The Chemistry of Sherlock Holmes

By Louise Haskett


“Our chambers are always full of chemicals.” “He is a first-class chemist.” “The chemical corner” and “the acid-charred bench of chemicals.” “His hands were invariably . . . stained with chemicals.” These few brief references to the chemical practices of Sherlock Holmes are only a sample of the abundant quotations to be found throughout the sixty stories of the world’s most famous consulting detective. And his interests were not merely limited to that one subject. “[He is] an enthusiast in some branches of science . . . He appears to have a passion for definite and exact knowledge.” It was this passion for overall scientific and forensic comprehension that led Holmes into unusual analyses and made him a 19th Century “Renaissance man” — an expert specializing in everything.

            Due to the quantity of controversy surrounding him, it is exceedingly interesting to examine a few of Sherlock Holmes’ chemical activities that are explicitly described in the stories, to give the opinions of the experts and critics on the accuracy of these activities, and to show how Holmes was an early pioneer in the development of scientific crime detection.

            In certain instances, Dr. John H. Watson, narrator of the stories, gives detailed descriptions of Sherlock and his experiments:


                        Holmes was . . . working hard over a chemical investigation. A large curved

                        retort was boiling furiously over the bluish flame of a Bunsen burner, and

                        the distilled drops were condensing into a two-litre measure. . . . He dipped

                        into this bottle or that, drawing out a few drops of each with his glass pipette,

                        and finally brought a test-tube containing a solution over to the table. In his

                        right hand he had a slip of litmus-paper

                                    “You come at a crisis, Watson,” said he. “If this paper remains blue, all

                        is well. If it turns red, it means a man’s life.” He dipped it into the test-tube, and

                        it flushed at once into a dull, dirty crimson.


            At other times, references are quite vague and misleading. For example, Holmes relates, “I spent some months in a research into the coal-tar derivatives, which I conducted in a laboratory at Montpelier, in the South of France.” Critics argue that in 1894 (the year of which Sherlock is speaking) there was nothing revolutionary to be investigated in coal-tar derivatives; and besides, Germany was the dominant location for such procedures prior to World War I, not France. The reference thus becomes so clouded that meaningful interpretation is extremely difficult.

            In addition to out-and-out chemical experiments, the Canon includes more than a dozen mentions of poisons — toxicology being an important part of criminal investigation. Sherlock readily connected his chemical interest and ability with analysis of poisons. One interesting, even exotic, example is that of radix pedis diaboli (or “devil’s-foot root”), a West African root-extract used as an ordeal poison. The entire story of a drug that produces such bizarre results has been considerably ridiculed until the relatively recent development of a synthetic compound named lysergic acid diethylamide or, commonly, LSD. The hallucinatory effects are almost exactly those of the root powder. Since LSD is prepared from a natural alkaloid, it is conceivable to assume that such a compound could exist in an as yet unidentified root.

            Another question dealing with poison involves pills supposedly prepared from “South American arrow poison . . . so powerful that the least grain meant instant death.” Controversy has arisen that curare, the most conventional of such poisons, does not result in symptoms identical to those of the murdered man. Therefore, nicotine has been suggested as one possibility. Another choice of one of the erythrina alkaloids. A third possibility is that the reference is to a South American ordeal poison — either physostigmine or eserine. “This is highly potent, readily absorbed by the mouth, and the victim remains conscious nearly to the time of death; all the facts are consistent with [the story’s] account,” says Dr. George B. Koelle.

            The first science to be used in criminal investigation was forensic medicine, or autopsy. According to Charles Sannie, “It is even more necessary to employ scientific methods in cases of poisoning, for it is obvious that a ‘chemical crime’ is directly connected with chemical methods.” Sherlock Holmes dealt with synthetic poisons and natural products from the animal, vegetable, and bacteriological realms. These embrace opium, the Portuguese man-of-war, chloroform, the possible oriental plague bacilli, vitriol (sulfuric acid), and potassium cyanide (prussic acid). Holmes’ knowledge of toxicology in all of its forms is definitely tested to its limits throughout the stories.

            To return to more conventional chemistry, the following exchange appears in “A Case of Identity”:


                                    I found Sherlock Holmes alone, however, half-asleep . . . A formidable

                        array of bottles and test-tubes, with the pungent cleanly smell of hydrochloric

                        acid, told me that he had spent his day in the chemical work which was so dear

                        to him.

                                    “Well, have you solved it?” I asked as I entered.

                                    “Yes. It was the bisulphate of baryta.”

                                    “No, no, the mystery!” I cried.


“Barium bisulfate does not exist . . .” wrote one professor (Dr. Remsen T. Schenck). He was countered by another Sherlockian student (L.S. Holstein) with: “A reference to Mellor’s Inorganic Chemistry (Vol. III, p. 784) — a universally recognized authority — will elicit the information that the bisulfate does exist; and, in addition, Mellor states its known properties . . .” The editors of the Catalogue of the Sherlock Holmes Exhibition wrote: “Barium Hydrogen Sulphate (Bisulphate of baryta) [is a] substance . . . first prepared by J.J. Berzelius in 1843 . . . It is decomposed by water . . . Apart from some doubt as to its precise structure, the compound is of little interest, and has never been more than a chemical curiosity.” Of course, it is possible that Holmes simplified his account of the actual experiment in his remark to Dr. Watson. “There is no stable bisulphate of baryta,” according to D.A. Redmond, because “barium and the sulphate ion are both divalent: BaSO4 is the formula.” From this fact, it is obvious that no simple salt is under consideration. Barium hydrosulfate can be produced from barium sulfate in concentrated sulfuric acid. This is BaSO4 H2SO4 and decomposes in water or alcohol. However, Watson did not refer to sulfuric acid. Trying a different approach, analyses of barium compounds are frequently dissolved away from fused masses of carbonates by hydrochloric acid. This must be the “pungent cleanly smell.” Mr. Redmond further expands with the possibilities of the large family of barium-sulfur compounds ranging from the acid sulfide, Ba(SH)2, to the double salts, e.g. Ba(OH)2(SH)2. Perhaps Sherlock was doing a quantitative analysis on such a salt.

            An even more interesting speculation is that the compound was, in fact, the same substance used in The Hound of the Baskervilles to create the horrible hound’s “huge jaw . . . dripping with a bluish flame.” Bologna phosphorus (in actuality, barium sulfide) shines luminously with a bright golden light. Had this been what Sherlock was analyzing, he may have discovered his unknown to be the hexasulfide of acetone. “Then perhaps I had better postpone my analysis of the acetones,” Holmes once remarked to Watson. A clear pattern develops in all of Holmes’ extended research! One wonders if those familiar “coal-tar derivatives” fit into the same scheme as well.

            Possibly the most well-remembered of all Sherlock Holmes’ experiments comes in the opening story, A Study in Scarlet:


                                    “I’ve found it! I’ve found it,” he shouted to my companion, running

                        towards us with a test-tube in his hand. “I have found a reagent which is

                        precipitated by haemogloblin, and by nothing else.” Had he discovered a gold

                        mine, greater delight could not have shone upon his features . . . “It is the most

                        practical medico-legal discovery for years, [he said] . . . Now I add this small

                        quantity of blood to a litre of water.” . . . As he spoke, he threw into the vessel

                        a few white crystals, and then added some drops of a transparent fluid. In an

                        instant the contents assumed a dull mahogany colour, and a brownish dust was

                        precipitated to the bottom of the glass jar.


While some critics (Professor Schenck again, for one) claim, “this can be neither of the known methods for the detection of blood,” a test for blood as early as 1853 resulted in brownish crystals. Also Sonnenschein’s test (1872) treated a suspected bloodstain with tungstate of sodium and acetic acid creating a “voluminous reddish-brown or chocolate coloured precipitate if blood be present.” The Sherlock Holmes test was most likely of this type.

            It was in the years immediately following Homes’ discovery that additional tests were developed for the identification of human blood as distinguished from animal blood. In 1900, Karl Landsteiner began his work on the separation of unique blood groups. This is now universally used in disputed parentage cases as well as criminal investigations. Blood group determinations are also used in serology — the identification of blood, seminal, saliva, and, occasionally, other body fluid stains.

            The modern approach to criminalistics would be barely recognizable to Sherlock Holmes. But there is no doubt that he can be considered a major forerunner of modern day forensic chemistry. “The development of the science of police work is comparatively recent. The scientific method was exploited in fiction, notably by Conan Doyle’s masterly creation, Sherlock Holmes, as early as the latter 19th Century,” said Ralph F. Turner. Modern techniques are practically limitless, but few escape some parallelism with Holmes’ work. For instance, microscopy in laboratory analysis is especially important. “The Adventure of Shocombe Old Place” opens with a double emphasis on this method of investigation:


                        Sherlock Holmes had been bending for a long time over a low-power microscope.

                        Now he straightened himself up and looked around at me in triumph.

                                    “It is glue, Watson,” said he . . . “Those hairs are threads from a tweed

                        coat. The irregular grey masses are dust. There are epithelial scales on the left.

                        Those brown blobs in the centre are undoubtedly glue . . . Since I ran down that

                        coiner by the zinc and copper fillings in the seam of his cuff, they [Scotland Yard]

                        have begun to realize the importance of the microscope.”


Of course, today the aids of photography and spectroscopy have added immeasurably to the capabilities of microscopic analysis and so-called applied optics.

            Another field in scientific crime detection is the examination of written documents. Here one finds Holmes “engaged with a powerful lens deciphering the remains of the original inscription upon a palimpsest.” Valuable fragments of ancient literature, as well as recent writings, have been recovered in manuscripts by the use of chemical reagents; and Holmes was almost certainly making use of his chemical corner in this instance. Today, both infrared and ultraviolet light may be employed in this same operation.

            The scientific (and especially criminal) investigation of crime has overwhelmingly progressed from the nostalgic Victorian world of Sherlock Holmes. But this cannot detract in the least from the great analytical abilities of the Master Detective. The perpetuation of science and the elimination of crime were his sole aims. Who else would go so far as “beating the subjects in the dissecting rooms with a stick . . . to verify how far bruises may be produced after death”? Or who else would elicit such a comment as: “I could imagine his giving a friend a little pinch of the latest vegetable alkaloid, not out of malevolence, you understand, but simply out of a spirit of inquiry in order to have an accurate idea of the effects. To do him justice, I think he would take it himself with the same readiness.”

            His curiosity achieved results: His scientific talents ranged from mineralogy to medicine. Yet there was one more scientific field in which Holmes more than excelled. In a list of Sherlock’s abilities and limitations, Watson was obliged to write: “7. Knowledge of Chemistry — Profound.” That was Sherlock Holmes.



Major Sources


Baring-Gould, William S., The Annotated Sherlock Holmes, 2 vols. New York: Clarkson N. Potter, 1967.


Clark, John D., “A Chemist’s View of Canonical Chemistry,” The Baker Street Journal, Sept. 1964; p. 153-155.


Fitzgerald, Maurice J., Handbook of Criminal Investigation. New York: Arco Publishing Co., 1969; p. 34-42; 191-197.


Hendrickson, J. Raymond, “De Re Pharmaca,” Leaves from the Copper Beeches. Narberth, Pa.: Livingston Publishing Co., 1959; p. 11-14.


Koelle, George B., “The Poisons of the Canon,” Leaves from the Copper Beeches. Narberth, Pa.: Livingston Publishing Co., 1959; p. 91-96.


O’Hara, Charles E., and Osterburg, James W., An Introduction to Criminalistics. New York: The MacMillan Co., 1949; p. 349-424.


Redmond, D.A., “Some Chemical Problems in the Canon,” The Baker Street Journal, Sept. 1964; p. 145-152.


Rhodes, Henry T.F., Forensic Chemistry. New York: Chemical Publishing Co., 1940; p. 53-66.


Sannie, Charles, “The Scientific Detection of Crime,” The Annual Report of the Board of Regents of the Smithsonian Institution, 1954; p. 337-361.


Other References


Andresen, Povl H., The Human Blood Groups. Springfield, Ill.: Charles C. Thomas Publisher, 1952; p. 91-100.


Brooks, Benjamin T., The Chemistry of Petroleum Hydrocarbons. New York: Reinhold Publishing Corporation, 1954.


Fisher, Jacob. Faces of Deceit. New York: Carlton Press, 1963; p. 201-225.


Hoover, J. Edgar, “Physical Science in the Crime-Detection Laboratory,” Annual Report of the Board of Regents of the Smithsonian Institution, 1939; p. 215-222.


Snyder, Laurence H., Blood Grouping in Relation to Clinical and Legal Medicine; p. 191.


Turner, Ralph F., Forensic Science and Laboratory Technics. Springfield, Ill.: Charles C. Thomas, Publisher, 1949; p. ix-xi; 48; 131-179.


Wilson, Philip J., Jr., Coal, Coke, and Coal Chemicals. New York: McGraw-Hill, 1950; p. 91-92.


[Editor’s Note: This excellent article by Hated Rival Louise Haskett first appeared in the book Clients’ Case-Notes, edited by Brian MacDonald, in 1983. It has been out of print for most of the ensuing two decades, and we are proud to reproduce it here for a new generation of Sherlockians. If you have any comments or questions for Louise, please contact her care of this Web site. (See our Contacts page.)]