Speaker 1: Section fifteen of the Science History of the Universe, Volume four.
Speaker 1: This is a LibriVox recording. All LibriVox recordings are in
Speaker 1: the public domain. For more information or to volunteer, please
Speaker 1: visit LibriVox dot org. Recording by Lawrence Trask, Mount Vernon,
Speaker 1: Ohio interface audio dot com. The Science History of the Universe,
Speaker 1: Volume four, edited by Francis Rolt Wheeler. Chemistry, Chapter eleven,
Speaker 1: Bersilius and the development of the atomic theory. Complete success
Speaker 1: had rewarded the exertions of Lavossier, and through the efforts
Speaker 1: of Praust Richter, Dalton, gayla Sac and Davy, the spirit
Speaker 1: of order was creeping in on all sides. But it
Speaker 1: was exceedingly fortunate for chemistry that an investigator with the
Speaker 1: sense of coordination that Bersilius possessed should have made his
Speaker 1: advent just at this time when laws required confirmation and
Speaker 1: theories nourishment. The foundations of the new system required extension
Speaker 1: and generalization, And how opportune was the appearance of one
Speaker 1: who could illumine the whole domain of chemistry. Brasilius ruled
Speaker 1: as an autocrat for over a quarter of a century,
Speaker 1: and the modern chemist can hardly over extol his obligation
Speaker 1: to him John's Jacob Bersilius was born at Walversunda in Ostergotland, Sweden,
Speaker 1: on August twentieth, seventeen seventy nine. His father was a
Speaker 1: schoolmaster in Linkoping and died four years after the birth
Speaker 1: of his son, who for some time afterward had to
Speaker 1: endure many privations. Brasilius studied medicine at Uppsala and subsequently practiced,
Speaker 1: but he had early acquired it a vote to chemistry
Speaker 1: and kept in close touch with it. He was but
Speaker 1: twenty when he undertook his first extensive chemical research, an
Speaker 1: investigation of the medical springs at mediev in the neighborhood
Speaker 1: of his birthplace. A short time after, in eighteen oh two,
Speaker 1: in conjunction with Heisinger, he commenced the examination of the
Speaker 1: action of the electric current on varioussaults, with the most
Speaker 1: far reaching results for chemistry and for himself. For almost immediately.
Speaker 1: The desire to keep so promising a student in Stockholm
Speaker 1: induced the authorities to create for him a new academic position,
Speaker 1: that of Assistant Professor of Medicine, Botany and Pharmacy at
Speaker 1: the University of Stockholm. In eighteen oh seven he was
Speaker 1: installed in the chair of Medicine and Pharmacy, and also
Speaker 1: taught chemistry at the Military College from the year eighteen
Speaker 1: oh six. In eighteen fifteen he accepted the chair of
Speaker 1: Chemistry in the Scherergico Medical Institute of Stockholm, where he
Speaker 1: accomplished the researches which made him famous, and where his
Speaker 1: lectures enabled him to impress his views upon the rising
Speaker 1: generation of chemists. Among his pupils may be mentioned Heinrich
Speaker 1: and Gustav Rose, Mitcherlich, Whohler, Christian gautleb Melen, Magnus, Mozander
Speaker 1: Zanberg and Cefstrom. From the year eighteen eighteen, when he
Speaker 1: was nominated permanent secretary to the Stockholm Academy, of which
Speaker 1: he had been a member since eighteen o eight, and
Speaker 1: more particularly after eighteen thirty two, when Mozender succeeded him
Speaker 1: in his chair. Brazilius devoted himself to literary work with
Speaker 1: a subservience which has hardly been equalled from a utilitarian
Speaker 1: standpoint by any chemist before or after him. He died
Speaker 1: on the seventh of August eighteen forty eight. Brasilius was
Speaker 1: an exceptional observer and a most accurate and operose investigator,
Speaker 1: exhibiting very close attention to details. It is difficult to
Speaker 1: render an account of his achievements, as they extended over
Speaker 1: almost the entire field of chemistry and produced reforms of
Speaker 1: great importance. And one must not forget that the laboratory
Speaker 1: in which Brasilius accomplished his famous researches was small and
Speaker 1: imperfectly equipped. To give Wohler's description of his first visit
Speaker 1: to it, no water, no gas, no hoods, no oven
Speaker 1: were to be seen. A couple of plain tables, a blowpipe,
Speaker 1: a few shelves with bottles, a simple apparatus, and a
Speaker 1: large water barrel whereat. Anna, the ancient cook of the establishment,
Speaker 1: washed the laboratory dishes, completed the furnishings of this room,
Speaker 1: famous throughout Europe for the work which had been done
Speaker 1: in it. In the kitchen, which adjoined and where Anna cooked,
Speaker 1: was a small furnace and a sand bath for heating purposes.
Speaker 1: Brasilius introduced many improvements in analytical chemistry. It was he
Speaker 1: who first employed fall smaller amounts of substances than the
Speaker 1: large quantities recommended by Claproth, who introduced the spirit lamp
Speaker 1: which bears his name, thereby rendering the incineration of filter
Speaker 1: paper and the ignition of precipitates facile, and who worked
Speaker 1: out many new methods of analysis. Among the latter were
Speaker 1: his plan of decomposing silicates by the aid of chlorine.
Speaker 1: He enriched mineralogy by many analyses of minerals and mineral waters,
Speaker 1: and in a number of these, for example those of
Speaker 1: platinum ores, he devised new methods of separation. Brasilius was
Speaker 1: the first to characterize minerals as being in every respect
Speaker 1: chemical compounds, and he classified them similarly to substances prepared artificially.
Speaker 1: He was also able to demonstrate that the doctrine of
Speaker 1: chemical proportions and consequently the atomic theory, was applicable to minerals.
Speaker 1: The close attention which Bersilius gave to details resulted in
Speaker 1: the discovery of selenium eighteen seventeen, therhea eighteen twenty eight,
Speaker 1: and in conjunction with Heisinger and independent of Klaproth, he
Speaker 1: discovered seria eighteen o three. He also discovered many new
Speaker 1: chemical compounds, among which were the compounds of selenium with
Speaker 1: hydrogen and oxygen, and some molydenum compounds. Isolated the elements
Speaker 1: silicon eighteen ten, zirconium and tantalum eighteen twenty four, and
Speaker 1: extended the knowledge of the platinum metals. Passages in the
Speaker 1: work of Brasilius indicate that he regarded the firm establishment
Speaker 1: of the doctrine of chemical proportions, and in conjunction with
Speaker 1: this the determination of the atomic weights of the elements
Speaker 1: and the constitution of chemical compounds, as his main task.
Speaker 1: To quote from his Leerbruck Derkschemie fifth edition, I resolved
Speaker 1: to make the analysis of a number of salts, whereby
Speaker 1: that of others might become superfluous. I soon convinced myself
Speaker 1: by new experiments that Dalton's numbers were wanting in that
Speaker 1: accuracy which was requisite for the practical application of his theory.
Speaker 1: I recognized that if the newly arisen light was to spread,
Speaker 1: it would be necessary to ascertain with the utmost accuracy
Speaker 1: the atomic weights of all elementary substances, and particularly those
Speaker 1: of the more common ones. Without such work, no day
Speaker 1: would follow the dawn. This was their for the most
Speaker 1: important object of chemical investigation at the time, and I
Speaker 1: devoted myself to it with unresting labor, after work extending
Speaker 1: over ten years I was able in eighteen eighteen to
Speaker 1: publish a table which contained the atomic weights, as calculated
Speaker 1: from my experiments of about two thousand simple and compound substances.
Speaker 1: In the years eighteen twelve to eighteen sixteen, Brazilius investigated
Speaker 1: the stages of oxidation of most of the metals and
Speaker 1: metalloids than known, and by determining the composition of these oxides,
Speaker 1: confirmed the law of multiple proportions. His analytical work greatly
Speaker 1: surpassed that of Dalton, and in the rules established for
Speaker 1: his guidance in deciding the number of atoms in a
Speaker 1: given compound or molecule, he exhibited a far greater knowledge. Still,
Speaker 1: his rules were in some respects arbitrary and unsatisfactory. He
Speaker 1: took oxygen equals one hundred as his standard, giving as
Speaker 1: his reason for this preference. The following to refer the
Speaker 1: other atomic weights to that of hydrogen offers not only
Speaker 1: no advantages, but has in fact many inconveniences, seeing that
Speaker 1: hydrogen is very light and is seldom a constituent of
Speaker 1: inorganic compounds. Oxygen, on the other hand, unites all the
Speaker 1: advantages in itself. It is, so to speak, the center
Speaker 1: point round which the whole of chemistry revolves. This view
Speaker 1: is again at the present time held by many chemists,
Speaker 1: who take sixteen as the atomic weight of oxygen, and
Speaker 1: base the atomic weights of all the other elements upon
Speaker 1: this number. Brasilius began his work at the time when
Speaker 1: Wallaceton was attempting, by his use of the term equivalents
Speaker 1: to eliminate the question of atoms. Thompson was employing the
Speaker 1: standard oxygen equals one, considering that this number would give
Speaker 1: more of the atomic weights as whole numbers, and failing
Speaker 1: to perceive that the law of volumes had any particular
Speaker 1: significance from the atomic standpoint. Brazilius, however, perceived in the
Speaker 1: law of volumes a corroboration of the atomic theory, and
Speaker 1: allowed himself to be guided by it in his views
Speaker 1: upon the number of atoms in chemical compounds, and consequently
Speaker 1: upon the numerical values of the atomic weights. His volume
Speaker 1: Theory contained the attempt to combine gay Lussac's law with
Speaker 1: the atomic theory. He set forth the atomistic view, which
Speaker 1: he had himself put into shape under the influence of
Speaker 1: the law of volumes, definitely and conclusively in two papers.
Speaker 1: He started with the assumption that in the case of
Speaker 1: every simple substance, when it was in the gaseous form,
Speaker 1: one volume corresponded with one atom, and therefore made use
Speaker 1: of the designation volume atoms for those smallest particles. Wherever
Speaker 1: it was practicable, he attempted to measure the volumes of
Speaker 1: the combining substances, and from these deduced the atomic numbers.
Speaker 1: The analysis of the compound in which the volumes of
Speaker 1: the elementary constituents were known led him to the true
Speaker 1: determination of the atomic weights of the latter. For example,
Speaker 1: from the fact that water consists of two volumes of
Speaker 1: hydrogen and one of oxygen, he deduced the atomic composition
Speaker 1: of water, which holds at the present day, together with
Speaker 1: the relative atomic weights of oxygen and hydrogen. And from
Speaker 1: the mode of formation of carbonic oxide and carbonic acid
Speaker 1: he arrived at the true composition of these compounds, and
Speaker 1: at the atomic weight of carbon, and so forth. Still,
Speaker 1: the use which Bersilius made of gay Lussac's law was
Speaker 1: too limited to free him from the necessity of employing
Speaker 1: rules for deciding the number of atoms in compounds. In
Speaker 1: eighteen eighteen, Brasilius gave a table of atomic weights which
Speaker 1: contained values which compare favorably with those of other observers.
Speaker 1: Nine years later he published another table which brought his
Speaker 1: atomic weights still closer to those now current. The reason
Speaker 1: given by Brasilius for having in eighteen twenty six many
Speaker 1: of the atomic weights assigned to the metals in eighteen
Speaker 1: eighteen was as follows. It is known that the oxide
Speaker 1: of chromium contains three atoms of oxygen. Chromic acid, for
Speaker 1: the same number of chromium atoms, contains twice as much oxygen,
Speaker 1: which would be six atoms, but in its neutral salts,
Speaker 1: chromic acid neutralizes an amount of a base containing one
Speaker 1: third as much oxygen as it contains itself, a relation
Speaker 1: found to hold in the case of all acids with
Speaker 1: three atoms of oxygen, for example, sulphuric acid and sulfates.
Speaker 1: In order to harmonize the multiple relation between the amount
Speaker 1: of oxygen in the oxide and in the acid, it
Speaker 1: is most probable that the acid contains three atoms of
Speaker 1: oxygen to one atom of chromium, and the oxide three
Speaker 1: atoms of oxygen to two of chromium. Isomorphous with the
Speaker 1: oxide of chromium are those of manganese, iron, and aluminum.
Speaker 1: Those also we know to contain three atoms of oxygen,
Speaker 1: and consequently must represent them as containing two atoms of
Speaker 1: the radical. But if the fire feric oxide consists of
Speaker 1: two fe plus three oxygen, the ferrous oxide is fe
Speaker 1: plus oxygen. But if the ferric oxide consists of two
Speaker 1: ferric plus three oxide, the ferrous oxide is ferric plus oxide,
Speaker 1: and the whole series of oxides isomorphous with it contains
Speaker 1: one atom of the radical and one atom of oxygen.
Speaker 1: Thus we see that E. Mischerlich's law of isomorphism that
Speaker 1: compounds of analogous composition and containing the same number of
Speaker 1: atoms crystallize in the same crystalline form, announced in eighteen nineteen,
Speaker 1: and which berzelis regarded as the most important since the
Speaker 1: establishment of the doctrine of chemical proportions, was an aid
Speaker 1: in testing his atomic weight determinations, for according to him,
Speaker 1: isomorphism indicated similarity in atomic constitution. Brazilium further showed that,
Speaker 1: with the exception of cobalt and silver, the law of
Speaker 1: specific heat justified the change made in eighteen twenty six.
Speaker 1: This law was advanced in eighteen nineteen by P. L.
Speaker 1: De Long and TA. Pettitt, who in investigating the specific
Speaker 1: heats of the metals and other bodies, reached the important
Speaker 1: conclusion that these were very nearly inversely proportional to their
Speaker 1: atomic weights. Multiplied by their atomic weights, the specific heats
Speaker 1: gave a constant quantity. This resulted in the law as
Speaker 1: stated by them, the atoms of the different elements have
Speaker 1: the same capacity for heat. It is not difficult to
Speaker 1: perceive that by means of the specific heat, one could
Speaker 1: readily approximate the true atomic weight and arrive at a
Speaker 1: decision as to which of the two or more possible
Speaker 1: figures represented the true weight. There were exceptions to the law,
Speaker 1: which have been explained only in late years. However, the
Speaker 1: law was extended to simple chemical compounds and proved of
Speaker 1: great assistance after it was more fully understood. Brasilius opposed
Speaker 1: the acceptance of it at first, in part because it
Speaker 1: would necessitate a revision of his table of atomic weights
Speaker 1: and might endanger the accepted views as to some of
Speaker 1: the atomic relations. He gradually gave up this position, however,
Speaker 1: when the law was confirmed by other workers and more
Speaker 1: accurate determinations were made than the first ones of DeLong
Speaker 1: and Petit, Brazilius substituted for Dalton's geometrical symbols a more
Speaker 1: convenient system of chemical notation, which to give his own words,
Speaker 1: might facilitate the expression of chemical proportions. Showed briefly and
Speaker 1: clearly the number of elementary atoms in each compound, and,
Speaker 1: after the determin termination of their relative weights, present the
Speaker 1: results of each analysis in a simple and easily retained manner.
Speaker 1: The atom of each element was represented by the initial
Speaker 1: letter of its latinized name, a second letter being added
Speaker 1: when two elements had names beginning with the same capital.
Speaker 1: An index number was added when more than one atom
Speaker 1: was present. A compound was thus represented by placing the
Speaker 1: proper number of these symbols side by side. Thus H
Speaker 1: is hydrogen cl is chlorine and HCl is hydrogen chloride.
Speaker 1: Brazilius assumed the existence of certain double atoms. Where two
Speaker 1: atoms of an element occur together. These were indicated by
Speaker 1: a mark across the symbol. Thus H with a stroke
Speaker 1: through it followed by O was water, or as it
Speaker 1: is now written H two O for it can venient's sake.
Speaker 1: An atom of oxygen was often indicated by a point
Speaker 1: or dot. Thus, carbon dioxide C with two dots above it,
Speaker 1: nitrous acid N with four dots above it, potassium nitrate
Speaker 1: k N with three dots above the N. These symbols
Speaker 1: were a great advance over those suggested by Dalton, which
Speaker 1: were diagrammatic and quite unpractical. Dalton, however, criticized the system
Speaker 1: of notation of Berzelius, saying that brazilius symbols are horrifying.
Speaker 1: A young student in chemistry might as soon learn Hebrew
Speaker 1: as make himself acquainted with them. Brasilius adopted dualism as
Speaker 1: the basis of his chemical system. He extended the term
Speaker 1: atom so that it included what he regarded as compound atoms,
Speaker 1: which were built up of two parts, each of which
Speaker 1: might be a simple atom or a single simple atom.
Speaker 1: This was the dual structure which dominated all his views
Speaker 1: with regard to chemical phenomena, and far more than a
Speaker 1: decade held a pre eminent position in chemistry. Brazilius seemed
Speaker 1: to have formed this idea of dualism from his observations
Speaker 1: upon the volumes of gases. For a certain number of
Speaker 1: these gases, the equivalent is formed of two atoms. This
Speaker 1: was true not only of hydrogen, but of nitrogen, chlorine,
Speaker 1: and others in the form of vapor. The atomic weights
Speaker 1: of these bodies represent also the specific gravities or the
Speaker 1: weights of one volume compared with one volume of the standard.
Speaker 1: But since it requires two volumes of nitrogen two volumes
Speaker 1: of chlorine, et cetera to form the first stage of
Speaker 1: oxidation with oxygen, two volumes of nitrogen et cetera, represent
Speaker 1: the equivalents of these bodies compared with oxygen. Berzelius consider
Speaker 1: that these atoms therefore were united two and two, and
Speaker 1: called them the double or compound atoms. A uniform method
Speaker 1: of considering compounds dualistically became possible to a still greater
Speaker 1: degree in the light of electrical chemical phenomena, and Brasilius
Speaker 1: introduced this into chemistry and established it. Davy had inclined
Speaker 1: to the assumption that electrical processes and the phenomena of
Speaker 1: chemical affinity arose from a common cause. His electrochemical theory
Speaker 1: was characterized by the axiom that the small particles of
Speaker 1: substances which have an affinity for one another only become
Speaker 1: oppositely electrified upon contact. The researches of Brasilius, however, caused
Speaker 1: the abandonment of this principle, while otherwise many of Davey's
Speaker 1: original ideas were retained. Davy advanced ideas as to the
Speaker 1: manner in which he considered chemical and electrical phenomena to
Speaker 1: be related, but he never succeeded in producing a theory
Speaker 1: which might serve as the basis of a chemical system.
Speaker 1: This was accomplished by Brasilius, and therefore his views are
Speaker 1: of greater importance in the development of chemistry than those
Speaker 1: of Davy are. To quote from A. Leydenberg's lectures on
Speaker 1: the History of chemistry. According to Brasilius, it is not
Speaker 1: only when two substances are brought into contact that electricity
Speaker 1: is generated, but it is a property of matter, and
Speaker 1: in every atom two oppositely electrical poles are assumed. These
Speaker 1: poles do not, however, contain equal quantities of electricity. The
Speaker 1: atoms are unipolar, the electricity of the one pole predominating
Speaker 1: over that of the other. And thus every atom and
Speaker 1: therefore every element, appears to be either positively or negatively electrical.
Speaker 1: In this respect, it is possible to arrange the elementary
Speaker 1: substances into a series, so that each member is always
Speaker 1: more electronegative than the next. Succeeding one. Oxygen stands at
Speaker 1: the top and is absolutely electronegative, while the other substances
Speaker 1: are only relatively positive or negative according as they are
Speaker 1: compared with elements which come before them or after them
Speaker 1: in the electrical series. This series does not constitute a
Speaker 1: table of affinities in the Jeffrey Bergmann sense, and it
Speaker 1: does not express the affinity of the individual substances. For oxygen,
Speaker 1: for example, Brazilius has not forgotten Berthelet's teaching that affinity
Speaker 1: is not of a constant character and independent of the
Speaker 1: physical conditions, as he supposes this unipolarity to be, and
Speaker 1: he is also well aware that oxygen can be removed
Speaker 1: moved from metallic oxides by carbon or sulfur, that is
Speaker 1: to say, by other electronegative substances. With him, affinity depends
Speaker 1: principally upon the intensity of the polarity, for example, upon
Speaker 1: the quantity of electricity which is contained in the two poles.
Speaker 1: This is variable, however, especially with changes of temperature, and
Speaker 1: generally speaking is increased by furnishing more heat, which explained
Speaker 1: why certain combinations only occurred at a high temperature. Chemical
Speaker 1: combinations of the elements or compounds consisted, according to Brasilius,
Speaker 1: in the attraction of the dissimilar poles of the small
Speaker 1: particles and in the consequent neutralization of the different electricities.
Speaker 1: When positive electricity predominated in the original substance, then an
Speaker 1: electro positive compound resulted, and vice versa. If the electricities
Speaker 1: neutralized one another, then an electrically indifferent product was the result. Oxygen,
Speaker 1: as the most electronegative element, served Brasilious here as the
Speaker 1: standard by which to determine the kind of polarity of
Speaker 1: the various elements. Those elements which yielded basic compounds with oxygen,
Speaker 1: even although only their lowest oxides were basic, were classed
Speaker 1: as electropositive, and those whose oxides were acids as electronegative.
Speaker 1: Following this principle, he arranged the simple substances in a
Speaker 1: series in which oxygen as the first member, was followed
Speaker 1: by the other metalloids, while hydrogen formed the bridge between
Speaker 1: the latter and the metals, the whole ending with sodium
Speaker 1: and potassium. Such conceptions form the substance of his electrochemical theory,
Speaker 1: which constituted the basis of the dualistic theory of chemical composition.
Speaker 1: Brasilius established it as follows. If the electrochemical views are accurate,
Speaker 1: it follows that every chemical combination depends wholly and solely
Speaker 1: upon two opposite forces, namely the positive and the negative electricities,
Speaker 1: and that every compound must be composed of two parts
Speaker 1: united by the effects of their electrochemical reactions. Since there
Speaker 1: is not any third force. From this, it follows that
Speaker 1: every compound substance, whatever the number of its constituents may be,
Speaker 1: can be divided into two parts, of which the one
Speaker 1: is positively and the other is negatively electrical. Thus, for example,
Speaker 1: sulfate of soda is not composed of sulfur oxygen and sodium,
Speaker 1: but of sulfuric acid and soda, each of which can
Speaker 1: in turn be separately divided into an electropositive and an
Speaker 1: electronegative constituent in the same way. Also, alum cannot be
Speaker 1: regarded as immediately composed of its elementary constituents, but is
Speaker 1: to be looked upon as the product of the reaction
Speaker 1: of sulfate of aluminum as negative element, with sulfate of
Speaker 1: potash as positive element. And thus the electrochemical view justifies
Speaker 1: what I have said with respect to compound atoms of
Speaker 1: the first, second, third, etc. Orders. In the year eighteen nineteen,
Speaker 1: when Brazilius contributed a complete exposition of his electrochemical theory,
Speaker 1: he was convinced that all acids contained oxygen. In his view,
Speaker 1: water assumed in hydrated acids the role of a weak
Speaker 1: electropositive constituent, and in metallic hydroxides that of a weak
Speaker 1: electronegative one. The hydrates of sulfuric acid and of cupric
Speaker 1: oxide therefore receive the formula H two so three CuO two.
Speaker 1: The binary conception, which had already been applied by Levosier
Speaker 1: to acids and bases, and even by Ruelle to salt,
Speaker 1: thus received the strongest support from the electrochemical theory and
Speaker 1: was materially developed as a result. Finally, however, the theory
Speaker 1: of the oxygen acids based on the tenet established by
Speaker 1: Levosia was abandoned by chemists during the second decade of
Speaker 1: the nineteenth century as a knowledge of facts in opposition
Speaker 1: to it augmented, and at last Brasilius convinced himself of
Speaker 1: the existence of acids free from oxygen, at which time
Speaker 1: the unadaptable system of dualism began to decline in favor.
Speaker 1: It had explained, however, the mysterious chemical force, even though
Speaker 1: the identification of chemical affinity with electrical polarity was one
Speaker 1: not justified by the facts at hand, and dominated chemistry
Speaker 1: for two decades. As a result of the efforts of Brazilius,
Speaker 1: chemistry was now in the possession of a comprehensive theory
Speaker 1: of chemical reaction, a rational and systematic nomenclature, and a
Speaker 1: large quantity of experimental data. He was responsible for a
Speaker 1: solid basis in the laws of constant proportions and multiples,
Speaker 1: and the table of atomic weights, which he published in
Speaker 1: eighteen twenty seven, was remarkably accurate the determinations approaching the
Speaker 1: more exact work of the present time. These contributions equipped
Speaker 1: chemistry for the period of remarkable extension in the accumulation
Speaker 1: of data and in the formulation of theory, which the
Speaker 1: past eighty years have witnessed. Mention has been made of
Speaker 1: the law of DeLong and Petit and of the law
Speaker 1: of Mischelik. The exceptions to the former exhibited by many
Speaker 1: of the non metals in a greater or lesser diminuation
Speaker 1: of the atomic heats, have only in some measure been
Speaker 1: explained in recent years by the proof that the specific
Speaker 1: heats of such elements vary greatly with the temperature. In
Speaker 1: the case of simple chemical compounds, a relation was soon
Speaker 1: found between their specific heats and atomic weights by Newman
Speaker 1: in eighteen thirty one, who said, I find that for
Speaker 1: compound substances a simple relation exists between the specific heats
Speaker 1: and the stoichiometric quantities. And I call storchiometric quantities the
Speaker 1: amounts of substances which, as for instance, in the case
Speaker 1: of the anhydrous carbonates, contain the same amount of oxygen,
Speaker 1: while in the case of sulfur compounds, the amount of
Speaker 1: sulfur is the measure of the stoichiometric quantity. For chemically
Speaker 1: similar substances, the specific heats are inversely proportional to the
Speaker 1: storchiometric quantities, or what comes to the same thing, the
Speaker 1: storrecheometric quantities of chemically similar substances have the same heat capacity.
Speaker 1: The investigation of the carbonates first led me to the
Speaker 1: discovery of this law. Renault, who extended the empirical basis
Speaker 1: of the law of constant atomic heat in eighteen forty
Speaker 1: while engaged in investigations on the specific heats of compounds
Speaker 1: corroborated Newman's results, but it was reserved for copp in
Speaker 1: eighteen sixty five to definitely prove that the connection between
Speaker 1: the specific heat and the composition of a compound holds
Speaker 1: in the perfectly simple and general manner enunciated by Pettit
Speaker 1: and DeLong, and that heat capacity is of the nature
Speaker 1: of an additive property. The law of Mitcherlik was the
Speaker 1: outgrowth of coordinating physical form with chemical composition, a question
Speaker 1: which until the time of Ijured Mitscherlik seventeen ninety one
Speaker 1: four to eighteen sixty three had been attacked entirely from
Speaker 1: the crystallographic side. In eighteen oh one, Abe Hoy seventeen
Speaker 1: forty three to eighteen twenty two, the founder of the
Speaker 1: science of crystallography, produced a system of mineral classification based
Speaker 1: first on their crystalline character and secondly on their chemical composition.
Speaker 1: His guiding principle was that every difference in the fundamental
Speaker 1: form of a crystal implied difference in its chemical composition.
Speaker 1: This supposed law was supported by numerous facts, but there
Speaker 1: were also on record well defined and undoubted exceptions as
Speaker 1: far back as seventeen seventy two, REMAE. Delisle had observed
Speaker 1: that copper sulfate and ferris sulfate crystallize from a mixed
Speaker 1: solution in the form of the latter, and in seventeen
Speaker 1: eighty eight Klaproth established the chemical identity of rombohedral calcite
Speaker 1: and rhombic argonite. Mescherlik was the first to recognize definitely
Speaker 1: the relation between crystalline form and chemical constitution. He explained
Speaker 1: the occurrence of isomorphous crystals in substances of different nature
Speaker 1: by demonstrating that they possessed a similar chemical composition. For instance,
Speaker 1: he found, on examining the salts of phosphoric and arsenic
Speaker 1: acids that only those of analogous composition and containing equal
Speaker 1: amounts of water of crystallization were isomorphous. His subsequent investigations
Speaker 1: of selenates and sulfates, of the isomorphism of magnesium and
Speaker 1: zinc oxides, and of iron, chromium and aluminium salts confirm
Speaker 1: the intimate connection existing between crystalline form and chemical composition.
Speaker 1: Primarily after making these observations, Micherlich was of opinion that
Speaker 1: isomorphism depended chiefly on the number of the elementary particle,
Speaker 1: but He soon became convinced that the chemical nature of
Speaker 1: these had also to do with it. The importance of
Speaker 1: Mescherlik's work met with immediate recognition, and data in support
Speaker 1: of the law were quickly accumulated. With regard to its
Speaker 1: deductive application, it is employed for purposes of classifying the
Speaker 1: elements and of atomic weight determinations. From the isomorphism of
Speaker 1: the salts of an acid of selenium with sulfates and chromates,
Speaker 1: Mescherlik was led to the discovery of that acid, selenic acid,
Speaker 1: and his recognition of the isomorphism with potassium sulfate of
Speaker 1: the green potassium salt of a manganese acid, and of
Speaker 1: the isomorphism with potassium percholate of the red potassium salt
Speaker 1: of another manganese acid, has revealed the true composition of
Speaker 1: these two acids. It has been mentioned how the isomorphism
Speaker 1: of sulfates and chroma induced Brazilius to modify the formula
Speaker 1: of basic chromic oxide and a subsequent having of the
Speaker 1: atomic weights of most of the metals. He still adhered
Speaker 1: to the idea that the amounts of the elements contained
Speaker 1: in equal gaseous volumes were proportioned to their atomic weights. However,
Speaker 1: this assumption was soon invalidated by the remarkable results of
Speaker 1: an investigation which exercised such a marked influence on the
Speaker 1: views of many chemists that it must be described at
Speaker 1: this point. This was the work of Jean Baptiste Andre
Speaker 1: Dumas eighteen hundred to eighteen eighty four on the atomic weights.
Speaker 1: In eighteen twenty seven, Dumas published a paper entitled Memoir
Speaker 1: on some Points of the Atomistic Theory, in which he
Speaker 1: stated the object of these researches is to replace by
Speaker 1: definite conceptions the arbitrary data on which nearly the whole
Speaker 1: of the atomic theory is based. Dumas showed that the
Speaker 1: conception of the equivalent cannot be employed as the basis
Speaker 1: of a system because it loses its significance when it
Speaker 1: is extended further than to acids, to bases, and to
Speaker 1: other substances which closely resemble each other oxides and sulfides,
Speaker 1: and particularly that it becomes quite obscure when the attempt
Speaker 1: is made to identify the equivalent with the combining weight,
Speaker 1: since very many substances can combine in several proportions. For example,
Speaker 1: eight parts of copper are combined with one part of
Speaker 1: oxygen in cuprous oxide, while for eight parts of copper,
Speaker 1: two parts of oxygen are contained in cupric oxide. Calculated
Speaker 1: from these numbers, the equivalent of copper referred to that
Speaker 1: of oxygen as unity is eight or four. In order
Speaker 1: to confirm his ideas, Dumas adopted Avogadro's hypothesis as a
Speaker 1: and devised in eighteen twenty seven an admirable method for
Speaker 1: the determination of vapor densities. He determined that the determination
Speaker 1: of the density of vapors and gases elementary as well
Speaker 1: as compound, was necessary to elucidate the question of the
Speaker 1: composition of the elementary molecule, but his practice did not
Speaker 1: agree with his theory. He and his contemporaries argued from
Speaker 1: the premise that the vapor densities of elements are proportional
Speaker 1: not only to their molecular weights, but also to their
Speaker 1: atomic weights, which of course involved the unwarranted assumption that
Speaker 1: all elementary gaseous molecules are composed of the same number
Speaker 1: of atoms, for example of two. He was successful in
Speaker 1: elaborating a method for conducting determinations of this kind at
Speaker 1: high temperatures, and used it for ascertaining the relative densities
Speaker 1: of the vapors of iodine, phosphorus, sulfur, mercury, etc. His results,
Speaker 1: from which he anticipated confirmation of his views, induced him
Speaker 1: to abandon them. He found the density of phosphorus vapor
Speaker 1: to be twice as great and that of sulfur vapor
Speaker 1: to be three times as great as he had previously assumed,
Speaker 1: while that of mercury vapor was only one half of
Speaker 1: what he had supposed. In view of these facts, he
Speaker 1: began to doubt. In fact, he declared that even the
Speaker 1: simple gases do not contain in the same volume the
Speaker 1: same number of chemical atoms. According to him, the assumption
Speaker 1: could still be made that there is the same number
Speaker 1: of molecular or atomic groups present in equal volumes of
Speaker 1: all gases, but that this is only a hypothesis which
Speaker 1: cannot be of service. Dumas was obliged to admit that
Speaker 1: gay Lussac's law, when applied in the way he had
Speaker 1: applied it to the determination of atomic weights, furnished erroneous result. Hence,
Speaker 1: he believed that it could not be employed for this purpose,
Speaker 1: and he abandoned Avogadro's hypothesis. Brasilius also was able no
Speaker 1: longer to maintain the law of volumes so far as
Speaker 1: its application in atomic weight determinations was concerned, and confined
Speaker 1: his proposition to the permanent gases. The reform which Dumas
Speaker 1: had aimed at was therefore without result, and if anything,
Speaker 1: he had merely introduced obscurity into the atomic weight system
Speaker 1: of Brasilius. As a result, chemists regarded Avigadro's law with indifference.
Speaker 1: The law of DeLong and Pettit was shown also to
Speaker 1: have some unexplained exceptions, and Mischelik by his further discovery
Speaker 1: of dimorphism, which had thrown much doubt upon his law
Speaker 1: of isomorphism. Consequently, at the close of the thirtieth year
Speaker 1: of this century, the atomic theory was regarded by many
Speaker 1: chemists as either disproved or excluded to a very hypothetical position.
Speaker 1: Even gay Lussac and Leibik doubted whether it was possible
Speaker 1: to determine the relative weights of the atoms worth certitude,
Speaker 1: and would have left the atomic weights out of consideration,
Speaker 1: substituting the establishment of equivalents. Leopold Gamelen, however, was at
Speaker 1: the head of the movement to supplant the system of
Speaker 1: Brazilius by the equivalents of Wallaceton. According to Gamelon, there
Speaker 1: was no strict distinction between mixtures and compounds, and this
Speaker 1: demonstrates that he did not believe in the real existence
Speaker 1: of atoms. Two substances, especially when they possess only a
Speaker 1: weak affinity for each other, can combine, according to him,
Speaker 1: in an infinite number of proportions. But the greater the affinity,
Speaker 1: the greater is their tendency to combine in few proportions.
Speaker 1: Only these proportions then stand to each other in simple relations.
Speaker 1: There can therefore be assigned to every substance a certain
Speaker 1: weight in which it combines with definite weights of other elements.
Speaker 1: This weight is the stoichiometric number, the chemical equivalent, the
Speaker 1: mixture weight or atomic weight, and so on. Compounds are
Speaker 1: composed in such proportions that one mixture weight of one
Speaker 1: substance is united to a quarter, a third, a half,
Speaker 1: two thirds, three quarters, one, one and a half, two,
Speaker 1: two and a half, three, four, five, six, seven, or
Speaker 1: more mixture weights of the other. According to Gamelon, guy
Speaker 1: Lussac's law runs as follows. One measure of an elastic
Speaker 1: fluid substance combines with one, one and a third, two,
Speaker 1: two and a half, three, three and a half, and
Speaker 1: four measures of the other. Gamelin's table of equivalents is
Speaker 1: well known. It ran h equals one, one, oh equals eight,
Speaker 1: s equals sixteen, c equals six, etc. Water was written
Speaker 1: ho and in formula. Generally, the attempt was made to
Speaker 1: replace by simplicity what they had lost in conception and
Speaker 1: in purpose. As Leidenberg observes, chemistry was to become a
Speaker 1: science of confined observation, indeed, almost to description alone. Skill
Speaker 1: in manipulation was all that was required. Speculation was banished
Speaker 1: as dangerous. It had come to this then, inorganic chemistry
Speaker 1: and connection with physics had not been able to maintain
Speaker 1: the conception of the atom. By the assistance of the
Speaker 1: growing science of organic chemistry, however, the theories of chemistry
Speaker 1: were rescued and advanced, and the atomic theory was re introduced.
Speaker 1: But reference must be made to the status of the
Speaker 1: atomic theory in a England at this time. In England,
Speaker 1: in the eighteen thirty three edition of Edward Turner's Elements
Speaker 1: of Chemistry, the atomic theory is referred to as follows.
Speaker 1: In consequence of the satisfactory explanation which the laws of
Speaker 1: chemical union received by means of the atomic theory, it
Speaker 1: has become customary to employ the term atom in the
Speaker 1: same sense as combining, proportion or equivalent. A discovery of
Speaker 1: great importance was made in eighteen thirty four when Michael
Speaker 1: Faraday seventeen ninety four to eighteen sixty seven, professor in
Speaker 1: the Royal Institution of London, who had been engaged in
Speaker 1: studying quantitatively some changes produced by the passage of a
Speaker 1: current of electricity, detected the connection which existed with the
Speaker 1: combining numbers of the elements, and thereby deduced his law
Speaker 1: of electrical equivalents. Faraday made the observation that the samealvanic
Speaker 1: current decomposed electrolytes, for example, water, hydrochloric acid, and metallic chlorides,
Speaker 1: in such a manner that equivalent amounts of hydrogen or
Speaker 1: metal were separated at the negative pole, and the corresponding
Speaker 1: quantities of oxygen or chlorine at the positive He classified
Speaker 1: these facts together under the title of the law of
Speaker 1: definite electrolytic action. In the determination of electrochemical equivalents, he
Speaker 1: perceived a sure auxiliary means for adjusting chemical atomic weights
Speaker 1: in doubtful cases. End of Section fifteen. Recording by Lawrence Trask,
Speaker 1: Mount Vernon, Ohio, interfaceaudio dot com