THE DEVELOPMENT OF THE MARSH TEST FOR ARSENIC STEWART H. WEBSTER National Institute of Health, Bethesda, Maryland
ONEHUNDRED and ten years ago Lewis Thompson associated with his name. Marsh, a practical chemist in England and C. H. Pfaff in Germany;independently a t the Royal Arsenal a t Woolwich in London, became and almost simultaneously, discovered a volatile com- the assistant to Michael Faraday upon the latter's pound of antimony and hydrogen called, first, anti- appointment to the Royal Military Academy in Decemmoniuretted hydrogen and, later on, antimony hydride ber, 1829. Marsh was an inventor in his own right, or stibine (SbHa). Within a period of five or six years having received the large silver medal and 30 guineas in following this discovery, numerous investigations of 1823 from the Society of Arts in recognition of his the physical and chemical properties of the gas were electromagnetism apparatus. Besides his electrical made, the literature carrying the names of more than 15 scientists who published their findings. This surprising interest in a gas which is so little known in our present day can be understood only in the light of an event which occurred a year earlier, in 1836. Up to this time there were no satisfactory tests for small amounts of arsenic found as an impurity in many substances used in commerce, such as steel, sulfuric acid, or drugs. The iron pyrites used as a source of the sulfuric acid made by the lead chamber process almost always contained arsenic so that, unless specially purified, the acid was likely to be contaminated xith this element. Hydrochloric acid and a multitude of other products made from impure sulfuric acid were likewise subject to arsenical impurities. It was, therefore, often necessary to make qualitative ursmic dctcrminutions. 3Iorcover, :irscnic was of ; wl~.;idrrable mdico-legal impurtance. 3lellor ( 1 . , hrlicvm thut :IS far us publisl.cd rrronls are c~~ncrrnctl. \ preparatiun> oi arsenic haw been more frrqurutly uscd ior rrirnind pu~posei ~ h a nh~i\:c any (~thcrpoisons. Most of the t ~ s t fur s a r w ~ i cwhich were in us? 1111 t u t,his time devended uvon vrecivitatina the arseliical - material in some recognizable form, thus requiring considerable time and comparatively large amounts of the material for identification. In 1775. durine his celebrated investieations on arsenic, C. W. S>heele discovered the volatile compound of arsenic and hydrogen known as arseniuretted hydrogen and, later, arsenic trihydride or arsine (AsH3). . Work was continued by other chemists, among them JAMES MARSH J. L. Proust, E. Soubeiran;J. F. Simon, and C. H. Ill-tration tak.n from W. T. Vinoent'e "Th. Record. of the Woolwich Pfaff. with arsine in A. District:' Volume I. Wodwich end Virtu. end Company. London. 1888-89, page 340 F. Gehlen died from breathinp this substance. This was the first of many accidents with this compound recorded in the literature. It appears that Scheele, and metallurgical interests, Marsh nas devoted to a who discovered and investigated the properties of both study of poisons and their effects ( 2 ) . As a result of anine and prussic acid (HCN), must have led a charmed the frequent need for arsenic analyses, he developed life to have avoided the lethal action of these toxic his novel test which depended on the fact that when compounds. arsenical material came in contact with hydrogen It remained for James Marsh (1794-1846) to make freshly liberated by the action of zinc and dilute acid, use of arsine as a basis for the test which came to be hydrogen gas containing a small amount of arsine was
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evolved. The mixed gases were then ignited and the flame was allowed to play on a cold plate of window glass, on which was then deposited a metallic mirror consisting largely of metallic arsenic. The method could be applied not only to inorganic materials but to biological substances as well, and hence could be used for toxicological and forensic purposes. In Figure 1 is shown a copy of two forms of the original Marsh apparatus, resembling a kind of Dobereiner's hydrogen lamp. These were essentially miniature Kipp generators and provided for production and storage of gas until enough had been obtained to ignite and test for the presence of arsenic.
test to be epoch-making in its importance, making all the previous methods for the evaluation of arsenic almost superfluous. It was Mohr who advocated using a porcelain plate intead of a glass plate. Liebig added his praises, emphasizing the extreme sensitivity of the test, and suggested,changes in the method to the effect that instead of allowing the hydrogen flame to impinge on a cold glass or porcelain plate, he decomposed the arsine thermally by passing it through a glass tube heated to redness. In this way the metallic arsenic could be recognized as a shining mirror on the inside of the tube. Since the arsine was decomposed as fast as it passed over the heated portion, the deposit would build up and increase with time, thus enhancing the sensitivity of the test. In addition, there was no need for violent evolution of the hydrogen. Indeed, Liebig found that this rapid action was to be avoided, since it was likely to carry particles of the solution along with the gas by entrainment. On reaching the heated portion of the tube, these foreign materials would deposit on the glass and might be misinterpreted for arsenic. Liebig saw that antimony interfered, but he failed to recognize that a volatile compound of antimony was formed under such conditions. Berzelius (11) soon brought out a modification of Marsh's method in which the hydrogen and arsine were passed through a glass tube filled with reduced copper and heated externally, whereby copper arsenide was formed. Since this material could be weighed, the procedure of Berzelius seemed to offer a great advantage z." over the merely qualitative method of Marsh and Liebig. Even though Berzelius was not able to demonstrate complete recovery of %mall amounts of arsenic by his nfodification, he remained adamant reIt is not certain whether Marsh perfected his test garding its superiority. before 1836, but he was presented with the large gold Ironically enough, as Lockemann (12,lS)has pointed medal by the Society of Arts of London on April out, the designation of the term "Marsh-Berzelius 22, 1836, for this "valuable contribution." The method" for the usual thermal decomposition method London Medical Gazette published (3) in the July 23rd is quite common but is incorrect, for it should be known issue the "Account of a new method +of separating as the "Marsh-Liebig procedure." small quantities of arsenic from substances with which Although the Marsh test was a qualitative method, i t may be mixed," by James Marsh, Esq., of the Royal it was of interest to determine the limits of its sensitivity. Arsenal, Woolwich. While this .communication ap- As practiced a t this time i t was possible to detect somepears to have been taken from Volume 51 of the So- what less than 10 micrograms of arsenic (as As) in cieties' Transactions an article by the same title ap- ' / * o ~ f the time it would requirefor large amounts by pearing in the Edinburgh New Philosophicul Journal in the usual gravimetric procedure. It is not strange, October of the same year (4) bore a note indicating that therefore, that the new method was 'so widely adopted the article was to be included in these Transactions. almost immediately. Modifications of Marsh's method soon appeared, Buchner (14)recounts that previous to the discovery era path (6) suggesting the use of a mica plate cooled of antimony hydride the textbooks of chemistry did not by water instead of the window glass which often mention such a gas nor did they state whether attempts cracked, due to the intense heat of the hydrogen flame. had been made to prepare it. Buchner and also Marsh's original article was widely reprinted, ap- Chevallier (15) observe that G. S. SBruUas, principal pearing during the following year in German in pharmacist at the Military Hospital of Metz, published Dinglers Polgtechnisches Journal (6) and from there in work in 1821 in which it appeared that he had been the Reperlorium fiil. die Pharmacie (7) and in Liebig's dealing with antimony hydride, but since the deposit Annalen der Phannan'e. (8). In the latter publication, from the decomposition was believed to be arsenic, following the article by Marsh, there were attached two he drew the erroneous conclusion that all antimony supplements, one written by F. M. Mohr (9)and the contained arsenic! other by ~ u s t u Liebig s (lo).- Mohr believed the Marsh 1t is evident that the almost simultaneous discovery
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of stibine by Thompson and Pfaff came about as a result of investigating the Marsh test. Although Thompson does not specifically state this to be the case, Pfaff mentions that he discovered stibine quite accidentally when he was testing some tartar emetic for the presence of arsenic. Unlike SBrullas, however, he investigated the deposit more carefully and realized that a new compound of antimony had been prepared. Thompson's account appeared in the London and Edinburgh Phzlosophical Magazine (16) in May, 1837, and then in the Journal fiir praktische Chemie (17 ) for the same year. Pfaff who had already worked on arsine, published his paper in the Annalen der Physik und Chemie (18). Both of these scientists understood that the Mamh test would be invalidated unless the deposit of metal could be identified as either arsenic or antimony. The result of these publications in England and on the continent produced almost electric response. Simon's account (19) of his researches on the properties of stibine appeared in 1837. This was followed by those of Vogel (20) in 1838, Marsh (21, 22) in 183-1 Capitaine (23) in 1839, Chevallier (15) in the same year, Rose (24, 26) in 184041, Lassaigne (26, W ) also in 1840-41, Jacquelain (28, 29) in 1840 and 1843, Dupasquier (30) in 1842, Brett (31) in the same year, and Meissner (52) also in 1842. Numerous commissions were appointed to investigate the status of the Marsh test, with particular reference to the medico-legal aspects. J. B. Boussingault, J. B. Dumas, H. V. Regnault, and L: J. Th6nard were assigned to this task by the Paris AcadBmie des Sciences and, after receiving advice and consultation, this commission reported in 1841 (33). The method finally recommended was the modification proposed by Liebig. Brett (51) attempted to distinguish between antimony and arsenic deposits by their appearances. Since arsine decomposed a t a higher tempe~aturethan stibine, metallic arsenic tended to be deposited a t some distance beyond the heated portion of th8 tube, while antimony was inclined to be deposited on either side of the heated zone. However, chemical methods were more useful in identifying the two elements, especially when both were present. Vogel (80) dissolved the residue in aqua regia and formed a precipitate with hydrogen sulfide, arsenic giving a golden yellow precipitate soluble in ammonia, and antimony giving an orange-red precipitate insoluble in ammonia. Realizing that his test wasnot all that he had hoped it would be, Marsh (21, 22) advocated absorbing the product from the burning gases in a drop of water suspended on the underside of a glass plate and then testing this drop with Hume's solution (ammoniacal silver nitrate) from which a yellow color due to silver arsenite was given by arsenic but more was given by antimony. Accordmg to Lockemann (34),Bischoff (36)later found it possible to separate the two elements by adding alkaline hypochlorite solution, which completely dissolved the arsenic deposit but not the antimony. This is the procedure commonly in use today.
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Search continued for a modificationof Marsh's method which would give a quantitative evaluation of these two elements. This required more than a quarter of a century for accomplishment. It appeass that Stratingh, a Dutch pharmacist, was the first to suggest the use of mercuric chloride rubbed on paper as a test for arsine (36) although the reaction between the mercury salt and the hydrides of arsenic and antimony had been known to Pfaff (18) in 1837. Mayenpon and Bergeret (37) apparently did not know of Stratingh's work and independently silggested using mercuric chloride paper to absorb arsine and stibine from a gas mixture. It was five years later, in 1879, that Gutzeit (38),discussing revisions of the German pharmacopoeia, suggested a modification of Marsh's method for determining the arsenic in hydrochloric acid. Gutzeit advocated substituting silver nitrate for the mercury salt and thus quantitatively determined the evolved arsine (39). Chemists soon recognized that other volatile hydrides, such as SbHs, H2S and H,Se, would form precipitates with silver'nitrate so that suitable modifications have continued to be devised so as to improve both the sensitivity and selectivity of the test. Oddly enough, although the great toxicity of arsine was soon recognized after its discovery in 1775, the similarly high toxicity of stibme apparently escaped recognition for many years after the physical and chemical properties had been investigated. Even in 1859 we 6nd Hannon (40,4l) recommending its use in pneumonia and in certain other respiratory diseases. Stock (42) has pointed out that the only reasonable explanation for this strange situation can be laid to the fact that in so maqy cases the investigators were dealing with impure mixtures containing only a very small percentage of stibine. Indeed, it was not until 1901, 64 years after its discovery, that Stock and his coworkers (@) first succeeded in producing the gas in a pure condition. Adequate investigation of its toxic properties was not carried out until more than a century had elasped The discovery of new compounds has frequently resulted from the search for sources of impurities and interference. One of the most interesting cases of this was the development of the test for arsenic by James Marsh over a century ago. Although chemistry has advanced tremendously since that time, the analysis of mixtures containing small quantities of volatile hydrides is not yet satisfactory. In the continuing search for better and more sensitive methods, the historical background should serve not merely to acquaint us with previous mistakes and achievements, but to indicate the challenging possibilities of further knowledge offered by these complications and interferences.
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LITERATURE CITED (1) MELLOR, J. W., "A Comprehensive Treatise on Inorganic and Theoretical Chemistry," Vol. IX, Longmans, Green, and Company, London, 1922-37, p. 42. (2) "Dictionary of National Biography," Oxford University Press, London, Vol. 12, 1921-22, p. 1100. (3) M a ~ s aJ., , London Med. Gaz., 18, 6 5 0 4 (1836).
MARSH,J., Edinburgh Nezu Phil. J., 21,229-36 (1836). HERAPATH, W. B.. Mag. Pop. Seiace. 2,37140 (1836). MARSH,J., D i n g h Polytech. J., 63,44&54 (1837). J., Repert. Pharm., [2] 9, 220-33 (1837). MARSH, MARSH, J., Ann. Phmm., 23, 207-16 (1837). MOHR,F. M., ibid., 23,217-23 (1837). LIERIG,J., ibid., 23, 225-37 (1837). J., Ann. Physik Chem., I21 42, 159-63 (1837). BERZELIUS, G., Z. angew. Chem., 18,416-29 (1905). LOCKEMIINN, LOCKDMANN, G., Chem. Zt., 36,14654 (1912). Buc~Nea,L. A,, Repert. Pharm., [2] 13,245-55 (1838). A,, J. chim..mdd., 121 5,355-8 (1839). CHEVALLIER, L.,Phil. Mag., 131 10,353-550837). THOMPSON, L., J. prakt. Chem., [91 11, 369-71 (1837). THOMPSON, PFAFF,C. H., Ann. Physik Chem., (21 42, 3 3 M 7 (1837). J. F., ibid., [21 42, 563-71 (1837). SIMON, VOGEL, A,, J. p d t . Chem., 13, 55-60 (1838). MARSH, J., Phil. Mag., [3] 15, 28% (1839). J., ibid., [31 18, 442-3 (1841). MARSH, H., J. pharm. chim., [2] 25, 516-25 (1839). CAPITAINE, ROSE,H., Ann. Physik Chem., I21 51,423-7 (1840). ROSE,H., Ann., 37, 33941 (1841).
LAS~AIGNE, J. L., J. ehim. d d . [2] 6,63841 (1840). J. L., ibid., [2] 7, 440-4 (1841). LASSAIGNE, V. A,. Packet deposited by him on October JACQUELAIN, 19, 1840. V. A,, Compt. rend., 16.28-31 (1843). JACQUELAIN, A,, ibid., 14, 51.14 (1842). DUPASQUIER, BRET~, R. H., Phil. Mag., [3] 20,403-8 (1842). MEISSNER, W., J. prakt. Chem., 25,243-6 (1842). Compt. rend., 12, 1076-1109 (1841). G., Pharm. Zt., 81,1127-30 (1936). LOCKEMANN, Pharm. Zentr., 11, 419 (1840). BISCHOPF, VAN DER WIELEN, P., Pharm. Weekblad, 73, 1395 (1936). rend., 79, 118-21 (1874). MAYENGONAND B E R ~ R ECompt. T, GUTZEIT, H., Pharm. Zt., 24,2634 (1879). CROSSLEY, H. E., J.Soe. Chem. I d . , 55,272T-276T (1936); and ARNAUD, F. W. F., Analyst, 61,757 (1936). J. D., Prase mdd. Belge, 11, 359-60 (1859). HANNON, J. D., Chem. News, 1, 94-5 (1860). HANNON, Ber., 37, 893 (1904). STOCK, A,, AND 0. GUTTMANN, STOCK, A,, AND W. DOHT,ibid., 34,233944 (1901). WEBSTER, S. H., J. Id. Hyg., 28, 177 (1946).
