M. Carey Lea, Chemist, 1823-1897 EDGAR FAHS SMITH
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The peroxide of manganese (Mn203 has never been investiHUNDRED years ago (1823), Matthew Carey Lea was born. His contributions to chemistry gated, as its existence has, until lately, been questioned by same of the first chemists in Europe, and the tendency of its salts to brought him honor and distinction among his colleagues convert themselves into proto-salts. contributed to render it throughout the world, so that pause may well be made problematical whether it was not merely the protoxide disguised. to let them pass in brief review. Few chemists of his Intempting this digression, it may be temarked day knew him personally; in fact, students of chemistry in this country would probably not give his name if that when Carey Lea finally left the Booth, Garrett, called upon for a list of American scientific worthies, and Blair laboratory i t was to enter a private laborahence a brief consideration of his achievements will be tory installed in his home a t Chestnut Hill. There in order. They will augment our pride in the men nearly all his later experimental work was done. But who wrought in chemistry before these very modern the notebooks of that work were, upon his death, dedays when, on all sides, there is heard a demand for stroyed in accordance with his own desire. Among research, forgetting that the past in chemistry, even these was a list, preserved from boyhood, of the in this country, can present many excellent examples of chemicals and apparatus imported by his father for earnest devotion to the purely scientific aspects of his use. chemistry. Lea showed a decided penchant for chemical theory. Carey Lea (as he was usually called) was a true He was much concerned about the chemical properties researcher. His first study, published in 1841, related of atoms and their numerical relations, undertaking to to the Southern Coal Field of Pennsylvania. His show "that the number of 44.45 plays an important father had expressed the thought that "the hard or part in the science of stoichiometry, and that the relahighly carbonized anthracite of the eastern end of the tions which depend upon it are supported, in some Southern coal field changes to bituminous in the west- cases a t least, in a remarkable manner, by analogies of ern end by nearly regular gradations." The results atomic volume." This relation was found to extend obtained by Carey Lea showed "that the bituminous to no less than 48 of the elements. The first germs of qualities of the coal increase with considerable regu- the periodic law, not, however, clearly enunciated, larity from Tamaqua (the easternmost end) to Rattlmg were in his thoughts. And in 1875 and 1876 he published two ingenious papers on the color relations of Run (the westernmost extremity)." Lea did this work when he was but 18 years old, in ions, atoms, and molecules. As early as 1858 Lea became interested in picric the laboratory of Booth, Garrett, and Blair, where he had gone to familiarize himself with practical chemistry. acid, giving a new method for its preparation and also He loved scientific pursuits. He never went to school descriptions of many new salts including the urea and or college. His remarkable training was "through the quinine picrates. He concluded that pic& acid was best private tutors procurable." His intellectual wholly unreliable as a test for potash, and, indeed, a powers were immense. He knew literature, math- better test for soda. Shortly after the beginning of the Civil War he ematics, languages, and the natural and physical advised the United States Government that picric acid sciences. After his &st venture into experimental chemistry would be an explosive of greater power than black he gave himself to the study of law, and was admitted powder. Its smokelessness appealed to him as an to the bar in 1847, a t the age of 24. But this profession advantage. The federal government, however, failed he abandoned and journeyed to Europe, hoping to to appreciate the importance of using an explosive regain his health which had become precarious. How- outranging anything in use a t the time, and i t was ever, his hopes were not realized, and he returned to not until 50 years after that high explosives on a the old laboratory on Arch Street (Booth, Garrett, and picric acid basis were adopted. To separate the ethylamines Lea recommended the Blair) with the view of perfecting - himself still further use of their piuates: triethylamine picrate being in chemistry. In his earlier days in the Booth, Garrett, and Blair extremely insoluble, diethylamine extremely soluble and ethylamine intermediate. He gave some considerlaboratorv. ,. he had as fellow student in chemistrv his brother, Henry Charles Lea, who later in life was ation to the methyl bases and the preparation of urearegarded as the first and greatest of modern scientific with good and definite results. By the interaction of historians. He was the author of 17 volumes on naphthylamine and sulfuric acid he obtained ionaphMediaeval History and Law. And this same younger t h i n e a new coloring matter. On dropping a bit of brother, a t the age of 12 years, was busily engaged gelatine into a mercuric nitrate solution the latter gradin a study of manganic oxide, the results appearing ually assumed a deep red coloration+ new and valuin May, 1841, in the American Journal of Science. able test for gelatine. Lea did not regard as reliable The paper is interesting and valuable. Few chemists, the determination of the melting point of methyl oxalate a t the age of 16, have ventured forth with such an as a means of ascertaining the purity,of methyl alcohol excellent production. He began: (containing ethyl alcohol). For the detection of prussic 57'7
acid he suggested the addition of a ferrous salt containing a little uranic nitrate, when a beautiful purple colored precipitate was formed. A great increase of delicacy in the reaction between starch and iodine was observed by Lea on adding chromic acid to the solution. He also wrote on a new method of determining the relative affinities of certain acids, which was based on the amount of base which it can retain in the presence of a strong acid selected as a standard of comparison for all acids. Two new methods were proposed by Lea for the reduction of platinic to platinous chloride-ne by the action of potassium sulfite, the other by that of alkali hypophosphites. He also demonstrated that a solution of iodoquinine affords a means of detecting free sulfuric acid, even in traces, in presence of combined sulfuric acid. In a collection of miscellaneous pamphlets, once the property of Carey Lea, are several contributions of Carl Claus on "Chemie der platinmetalle" fully annotated in the marginal way, thus revealing that Lea had more than ordinary interest in this very important group. He studied its members with care, using material furnished bv his former teacher.. Tames Curtis Booth. Among the new facts disclosed by him is the
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use of oxalic acid for the h s t time in purifying ammonium iridium chloride, and the discovery of a reaction for ruthenium which proved most helpful. If to a solution of sodium hyposulfite there be mixed ammonia and a few drops of ruthenium sesquichloride, a magnificent red-purple liquid will be produced, which, unless quite dilute, will be black by transmitted light. The chief value of this test was found to lie in the fact that it is capable of detecting ruthenium in tae presence of iridium. Lea thought it valuable in testing the purity of iridium for "if the suspected iridium salt be boiled with hydrochloric acid and ammonia added until the liquid assumes a pale olive color, then, on adding the hyposnlfite and boiling, any increase of color indicates the presence of impurity. If the liquid acquires a red color, ruthenium is present; if a wine color, platinum is probably present, and if brown, palladium is indicated.'' Lea applied ruthenium sesquichloride to detect sodium hyposulfite. An adequate idea of Lea's voluminous work, as investigator, cannot be given in a narrow compass, such as this article. The student should turn to the pages of the American Journal of Science, beginning with the year 1858 and read forward to the year 1897, then some deduction may be drawn of the vastness of Lea's labors. These papers deserve very careful study. There is such an abundance of originality in them. In the volume of the Chemical News for 1862 will also be found four additional contributions. A review of all this material would furnish many topics for seminar consideration. But the greatest of all Lea's efforts to extend the borders of human knowledge are those dealing with the chemistry of light; for in photochemistry he was a true pioneer. He blazed the way. Quite early in his l i e the startling invention of photography from the hands of Daguerre drew his most thoughtful attention. He saw its enormous possibilities and promptly began a fundamental study of its chemistry, also its physics, and its practical value. From this study came the only book he ever wrote, entitled "Photography." It passed through two editions and was everywhere regarded as standard. Its perusal reveals the masterful mind which prepared it. It is absolutely scientific in its discussion of the problems of photography. But, foreign scientists were first in recognizing the value of Lea's efforts in this new field. They declared them to have a lasting, permanent value, in scientific photography, and that they were all fundamentally important in physicochemical research. Indeed, these researches were genuine classics. For colloid chemistry they possessed an ever increasing interest and value. Lea's "colloid silver" and "photohaloids" were translated and heralded abroad as epoch-making studies. Perhaps it is somewhat of a reflection upon American chemists that the importance of these studies was first emphasized by foreign chemists. However, other American laborers in the field of chemistry had their remarkable discoveries DaSS unnoticed, until attention was drawn to them by the regard in which they were
held by coworkers in other lands, as for exampleJ. Willard Gibbs and his phase rule, Robert Hare and his classic work on the electric furnace, and others. To be the discoverer of the amorphous forms of silver is no mean distinction. When these come under the eye of chemists enthusiasm is immediately kindled, and there arises an inquiry as to their discoverer. As remarked, few chemists knew Lea personally. He was a recluse in a certain sense, for he rarely appeared in the company of scientists or other groups of men. Quietly, unostentatiously, he iabored on very independently, until his contributions to purely photographic subjects reached the number of 300, to be found on the pages of the English and American journals devoted to this subject, while no less than a hundred papers devoted to more special chemical matters are found on the pages of the American Journal of Science, to which reference has already been made. In addition to his numerous chemical papers Lea published many others in the domain of physics. He further elaborated certain pieces of apparatus which proved helpful in laboratory work. And thus the course of his scientific endeavor proceeded, for he was a most industrious worker in all regions of his favorite science. He was a very acute observer. He knew the literature of chemistry, both past and present. He had an intense
love of truth. He always had in hand the facts upon which he based expressed opinions. His opinion was recognized as the final opinion in photographic chemistry both in this country and in Europe. He was likewise devoted to literature, the classics, and art. For one so eminent in his science he belonged to few scientific organizations&z., the Franklin Institute and the National Academy of Sciences, to which he was elected in 1895. An accident in his laboratory, in early life, so seriously injured one of his eyes that it eventually was removed. His devoted wife read to him for many years so that he was able to keep up his interest in the current work of scholars at home and abroad. Carey Lea was the son of Isaac Lea, a distinguished naturalist, who served as president of the Academy of Natural Sciences in Philadelphia, and of the American Association for the Advancement of Science. It was an old Quaker family into which Carey Lea was born August 18, 1823. He was married twice, first to his cousin, Elizabeth Lea Jaudon, and after her death to Eva Lovering. Carey Lea died March 15,1897. The various apparatus owned by Lea was bequeathed to the Franklin Institute in Philadelphia. The life story of Lea is most interesting. He was, indeed, a bright star in the chemical firmament of America!
