ACKNOWLEDGMENT
The authors thank mrilliam H. Chief of the xeurosurgical Service a t the Massachusetts General Hospital, for his interest and encouragement. The technical assistance of Beverly Whitman is gratefully acknowledged. LITERATURE CITED
( 1 ) Berger, K. C., Truog, E., IND.ENG. CHEM.,ANAL.ED.11, 540 (1939). ( 2 ) Ellis, G. H., Zook, E. G., Baudisch, O., ASAL. CHEM.21, 1345 (1949).
( 3 ) Faut,h, M. I., McSerney, C. F., Ibid., 32, 91 (1960). ( 4 ) Hill, W, H,, Johnston, hf, S,,Merrill, J. A I . , Palm, B. J., ,4m. Ind. H y g . Assoc. J . 21, 312 (1960).
( 9 ) Sweet, W. H., Soloway, A. H., Wright, R. L., J . Pharm. E@. Therap. 137, 263 (1962).
A . H. SOLOWAY J. R. ~ I E S S E R Neurosurgical Service of the ( 5 ~ , H ~ , I " , ~ H ~ ~ , ~ i ~ Massachusetts ~ ~ , ~ General Hospital 1,, 124 (1958), Mass' (6) McDcugall, D., Biggs, 11. A . , AKAL. This work was supported by a grant from CHEM.2 4 , 5 6 6 (1952). ( 7 ) Pfitzer, E. A , , Seals, J. hl., Am. Ind. the C . S. Atomic Energy Commission Hyg.Assoc. J . 20, 392 (1959). under contract No. AT(30-1) 1093 and by (8) Soloway, A. H., Wright, R. L., the National Cancer Institute, U. S. Messer, J. R., J.Pharm. Ezpt2. Therap. Public Health Service Grant, No. '2-3174 134, 117 (1961). Rad.
72;hF:2yi
Direct Method for the Determination of Organic Carbon in Sediments SIR: A means of identifying a source rock and assigning a relative value as a source rock to sediments has been reported by Philippi ( 3 ) . Identification is dependent upon differentiating between indigenous and migrated oil. The total organic matter and the extractable hydrocarbon content in sediments are used as the criteria for this differentiation. Assignment of a relative value as a source rock is based on the extractable hydrocarbon content. The determination of the total organic matter in sediments mould be a difficult task and can not be handled well on a routine basis. A reasonable substitute for the total organic content would be the total organic carbon content. Methods for the determination of carbon depend upon oxidation of carbon to carbon dioude and subsequent measurement of the carbon dioxide produced. Methods reported in the literature are primarily concerned with the total carbon in organic compounds (4, ?) or the carbon in steel (6, 8). The most generally used procedure to oxidize carbon to carbon dioxide is by combustion in an osygen atmosphere. The carbon dioxide is generally measured by either the volume or the weight of gas
Table 1.
produced. The measurement of the total carbon in soil is usually done by a dichromate oxidation of the carbon follon ed by weighing the carbon dioxide produced (1, 5 ) . Sediments contain varying amounts of inorganic carbonates that will decompose with either heat or acid to yield carbon dioxide. The carbon dioxide from the carbonates will be measured with the carbon dioxide from the organic matter. The determination of organic carbon then becomes a twostep process: first the determination of total carbon, then the determination of carbonate or inorganic carbon, the difference representing the amount of organic carbon present in the sample. Frequently the amount of organic carbon will be small relative to the carbonate carbon. This is an undesirable situation because the final result is a small number obtained by subtracting one large number from another large number. Frost ( 2 ) proposed the use of hydrofluoric acid and then nitric acid to remove carbonate minerals, sulfides, and most of the silicate and clay minerals prior to the determination of organic
EXPERIMENTAL
Methods of Analysis. For both methods the samples were ground to -100 mesh and dried for 2 hours a t 110' C. before samples were weighed for analysis. Carbon dioxide was removed from the oxygen and nitrogen sweep gases by the use of ascarite. Direct Organic Carbon. One gram samples were accurately weighed and transferred to 250-ml. beakers, and 100 ml. of 15% hydrochloric acid (by volume) was carefully added to the sample. The sample was allowed to stand a t room temperature for 24 hours. After the acid treatment, the sample was filtered through a Gooch crucible containing about 0.25 gram of asbestos. The sample was washed and then dried for 2 hours at 110" C. The sample was then transferred to a combustion
Comparison of Direct and Indirect Methods for Organic Carbon
Carbon. % -. Indirect CarDirect, Total bonate Organic Organic I
Sample Argillaceous limestone 9 70 9 15 ( S B S la). 0 18 Gray shale 1 1 24 0 28 0 00 Green shale 0 53 6 33 Gray shale 2 4 52 1 40 Black shale a Sational Bureau of Standards sample la carbon 0 63SC
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carbon. I n this manner, the organi carbon can be determined directly. The modification proposed here is the removal of the carbonate carbon by the use of hydrochloric acid so that the organic carbon can be determined directly. This direct procedure is compared with the indirect, two-step procedure consisting of separate determinations for total carbon and carbonate carbon.
ANALYTICAL CHEMISTRY
"
0 55 1 06 0 28 5 80 3 12
0 1 0 5 3
64 06 23 76 21
Average organic
Table II. Standard Deviation and Relative Standard Deviation for Direct and Indirect Carbon Methods
Direct Sample Argillaceous limestone Gray shale 1 Green shale Gravshale 2 BlaEk shale
Carbon,
%
0 64 1 06
0 23 5 76 3 21
Std. dev. 1 0 021 f O 040 f 0 019 f O 083 zk0 083
Indirect Rel. std. dev.
Carbon,
3 3 8 1 2
0 1 0 5
28 i7
23 44 59
C/o
55 06 28 80 3 12
Std. dev. f0 031 *(I 056 1 0 024 f O 103 1 0 112
Rel. std. dev. 5 5 8 1 3
64 28 57 78 59
boat and ignited at 900” C. for 0.5 hour in a tube furnace with an oxygen flow of 100 ml. per minut(,. The carbon dioxide produced was absorbed on ascarite and weighed. FTater was removed with magnesium perchlorate and sulfur oxides were removed by potassium dichromate in sulfuric acid. 1 blank was determined. Total Carbon. Organic and Carbonate Carbon. This method is similar to the direct organic carbon method. There is no acid treatment; the sample is dried, xeighed, and then ignited a t 1120” C. rather than 900” C. The increased temperature is needed for the complrte decomposition of carbonates. Carbonate Carbon. The carbon dioxide was produved by acid decomposition of the carbonates. T h e samplrs ucre heated a t 75” C. for 2 hours in contact with 50% (by volume) phoiphoric arid. T h e carbon dioxide produced was absorbed on ascarite and weigkied. K a t e r was removcd before the ascarite by magnesium perchlorate. Sitrogen was
used t o flush t h e reaction bottle and transfer the carbon dioxide. RESULTS
Five samples were used to compare the two methods for organic carbon. With the exception of the argillaceous limestone, the samples were all obtained from oil well cores. Each sample was analyzed by each method a minimum of six times and the results shown in Table I are averages. There is very little difference in the results obtained by both methods. The principal advantage of the direct carbon method is in the determination of small amounts of organic carbon in the presence of large amounts of carbonate carbon. The standard deviation and the relative standard deviation were calculated for both methods. These results are given in Table 11. The standard deviation is higher for the indirect carbon method because of the two methods required to obtain the organic carbon.
LITERATURE CITED
(1) B e y , Firman E., “Chemistry of the
Soil, pp. 328-31, Reinhold, New York, 1955. (2) Frost, I. C., paper 217, U. S. Geological Survey professional Paper 400-B, p. 480-3, 1960. (3) Philippi, G. T., “Identification of Source Beds by Chemical Means,” presented at the 42nd Annual Meeting of the American Association of Petroleum Geologists,,‘l957. (4) Pregl, Fritz,,, Quantitative Organic Microanalysis, 5th ed., pp. 37-70, J. and A . Churchill, Ltd., London, 1951. (5) Scott, Wilfred W., “Scott’s Standard Methods of Chemical Analysis,” 5th ed., pp. 229-31, Van Kostrand, T e n York, 1965. (6) Zbid., pp. 235-43, 1616. ( 7 ) Steyermark, A , , “Quantitative Organic Microanalysis,” pp, 82-1 21, Blakiston, New York, 1051. (8) Willard, Hobart €I., Iliehl, Harvey, “Advanced Quantitative Analysis,” pp. 209-14, Van Sostrand, Ken. York, 1950. J. L. EILINGBOE J. E. WILSOK Marathon Oil Company Littleton, Colo.
Determination of Some Diamines in the Presence of Adipic Acid, Amines, and Amino Acids SIR: Many literature references (3, 4,6 ) to the determination of amines as Schiff bases in acidic or neutral media are available. These methods may be summarized as direct gravimetric, combination volumetric-spectrophotometric, and indirect volumetric procedures. Some mention of the diamines is made in these articles. More recenbly, however, Hupgins and Drinkard ( 2 ) reported the determination of ethylenediamine in the presence of large amounts of the hydroxy-alkylamines, ethanolamine, and n-hydr0:iyethylethylenediamine. The current work described here is concerned with the di:-ect determination of diamines (either as hydrochloride salts or as free amines) in the presence of carboxylic and amino acids and amines nithout separation of these materials. EXPERIMEYTAL
Reagents. All reagents were used as supplied by laboratory chemical manu f a c t ur er s without further p urification. SALICI.LALI)EHYIIE E,OLUTIOK. To 5.0 grams of sodium h y d r x i d e in 200 ml. of water add 10 ml. of srtlicylaldehyde and stir rapidly with a Mag-mix (E. H. Sargent 8: Co., Cat h-0. S-i6490) until all of the ail is dissolved. If a precipitate forms. filter through E medium-poro.it\sintered-glass filter. ‘This reagent is not stable and Fhould be prepared daily.
SULFURIC ACID SOLETION.Concentrated sulfuric acid (93.20/0), 1 part, is added to 5 parts water (by volume). This solution is approximately 27% sulfuric acid by weight. Procedure. The general procedure of Huggins and Drinkard ( 2 ) which was used with slight modification is given below. A 0.4-gram sample weighed to the nearest 0.1 mg., containing from 0.10 to 0.20 gram of the diamine, was dissolved in 300 ml. of deionized water in a 400-ml. beaker. To this solution, 50 ml. of aqueous 5% (by volume) basic salicylaldehyde solution was added, accompanied by vigorous stirring with a glass rod. The solution became cloudy and was allowed to stand for 30 minutes with occasional stirring. After standing, the pH was adjusted to 8.3, using a Beckman Model GS pH meter by the dropwise addition of 27% aqueous sulfuric acid (by weight). Samples containing monofunctional amines were adjusted to pH 11.0 in the same manner. After adjustment of the pH, the samples were allowed to stand at ambient temperature for 1 hour and the precipitated salicylaldimine was collected on a previously tared Gooch crucible with asbestos mat. The washed precipitates were dried in a 70” C. oven for 5 hour?, cooled, and neighed. The hesaniet,hylenediamine (HMD), p-phenylenediamine (p-PDA4),ethylenediamine, benzidine (HDH), and hydrazine are reported as % HAID.2HC1, % p-PDA, yc ethylenediamine, yo benzidine dihydrochloride, and yohydrazine, respectively.
RESULTS AND DISCUSSION
To evaluate the quantitative nature of the overall recovery of the diamine in the above procedure: synthetic samples of the diamines and mistures containing diamine, adipic acid, and amino acids or amines were run. These results are tabulated in Tables I, 11, and 111. The data reported represent triplicate runs. I n the case of 0.12 gram of HMD 2HC1, Table I, they are representative of a replicate of nine runs. To determine the diamine content of mistures containing the diamines in the presence of large quantities of dibasic acids, amino acids, and monofunctional amines without subsequent seliaration, a gravimetric procedure was developed by which the diamine is precipitated quantitatively as a Schiff’s base with basic salicylaldehyde as a salicylaldimine without interference from either adipic acid or the amino-acids, e-amino-ncaproic acid hydrochloride It-ACA)! glycine, anthranilic acid, taurine, or dl-aspartic acid. The monofunctional amines, n-propyl, o-toluidine, aminoethylpiperazine, and aniline, in the presence of the diamines, did not interfere with the diamine det,ermination by precipitating also as their respective imine adducts a t a p € i of 11.0. Only in the case of n-hexylamine, however. was t h r r t preciliitation interference by the monofunctional amine. In this case mixtures of adipic VOL. 36, N O . 2, FEBRUARY 1964
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