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Jo e A. Vinson I organic Qualitative Analysisand W illiam T. GrabowskiUniversity ofScranton

Scranton, Pennsylvania 18510 I An improved sodium fusion procedure and a new testfor Nan d SQualitative organic analysis has traditionally been a

structured course for upper division chemistry majors. Inmany schools, infrared and nm r analyses are now taught inthe sophomore course and used by students, along with wetchemical tests. for th e identification of unknown oreaniccompounds. 1; th e interest of greater safety in the s i i u mfusion method an d in i m~ t ov i nend simnlifvine the elementaltests,we have develo pei a newsodium ?usLon~rocedure nda new single reagent test for nitrogen and sulfur.Experimental ProceduresSodium Fusion

In a small tes t tuhe place about 0.5 g of sodium-lead alloy (dri-Namfrom J. T. Baker Chemical Company). Clamp the tube in a verticalposition and heat with a flame until the alloy melts and fumes of so-dium are seen up the walls of the tuhe. Do not heat the alloy to red-ness. Add a few drops of liquid sample or 10mg of solid. During ad -dition be carefulnot to get any sample on thesides of the tuhe. Heatgently, if necessary, until the reaction is initiated; remove the flameuntil it subsides, then heat to redness fora minute or twoand let cool.Add3 ml of H2 0and heat gently for a few minutes to react the excesssodium with the water. Filter the solution, if necessary. Wash the filterpaper or dilute the decanted reaction mixture with about 2 ml of waterand proceed with the elemental analysis.Nitrogen or Sulfur Test

I'ut ahout 10drops of the fusion solution in a small test tube andsaturate it with sohd sodium birarhonaw. Shake toensure saturationand check towe if excess solid is ur wn t. Then add 1or 2 drops of thesaturated solution (it is permissible to transfer some of thesolid so-dium bicarbonate) to a test tube containing about 20 droos of a 1%~ ~p-nitrohenzaldrhydesa>lurionmdimethylsulfmide IPNBreagentr.This reagent should he discarded if the initial yellow cdur darkensand should be stored in a brown hottle A purple color indicates ni-trogen is present. A green color indicates sulfur is present. If bothsulfur and nitrogen are present, only a purple color will he visible.Therefore, if a positive test for nitrogen is observed with PNB, a testfor sulfur hv another method should he emoloved. The lead acetateor sodium &ro-prusside test ( 1 )are suitadle. if only a positive testfor sulfur is observed by the present method, then nitrogen is def i-nitely absent.&logen Tests

Transfer about 10 drops of the fusion solution into a test tuhe, ac-idify with dilute nitric acid, and boil to remove any hydrogen cyanideand hvdrozen sulfide. Add 1droo of aqueous silver nitrate to the so-lutio'. A i h i te o yellow cloud or precipitate indicates th e presenceof chloride, bromide, or iodide. Specific tests are then necessary toidentify the halogen(s) present.

Presented ar the 169th National Meeting of the American ChemicalSociety, Chemical Education Dwision. Philadelphia, I 'ennrylvania.

Results and Discu sionFusionAlthough the Lassaigne procedure (1-3). commonly known as thesodium fusion test, is easy to perform, there are hazards in the use ofmetallic sodium: handling difficulties, instability in air, ignition ofhydrogen during reaction with water, exothermic reactions with someoreanim. and d is ma l ~rohl ems. he newer calcium oxide-zinc fusion. . . . ~~ ~ ~procedure ( 4 ) rs less hnmrdous than sodium fusion. Nitrogen corn.puundr are converted to ammonia whrrh ~u deterted hy indicatorpaper. A blank must be n m ~imultanroualyo distinguish hetweena true and false positive test. False negatives result from eompoundasuch as 3,5-dinitrobenzoie acid and false positives result from poortechnique when the fusion mixture sulatters onto the indicatorPaper.The use of a lead allov with sodium in the ratio 9:l is described bvLance (5) for the decompmltian of orgames contamlog heteroele-ments. The alloy ism a dry, gmnular fo m and gives no d~ffiru ltymhandling. It isfairly stable in air and is easily stored in a screw-cappedjar. When the material is added to water, it falls to the bot tom of the&ntainer eivina a non-vigorous reaction without any ignition of thehydrogen. lt is ko mm en de d that t hr residues from sbdium fusionwith the alloy be pooled in an open vessel and disposed of properlyin order tominimize lead pollution.Elemental Analysis

Nitrogen is the most difficult element to detect. During sodiumfusion. cvanide ion is formed from the nitroeen in the oreanic eom-pound. cyanide ion is usually detected by t

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Table 1. Dif f ic u l t Ni t rogen CompoundsDescriptionof Fusion Color and

Type Compound Reaction Ratep ~ iy n i t ro m-din i trobenzene moderate purple-rapidpic l ic acid v io lent purple-mediumALO a r o be n le n e m od er at e o u r ~ l e - r a ~ idmet hyl orange. slow, charred purple-mediumsodiu m SaltD ia zo ~ a s t l ue B moderate pink-slowFast Red Salt B fast purple-rapidAm ino Aci d phenyiaianine fast purple-rapidarpartic acid fast purple-rapidProtein bovine albumin slow purple-rapid

hemo giobi n 11ow.charred purpl e-rapi dAminonap- 4-amin o- l-nap tnalen fast p ink-s lowthalene ruif oni c acidSulfonicAcid 8-amino-3-napthaiene fast purple-slows ~ l f o n i c c idNit r i te but y l n i t r i te fast purple-rapidi~ op en ty l i t r i te fast purple-rapid

Table 2. Sulfur CompoundsComoound Co lor w i t h PNB

IUI~OI~I~CYI~Cw i d g reen2-mercatoethanol greendimethyl ru i fox ide l ight greencarbon dirulf id e dark greenthiophenol greenp-toluenerulfonic acid greenthiophene greentetrahydrothiophene-1.l.dioxide yellow green

method, was used for the analysis of difficult to detect nitrogencompounds. The results are shown in Table 1.Only in the case ofpicricaeid was thereaction violent with the sodium alloy. A lessvig-orous reaction occurred if small amounts of pierie acid were addedintermittently. Heating is necessary for those compounds with slowreactions and should be used routinely with unknowns. Color devel-ooment with P N B eaeent occurred within 15 s for all compoundsekceot the slaw reactin; ones. These took a minute or two f i r color~.formation g w n g n pmk i,r pinkish-purple rd ur wrth PNR. This ispnnbahly a conrenrmtion cfferi, i r , that rheam~unt t cyanidrformrdfrom fusion in these eases is low.Table 2 lists the sulfur compounds which were tested. All of thesecompounds reacted rapidly with the sodium alloy. The green colorwas not stable and disappeared after 5 mi". It could be reformed bythe addition of anotherdrooof fusion mixture which had been satu-rated with sodium bicarbonate.The sensitivity of the method was determined using a standard

Table 3. Representative Com pound r Given As UnknownsCo mpo und Element(s) Present

~d iph eny l th i ou rea N. Sethyl carbamate Np-bramoaniiine N. Xcoumarin nonecarbon tetrabromidebenzophenonep-nitrochiorobenzenetribenzyiamined iben ly ltetraethyl ammo nium bromide~ . t ~ l ~ e n e ~ ~ l f o n i ~cidb-ni t robenryl bromide4-amlno-l-napthaiene ru l f onic acidd imethy i ru i fox ideglycyiglycineiodb fo rm

XnoneN. XNnoneN. Xs

aqueous solution of sodium cyanide saturated with sodium bicar-bonate. One drop was added to 20 drops of P N B eagent. A brown-purple color was barely evident with 0.25 pg of cyanide. This sensi-tivity is slightly better than the benzidine test (0.5 pg) and much betterthan Prussian Blue. Hydroxide ion gives a purple color but this in-terference is eliminated by lowering the p H of the fusion mixture bysaturating with sadium bicarbonate. No interference was noted withany other anion tested.N o problems in either prmedure or identification were encounteredwith comoounds in Table 3 eiven as unknowns to a class of 150 stu-dents rf th e pnx edu reu nr tc~~'llou.edurrrrtlv. The t w o critical stepsnerwiary for good r ~ s d t cre first, suffiricnr hraring uf the sodiumalhy with the unkncnvn and second, complrtc saturation uf theaqueous filtrate with sodium hiearbonate.

SummaryThe proposed sodium allay fusion procedure is suitable for use inorganic qualitative analysis and is safer with regards to handling anddisoosal than the commonlv used sodium fusion method. The o-ni-trobenzaldehyde color tes t rs asimple, rapid, and sensitive color testfar nitrogen or sulfur.

LiteratureCitedIllCherunii. N. D. and Entriken, J. B., "SemimicroQualitafiveOqanic Analysis." 2nd Ed.,Intorscience Publishen. Inc.. Ne w York. 1957. DD.172-180.121 Pasto, D. J., and john^^. C. R.. "Orzanic Structure ~eterminstiun: ~rentiee-~sli.Inc..Eneiewood Cliffs. N.J.. 19R9.p. 916.I91 Shriner, R. L., Funm,R.C.,and Cruiin.D. Y.."TheS*rtematiclndentiflcationnforgmieCompounda,"Sth Ed.. John Wiiey andLmr. n c . New York, 1969.p. 62.141 Snyder, C. H..Sickcin,J. P.. and Del Valie. C.I.,.CHEM. EDUC..SO.72 lL973l.IS1 Lance.R. C..Barnard.A. L a n d JW,E F . .M ic ro rh rm. J.. 20, LO? ll8751.(fiJ Campheli,K. N..sndCemphell. B. K. &C HEM EDIIC..27,2SI 119501.171 Cuiihaut,G.G..and Kmmer. D.N . , A o o i .Chrm.. 38.894 119661.18) McCu1iuuph.T.i.. J.CHEM EDUC..50,656 119731.