Determination of Nitrile-Type Nitrogen with Ordinary Kjeldahl Digestion CECIL H. VANETTEN AND MARY B. WIELE h'orthern Regional Research Laboratory, Peoria, I l l .
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EARLY all published methods for the Kjeldahi tletermination of nitrogen in nitrile-type compounds specify a reducing t wntment, usually with iodide ion, before the sulfuric acid digestion of the compound. Friedrich et al. (3)considered it necessary to treat nitrile compounds with hydriodic acid in a sealed tube n t 200" C. in order to determine all the nitrogcn present. ThP!. rrIiort analyses on only one nitrile compound which rontairicd 3 nitropo group as well. The most recent work 011 use of rctluring ngents in the determination of nitrile nitrogen is that of ROPC anti Ziliotto ( 6 ) . They, however, were concernetl on1~-with a comparison of reducing agents, and reported no results on the determination without reducing treztment. Davis and Wedemart ( 2 ) were able to determine acrylonitrile nitrogen hy the ordinary Kjeldahl procedure. Sulfuric acid hydrolyzes nitriles to the corresponding a d anti aninionia ( 5 ) . Any reducing treatment, therefore, should be unnecessary in the Kjeldahl procedure. This paper present3 results obtained when nitrile-type nitrogen was determined by thr Kjeldahl procedure without preliminary reducing treatment.
gcn microdetermination.
This capillary \\as crushed under the wlfuric acid with a stirring rod. When the sample was hydrolyzed in a sealed t,ube with 90% sulfuric acid before digestion, larger capillaries were used in which 10 to 20 mg. of the sam le :ind about 0.2 rnl. of the acid were introduced. These s e a i d t u l m were heated for 1 to 2 hours a t 95" C. or held at room temIwr:tture as indicated in Table I. As was pointed out by Rose and Ziliotto (e), it was necessary t,o use concentrated sulfuric acid because loss of nitrogen sometimes occurred if dilute sulfuric acid was used. For example, when 5 ml. of water were added t o 1 ml. of acid before digestion in the determination of furonitrile and benaonitrile, over 90% of the nitrogen was lost. This was attributed to steam distillation of the compound. Six of the compounds analyzed were analytical reagent grade or I , h t m a n Xhite Label compounds. All others reported were c:ompounds prepared at this laboratory. Their purity was indicated by the Dumas nitrogen values reported or by carbon and hydrogen analyses. Aceto-, :tcrylo-, :tnd henzonitriles were retlistilled. RESULTS
Results obtained from 72 dcterrninations on 18 different nitrileAverage recovery of The micro- and semimicro-Kjeldahl procedures used were esnitrogen for the 18 compounds was 98.96%. For comparison, the sentially those described by Clark ( 1 ) except where otherwise average of 103 determinations on acetanilide (NBS S o . 141), used noted in Table I. :t- a standard over a period of years, wts 99.23% of theory (found 10.29%; theory 10.37%). As a further check on the acIn the case of the volatile liquids, the sample was weighed in n curacy and precision of the method, 22 replicate analyses were small eapillary similar t o the type used in the carbon and hydrorun on the sodium halt of cyanoacetic acid which was shown by analysis to be pure (found: carbon 33.5%, hydrogen 1.90%, sodium 21.5%, Tahle I. Nitrogen Values Obtained on Nitrile Compounds Without nitrogen by Dumas 13.0%; theory: carbon Reducing Treatment 33.6'%, hydrogen 1.877& sodium 21.5'%, nitroNitrogen b y Ordinary Kjeldahl gen 13.08%). The arithmetical average of the No. of Av. Sitrogcn deter=tmean 22 Kjeldahl analyses was 12.88%, with a stnndby Dumas. Theory, minadeviation, ard deviation of 0.11%. The arithmetical av% % Compound tiona 'ib erage of 10 analyses of the acetanilide sample Solids 13.0 13.08 S a salt of cyanoacetic acid run a t the same time as the sodium salt of cyano9.2i 9.52 Cyanobenzoic acida ... 11.95 AV-Cyanoethyl tyrosineb acetic acid was 10.27%with a standard deviation 23.1 23.20 "J-Dicyanoethyl glycine 16.6 16.65 ,V-Cyanoethyl proline of 0.08%. 17.5 17.55 iV-Dioyanoethyl aspartic acid Acrylo- and benzonitrile analyzed slightly ,.. 26.65 Tricyanoethyl histidine ... 31. 81 Tricyanoethyl amine below theory when digested directly in an ... 19.89 IGFe(CN)sb3H20C ... 25.51 I
