The case of magnesium (N=12) and oxygen (N=8) is similar except that two electrons are transferred from the magnesium to the oxygen atom. The resulting ions have their electrons arranged exactly like those of the neon atoms and the ions of sodium and fluorine. Therefore, the crystalline form of magnesium oxide and sodium fluoride should be identical, and this prediction of the theory has been confirmed experimentally by Dr. A. W. Hull by the X-ray method. Because of the much greater forces acting between the ions as a result of the double charges, the stability of the magnesium oxide is much higher than that of the sodium fluoride. This is manifested by the high melting point, low conductivity, low solubility, and hardness of magnesium oxide.

Phosphorus (N=15) and sulphur (N=16) have, respectively, 5 and 6 electrons more than neon, and are thus capable of giving up these numbers of electrons. If these elements are brought into contact with an excess of fluorine (which because of its proximity to neon has a particularly strong tendency to take electrons) all the extra electrons pass to fluorine atoms. Thus a sulphur atom will supply electrons to 6 fluorine atoms and will form the compound SF.. The force acting between the fluorine ions and the central sulphur ion is still electrostatic in nature it must be nearly 6 times greater than the force between sodium and fluorine ions. Furthermore, the 6 fluorine ions would surround the sulphur ion so that there would be little stray field of force. Therefore, we should not expect sulphur fluoride to be salt-like in character but to consist of very stable molecules having weak external fields of force and, therefore, readily existing in the form of a gas. As a matter of fact, this extraordinary substance has these properties developed to such a degree that it is an odourless and tasteless gas with a boiling point of 62 deg. Phosphorus pentafluoride, as it would be expected from its less symmetrical structure, is a gas having greater chemical activity.

The fluosilicate ion SiF-has a structure exactly like that of the sulphur fluoride molecule, since the number and arrangement of the electrons are the same. This is clear if we consider that the atomic number of silicon is 14 while that of sulphur is 16. Thus if we should replace the nucleus of the sulphur atom in a molecule of sulphur fluoride by the nucleus of a silicon atom, without disturbing any of the surrounding electrons, we would have removed two positive charges and would obtain a negative ion with two negative charges of the formula SiF,-. In the presence of potassium ions we would then have the familiar salt potassium fluosilicate. The theory is thus capable of explaining typical complex salts. In fact, it is applicable to the whole field of inorganic compounds covered by the work of Werner, and helps to simplify the theory of such compounds. There is no time, however, to go into this subject.

The simple theory of atomic structure which we have discussed thus far explains perfectly what has usually been called "the maximum positive and negative valence." The maximum positive valence represents the number of electrons which the atom possesses in excess of the number needed to form one of the particularly stable configurations of electrons. On the other hand, the maximum negative valence is the number of electrons

which the atom must take up in order to reach one of these stable configurations.

For example, magnesium has a positive valence of two, since its atomic number is 12, while that of neon is 10. Sulphur has a positive valence of 6, since it has 6 electrons more than neon; but it has a negative valence of two because it must take up more electrons before it can assume a form like that of the argon atom.

It is clear, however, that this theory of valence is not yet complete. It is not applicable to those cases where we have usually taken valences of 4 for sulphur, or 3 and 5 for chlorine, &c. But more especially it does not explain the structure of organic compounds and such substances as H1, Cl2, O2, N2H,, PC,, &c. (The theories of Kossel, Lacomblé, Teudt, &c., which have recently been proposed in Germany, have not advanced beyond this point and are therefore very unsatisfactory as a general theory of valence.)

J. J. Thomson, Stark, Bohr, and others had suggested that a pair of electrons held in common by two adjacent atoms may function in some cases as chemical bonds between the atoms, but this idea had not been combined with the conception of the stable groups of electrons or octets. G. N. Lewis, in an important paper in 1916, advanced the idea that the stable configurations of electrons in atom could share pairs of electrons with each other, and he identified these pairs of electrons with the chemical bond of organic chemistry. This work of Lewis has been the basis and the inspiration of my work on valence and atomic structure.

As a result of the sharing of electrons between octets, the number of octets that can be formed from a given number of electrons is increased. For example, two fluorine atoms, each having seven electrons in its outside shell, would not be able to form octets at all except by sharing electrons. By sharing a single pair of electrons, however, two octets holding a pair in common required only 14 electrons. This is clear if we consider two cubes with electrons at each of the eight corners. When the cubes are placed so that an edge of one is in contact with an edge of the other a single pair of electrons at the ends of the common edge will take the place of four electrons in the original cubes. For each pair of electrons held in common between two octets there is a decrease of two in the total number of electrons needed to form the octets.

Let e represent the number of electrons in the outside shell of the atoms that combine to form a molecule. Let n be the number of octets that are formed from these e electrons, and let be the number of pairs of electrons which the octets share with one another. Since every pair of electrons thus shared reduces by two the number of electrons required to form the molecules it follows that e=8n-2p or p=4(8n—e).

This simple equation tells us in each case how many pairs of electrons or chemical bonds must exist in any given molecule between the octets formed. Hydrogen nuclei, however, may attach themselves to pairs of electrons in the octets which are not already shared. For example, in the formation of hydrogen fluoride from a hydrogen atom and a fluorine atom there are 8 electrons in the shells (e=8). We place n-1 in the above equation and find p=0. In other words, the

fluorine atoms do not share electrons with each other. The hydrogen nucleus having given up its electron to the fluorine atoms attaches itself to one of the pairs of electrons of the fluorine octet, and thus forms a molecule having a relatively weak external field of force. As a result, hydrogen fluoride is a liquid of low boiling point instead of being salt-like in character.

The equation given above is applicable to all types of compounds. For example, if we apply it to substances such as sodium fluoride, sulphur fluoride, or potassium fluosilicate, which were previously considered, we find in each case p=0. In other words, there are no pairs of electrons holding the atoms of these compounds together. On the other hand, if we consider the compound NH, we find p=1. Since there are only two octets, the pair of electrons must be between the two nitrogen atoms while the hydrogen nuclei attach themselves to pairs of electrons of the nitrogen octet. It can be readily shown that this simple theory is in fact identical with the accepted valence theory of organic chemistry and leads to the same structural formulas as the ordinary theory in all those cases where we can take the valence of nitrogen to be 3, oxygen and sulphur 2, chlorine and hydrogen 1. In other cases, such as those where quinquivalent nitrogen has been assumed, the new theory gives results different from the old, but in each case in better agreement with the facts.

The theory indicates a series of new relationships between certain types of substances which I have termed isosteric substances. For example, it indicates that the molecules of carbon dioxide and nitrous dioxide and nitrous oxide should have nearly identical structures and this is borne out by the extraordinary similarity in the physical properties of these gases. Nitrogen and carbon monoxide constitute another pair of gases which are similarly related. The same theory also points out a number of previously unsuspected cases of similarity of crystalline form (isomor phism.)

It is clear that in the past the term valence has been used to cover what we may now recognise as three different types of valence, as follows:Positive valence: the number of eletrons an atom can give up.

1.

RUSSIA'S CONTRIBUTION TO SCIENCE.* By ALEXANDER PETRUNKEVITCH, Ph.D.

WHILE Russian literature, Russian music, Russian art, and Russian dance are fairly well known to the American people, few realise the extent of Russia's contribution to science. This is quite pardonable considering the lack of knowledge on the part of the broad public of the ever growing achievements of exact science in all its branches, regardless of nationality, and taking into account also the difficulty of even casual acquaintance with subjects which require special training. To this must be added that a great deal of the work published by Russian scientists has been written in foreign languages, mostly in German and French periodical publications, while Russian publications are few and of these only one or two are known to foreigners.

In Russia itself education in general and science in particular has been for a long time unpopular, has been limited to a comparatively small circle of people and has even at the present time not yet penetrated into the broader masses. Purely clerical knowledge of the Tsarist Russia gave way to military training and to such education as was necessary for service in the bureaucratic institutions created by Peter the Great. Later humanistic studies and law became the standard of good education and dominated Russian society and Russian thought until comparatively recently. Medicine of course was early recognised as necessary knowledge, yet the people regarded it in the light of special knowledge rather detrimental to broad education. Applied science, such as engineering, was for a long time looked upon in the same way with the additional stigma of mistrust. Pure science has been looked upon rather as a hobby for men with sufficient means, dangerous in as far as it inclined to produce a critical attitude toward religion and the established order of things, undesirable inasmuch as it did not open any other field for activity than an academic career, and insufficient as a general basis for broad education. Yet in the second half of the past century pure science came into its own, conquered the opposition of society and furnished many a name looked upon with esteem and even admiration in Russia and far beyond its political frontiers.

To say that Russia might have produced a great deal more in the field of science than it actually has produced, had the development of the country been allowed to proceed normally, is not a mere figure of speech or an excuse, an attempt as it were to find extenuating circumstances for natural shortcomings. In a country where the word "constitution" was struck by the censor even from the pages of learned investigations, where the chief duty of the Secretary of Education was to devise means to prevent the spreading of knowledge, creative work in science was more than simply hampered, it was often physically impossible. Yet a glance at a list of works published by Russian scientists will show the productivity and many-sidedness of the Russian genius. There is scarcely a field of science in which Russians have not done some creditable work, increased the

* From the Transactions of the Connecticut Academy of Arts and Sciences, June, 1920.

store of our knowledge, cleared up some intricate problem or opened new chapters, and set forth new questions.

And all this had to be done in the face of great dificulties of which western institutions have no idea. There was always a lack of funds and a lack of men, a lack of institutions and a lack young men to be trained for such institutions. The educational system was borrowed from Germany, its negative qualities were intensified while the most important positive qualities were partially or completely suppressed. The Russian national character was not taken into account by that system foreign to its spirit which was put as it were into a straight-jacket and had its wings clipped by two most efficient tools in the hands of autocracy-censorship and espionage. Used persistently with only occasional short intermissions, during more than one century, and embracing all phases of national and private life, being constantly present in all university recitation halls, laboratories, and even private offices, censorship and espionage ruined the relationship between teacher and pupil, affected the character of the institutions, and prevented the normal development of many a promising youth.

To understand the ruinous influence of espionage and censorship on national character and the productive genius of the people one must have grown up and gone through the schools in Russia. The offices of inspector and his aids in every secondary school were especially created to control not only the behaviour of pupils in the school, but their life outside of school walls. The teachers themselves were subject to this supervision and dreaded the never-closing Argus eye of the inspector. The duties imposed on them, the general atmosphere of life amidst poverty, suspicion, bribery, and Simonism, prevented the teachers of secondary schools from doing original work of any character. Such work, not uncommon in Germany, is of the rarest occurrence in Russia, and only teachers of quite remarkable ability managed to step out of the high-school routine and drudgery into the broader field of an academic career. The Russian "Gymnasia," the Russian "Realnoje Utchilishtche" were patterned after the German "Gymnasium" and "Realschule," but the spirit of reactionary orthodox Russian autocracy was added to the German worship of authority and discipline of mind and will, and coupled with corruption, pervaded everything and corrupted and perverted the growing mind.

It is

a wonder under the circumstances that the mind, the spirit of Russian youth was not completely crushed in its instinctive upward struggling for light and knowledge and free expression of self.

The entrance into the sacred precincts of the highest education was purposely made difficult to prevent an undesirable growth of knowledge in wider circles. Only pupils who had studied in a gymnasium and had therefore had seven years of Latin and six years of Greek, and who passed the examinations at the end of their studies extending altogether over eight years, had the right to study at a university. Yet it may not be quite out of place to mention here that a boy entering the university in Russia knows no more of mathematics than a high-school boy in America and knows even less of physics and chemistry, while biology was not on the programme of studies

at all.

One was allowed to postpone military training until after the studies at the university had been finished, and in the cases of men preparing for an academic career military training was altogether waived. This exemption applied both to those who became teachers at schools and professors at universities. But the requirements for professorial positions were so high, as we shall see later, that the exemption from military training was in no sense an inducement.

On entering the university the student had to follow a prescribed course of studies through all four years, but could and was expected to take also other courses, provided they did not coincide with the obligatory ones. A course in theology, i.e., in the dogma of the Russian orthodox church, was compulsory for every student in the first year of his studies. Compared with the American colleges the work at the Russian universities is much heavier, the number of hours is considerably greater, and the number of subjects required cover a much wider range. It was customary to work Saturday afternoon and some classes were given even on Sunday mornings, as for example entomology at the University of Moscow at the time that I was studying there. To give an idea of the scope of studies required at a Russian university from a student in natural sciences preparing for an academic degree, I shall simply enumerate the subjects which I myself had to study in Moscow: Physics (four hours per week during two years); inorganic chemistry (first year); qualitative analysis and quantitative analysis (second year); organic chemistry (third year); physical geography (one year); geology and paleontology (one year); mineralogy and crystallography (one year); meteorology (one year); human anatomy (one year); physiology (one year); histology and embryology (one year); introduction to zoology (one year); invertebrate zoology (one year); vertebrate zoology (one year); entomology (one year); botany (three years) including general morphology, anatomy, physiology, and systematics; and theology (one year). In the first and second year the spare hours were given to economics and principles of law. During the last term of the fourth year a thesis has to be written on a subject assigned by the professor, consisting of a review of work done by other workers, and some original investigation. After a six-hour written examination on some subject in the department of study chosen by the student, and after oral examinations in all subjects studied during the third and fourth year, those studied during the first and second year having been disposed of previously, the student receives a university diploma conferring on him the degree of Candidat rerum naturalium, which as may readily be seen is a much higher degree than either the corresponding degree of the German universities, or the B.A. of American colleges. It will also be seen from the foregoing that the training of a Russian student at the end of his studies is in every respect broader and covers a much wider range of subjects than either that of an American or a German student.

Students with exceptionally high standing, who desire to follow an academic career, are allowed to continue their studies at the university after they have received their degree. They have no more lectures to attend, but receive a general outline of reading and work to be done as a prepara

tion for an examination which will give them the right to present a thesis for the degree of Magister in the subject which they have chosen, i.e., Magister of Chemistry, Magister of Botany, &c. This examination may under no circumstances take place sooner than two years after the examination for the degree of Candidat. It is one of the stiffest examinations imaginable and the amount of reading required is simply appalling. To give even an approximate idea of the ground which has to be covered by the candidate during these two years, I shall only mention that in my own case the books recommended to me by my professor occupied more than a five foot shelf and contained such works as Bronn's Classen und Ordnungen and similar works, all of which were supposed to be used not as reference books but as text books and the detailed information contained in them to be kept in one's memory ready to be drawn upon at a moment's notice. It has happened time and again that candidates were flunked because they were unable to produce from memory facts which the examining professor himself knew only because he was recently engaged in research on the subject.

After the successful passing of this examination the candidate receives the title of Magistrant and is admitted to lecturing and laboratory work in the capacity of a privat-dozent, a title also borrowed from the Germans. At the same time he must present his thesis for public discussion before he receives the degree of Magister. This dissertation has to be the result of an original investigation and to cover the ground thoroughly. It has to review the literature of the subject as far back as possible, in some cases going actually back to Aristotle. The public defence is no sinecure, for the officially appointed opponents take especial pleasure in tearing the arguments and evidence to pieces and in pointing out the slightest flaw in the treatment of the problem.

If the degree has been awarded the holder of it may now be appointed "extraordinary professor." Within not less than two years nor more than ten he has to present a second dissertation for the highest degree attainable, that of Doctor, not Doctor of Philosophy as in Germany or America, but Doctor of the special science which he has chosen. The degree of Doctor of Philosophy in the American sense of the term does not exist in Russia, and whenever a professor is in possession of a Russian degree of Doctor of Philosophy, that means that he is a specialist in philosophy.

It will be seen that it is utterly impossible for a Russian to possess more than one degree of Doctor, unless it be an honorary degree which is scarcely ever given. The only exception is the degree of Doctor of Medicine, which strange to relate, does not need to be preceded by a Magister degree, is often given for some quite unimportant and small piece of work, and comes nearest to the German M.D., especially since it has to follow upon an examination without which practice is not allowed. But the training of the medical student in Russia is also vastly broader than in the United States, and the scope of knowledge possessed by the average Russian practicing physician has often been a subject of admiration to foreigners.

But the amount of work required of those who prepare for an academic career has also its negative side. Memory is easily overburdened with unnecessary details, much valuable time is lost in

gathering the knowledge required for the examinations, and perhaps still more in reading and reviewing the work done by others, which in the majority of cases has long ago lost all scientific value and in many cases might have been better forgotten altogether. What with the academic duties of lecturing, laboratory work, committees, &c., the creative ability is easily stunted, and unfortunately it is not an uncommon occurrence that the dissertation for the Doctor's degree is the last original work of the overburdened professor. Only the more talented and more pertinacious hold out under the strain and continue as investigators.

And all the time the outside life invades the peaceful premises of the university and asserts itself in the most uncomproimsing manner. Neither the Russian student nor the Russian professor can avoid its influence. Censorship and espionage are more developed and stricter in the university than elsewhere, and it seems that in this respect the renowned Bolshevik reformers and heralds of educational freedom for the poorest citizen have far outdone the old Tsarist advocates of the muzzle and whip. But censorship and espionage notwithstanding, the professor and student alike have to possess a distinct reputation as belonging either to the progressive or to the reactionary political group, and no liberal minded assistant may continue indefinitely to assist a reactionary professor. He has ultimately either to ally himself definitely with the reactionary elements or to resign. As a general rule we may say that the best work was done by progressive professors, although some very reactionary men have contributed creditable work in their particular field of learning. But real expression of political views was not possible except for a short period in the sixties and again after the revolution of 1905, and even then it had to be sufficiently guarded.

The first scientific institution created in Russia was the Imperial Academy of Sciences, and its foundation was due to the genius of Peter the Great, who conceived the idea and had conferences regarding its execution with Heinrich Fick as early as 1718. Dr. Blumenrost prepared a project which was approved by Peter in 1724 and according to which the Academy should be not only a research, but also an educational institution. Peter died in 1725 and it was his widow Catherine the First who ordered the opening of the Academy on November 12, 1725, and fixed its yearly budget at 24012:00 Roubles. Foreigners, mostly Germans, were invited as professors. About the year 1727 there were seventeen of these, including such men as Hermann and Goldbach in mathematics, Nicholas Bernulli in mechanics, Buerger in chemistry, Biefinger in physics, Duvernoie in anatomy and zoology, Leonhard Euler in mathematics, &c. The eight students who had to study with these professors were all Germans, all imported for the purpose from Germany. By the year 1742 there were as many as twelve students. In 1747 the Academy was divided into two sections-the Academy proper, and the University. The internal organisation of the Academy was changed in 1803 and again in 1836 and in 1841, when it was sub-divided into three sections. The Memoirs of the Academy are so well-known and contain so many important articles in all branches

of science that we do not need to consider them here further.

The Academic University died a natural death through lack of students, and the first Russian university must be considered to be the University of Moscow, which was opened in 1754, and had as many as one hundred students in 1758. In 1804 a constitution was adopted, framed on German model by W. N. Karasin. This constitution recognised the autonomy of the university and was extended to the newly founded universities in St. Petersburg, Kazan, Kharkov, Vilno, and Dorpat. In 1830 the University of Vilno was abolished and that of Kiev opened. In 1835, however, the constitution was modified. The number of students was limited, and the Government appointed special curators to control university affairs. The last traces of academic freedom were obliterated in 1849, when the new constitution framed by Prince Shirinsky-Shikhmatoff was introduced into all universities. All executive officers and all professors were from now on appointed and not elected, and "harmful" sciences, such as constitutional law, were forbidden. The liberating and progressive movement at the beginning of the sixties brought with it a change in the universities also. A new constitution prepared by Golovin restored academic freedom, but only for a short period. In 1866 Count Dmitri Tolstoy was appointed Secretary of Public Instruction and began immediately to interfere with the work of the universities by means of special decrees. A constitution prepared in accordance with his suggestions was introduced in 1884, when Delyanoff was Secretary, and from now on until the revolution of 1905 the universities were entirely under the strictest control of the government. A short breathing space after the revolution, then oppression worse than before; then again a sudden wonderful efflorescence of freedom in 1917 and now almost complete ruin under the Bolsheviki!

Such is the sad history of the Russian universities which played such a glorious rôle in developing Russian youth, in combating reaction based on ignorance and avarice, and in contributing through the patient work of their professors to the store of human knowledge. Orly a century of existence, a century of martyrdom! During that time many thousands of students were never allowed to finish their education, some banished to Siberia, others imprisoned, many killed. And during that time many professors were removed from office, banished, censured, imprisoned, broken in spirit. And in the aftermath of the revolution some of the best among them have died of starvation others have been executed and all execrated as enemies of the proletariat.

Yet even in the darkest hours and years of reaction the universities continued their work in science. Every university has its own publications in the shape of transactions or proceedings, or of similar publications of societies organised by the universities. Especially well known are the publications of the St. Petersburg Mineralogical Society, of the St. Petersburg Society of Naturalists, of the Moscow Society of Naturalists and of the Moscow Friends of Natural Sciences, Anthropology, and Ethnography. But, other publications, such as the Proceedings of the Society of Naturalists of Kazan, founded in

1869, and those of the corresponding society of Kiev, also founded in 1869, and of Kharkov contain many valuable and important articles. Men who studied at universities but who were forced by circumstances to live in cities which had no university or other higher educational institution, founded small scientific societies, little local museums, as the Society of Naturalists in Ecaterinburg, which publishes its own proceedings, another similar society in Saratov, again one in Tiflis, and anthropological and ethnographical museum in Twer, and so on. The foreigners can have scarcely any idea as to how much all these publications contain of material referring to local fauna, local flora, local ethnography, &c. The various Governmental Departments have been also publishing many important contributions to our knowledge both in pure and applied sciences, geological, mineralogical, entomological, investigations. Reviews of Russian contributions to the various branches of science have been printed from time to time, such as Anatoli Bogdanoff's "Materials for the History of Pure and Applied Zoology and of Allied Branches of Knowledge in Russia," 1850; Sabaneeff's "List of books and papers on hunting and nature study," 1883; G. A. Kojewnikoff's "Reports about Russian Zoological Literature," 1893, &c., but the special work which was in preparation when the revolution disrupted all university work in Russia, and which was to embrace all branches of science in a way similar to the volume dealing with humanistic sciences, has been interrupted by the upheaval and may have been lost. (To be continued).

EDITORIAL.

WITH a view to increasing the usefulness of the CHEMICAL NEWS, it has been decided to introduce in the near future a new feature in the method of publication. It was the aim of the late Sir William Crookes, that the CHEMICAL NEWS should thought among Chemists and Physicists, and in be the medium for the publication of original its columns most of the discoveries of the past fifty years have appeared; in some cases the CHEMICAL NEWS was the first organ of publication.

The present Editor desires that the Journal shall maintain its useful character, and is anxious to meet as far as possible the many suggestions that have been made to this end,

Recently numerous original communications have been received, but lack of space and difficulties in printing have caused delay in publication; these difficulties are likely to increase rather than diminish.

It has therefore been decided to arrange a weekly "Editorial Notice", to announce, and if possible give a brief summary of, any papers received during the week, but of which, for the reasons stated, publication may have to be deferred.

The Editor therefore suggests to authors that a short summary should accompany original com