Humphry Davy, Poet and Philosopher (Thorpe)

Humphry Davy, Poet and Philosopher by Thomas Edward Thorpe, and edited by Sir Henry E. Roscoe, was published in 1896 as part of the Century of Science Series. In this work Thorpe was able "to condense the somewhat diffuse biographies of Humphry Davy, written by Dr. Paris and Dr. John Davy, and to give, in moderate compass, all the information concerning him that we need to remember."1

frontispiece for Humphry Davy, Poet and Philospher (1896) by Thomas Edward Thorpe

QuotesEdit

PrefaceEdit

(May 1896)
  • Dr. Paris is not unfrequently inaccurate in his statements as to matters of fact, and disingenuous in his inferences as to matters of conduct and opinion. The very extravagance of his laudation suggests a doubt of his judgment or of his sincerity, and this is strengthened by the too evident relish with which he dwells upon the foibles and frailties of his subject. The insincerity is reflected in the literary style of the narrative, which is inflated and over-wrought.
  • Sir Walter Scott, who knew Davy well and who admired his genius and his many social gifts, characterised [Paris'] book as "ungentlemanly" in tone; and there is no doubt that it gave pain to many of Davy's friends who, like Scott, believed that justice had not been done to his character.
  • Dr. Davy's book... whilst perhaps too partial at times... is written with candour, and a sobriety of tone and a directness and simplicity of statement far more effective than the stilted euphuistic periods of Dr. Paris, even when he seeks to be most forcible.
  • When... I have had to deal with conflicting or inconsistent statements in the two works on matters of fact, I have generally preferred to accept the version of Dr. Davy, on the ground that he had access to sources of information not available to Dr. Paris.
  • Davy played such a considerable part in the social and intellectual world of London... that... his name frequently occurs in the personal memoirs and biographical literature... and a number of journals and diaries, such as those of Horner, Ticknor, Henry Crabb Robinson, Lockhart, Maria Edgeworth, and others that might be mentioned, make reference to him and his work, and indicate what his contemporaries thought of his character and achievements. Some of these references will be found in the following pages.
  • Londoners... owe the Zoological Gardens, in large measure, to a Professor of Chemistry in Albemarle Street, and that the magnificent establishment in the Cromwell Road, South Kensington, is the outcome of the representations, unsuccessful for a time, which he made to his brother trustees of the British Museum as to the place of natural history in the national collections. Davy had a leading share also in the foundation of the Athenæum Club, and was one of its first trustees.
  • I am... indebted to Dr. Rollenston for the loan of a portrait representing Davy in Court dress and in the presidential chair of the Royal Society, which, reproduced in photogravure, forms the frontispiece to this book. The original is a small highly finished work by Jackson, and was painted about 1823. The picture originally belonged to Lady Davy, who refers to it in the letter to Davies Gilbert (quoted by Weld in his "History of the Royal Society"), in which she offers Lawrence's well-known portrait to the Society, and which... the Society nearly lost through the subsequent action of the painter.
  • It is not necessary to belittle Davy in order to exalt Faraday; and writers who, like Dr. Paris, unmindful of George Herbert's injunction, are prone to adopt an antithetical style in biographical narrative have, I am convinced, done Davy's memory much harm.

Ch. VI. The Isolation of the Metals of the Alkalis.Edit

  • With the exception of a rapid journey into Cornwall, for the sake of seeing his family, he spent the greater part of the summer and autumn of 1807 in town. He had been made Secretary of the Royal Society in succession to Gray, and was obliged to be in or near London in order to see the Philosophical Transactions through the press. From the Laboratory Journal it would appear that he was occupied at this time on a variety of disconnected investigations such as the nature of Antwerp Blue, and the effect of electricity on flame. In a letter to Davies Gilbert, dated September 12th, he states that he has been a good deal engaged in experiments on distillation for revenue purposes.
  • Towards the end of this month, or during the first week of October, he resumed his experiments with the voltaic battery, and he was led to study its action on the alkalis. There is some evidence that he had attacked the same question at Bristol.
  • In a note-book of that period, under date August 6th, 1800, is the following sentence: "I cannot close this notice without feeling grateful to M. Volta, Mr. Nicholson, and Mr. Carlisle, whose experience has placed such a wonderful and important instrument of analysis in my power"...
  • This is immediately followed by "Query: Would not potash, dissolved in spirits of wine, become a conductor?" And he then gives an account of some experiments on the action of voltaic electricity on aqueous solutions of ammonia, caustic potash, and hydrochloric acid, which apparently led to the same result as that already obtained by Nicholson and Carlisle in the case of water.
  • [H]e said of the alchemists that "even their failures developed some unsought-for object partaking of the marvellous"—and the statement in this case is even more true of himself.
  • Each phase in the story of this discovery indeed partakes of the marvellous. Sometime during the first fortnight in October, 1807, he obtained his first decisive result; and on the 19th of November he delivered what is generally regarded as the most memorable of all his Bakerian lectures, "On some new Phenomena of chemical Changes produced by Electricity, particularly the Decomposition of the fixed Alkalies, and the Exhibition of the new substances which constitute their bases; and on the general Nature of alkaline Bodies."
  • Few discoveries of like magnitude have been made and perfected in so short a time, and few memoirs have been more momentous in result than that which Davy put together in a few hours, and in which he announced his results to the world.
  • The whole work was done under conditions of great mental excitement. His cousin Edmund Davy,.. his assistant, relates that when he [Humphrey Davy] saw the minute globules of the quicksilver-like metal burst through the crust of potash and take fire, his joy knew no bounds; he actually danced about the room in ecstasy, and it was some time before he was sufficiently composed to continue his experiments. The rapidity with which he accumulated results after this first feeling of delirious delight had passed was extraordinary.
  • Before the middle of November he had obtained most of the leading facts. In a letter dated November 13th he tells W. H. Pepys
"I have decomposed and recomposed the fixed alkalies, and discovered their bases to be two new inflammable substances very like metals; but one of them lighter than ether, and infinitely combustible. So that there are two bodies decomposed, and two new elementary bodies found."
  • [H]e seldom entered the laboratory before ten or eleven in the morning, and rarely left it later than four, and he was scarcely ever known to visit it after he had dressed for dinner.
  • Except when preparing a lecture, he seldom dined in his rooms at the Institution: his brother tells us that his invitations to dinner were so numerous that he was, or might have been, constantly engaged; and after dinner he was much in the habit of attending evening parties, and devoting the evening to amusement, "so that to the mere frequenters of such parties he must have appeared a votary of fashion rather than of science."
  • The Bakerian lecture in which Davy announces the discovery of the compound nature of the fixed alkalis opens with a reference to the concluding remarks of his lecture of the previous year, "that the new methods of investigation promised to lead to a more intimate knowledge than had hitherto been obtained concerning the true elements of bodies. This conjecture, then sanctioned only by strong analogies, I am now happy to be able to support by some conclusive facts."
  • In the first attempts he made to decompose the fixed alkalis he acted upon concentrated aqueous solutions of potash and soda with the highest electrical power he could then command at the Royal Institution—viz. from voltaic batteries containing 24 plates of copper and zinc of 12 inches square, 100 plates of 6 inches, and 150 of 4 inches, charged with solutions of alum and nitric acid; but although there was high intensity of action nothing but hydrogen and oxygen was disengaged.
  • He next tried potash in igneous fusion, and here the results were more encouraging: there were obvious and striking signs of decomposition; combustible matter was produced accompanied with flame and a most intense light.
  • He had observed that although potash when dry is a nonconductor, it readily conducts when it becomes damp by exposure to air, and in this state "fuses and decomposes by strong electrical powers."
"A small piece of pure potash, which had been exposed for a few seconds to the atmosphere, so as to give conducting power to the surface was placed upon an insulated disc of platina, connected with the negative side of the battery of the power of 250 of 6 and 4, in a state of intense activity; and a platina wire communicating with the positive side was brought in contact with the upper surface of the alkali. ..."
"Under these circumstances a vivid action was soon observed to take place. The potash began to fuse at both its points of electrization. There was a violent effervescence at the upper surface; at the lower, or negative surface, there was no liberation of elastic fluid; but small globules having a high metallic lustre, and being precisely similar in visible characters to quicksilver appeared, some of which burnt with explosion and bright flame, as soon as they were formed, and others remained, and were merely tarnished, and finally covered by a white film which formed on their surfaces."
  • It is frequently stated that Davy was enabled to isolate the metals of the alkalis because of the large and powerful voltaic battery which he had at his disposal in the Royal Institution. This is not correct. The battery he employed was of very moderate dimensions, and not by any means extraordinary in power. It was the success he thus achieved that caused the large battery, which is probably referred to, to be constructed, by special subscription, in 1809.
    • (a footnote.)
  • The platina... was, he found, in no way connected with the result: a substance of the same kind was produced when copper, silver, gold, plumbago, or even charcoal was employed for completing the circuit.
"Soda when acted upon in the same manner as potash, exhibited an analogous result; but the decomposition demanded greater intensity of action in the batteries, or the alkali was required to be in much thinner and smaller pieces."
"The substance produced from potash remained fluid at the temperature of the atmosphere at the time of its production; that from soda, which was fluid in the degree of heat of the alkali during its formation, became solid on cooling, and appeared having the lustre of silver."
  • It would seem from his description of its properties that the potassium he obtained was most probably alloyed with sodium derived from impure potash. Potassium is solid up to 143° F.; but, as Davy subsequently found, an alloy of potassium and sodium is fluid at ordinary temperatures.
  • When the potassium was exposed to air its metallic lustre was immediately destroyed, and it was ultimately wholly reconverted into potash by absorption of oxygen and moisture.
  • With the substance from soda the appearance and effects were analogous.
  • When heated in oxygen to a sufficiently high temperature, both substances burnt with a brilliant white flame.
  • On account of their alterability on exposure to air, Davy had considerable difficulty in preserving and confining them so as to examine the properties of the new substances. As he says, like the alkahests imagined by the alchemists, they acted more or less upon almost every body to which they were exposed.
  • He eventually found that they might be preserved in naphtha.
  • The "basis" of potash at 50° F. was a soft and malleable solid with the lustre of polished silver.
"At about the freezing point of water it becomes harder and brittle, and when broken in fragments, exhibits a crystallized texture, which in the microscope seems composed of beautiful facets of a perfect whiteness and high metallic splendour."
  • It may be converted into vapour at a temperature approaching a red-heat, and may be distilled unchanged; it is a perfect conductor of electricity and an excellent conductor of heat. Its most marked difference from the common run of metals was its extraordinarily low specific gravity.
  • Davy endeavoured to gain an approximation to its relative weight by comparing the weight of a globule with that of an equal-sized globule of mercury.
  • Although no great stress can be laid on numbers so obtained, they serve to indicate that Davy had not yet obtained the pure metal.
  • The "basis" of soda is described as a white opaque substance of the lustre and general appearance of silver. It is soft and malleable, and is a good conductor of heat and electricity. Its specific gravity was found by flotation in a mixture of oil of sassafras and naphtha... It was found to fuse at about 180° F. (the real melting point of sodium is 197.5°). Its action on a number of substances—oxygen, hydrogen, water, etc.—is then described, and its general behaviour contrasted with that of the "basis" of potash.
  • Davy then attempted to determine the amount of the "metallic bases" in potash and soda respectively... the results are fairly accurate.
  • He then enters upon some general observations on the relations of the "bases" of potash and soda to other bodies.
"Should the bases of potash and soda be called metals? The greater number of philosophical persons to whom this question has been put, have answered in the affirmative. They agree with metals in opacity, lustre, malleability, conducting powers as to heat and electricity, and in their qualities of chemical combination."
"Their low specific gravity does not appear a sufficient reason for making them a new class; for amongst the metals themselves there are remarkable differences in this respect, and in the philosophical division of the classes of bodies, the analogy between the greater number of properties must always be the foundation of arrangement."
"On this idea, in naming the bases of potash and soda, it will be proper to adopt the termination which, by common consent, has been applied to other newly discovered metals, and which, though originally Latin, is now naturalized in our language."
"Potasium [sic] and sodium are the names by which I have ventured to call the new substances; and whatever changes of theory, with regard to the composition of bodies, may hereafter take place, these terms can scarcely express an error; for they may be considered as implying simply the metals produced from potash and soda. I have consulted with many of the most eminent scientific persons in this country, upon the methods of derivation, and the one I have adopted has been the one most generally approved. It is perhaps more significant than elegant. But it was not possible to found names upon specific properties not common to both; and though a name for the basis of soda might have been borrowed from the Greek, yet an analogous one could not have been applied to that of potash, for the ancients do not seem to have distinguished between the two alkalies."
  • [S]uch was his position in England at this period, that a Bakerian lecture seemed to be expected from him at each succeeding session of the Royal Society as a matter of course, and he was always ready to respond to the expectation, even if he did not invariably satisfy it.
  • On November 16th, 1809, he read his fourth Bakerian lecture. It was "On some new Electrochemical Researches on various Objects, particularly the metallic Bodies, from the Alkalies and Earths, and on some Combinations of Hydrogene."
  • He begins by again drawing attention to the various surmises which had been made respecting the true nature of potassium and sodium. Although these substances had been isolated, and in the hands of chemists for upwards of two years, their properties were so extraordinary when compared with those of the metals in general, that many philosophers hesitated to consider them as true metals.
  • Gay Lussac and Thenard... regarded them as compounds of potash or soda with hydrogen; [F. R.] Curaudau as combinations of carbon or carbon and hydrogen with the alkalis; whilst an ingenious inquirer in this country communicated to Nicholson's Journal his belief that they were really composed of oxygen and hydrogen!
  • Davy, in the light of the fuller knowledge he obtained from Gay Lussac and Thenard's paper in the "Mem. d’Arcueil"... had no difficulty in again proving "that by the operation of potassium upon ammonia, it is not a metallic body that is decompounded, but the volatile alkali, and that the hydrogen produced does not arise from the potassium, as is asserted by the French chemists, but from the ammonia."
  • M. Curaudau's hypothesis is shown to be based upon the accidental association of naphtha with the metals he employed.
  • In repeating some experiments of Ritter's, designed to show that potassium contained hydrogen, Davy was led to the discovery of telluretted hydrogen, the properties of which he describes in some detail. Tellurium at that time was regarded as a metal, but Davy points out its strong analogies to sulphur, with which element, indeed, it is now classed.
  • The paper is noteworthy for the clear distinction which is drawn for the first time between potash hydrate (potassium hydroxide of modern nomenclature) and potassium oxide, the product formed by heating the metal in ordinary oxygen.
  • There is much in the rest of the paper that is ingenious and suggestive, and not a few isolated facts that seem to have been lost sight of, or rediscovered by subsequent observers, such... as the action of potassium upon metallic iron—an action which has vitiated the attempts to determine the vapour density of that metal in iron vessels.
  • Davy clings to the belief that nitrogen will turn out to be a compound substance, and with what pertinacity he importunes it to give up its components. At times he thinks he is on the verge of proof. "I hope on Thursday,” he wrote to his friend Children, "to show you nitrogen as a complete wreck, torn to pieces in different ways." But still nitrogen, with that passive immutability which is characteristic of it, in spite of every form of torture, remained whole and indissoluble. On this point he wrote in the Laboratory Journal under date February 15th:—"Were a description... to be given of all the experiments I have made, of all the difficulties I have encountered, of the doubts that have occurred, and the hypotheses formed ——." But the sentence was not finished. The attack was renewed and continued throughout the whole of the spring and summer, until, fairly baffled, Davy confessed himself beaten, and turned his attention to other matters.
  • Davy was perfectly reckless with apparatus; with him to think was to act, and he frequently had half a dozen experiments going on simultaneously, upon disconnected parts of the same inquiry.
  • His usual method of erasure was by dipping his finger in the ink-pot; and... he was simply "Death on pens!"

Quotes about Humphry Davy, Poet and PhilosopherEdit

  • Dr. Thorpe has succeeded excellently in his endeavour to condense the somewhat diffuse biographies of Humphry Davy, written by Dr. Paris and Dr. John Davy, and to give us in moderate compass all the information concerning him that we need to remember. In doing this he has also been able to add much that is valuable, which now appears for the first time. The portrait of Davy, by Jackson, reproduced in photogravure, which forms the frontispiece to Dr. Thorpe's volume, greatly adds to the interest of Humphry Davy: Poet and Philosopher.

See alsoEdit

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