It was often used in the quantitative or qualitative analysis of nitrates in agriculture and soil science before the development of ion chromatography, the predominant analysis method largely adopted worldwide today.
Devarda's alloy is a reducing agent that was commonly used in wet analytical chemistry to produce so-called nascent hydrogen under alkaline conditions in situ. In the Marsh test, used for arsenic determination, hydrogen is generated by contacting zinc powder with hydrochloric acid. So, hydrogen can be conveniently produced at low or high pH, according to the volatility of the species to be detected. Acid conditions in the Marsh test promote the fast escape of the arsine gas (AsH3), while in hyperalkaline solution, the degassing of the reduced ammonia (NH3) is greatly facilitated.
Long-debated question of the nascent hydrogen
Since the mid-19th century the existence of true nascent hydrogen has repeatedly been challenged. It was assumed by the supporters of this theory that, before two hydrogen atoms can recombine into a more stable H2 molecule, the labile H· free radicals are more reactive than molecular H2, a relatively weak reductant in the absence of a metal catalyst. Nascent hydrogen was supposed to be responsible for the reduction of arsenate or nitrate in arsine or ammonia respectively. Nowadays, isotopic evidence has closed the nascent hydrogen debate, presently considered to be a Gedanken artifact of romanticism.
^Devarda, A. (1892). "Ueber die direkte bestimmung des stickstoffs im salpeter". Chemiker Zeitung. 16: 1952.
^Devarda, A. (1894). "Eine neue methode zur bestimmung des stickstoffs im chilisalpeter". Analytical and Bioanalytical Chemistry. 33 (1): 113–114. doi:10.1007/bf01335775. S2CID 97552792.
^Devarda, A.; J. Fields (1899). "Ueber stickstoffbestimmung". Analytical and Bioanalytical Chemistry. 38 (1): 55–57. doi:10.1007/bf01386922. S2CID 197597366.
^Feigl, Fritz (1961). "Spot tests based on redox reactions with Devarda's alloy and Raney alloy". Analytical Chemistry. 33 (8): 1118–1121. doi:10.1021/ac60176a018.
^O'Deen, William A.; Lynn K. Porter (1980). "Devarda's alloy reduction of nitrate and tube diffusion of the reduced nitrogen for indophenol ammonium and nitrogen-15 determinations". Analytical Chemistry. 52 (7): 1164–1166. doi:10.1021/ac50057a044.
^Laborda, F.; Bolea, E.; Baranguan, M. T.; Castillo, J. R. (2002). "Hydride generation in analytical chemistry and nascent hydrogen: when is it going to be over?". Spectrochimica Acta Part B: Atomic Spectroscopy. 57 (4): 797–802. Bibcode:2002AcSpe..57..797L. doi:10.1016/S0584-8547(02)00010-1. ISSN 0584-8547.
^Tommasi, D. (1897). "Comment on the Note of R. Franchot entitled "Nascent Hydrogen"". The Journal of Physical Chemistry. 1 (9): 555. doi:10.1021/j150591a004. ISSN 1618-2642.