Sodio

Joe A. Vinson and William T. Grabowski
University of Scranton Scranton, Pennsylvania 18510

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Qualitative organic analysis has traditionally been a structured course for upper division chemistry majors. In m a n y schools, infrared a n d n m r analyses are now t a u g h t in t h e sophomore course and used b y students, along with w e t chemical tests. for t h e identification of unknownoreanic ; compounds. 1 t h e interest of greater safety in t h e s i i u m fusion method a n d in i m ~ t o v i n e simnlifvine the elemental and tests, we have d e v e l o p e i a newsodium ?usLon~rocedure and a new single reagent test for nitrogen and sulfur.

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organic Qualitative Analysis
An improved sodium fusion procedure and a new test for Nand S
Results and Discusion

FusionAlthough the Lassaigne procedure (1-3). commonly known as the sodium fusion test, is easy to perform, there are hazards in the use of metallic sodium: handling difficulties, instability in air, ignition of hydrogen during reaction with water, exothermic reactions with some The oreanim. and d i s m a l ~rohlems. newer calcium oxide-zinc fusion .. . procedure ( 4 ) rs less hnmrdous than sodium fusion.Nitrogen corn. puundr are converted to ammonia whrrh ~u deterted hy indicator to paper. A blank must be n m ~imultanroualy distinguish hetween a true and false positive test. False negatives result from eompounda such as 3,5-dinitrobenzoie acid and false positives result from poor technique when the fusion mixture sulatters onto the indicator Paper. The use of a lead allov with sodium in the ratio9:l is described bv Lance (5) for the decompmltian of orgames contamlog heteroelem ments. The alloy is m a dry, gmnular f o m and gives no d~ffirulty handling. It is fairly stable in air and is easily stored in a screw-capped jar. When the material is added to water, it falls to the bottom of the &ntainer eivina a non-vigorous reaction without any ignition of the hydrogen. lt i s k o m m e n d e dthat thr residues from sbdium fusion with the alloy be pooled in an open vessel and disposed of properly o in order t minimize lead pollution.

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Experimental Procedures
Sodium Fusion In a small test tuhe place about 0.5 g of sodium-lead alloy (dri-Nam from J. T. Baker Chemical Company). Clamp the tube in a vertical position and heat with a flame until the alloy melts andfumes of sodium are seen up the walls of the tuhe. Do not heat the alloy toredness. Add a few drops of liquid sample or 10 mg of solid. During addition be carefulnot to get any sample on thesides of the tuhe. Heat gently, if necessary, until the reaction is initiated; remove the flame until it subsides, then heat to redness fora minute or twoand let cool. Add 3 ml of H 2 0and heat gently for afew minutes to react the excess sodium with the water. Filter the solution, if necessary. Wash the filter paper or dilute the decanted reaction mixture with about 2 ml of water and proceed with the elemental analysis. Nitrogen

Elemental Analysis Nitrogen is the most difficult element to detect. During sodium fusion. cvanide ion is formed from the nitroeen in the oreanic eompound. cyanide ion isusually detected by tlurionmdimethylsulfmide IPNBreagentr. This reagent should he discarded if the initial yellow cdur darkens and should be stored in a brown hottle A purple color indicates nitrogen is present. A green color indicates sulfur is present. If both sulfur and nitrogen are present, only a purple color will he visible. Therefore, if a positive test for nitrogen is observed with PNB, atest for sulfur hv another method should he emoloved. The lead acetate or sodium &ro-prusside test ( 1 ) are suitadle. i f only a positive test for sulfur is observed by the present method, then nitrogen is definitely absent.
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&logen Tests
Transfer about 10 drops of the fusion solution into a test tuhe, acidify with dilute nitric acid, and boil to remove any hydrogen cyanide and hvdrozen...