possibility that the natural products described as “chem ical elem ents” were m ixtures or even som e kinds o f co m pounds o f other chem ical elem ents and so liable to decom position using chem ical or physical m ethods. Such views were not at all unusual in the 19th century. At any rate there is good reason to say that m any chem ists then agreed that certain natural elem ents products w ere called “chem ical elem ents,” im plying that those products were no longer decom posable via chem ical m ethods. M any attem pts were m ade to classify those products in various classifications, “natural” and “artificial” alike. T he form er included classifications involving periodicity, to m ention those put forw ard by B eguyer de Chancourtois, New lands, O dling, H inrichs, M eyer, M endeleev and their m any continuators.
19th-century considerations about chem ical elem ents w ere generally linked to chem ical atom ic theories espoused by John D alton and his succes sors. But not all 19th-century system atists believed chem ical atom ic theory w as really necessary for the scientific study o f chem istry. W hat W ilhelm O stw ald, the outstanding physical chem ist, thought about that is well known, w hat the outstanding system atist M endeleev did is less w idely known. A c cording to M endeleev, chem ists could excellently do w ithout atom ic ter m inology in research. M endeleev considered him self to be a continuator of D alto n ’s w ork and used those terms him self, especially the term “ atom ic w eight,” yet that is a very debatable claim for calling him ju stifiab ly an “atom ist” in chem ical research. D escriptions o f him as a “m aterialist,” or an “instinctive dialectical m aterialist,” as Soviet historians, especially B. M. Kedrov, used to do until a short tim e ago, is likew ise a debatable idea. V iew ed from the angle o f m odern chem istry, M endeleev can be described as a representative o f disciplined eclecticism , an attitude w hich is perhaps best described as a m edley o f realistic view s (im plying that an objective reality does exist) with m inim alistic view s (that reality can only be known
Mendeleev’s First Periodic Table 109
by its appearance, and only quantifiable scientific law s can be form ulated).4 M endeleev’s faith in minimalistic concepts shows in his estrangem ent from any theories which involved atomistic theories in such or other versions, whether in D alton’s or W. Prout’s versions or those of J. J. Berzelius,5, S. Arrhenius, N. M orozov,6 and partly in Marie Sktodowska-Curie’s theory. At the same time, though, M endeleev was remarkably opposed to certain extrem ely posi- tivistic ideas, notably the theory advocated by Ostwald. A close look at the entire body o f M endeleev’s philosophical ideas could perhaps reveal som e in teresting facts, for considering his great prestige in the scientific com m unity he must have had quite great influence on the philosophical views o f his read ers.7 I am sure there is a great deal to be found there.
M endeleev’s first studies
In 1855 M endeleev graduated from the Physics and M athem atics Faculty of the M ain Pedagogical Institute (of Sainkt Petersburg) w here he had studied under he chem ist A. A. V oskresenski. On com pleting his curriculum at the college M endeleev subm itted a thesis called Izom orphism v svia zi s
drugim i otnosheniam i kristalicheskoi fo rm y k so sta vu .8 T hat was a very
penetrating study showing that M endeleev was very m uch at hom e w ith the W estern literature of the subject.
In Septem ber 1856 M endeleev subm itted a thesis for his first scientific title, M aster o f Chem istry, called Udelnyie obiom y, som e extracts from which w ere published in the same year,9 while the rem aining passages ap peared in print only one century later, in I9 6 0 .10 R eading that thesis you will find yourself w ondering how it w as possible that as excellent a study was produced at the M ain Pedagogical Institute, a college not renow ned for its excellence in chem ical research. No doubt one o f the reasons for that was the young scientist’s enorm ous talent and diligence, but V o sk resen sk i’s shrew d scientific guidance must have been a great help too.
In 1859 to 1861 M endeleev stayed at H eidelberg U niversity as a visiting researcher. M endeleev cam e hom e alm ost fully ripe for his future w ork as scientist, w hich he ow ed m ainly to his contacts to leading European chem ists and his part in the First Congress of Chem ists in K arlsruhe (1860). But then, he also w rote a rather unim pressive study, called C hastischnoie stseplenie
nekotorykh zhidkikh organicheskikh so ied in en ii,11 a result o f his H eidelberg
research activ ities.12
From K arlsruhe M endeleev wrote his tutor, V oskresenski, a lengthy let ter, w hich was actually a report on the congress debates. T he letter w as published already in the sam e year in Sainkt P etersb urg.13 The m ost im por tant point in the letter is M endeleev’s interest in the atom ic w eight values put forw ard by Stanislao Cannizzaro. But M endeleev’s does not seem to
have been impressed by Cannizzaro’s findings. There is some evidence (which I am going to point to later on in this article) that M endeleev kept to C. Ger- hardt’s old system o f atomic weights (1843). That had a great (adverse) effect on M endeleev’s further work on the classification of elements.
In fact, M endeleev cam e home from Heidelberg holding all the theo reti cal prem ises w hich he needed for his job , and so the stage was actually set for his attem pt to build the periodic system already at that stage. Som e difficulties persisted, o f course, the fact, for instance, that indium , In, had not been discovered by then. Indium , incidentally, gave M endeleev quite a hard tim e later on. Nor did M endeleev know a lot about cesium , Cs, an elem ent discovered only in 1860. Rubidium , Ru, and thallium , Tl, w ere both discovered only in 1861, so he could not have known anything about them either. Still, all the scientific data w hich were needed were at hand then, and yet for two reasons - both of them o f academ ic nature, if I am not m istaken - M endeleev did not try to classify the elem ents in 1861.
For one, M endeleev took a jo b with Sainkt Petersburg U niversity as reader in organic chem istry in that year. That was a new line in chem istry for him. He m ust have spent a lot o f tim e preparing his lectures, especially that he was also w orking on a book on organic chem istry at the sam e tim e. The book appeared in print in 1861 as Organicheskaia khim ia , 14 T hat was the first original organic chem istry textbook to be published in the Russian Em pire. The im portant fact about it is that it was written from the angle of the A vogadro-G erhardt theories. M endeleev also devoted m uch space in the book to physical properties of chemical organic com pounds. The book co n tains the follow ing list o f equivalents (and atom ic w eights) o f chem ical ele m ents in relation to hy d ro gen ,15
H = 1 As = 75 Fe = 28 Cl = 35.5 C = 12 Zn = 32.7 Br = 80 B = 11 Sn = 58.8 J = 127 Si = 14 Pb = 103.5 0 = 16 K = 39 Cu = 31.7 S = 32 Na = 23 Hg = 100 N = 14 Ca = 20 Ag = 108 P = 31.2 Ba = 68.5 Pt = 98.8
These figures dem onstrate that, first, M endeleev confused the notion of atom ic w eight with that o f equivalent, because he attributed equivalents to som e elem ents and atom ic weights to other ones, and, secondly, that he had not adopted C annizzaro’s position by then but rem ained - with a few m inor m odifications - faithful to G erhardt’s figures.
The other reason for his failure to start work on classifying chem ical elem ents already in 1861 was that M endeleev then still clung to G erh ard t’s
Mendeleev’s First Periodic Table 111
theory. B eguyer de Chancourtois was the first im portant system atist, albeit not chem ist, to take up C annizzaro’s values, and so that is led him to one part o f the periodic system in 1862.
In D ecem ber 1865, M endeleev was appointed professor at Sainkt Peters burg U niversity’s technical chemistry chair, but in O ctober of the same year he also took over the general chemistry chair there, which had been vacated by Voskresenski. Also in that year, M endeleev started his lectures in general and inorganic chemistry, which he continued in the following years.16
In one o f his published lectures o f 1867/68 M endeleev sets forth a table o f elem ents along with their atom ic w eig h ts.17 T hose figures show n that M endeleev had in the m eantim e inched closer to C annizzaro’s position. T he table is arranged in the alphabetical order o f nam es in Latin. It consists o f 63 elem ents, including a fictious one called didym ium , Di (not to be c o n fused w ith dysprosium , Dy). All those - and only those - elem ents were included by M endeleev in his first table o f 1869, along w ith the sam e m is takes as before.
M endeleev’s work as reader in general and inorganic chem istry resulted in the production o f his textbook Osnovy khim ii, the first part o f w hich (published in M arch 1869) sets forth the follow ing atom ic w eig h ts:18
H = 1 M g = 25 O = 16 Zn = 65.3 N = 14 Cu = 63.5 C = 6 Hg = 200 Cl = 35.5 Pb = 207 J = 127 P = 31 N a = 23 A1 = 27.4 K = 39 Cr = 52 Ag = 108 Mn = 55 S = 32 Fe = 56 C a = 40 Si = 28
C om pared with those in his O rganicheskaia khim ia the above atom ic w eights show M endeleev had dropped G erh ard t’s atom ic w eights system in favour o f C ann izzaro’s, with one rem arkable exception though. He attributed carbon, C, the value 6, w hich was as m uch as that attributed by G m elin (1827) and Dum as (1828). That was a big m istake, w hich M endeleev co r rected on 17 February 1869 in his table o f elem ents.
E m bracem ent of C annizzaro’s atom ic w eights was a precondition for the proposed classification o f elem ents to m ake sense from the point o f view o f chem ical theory. O ther system atists, about w hom I w rote e lse w h e re ,19 had adopted the Cannizzaro system before M endeleev did and so they could arrive at their own periodic tables earlier.
It is hard to say now exactly why it was only in 1869 that M endeleev em braced C annizzaro’s theory.20 I can only surm ise that on his return from H eidelberg in 1861 he found no one in Sainkt Petersburg to discuss his doubts seriously with. Russian and Soviet com m entators quite sim ply ignore this point. So, unless you m ake a thorough study o f M endeleev saw the truth in a sudden fit of illum ination on 17 February 1869. N ot so. M endeleev was led up tow ards his periodic table by his earlier studies, lectures and w riting the O snovy khim ii. It is also likely that his perusal o f W estern studies had induced him strongly both to drop G erhard t’s old system and indeed to take up the jo b o f classifying chem ical elem ents. This calls for a few words of com m ents.
C lassificatio n as such, not only o f chem ical elem ents but also o f o b je c ts stu d ied by m in eralo g ists and bio lo gists, w as a fa sc in atin g jo b to
M end eleev as early as durin g his colleg e studies at the M ain P ed ag ogical Institu te. S oviet com m entato rs, am ong them L. S. K erova, believ e that M end eleev w as strongly influ enced in his view s by th ree p ro fe sso rs o f the co lleg e, V oskresenski, S. S. K utorg and F. F. B randt. K erova says that his interest in biology induced M endeleev to em ploy, by analogy, the co m parative m ethod introduced in biology by G. C uvier and fruitfully developed by G erhardt and A. Laurent in chem istry. She also thinks M endeleev got im pulses from biology to look for a natural classification o f elem ents, w hich he opposed to different artificial classifications, and that he p lanned to w rite several books on topics w hich he found o f interest as an am ateur en cy clopaedist. If K erova’s findings are reliable, then the atm osphere at the M ain Pedagogical Institute m ust have indeed induced M endeleev to adopt an open-m inded attitude tow ards problem s w hich haunted scientists both in the R ussian E m pire and in W estern European countries. T hat o p en-m ind ed ness o f his found best expression in M en deleev’s chem ical view s, especially in his tenuous em bracem ent o f G erh ardt’s and L a u ren t’s positions on the one hand, and his half-hearted adoption of B erzeliu s’s theories w ith the rejection o f his dualistic (electrochem ical) theory o f com position o f ch em i cal com pounds.21
M any students of chem ical history have noticed that M endeleev was out for general laws in natural science. That desire found expression in the 1850s when he em barked on a study on specific volum es o f gaseous substances, w hich grew out of his fascination with N ew tonian m echanics and on which M endeleev believed all chem istry w ould rest in future. M endeleev, it will be recalled, studied possible applications o f the B oyle-M arriotte law show ing (as did others) that som e gases did not behave strictly in keeping with that law. M endeleev’s search for general laws is widely held to be evidence o f his allegedly m aterialistic outlook. Som e com m entators, B. M. Kedrov am ong them , regard M endeleev as a cham pion o f w hat they called spon taneous dialectical m aterialism . W hile it is undeniable that M endeleev did
M endeleev's First Periodic Table 113 show certain features o f dialectical thinking, that is really a far-fetched q ual ification on K ed ro v ’s part.
I am recallin g all th ese facts to put in co n tex t M e n d e le e v ’s a c c o m p lish m en ts in the classificatio n o f elem en ts, and to po in t out th at his s ta te m ents m ust be in terp reted very carefu lly . As far as his c la ssific a to ry w ork is concern ed, this m eans no m ore than this: he sought to p u t his natural classificatio n o f elem en ts on an o b jectiv e fo u nd ation. B ut tak in g that as evid en ce o f his being a m aterialist w o uld be a tall o rd er in d eed . M e n deleev fits w ell into that class o f scien tists w ho can be d e scrib ed as d is cip lin ed eclectics, a class w hich em b raced 19th-century m ate ria ls and po sitiv ists, am ong others.
M endeleev’s first periodic table
So, only after he had em braced C annizzaro’s system o f atom ic w eights could M endeleev proceed to the question o f classification o f elem ents, which took him eventually to his periodic table. From 17 February 1869 through to his death in 1907 M endeleev w orked on that m atter, continuing research done by his European and A m erican predecessors.22 The years o f 1869 to 1871 were his m ost successful period, w hich historians som etim es refer to as “the period of discovery,” during w hich he produced an im pressive 31 original studies on that matter.
In January 1869, M endeleev began to w rite the first tw o chapters o f the second part o f his O snovy khim ii. In keeping with his initial philosophy of studying elem ents by virtue o f their valencies, M endeleev began that work w ith a study o f the potassium group o f m onovalent elem ents. W hen he was done with the first two chapters M endeleev faced the question o f which group o f elem ents to take up next. The question w as com pounded by the occurrence - betw een the typically m onovalent potassium group and the typically bivalent group o f alkali earth m etals - o f the copper group o f m etals w hich behave like m onovalent elem ents tow ards som e com pounds and like bivalent (and even trivalent) tow ards other ones. At first M endeleev sought to discuss the copper group right after the potassium group, but he changed his m ind to look for som e other principle w hich w ould en ab le him to arrange elem ents in their natural groups. He thought o f the chem ical a f finity o f elem ents in the broad sense (not only their valencies) and their atom ic weights.
In February 1869, M endeleev m ade his first attem pt to classify all ele m ents. On the 17th of that m onth M endeleev had his first periodic table at hand. It was called Opyt sistem y elem entov osnovannoi na ikh atom nom vese
Ti = 50 Zr = 59 ? = 1 8 0 V = 51 N b = 94 T a = 182 Cr = 52 M o = 96 W = 1 8 6 M n= 55 Rh = 104.4 Pt = 1 9 7 .4 Fe = 56 Ru = 104.4 Ir = 1 9 8 Ni=Co=: 59 Pd = 106.6 Os = 1 9 9 Cu = 63.4 A g = 108 Hg = 200 Be = 9.4 M g= 24 Zn = 65.2 Cd = 112 B = 11 A1 = 27.4 ? = 68 U r = 1 1 6 Au = 197? C = 12 Si = 28 ? = 70 Sn = 1 1 8 N = 14 P = 3 1 As - 75 Sb = 1 2 2 Bi = 2 1 0 ? O = 16 Se = 32 Se = 79.4 Te = 1 2 8 ? F = 19 Cl = 35.5 Br = 80 J = 1 2 7 N a = 23 K = 39 Rb = 85.4 Cs = 133 Tl = 2 0 4 Ca = 40 Sr =: 87.6 Ba = 1 3 7 Pb = 2 0 7 ? = 45 Ce = 92 ?E r= 56 La = 94 ?Yt= 60 Di = 95 ?In = 75.6 Th = 118?
The elements arranged in this table look very m uch like a gam e of patience, which m akes this table similar to the one published by the English chemist W illiam Odling in 1864. In April 1869, F. N. Savchenko told M endeleev at a session of the Russian Chemical Society in Sainkt Petersburg that Odling pub lished in the Russian translation of his book (1867)24 a table which looked very m uch like M endeleev’s. M endeleev had this to say in reply (on 5 April that year), “But Odling says nothing about the m eaning o f his table, and as far as I can see he mentions it nowhere. I have had no idea of it, and I suppose most chemists have not either. If Odling believed his table was of any signif icance for theory, he would probably have written about that matter, which I think is of fundamental significance for chemistry. Yet in the book the table is called simply «Atomic weights and symbols o f elem ents».”25
There is no evidence to m aintain that M endeleev knew O d ling ’s table as he was developing his own. Let me therefore put it this way: the two tables are sim ilar to each other. But o f course it is very unlikely that M en deleev should not have known O dling’s table w hich was published in Russian translation two years before.
Soon after he published his first table M endeleev w rote an article called
Sootnoshenie svoistv s atom nym vesom elem entov, which appeared in the
official journal of the Russian Chem ical Society (1869). From w hat M en deleev says it follow s the article m ust have been w ritten not later than on 5 April 1869.26 A sum m ary o f the contribution in G erm an appeared in the sam e year in Zeitschrift f u r Chem ie27
Mendeleev's First Periodic Table 115 M endeleev’s article not only included the table o f elem ents o f 17 F eb ruary 1869 but also supplied an analysis and elucidation o f the w ay in w hich the table was developed. As he m akes a close account o f his reasoning, that article can be taken to be a reconstruction of the process that took M endeleev to his result several weeks before, nam ely on 17 F ebruary.28
M endeleev began with a discussion o f previous classifications o f chem i cal elem ents, those into (1) m etals and nonm etals, (2) by th eir respective relations tow ards hydrogen and oxygen, (3) by their electrochem ical order, and (4) by their valencies. He dism issed all o f them as unsatisfactory saying that “at present there is no general principle that could survive a rigorous critical analysis, one that could be relied upon as a foundation for ju d gm en ts on relative properties o f elem ents, and w hich w ould ju stify their allocation in a m ore or less exact system .”29 But he m entioned none o f the studies by chem ists in circulation then.
M endeleev criticised particularly sharply those classifications w hich w ere based on valencies (he used the word atom nost). He ju stly pointed out that som e elem ents have different valencies; lead, Pb, for exam ple, w hich was bivalent or tetravalent in relation to oxygen. If som e elem ents are know n to have different valencies, he concluded, then why not adm it right away that other elem ents, such as hydrogen, m ay also have different valencies? Such an approach w ould sweep away all difficulties in the explanation o f the existence or structure of any com pound, even though there can be no absolute certainty o f judgm ent either.3
Y et he conced ed he had no do u bt w h atev er that som e e le m en ts m ade up “ a natural sequence o f sim ilar form s o f ap p earan ce o f m a tte r.” T h at point, it will be recalled, w as d ebated by sy stem atists b etw een 1817 and 1860. M endeleev m entio ned only P. K rem ers, J. B. A. D u m as, M . von P etten k o fer, N. N. Sokolov and E. L enssen in th at co n n ectio n . It looks he had not read o ther studies by W estern sy stem atists. M e n d eleev in p a ss ing to u ch ed on the questio n o f allo tro py rejectin g attem pts to c lassify elem ents on the basis o f such or oth er allo tropic v arieties. In his o p in io n , it m ade no sense to classify allo trop ic v arieties o f e le m en ts, bu t only elem ents them selves. T he only pro perty o f e lem en ts th at co u ld be e x p ressed in q u an titative term s, and the only one to rem ain in v ariab le fo r each elem en t, was a to m ic w eight. G erh ardt and C an n izzaro , M e n d eleev argued, had supplied accurate enough values o f that p ro p erty , and so scien tists no lo n ger confu sed the notion o f e q u iv alen t w ith th a t o f atom ic w e ig h t.31 It will be observed, o f course, that M en d eleev ou g h t to have nam ed G erhardt in that conn ectio n , but only C an n izzaro.
T hat way M endeleev justified his choice o f atom ic w eight as the fun dam ental property o f classification o f elem ents. H e w anted to base his classi fication on a property w hich could be com pared inside the classified collec tion o f elem ents.
Referring to his first tentative classifications, M endeleev wrote, “In my first attem pt I did this: I picked bodies o f the sm allest atom ic weights and p ut them in the order o f their respective atom ic w eights. It turned out that there was som ething like a p erio d [italic mine] o f properties o f sim ple bo dies, and even when taken by their valencies elem ents follow one another according to the arithm etic sequence o f their values:
Li = 7; Be = 9.4; B = 11; C = 12; N = 14; O = 16; F = 19; N a = 23; M g = 24; A1 = 27.4; Si = 28; P = 31; S = 32; Cl = 35.5; K = 39; C a = 40; - ; Ti = 50; V = 51; - ; - .
In the class o f elem ents o f w eights over 100 you will notice an analogous uninterrupted sequences, this one:
Ag = 108; Cd = 112; U r = 116; Sn = 118; Sb = 122; Te = 128; J = 127. It turns out that Li, Na, K, and Ag are in the sam e m utual relationship to each other as C, Si, Ti, Sn or as N, P, V, Sb are tow ards one another. A t that point the question presented itself, w as it not in atom ic weights that properties o f elem ents w ere best expressed? W o uld n’t it m ake sense to class ify elem ents by virtue o f their atom ic w eights?”32
His use o f the term p erio d perhaps indicates that M endeleev thought o f a periodic classification as he was writing the article or even before. The order o f elem ents in M endeleev’s table is the sam e as that given by de C hancourtois in his Vis tellurique (1862) except for hydrogen, H, but with vanadium , V. O ther system atists in 1862 to 1869 put the elem ents in the sam e order.
M endeleev w ent on in the article, “In the proposed order, each elem ent is placed in keeping with its own atom ic w eight. This arrangem ent o f the know n sim ple bodies in the order o f their respective atom ic weights leads to the conclusion that the order o f atom ic w eights is not at odds w ith natural sim ilarities betw een the particular elem ents, indeed that such an arrangem ent directly indicates such sim ilarities. It suffices to arrange them in the follow ing six groups:
Ca = 40 Sr = 87.6 Ba = 137 N a = 23 K = 19 Rb = 85.4 Cs = 133 F = 19 Cl = 35.5 Br = 80 J = 127 O = 16 S = 32 Se = 79.4 Te = 128 N = 14 P = 31 As = 75 SB = 122 C = 12 Si = 28 Sn = 118
These six groups strongly point to a certain strict relationship betw een natural properties o f elem ents and their atom ic w eights. B ut that relationship
Mendeleev’s First Periodic Table 117 need not be one o f hom ology, because no h o m ologous d iffe re n c es are know n to exist for elem ents w hose values have been p rec isely d eterm in ed . A lthough the resp ective w eights o f sodium and p o tassiu m , flu o rid e and ch lo ride, oxygen and sulphur, carbon and silico n , each d iffe r by 16, those o f n itro gen and p h ospho ru s d iffer by 17, but even m ore im p o rtan tly , the differences betw een calcium and stro ntiu m , potassiu m an d ru b id iu m , ch lo ride and brom ide etc. are not the sam e, and the v ariatio n in them , first, betrays a certain reg u larity, and, secondly, it is m uch g re a te r than the d ifference w hich can be attrib u ted to the inaccu racy o f test resu lts. In the above figures you w ill n o tice a strict seq u en ce in ato m ic w eig h ts ho rizo n tally in the row s and vertically in the co lum ns. T e llu riu m ’s w eig h t is the only value w hich seem s to stand out from th e reg u la r seq u en ce, but it m ay w ell be that its value has been w rongly d eterm in ed , so if we tak e an atom ic w eight o f betw een 126 and 124 fo r it in stead o f 128, te llu riu m ’s value will fit in very n eatly ” .
All these observations of M endeleev’s had been m ade by his predecessors - systematists of the 1860s and, in some points, even way back in the 1850s. M endeleev w ent on, “All arrangem ents I have tried to m ake have led m e to conclude that atom ic w eight determ ines the nature o f an elem ent to the extent to w hich the w eight o f a particle determ ines the properties and m any reactions o f a com pound body. If that reasoning finds confirm ation in the application of this principle to the study o f elem ents, w e shall have m ade a step tow ards the day on which the differences and sim ilarities o f elem ental bodies are fully understood. I suppose the law [italics m ine] I am putting forw ard is not at odds with the overall drift o f natural science and that up to now no final p roo f has been provided, even though som e sketches o f it are available.”34
W hat “sketches” he was referring to is difficult to say. Since M endeleev used the term law, it may be useful to rem ark perhaps that N ew lands had used the sam e term before when putting forw ard his law o f octaves in re lation to chem ical elem ents.
Then M endeleev proceeded to a tentative table o f elem ents, giving the follow ing one (in a note to the article)35:
Li Na K Cu Rb Ag Cs - Tl 7 23 39 63.4 85.8 108 133 204 Be M g Ca Zn Sr Cd Ba - Pb B A1 - - - U r - - Bi? C Si Ti - Zr Sn - - -N P V As Nb Sb - Ta -O S - Se Te W -F Cl - Br - J - -19 35.5 58 80 106 127 160 190 220
This table, as M endeleev him self pointed out, was a planar projection o f a cubic arrangem ent, and so, if turned by 90°, it was essentially a spiral system . Spiral system s had been proposed by de C hancourtois (1862) and H inrichs (1867).
M endeleev seem s not to have been happy with this table, for alkali m etals and halogens, both groups being m onovalent (tow ards hydrogen), w ere too far from each other in it. So he tried a different arrangem ent, the one he built on 17 February 1869. Yet even that table did not m ake M en deleev entirely happy. If he had it published nonetheless, then only because the latest table seem ed the best o f all considering the figures then at hand and the things he knew about the sim ilarity o f elem ents. H is rem arks show that he was aw are o f the debatable nature o f his findings, especially those on elem ents on the fringes.
M endeleev com m ented, “M any points are still unclear, say the position o f elem ents w hich have not been explored well enough and w hich are in positions close to the m argins o f the table. V anadium , for one - if R oscoe’s findings are reliable - should be positioned in the nitrogen series, while its atom ic w eight (51) forces it betw een phosphorus and arsenic. Its physical properties seem to speak for the sam e placem ent o f vanadium : thus, vanadium oxychloride, VOC13 [I am using M endeleev’s ow n sym bols] is a liquid o f specific gravity 1.841 at 14° and boiling point at 127°, w hich also brings it closer, for that puts vanadium oxychloride above the corresponding phosphoric com pound. If we put vanadium betw een phosphorus and arsenic, w e should then open a separate colum n for vanadium , the way we did before. In that colum n, a position then opens for titanium in the carbon series. T i tanium is related to silicon and tin in the sam e m anner, in this arrangem ent, as vanadium is to phosphorus and antim ony. U nder it in the series where there are oxygen and sulphur, perhaps chrom ium should be placed, in which case chrom ium will be related to sulphur and tellurium in the sam e m anner as titanium is to carbon and tin. A ccordingly, m anganese should then be placed betw een chloride and brom ide. The follow ing part table w ould then emerge:
Si = 28 Ti = 50 ? - 70
P = 31 V = 51 As = 75
S = 32 Cr = 52 Se = 79
Cl = 35.5 M n = 55 Br = 80.
But of course that w ould break up the natural affinity o f m em bers o f one horizontal series, even though m anganese does display som e affinity to chloride, ju st as chloride does to sulphur.
M oreover it w ould be necessary to open up a new colum n betw een arsenic and antim ony, with niobium Nb = 94, w hich is analogous to
M endeleev's First Periodic Table 119 vanadium and antim ony, being put in that group o f bodies. In the group together with m agnesium , zink and cadm ium , perhaps indium (In = 75.6?) should be placed in that colum n, if it belongs to the sam e series (if it is less volatile than Zn and Cd). Zirkonium , w hich has a sm aller atom ic w eight than tin yet a greater one than titanium , w ould then have to be placed in the carbon and tin series, next to this last-nam ed elem ents. In that w ay, a free position w ould open up in that horizontal series for an elem ent betw een titanium and zirkonium .”3”
T hese observations are best p roof o f M endeleev’s intellectual acuity, so it is all the m ore disappointing that he did not try to arrange the table in the system he envisaged; he did that only tw o years later. B ut he was o f course wrong in his suggestion about the possible placem ent o f indium , and it w as only M eyer who placed that elem ent in the correct place (in 1870).
M endeleev w ent on, “Still, despite all that I finally resolved not to create the extra two colum ns, for then som e analogues w hich undoubtedly belong to different series w ould be left hanging. It suffices to indicate that M g, Zn and Cd are analogous in m any ways to Ca, Sr and Ba, and then I am sure it will be clear that a transfer of those bodies into one group M g = 24, Ca = 40, Zn = 65, Sr = 87.6, Cd = 112, Ba = 137 w ould violate the natural affinity of elem ents.”37
This shows that M endeleev was in two m inds. H e could have done either o f the follow ing two things: (1) he could have introduced the new colum ns in his table whereby he w ould have slightly “sim plified” the “p atience-like” pattern o f the table to m ake it m ore like the m odern form , yet at the price of slightly obscuring the sim ilarities betw een particular elem ents, or (2) he could have kept to the table o f 17 February 1869. He eventually chose the latter o f the tw o possibilities, apparently in an effort to keep to the natural sim ilarity o f elem ents. Later (in 1871) he returned to the form er possibility slightly m odifying his suggestions.
M endeleev further observed that all elem ents w hich are com m on in n a ture have atom ic weights betw een 1 and 60 (H, C, N, O, Na, Al, Fe, Ca, K, Cl, S, P, Si, M g), w hereas greater w eights w ere found in elem ents w hich are not com m on in nature and are relatively unexplored. N ew lands noticed the same fact (in 1872). But neither o f the tw o drew the right conclusions - that cam e only half a century later.
M endeleev was cautious about the positions he attributed to som e e le m ents, w hich show ed in the question m arks he put at som e elem ents (yttrium , thorium , indium ) w hich were little know n in the 1860s. B ut M endeleev very shrew dly observed that “The upper m em bers o f the fourth colum n (M n, Fe, Co, Ni, Zn) step down to low er m em bers o f the sam e colum n w here you will find Ca, K, Cl etc. So, cobalt and nickel, chrom ium , m anganese and iron are those elem ents which, by virtue o f their properties and atom ic w eights, m ark the passage from copper and zink to calcium and potassium .
Perhaps on account o f that their respective positions should be changed and instead o f being placed in the upper rows they w ould find them selves at the bottom ; then we w ould have got three colum ns o f elem ents w hich display m any sim ilarities, nam ely a colum n containing cobalt, nickel, chrom ium , m anganese and iron; a second colum n with cerium , lanthanum , didym ium , palladium , rhodium , ruthenium ; lastly, a third colum n including platinum ,O o iridium and osm ium .”
If you take him by his word, M endeleev erred in all these observations, yet it was precisely there that M endeleev later (in 1871) took up his idea o f triads o f iron-group m etals and platinum -group m etals (light and heavy m etals) w hich w as his original contribution.
M endeleev also studied the position o f hydrogen in the table. H e found that hydrogen “had not found any definite position, due to its sm all atom ic weight; it seems m ost natural to m e to put it in the series o f copper, silver and m ercury, even though it belongs to some unknow n series, below the copper series.”39 A gain, if you take this literally, M endeleev is wrong.
In connection with hydrogen’s unclear position in the table M endeleev thought it w ould be a very good idea to fill to gap caused by w hat he thought w ere m issing elem ents betw een hydrogen and borium and carbon. A m odem reader m ay be baffled by that idea, for except for helium M endeleev put in his table all those elem ents which w ere indispensable betw een the ju st-m e n tioned ones (that is, lithium and beryllium ). Perhaps he had by that tim e em braced the (w rong) hypothesis that beryllium , borium , carbon, nitrogen, oxygen and fluoride should all have lighter analogues, and that hydrogen should have a heavier analogue (above beryllium ). As for helium , M endeleev did not include it in his tables for decades. H e developed the hypothesis about the analogues shortly before his death (in 1905).
There is one m ore point o f significance. M endeleev left in his table four positions with no sym bols but only question m arks with num bers attributed to them: ? = 45, ? = 68, ? = 70, ? = 80. Those figures correspond to the follow ing elem ents discovered in the 19th or 20th centuries: scandium . Sc (1879), gallium , G a (1875), germ anium , Ge (1886), and hafnium , H f (1922). The inclusion o f those figures in the table was a first signal that M endeleev w ould forecast the existence o f som e other elem ents in future. M endeleev was not alw ays the first to m ake such forecasts, and people like J. W. Do- bereiner, M. Carey Lea, N ew lands, “Studiosus” , H inrichs or M eyer predicted the existence o f different elem ents before him.
M endeleev sum m ed up his article in the follow ing eight points, which he included in the above-m entioned abridged G erm an version o f the article.40
” 1. Properties o f elem ents included [in the table] by virtue o f their atom ic .weights evidently display a periodic nature.
2. E lem ents w hich appear sim ilar to one another in very general chem i cal term s have either sim ilar atom ic weights (like Pt, Ir, Os) o r consecutive
M endeleev’s First Periodic Table 121
constantly increasing atom ic w eights (like K, Rb, Cs). The constancy o f that increase has not been noticed by previous observers because in th eir calcu lations they did not use the conclusions o f G erhardt, R egnault, C annizzaro and others who have determ ined the true atom ic w eights o f elem ents.
3. A rrangem ent o f elem ents or their groups in the order o f their atom ic w eights corresponds to what is called valency (atom nost) and, to som e e x tent, to the difference in chem ical nature, w hich is clearly seen in the series, Li, Be, B, C, N, O, F and which exists in the other series.
4. Those sim ple bodies w hich are m ost com m on in nature have sm all atom ic w eights, and all elem ents o f small atom ic w eights have w ell-pro nounced properties. T hat is why they are typical [a w ord M endeleev attached great im portance to] elem ents. H ydrogen, as the lightest o f all, is ju stly shown separately as the m ost typical elem ent.
5. The value o f atom ic weight determ ines an elem en t’s p roperties, ju st as the value o f a particle [more precisely, M endeleev should say “m olecular w eight”] determ ines the properties o f a com pound body, and so com pounds should be studied not only for properties or quantities o f elem ents, not only for their reactions with one another, but also for their respective atom ic w eights. Thus, for exam ple, S and Te, Cl and J etc. display not only sim i larities but also very clearly certain differences betw een one another.
6. M any unknown sim ple bodies [more precisely M endeleev should have said “elem en ts”] are likely to be discovered, say elem ents sim ilar to A1 or Si o f values betw een 65 and 75.
7. The atom ic weight value can som etim es be corrected w hen its ana logues are known. The value of Te should not be 128 but 12 3 -1 2 6 ? [this question m ark is of significance at this point],
8. Som e analogues o f elem ents are visible by their atom ic w eights. U ranium , for one, turns out to be an analogue o f borium and alum inium , as a listing o f their com pounds will confirm .”41
The above points call for a w ord o f com m ent. Points 1-6 w ere know n to W estern European chem ists, especially system atists, betw een 1860 and 1869. Point 7 is M endeleev’s original idea, although he errs in his suggestion about tellurium , and again in that about uranium in point 8.
Let us go back to M endeleev’s table o f 17 February 1869. T h at table holds 63 elem ents, including a nonexistent one, didym ium , Di (dysprosium , Dy, w as discovered only in 1886). H elium , discovered in the co ro n a o f the sun in 1868, was the only known elem ent not to have been included in the table. M endeleev’s table can therefore be recognised as basically a com plete and disjunctive classification of elem ents into their natural groups. T he ele m ents w ere placed horizontally in their natural groups, as far as M endeleev could know them at the tim e. A ltogether there w ere 19 such groups in the table. O d lin g’s table (of 1864) consisted o f 18 such groups, N ew lan d s’s (1864) o f 10, M eyer’s (1868) o f 16 (including an em pty one). From the
standpoint o f chem ical properties, M endeleev’s table correctly classified a little over a m ajority o f elem ents except m anganese, Mn; m ercury, Hg; hy drogen, H (w hich ought to have been put in the group o f alkali m etals and/or carbon C and/or fluoride F); zink, Zn, and cadm ium , Cd, in one group along w ith beryllium , Be, and m agnesium , M g (these ought to have been split from each other, they way they were in subsequent years, but M endeleev still knew nothing about even or odd series at that tim e); uranium , U r (now U); gold, Au; thallium , Tl; lead, Pb; indium , In; thorium , Th; and their future triads: the iron-group and platinum -groups m etals - all these elem ents ought to have been put in a different order.
Altogether, then, M endeleev m ade tw enty-tw o m ajor m istakes about positions o f elem ents in their natural groups. C erium was only placed in the table, yet w ithout being classed together with any other elem ent. Erbium , Er, was debatably placed together with lanthanum , La, w hile yttrium , Y, w ith the nonexistent elem ent didym ium , Di, a totally w rong idea. So, M en deleev attributed wrong or debatable positions altogether to as m any as 27 elem ents - nearly one half o f those he took into account.
Then there is the question of atom ic w eights adopted by M endeleev. They w ere m ostly the same as the values C annizzaro presented to chem ists at the K arlsruhe o f 1860. Som e of them are very different from those held as true today; the weights now attributed to thorium , Th, and uranium , U, are tw ice as big as those quoted by M endeleev. A lso rem arkable is the p o si tion attributed (wrongly) to indium , In, w hich also has a wrong atom ic w eight.
W ith all those m istakes, M endeleev’s periodic table cannot be regarded as a very successful idea, w hich perhaps accounts for the lukew arm reception initially am ong w orld chem ists. Things changed only in subsequent years.
F or a conclusion
The above rem arks about M endeleev’s first article concerning the classi fication of chem ical elem ents lead us up to several im portant questions. The first one - which may seem preposterous considering w hat m ost leading w orld chem ists have written - is, did M endeleev develop his periodic table in 1869? This question may em barrass those who refuse to acknow ledge the feature o f “periodicity” in the tables proposed by de C hancourtois, New lands, Odling, H inrichs or M eyer. The critics put forw ard different argum ents against those other tables, such as (1) that they were not com plete; (2) that periodicity did not show in them well enough; (3) that the scientists who advanced them did not use the term “periodic” to describe them ; (4) that they confused the notions o f equivalent w ith that o f atom ic weight; (5) that they erroneously classified elem ents in the particular natural groups; (6) that
Mendeleev's First Periodic Table 123 they failed to foresee the existence and/or the properties o f undiscovered elem ents; (7) that they failed to develop their prelim inary findings; (8) that they w asted tim e trying to persuade the com m unity of professional chem ists each to their own priority in the discovery o f the periodic table; (9) that they ignored M endeleev’s table for several years; and (10) that they drew no philosophical conclusions from M endeleev’s table.
All these charges, how ever ju stified they may be to som e extent, m ake the answ er to the question only m ore difficult. Still, the question is im portant enough, because M endeleev is regarded as the m an w ho disco vered the p e riodic table in 1869, notw ithstanding the m any m istakes ju st m entioned. W hy, then, is his table regarded as a periodic table? I think there are two reasons for that: first, M endeleev’s initial hypothesis was advanced in the conclusion to his 1869 article; and, secondly, M endeleev’s table was retro spectively view ed via later obviously periodic tables - to this day - as the one w hich was all the tim e so. N either o f these reasons is unim portant, but I still think they do not invalidate the view that other scientists had developed periodic tables even before M endeleev. M endeleev’s 1869 table is as m uch a periodic table as those put forw ard by de C hancourtois, N ew lands, O dling, H inrichs and M eyer.
M y next question touches on a delicate point: did M endeleev ju st put together a periodic table, or did he also discover it? Scientific discovery as I see it42 im plies, as an indispensable com ponent, the quality o f inde
pendence of the scientist’s progress. D id M endeleev build his table inde
pendently? N obody in their right m ind will dem and that a scientist perform s everything entirely on his own. No scientist works in an em pty w orld, and everyone necessarily has to use other scien tists’ findings, h ow ever far away those others m ay be. Independence in that sense m eans no m ore than that nobody m ust steal som ebody e lse ’s findings in order to present them as their own. I have no reason at all to suspect that M endeleev in 1869 knew earlier studies by five other system atists - de C hancourtois, N ew lands, O dling, H in richs, and M eyer. Indeed, M endeleev him self said on several occasions he had not known the studies written by the first three.43 It is likely that he also did not know some studies by H inrichs, w hich appeared in p rin t in the United States, and anyw ay H inrichs used to follow a different path than did M endeleev. M eyer, then, rem ains as the likeliest rival o f M e n d eleev ’s for the title of discoverer of the periodic table. H ere is w hat M endeleev him self had to say about that.
W riting “On the History o f the Periodic L aw ” (1881), M endeleev said, “It is fair to use the term author o f a scientific idea to describe a m an who notices not only the its philosophical significance o f the discovery but also its practical im plications, and who is able to present the issue in such a m anner that everyone can convince them selves o f its truth. Subsequently the idea, as well as the substance, becom e indestructible. It m ay well be that
N ew lands published som ething like a periodic table before m e, but about J. L. M eyer not even that can be said. The present state o f affairs about the periodicity o f elem ents is a m erit neither o f M r N ew lands nor o f J. L. M eyer” [retranslated].44
M endeleev apparently evaded the question o f w hether or not he had draw n any ideas from M eyer’s studies. He m ay have know n M ey er’s article of 1864 though. Yet even if that was the case, M en deleev’s 1869 table resem bles by its “patience-shaped” appearance O d ling ’s table o f 1864 rather than M ey er’s o f the sam e year.
M endeleev, then, can be justifiably said to have developed his periodic table independently; or, to put it differently, he can be regarded as the d is coverer o f the table.
The next question I w ould like to pose is this: did M endeleev actually state the periodic law in 1869? In the 1869 article, he used the w ord “law ” only once, never using the term “periodic law ” or anything close to that,45 and there is nothing in the context to show he was using the w ord in re f erence to the idea o f periodicity. M endeleev m erely wrote, if I m ay say so, that “the value o f atom ic weight determ ines the nature o f each elem ent.” B ut that observation is so general that even John D alton and all his 19th- century follow ers could easily subscribe to it. In so general a form ulation, that rem ark cannot possibly be recognised as the form ulation o f the periodic law , and it is at best ju st a springboard for the form ulation prop er which cam e later, in his extensive study called D ie periodische G esetzm ässigkeit
der chem ischen Elem ente (1871 ).46
So, a perusal of M endeleev’s studies indicates that in his 1869 article M endeleev independently form ulated and partly ju stified the periodic table, w hich m eans that tantam ount to a discovery. In subsequent years, he m od ified and ju stified the table using the chem ical and physical know ledge avail able to him at the time.
For m any years historians o f chem istry used to hold w rongly that M en deleev discovered not only the periodic table but also the periodic law in
1869. That m istake was due, first, to their failure to see the difference b e tw een the table and the law. But they also seem not to have read closely enough M endeleev’s studies o f 1869 to 1871.
For want o f space I cannot discuss M endeleev’s other studies on the periodic table and the periodic law here. Interested readers m ay consult the relevant sections o f my book.47
1 C f. J. W . v an S p ro n se n , The P e rio d ic S y ste m o f C h em ic a l E lem en ts. A H is to ry o f the F irs t H u n d re d
Y e a rs, A m ste rd a m 1969.
2 S ee m y re v ie w s p u b lish e d fro m 1970 in d ifferen t jo u rn a ls in c lu d in g K w a rta ln ik H is to rii N a u k i i T e c h n ik i
M endeleev's First Periodic Table 125
3 C f. S. Z a m e c k i, Th e c o n c e p t o f scie n tific d is c o v e ry a n d th e h is to ry o f the f i e l d o f s c ie n c e (in P o lish ), W ro c la w 1988.
4 C f. S. Z a m e c k i, “O n th e b o o k E v o lu tsia id e i D. I. M e n d e le e v a v so v r e m e n n o i k h im ii (ed. b y B. P. N ik o lsk i an d L. S. L ilic h )” (in P o lish ), K w a rta ln ik H isto rii N a u k i i T e c h n ik i 1987 N o. 2.
5 C f. S. Z a m e c k i, “ M e th o d o lo g ica l issu es o f 1 9 th -cen tu ry c h em istry : Jó n s J a c o b B e rz e liu s ” (in P o lish ),
C zło w ie k i Ś w ia to p o g lą d 1984 N o. 2 ; sa m e au th o r, “ O n Y. I. S o lo v e v ’s an d V . I. K u rin n o i’s b o o k J o n s J a c o b B erzeliu s. Z h izn i d e ia te ln o st” (in P o lish ), K w a rta ln ik H isto rii N a u k i i T e c h n ik i 1983 N o. 1.
6 C f. S. Z a m e c k i, C la ssific a tio n o f c h e m ic a l e le m e n ts in the 19th cen tu ry. A h is to r ic a l m e th o d o lo g ic a l
stu d y (in P o lish ) W a rsz a w a 1992, in w h ic h I re fe r to N. M o ro z o v ’s v iew s as a c ase o f w ild sp e c u la tio n in
c h em ica l re search .
7 I th in k w e sh o u ld b e carefu l n o t to u n d e rra te the in flu en c e le a d in g sc ie n tis ts h a v e o n v ie w s o f b ro a d circ le s o f so ciety . In fact, th at in flu en c e m a y o fte n h av e b e en stro n g e r th a n th a t o f p ro fe s sio n a l p h ilo so p h e rs.
8 D. I. M en d e le e v , “ Iz o m o rfiz m v sv iazi s d ru g im i o tn o s h e n ia m i k ris ta lic h e s k o i fo rm y k s o s ta v u ,” in:
P e rio d ic h e sk i za k o n , e d ite d , in tro d u ce d an d an n o ta ted b y B. M . K e d ro w , M o sc o w 1958 p. 6 1 6 -6 3 5 .
9 D . I. M en d e le e v , “ P o lo z h e n ia iz b ra n n y ie d la z a s h c h ish c h e n ia n a step e n m a g is tra k h im ii,” in: P e r i
o d ic h e sk i z.akon. D o p o ln ite ln y ie m a te ria ły, e d ite d w ith c o m m e n ta rie s by B. M . K e d ro w , M o sc o w 1960 p. 9 - 4 2 .
111 Ibid., p. 4 2 -9 4 .
11 Part o f th is stu d y w as p u b lish e d in the S a in k t P e te rsb u rg jo u rn a l G o rn y i Z h u r n a l in I 8 6 0 pp. 3 8 0 -3 8 1 , 5 5 7 -5 8 2 .
12 S a in k t P e te rsb u rg ch em ists d id n o t th in k m u ch o f M e n d e le e v ’s H e id elb erg e n d e a v o u rs .
13 D. 1. M en d e le e v , “ K h im ic h e sk i k o n g re s v K a rlsru h e ,” S a n k t-P e r sb u r s k ie V e d o m o sti 1860 N o . 23 8 . 14 C f. D. 1. M en d e le e v , O rg a n ich e ska ia k h im ia 2 n d e d ., S a in k t P e te rsb u rg 1863.
15 Ibid., p. iv.
16 C f. D. I. M en d e le e v , Izb ran n y ie lektsii p o k h im ii, ed. by A. A. M ak a re n ia , M o sc o w 1968,. 17 C f. D . I. M en d e le e v , P e rio d ic h esk i z.akon. D o p o lo n ite ln y ie m a te ria ły , p. 2 1 0 -2 0 1 . 18 D. I. M en d e le e v . O sn o v y kh im ii 1st ed. p art i, S a in k t P e te rsb u rg 1869 p. 3 5 6 f.
19 S. Z a m e c k i, “C la ssific a tio n o f ch em ica l e le m e n ts in the 19th c e n tu ry ” (in P o lish ), C zło w ie k i
Ś w ia to p o g lą d 1977 N o. 9.
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21 C f. L. S. K ero v a, "N ie k o to ry ie o so b en n o sti tv o rc h e stv a D. I. M e n d e le e v a ,” in: E v o lu ts ia id e i D . I.
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“2 E s p e c ia lly J. P. C o o k e and G. D. H in rich s. C f. J. W . v an S p ro n se n , o p.cit. 23 I q u o te th is ta b le fro m M e n d e le e v ’s P e rio d ic h e sk i za ko n , o p .cit., p. 9. 24 C f. W . O d lin g , K u rs p ra k tic h e s k o i k h im ii, S a in k t P ete rsb u rg 1867, p. 224.
2 D . I. M en d e le e v , “S o o tn o sh e n ie sv o istv s a to m n y m v e so m e le m e n to v ,” Z h u r n a l R u s s k o g o K liim ic h e -
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26 Ibid., p. 77. 27
D. M en d e le e ff, “ U b e r die B ez ie h u n g e n d e r E ig e n s c h a fte n zu d e n A to m g e w ic h te n d e r E le m e n te ,” in:
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28 C f. B. M. K ed ro w , F ilo so fsk i analiz, p e rv y k li tru d o v D. 1. M e n d e le e v a o p e r io d ic h e s k o m za k o n e , M o sc o w 1959, p. 3 8 -5 7 . 29 “ D. I. M en d e le e v , S o o tn o sh en ie..., o p .cit., p. 64. 311 Ibid. 31 Ibid., p. 66f. 32 Ibid., p. 67. 33 Ibid., p. 68. 34 Ibid., p. 69. 35 Ibid., p. 70. 36 Ibid., p. 7 If. 37 Ibid., p. 72. 38 Ibid., p. 73. 39 Ibid., p. 75. 40 C f. n o te 27. 41 D . I. M en d e le e v , S o o tn o sh en ie..., o p .cit., p. 76f. 42 C f. n o te 3.
43 C f. D. I. M en d e le e v , S o o tn o sh en ie..., op .cit. an d a lso his a rtic le “ P e rio d ic h e s k a ia z a k o n n o s t k h im i- c h e s k ik h e le m e n to v ,” in: E n tsik lo p e d ic h e sk i slo v a r B ro k g a u za i Y e fro n a vo l. 2 3 p a rt. 45 , S a in k t P e te rs b u rg
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45 C f. n o te 34.
46 D. M e n d e le e ff, “ D ie p e rio d isc h e G e se tz m ä ssig k e it d e r c h e m isc h e n E le m e n te ," A n n a le n d e r C hem ie
u n d P h a rm a c ie S u p p le m e n tb a n d 8 H e ft 2, 1871, p. 1 3 3 -2 2 9 .
