July 15, 1932
265
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
SODIUM WEIQHEDAS NaZn(U0z)aAco .6H20
%
SODIUM DETD.VOLUMETRICALLY BY TITRATION OF URANIUM
%
0.44 0.45
0.44 0.45
0.30 0.15 0.15 0.074 0.074 0.037 0.037 0.015
0.30 0.14 0.14 0.074 0.074 0.037 0.036 0.014
0.008
0.008
0.0016
0.0017
0.29
0.29
Blenkinsop (6) has proposed a method in which the uranium is determined by reduction with titanium chloride. McCance and Shipp (17) have introduced a colorimetric method in which the uranium is determined with potassium ferrocyanide. NITRATECRYSTALLIZATION METHOD SPECIALRESGENTS. Mercuric chloride, saturated sohtion. Special nitric acid. Eight parts of 70 per cent nitric acid to 7 parts of water. PROCEDURE. Weigh on a rough balance an 8-inch (20.32em.) quartz dish, add 250 cc. of water, 10 cc. of mercuric chloride solution, 30 grams of fine aluminum drillings, and warm gently until reaction starts. Add 10 cc. of concentrated nitric acid and heat until vigorous reaction starts. Place the dish in a cooling pan and slowly add 390 cc. of concentrated nitric acid. If the mass becomes viscous, add another 100 cc. of water. When apparent action has ceased, heat on a hot plate until the solution of the sample is complete. If the weight of the liquid falls below 600 grams before solution is complete, add special nitric acid. Finally evaporate the solution to 600 grams, cool, with continual stirring, in a water bath, and, when dish and contents are cold, allow to stand for 1 hour or more. Filter the crystals formed through a 5-inch (12.7-cm.) Biichner porcelain funnel, using suction to dry the crystals. Press well with a flattened rod, and, when dry, wash with 50 cc". of concentrated nitric acid. Allow the wash acid to stand on the crystals for a few minutes before suction is again applied. Receive the filtrate in a 4.5-inch (11.43-cm.) quartz dish. Evaporate the solution until a hot saturated solution is obtained, crystallize, and allow to stand as before. Filter through a quartz funnel,
receiving the filtrate in a 3.25-inch (8.25-cm.) quartz dish. Wash with 10 cc. of concentrated nitric acid, add 2 cc. .of concentrated sulfuric acid, evaporate to dryness and bake until no more fumes are evolved, cool, add 10 cc. of ammonium hydroxide, and allow to stand overnight. Warm, filter into a platinum dish, return the paper to the dish, add 5 cc. of concentrated hydrochloric acid, macerate the paper, warm, and precipitate with ammonium hydroxide. Filter, and wash with hot, slightly ammoniacal 2 per cent ammonium chloride solution. Combine the filtrates and evaporate to approximately 25 cc., add 10 drops of concentrated sulfuric acid, pass in hydrogen sulfide gas, filter, and evaporate the filtrate to dryness. Ignite to drive OB ammonium salts, add a few cubic centimeters of water and 2 cc. of saturated ammonium carbonate solution, filter, evaporate to dryness, and ignite for 30 minutes at 500" C., cool, and weigh. Add a few drops of water, 2 drops of ammonium hydroxide, warm, filter, ignite the paper at 500" C., cool, and weigh. The loss in weight is sodium sulfate. The filtrate should be examined for magnesium. Return the crystals from the first and second crystallizations to the 8-inch (20.32-cm.) quartz dish, add 150 cc. of concentrated nitric acid and 50 cc. of water, evaporate to 580 grams, cool, and recrystallize. Repeat the procedure outlined above. Deduct a determined reagent blank. Sodium
=
sodium sulfate X 0.3238
Some results obtained by the foregoing methods are as follows : SAMPLE
1 2
3 4 5 6
FUBION-LEACH NITRATE URANYL METHOD CRYSTALLIZATION ACETATE
%
%
0.040 0.016
0.040 0.015 0.010
0.009 0.008
0,009
0.040 0.017
%
0.038 0.016
ACKNOWLEDGMENT The authors wish to acknowledge the contributions made by W. I. Sivitz, formerly of Aluminum Research Laboratories, and P. M. Budge, chief chemist of the Fairfield Works Laboratory, toward the development of the fusion-leach method.
I I. Spectrographic Analysis A. W. PETREY, Aluminum Research Laboratories, New Kensington, Pa. RE determination of sodium in aluminum may be made by means of the spectrograph, and the results agree with chemical analysis within satisfactory tolerances. Chief among the advantages of the spectrographic determination, as contrasted with chemical determinations, is the rapidity with which a series of results can be reported. Eight to ten specimens may be examined within 2.5 hours, or an average of not more than 20 minutes per sample. The presence of other alkalies or alkaline earths does not interfere with the determination and, at the same time, the presence or absence of such impurities is established. Methods using both the direct current arc and the condensed spark have been investigated. Solution of the metal in acida with subsequent arc excitation of the dry salt, as used by Nitchie (20) in the analysis of zinc, was not entirely successful because of the relatively low solubility of aluminum and the strong continuous spectrum of the graphite electrodes in the regionbof the sensitive sodium lines. The sodium con-
tent of the solvents is also to be considered. Sparking the metal did not seem sensitive enough to warrant an attempt a t development, as the smallest amounts could not be detected and the intensity gradient was not well marked for the higher amounts. The method which seems most applicable for determining sodium in aluminum is arc excitation of the metal itself between electrodes of graphite. Papish and O'Leary (91) determine chromium in fused alumina by the arc. Fesefeldt (11) uses a similar method for determining beryllium in aluminum oxide. Metallic aluminurn cannot be used very successfully as electrodes with the arc because of its relatively low melting point and the formation of a heavy crust of oxide on the tips which is nonconducting and nonvolatile. However, the metal burns readily in the graphite arc and, when used in this way, the continuous spectrum of the graphite is practically eliminated. Since solutions have not been found successful for this
ANALYTICAL EDITION
266 5889.96
5895.93
Sample 1 Sample 2 Sample 3 Standard 0 0 0 I r ~ Standard 0.002$ Standard 0 0057 Standard 0 017 Standard 0 0 2 2 Standard 0 045
1
1 5682.8
6164.4
5688.3
FIGURE1. DETERMINATION OF SODIUM METHOD
IN
6160.5
ALUMINUM BY FIRST
Sample 1, 0.008%; sample 2, 0.005%: sample 3, 0.0015%
d e t e r m i n a t i o n , synthetic standards are necessarily eliminated. Therefore, the standards used are samples of aluminum which have been carefully analyzed by the available chemiyl methods. A series of these standardized metals c o n t a i n i n g 0,000, 0,001, 0.002, 0.005,0.01,0.02, and 0.04 per cent sodium have been prepared and are used for all spectrographic determinations. Sodium in aluminum is estimated by four of its lines, the D lines a t XX 5889.97 and 5895.93, and the green lines a t XX 5682.68 and 5688.22. The D lines serve for amounts up to 0.02 per cent. The green lines are just visible a t 0.02 per cent and are more valuable for estimating amounts between 0.02 and 0.04 per cent, as they show a gradation of intensity which is more apparent to the eye than that of the D lines (Figure 1). The sensitive ultra-violet doublet a t X 3303, al-
Vol. 4, No. 3
though more sensitive than the green pair, is in general not i o valuable, as aluminurnsometime's contains a small amount of zinc, and in such cases the sodium lines are rendered useless by the zinc lines at X3303. For this reason, no attempt has been made in these laboratories to utiliae the ultra-violet sodium lines. -4 Littrow auto-collimating spectrograph with a quartz optical system is used for the determination. Eastman process panchromatic plates are used for photographing the spectra. PROCEDURE. Two 1.25-inch (3.18-cm.) l e n g t h s of 0.25-inch (0.64-em.) diameter r o u n d Acheson graphite rods are used for the electrodes. (A separate set is necessary for each sample photographed.) Drill a '/&nch (0.56-cm.) hole in one end of one of the pieces a b o u t 0.25 inch (0.64 c m . ) d e e p . This piece serves as the lower and positive electrode a n d s u p p o r t s the metal. The upper electrode is used solid. Place the t w o pieces of g r a p h i t e in the steel holders of the arc stand and give them 5889.96
Standard 0.001%
5895.53 I
----
Sample Standard 0.002% Sample Standard 0.006% Sample Standard 0.01% Sample Standard 0.02% Sample Standard 0.04%
FIGURE2. DETERMINATION OF SODIUW IN ALUMINUM BY SECOND METHOD Sample alternated with standards; sodium estimated aB 0.01%
1
FIGURE3. ARC STANDWITH ROTATINGELECTRODE HOLDERAND MOTOR
a preliminary burn for about a minute with a current of 6 amperes. This step is to volatilize any sodium in the electrode tips or any which may have been placed there by handling. Saw or shear from the specimen a section about inch (0.48 cm.) square by "8 inch (0.95 cm.) long. Place this piece of metal in a small beaker or crucible and cover with strong nitric acid. Place on a hot plate and heat near boiling for 4 or 5 minutes. Remove the metal from the acid with forceps, wash with distilled water, and dry. Place in the cavity of the lower electrode. With the spectrograph in correct adjustment, strike the arc and give an exposure of 1.5 minutes, with a current of 6 amperes at about 50 volts. The voltage is maintained as nearly constant as possible by focusing the images of the tip of the upper electrode and the image of the sample on two horizontal lines ruled on the slit diaphragm. This procedure keeps a constant distance between the two electrodes which is about all that is necessary to insure constant voltage. The samples for analysis and the standard samples are exposed under conditions as nearly identical as is possible. Comparison with standards is accomplished in either of two ways, one possessing the advantage of requiring less time, the other that of being somewhat more accurate. The two methods are illustrated in Figures 1 and 2, respectively. I n both schemes, intensities are matched visually without the aid of a measuring device such as a densitometer. The first
July 15, 1932
I N D U S T R I A L A N D E N G I N E E R I N G C H E M I ST R Y
method consists of photographing all the samples, in duplicate if desired, on one portion of the plate, and then adding all the standards on another portion of the plate, as in Figure 1. The second method alternates each sample with the standards so that the spectrum of the sample is always between two standards. Obviously, a better opportunity is offered for matching intensities, as shown in Figure 2. Small differences in sodium produce such noticeable differences in intensity that the second method is rarely used, the first being considered accurate enough for ordinary requirements. This method of analysis is based on the assumption of a constant exposure with an excess of metal always in the arc. To assist in accomplishing this end, a rotating holder for the lower electrode and a timing device are used. The rotating electrode holder shown in Figure 3 is made of steel with a fiber pulley, and is driven by a small motor mounted on the arc stand. Rotating the metal during the exposure keeps the image of the flame centered on the slit. Without this feature, the flame has a tendency to wander around the edges of the specimen or the graphite, often being shifted laterally enough to be thrown off the slit entirely. Accurate timing is controlled by means of a specially built device actuated by a Telechron motor. The apparatus is wired as an auxiliary circuit through a system of relays which allows the Telechron motor Lo run only when the arc is burning. As soon as the predetermined interval is complete, the timer opens the main contractor in the arc circuit and extinguishes the arc. A similar appliance is mentioned by Nitchie (20). Control of the exposure by some such means is very desirable when accurate timing is essential, as in this determination. The arc may be extinguished several times in a single exposure because of an oxide film, a draft of air, or other reasons. With such a device to record the successive intervals as they occur, the total exposure will be the same in time, regardless of the number of interruptions.
267
LITERATURE CITED (1) Allen, E. T., Am. J. Sei., 29, 156-7 (1910). (2) Barber, H. H., and Kolthoff, I. M., J . Am. Chem. Soc., 50, 1625-31 (1928). (3) Belasio, R., Ann. chim. applicata, 1, 101-10 (1914). (4) Bertiaux, L., Bull. SOC. chim., 35, 64-72 (1924); Chim. ind., 11, 40-4 (1924). ( 5 ) Bhattacharyya, H. P., Chem. News, 109, 38 (1914). (6) Blenkinsop, A,, J . AQT.Sci., 20, 511-16 (1930). (7) Caley, E. R., and Sickman, D. V., J . Am. Chem. Soc.. 52. 4247-51 (1930). (8) Diehl, W.,‘ Chem. Ind. (Germany),P1l,494 (1888); 2. anal. Chem., 44, 713 (1905). (9) Fairlie, D. M., and Brook, G. B., J. Inst. Metals, 32, 283-9 (1924). (10) Feldstein, P., and Ward, A. M., Analyst, 56, 245-8 (1931). (11) Fesefeldt, H., 2. phusik. Chem., A , 140, 254-62 (1929). (12) Gaith, R., Chem.-Ztg., 46, 745 (1922). (13) Handy, J. O., J . Am. Chem. Soc., 18, 766-82 (1896). (14) Hunt, A. E., Langley, J. W., and Hall, C. M., Trans. Am. Inst. Mining Met. Eng., 18, 560 (1890). (15) Jean, F., Rev. chim. ind., 8, 5-8 (1897); J. SOC.Chem. Ind., 16, 359 (1897). (16) Kohn-Abrest, E., “Recherches sur I’Aluminium,” pp. 10-24, Ch. Beranger, Paris, 1911. (17) McCance, R. A,, and Shipp, H. L., Biochem. J.,25, 449-56 (1931). (18) Moissan, H., Compt. rend., 121, 851-6 (1895); J . SOC.Chem. Ind., 15, 136 (1896). (19) Nicolardot, P., Bull. soc. chim., 11, 410-13 (1912). Em. CHEM.,Anal. Ed., 1, 1 (1929). (20) Nitchie, C. C., IND. (21) Papish, J., and O’Leary, W. d., Ibid., 3, 11 (1931). (22) Pattison, J. R., “Aluminium,” pp. 89-100, Spon and Chamberlin. New York. 1918. (23) Richards, “Aluminum,” 2nd ed., p. 477, Henry Carey Baird Co., Philadelphia, 1890. ,(24) Sainte-Claire Deville, H., “De L’Aluminium,” pp. 154-9, Mallet-Bacheliet, Paris, 1859. (25) Schurman and Schob, Chem.-Ztg.,48, 97-8 (1924). (26) Seligman, R., and Willott, F. J., J . Inst. MetaZs, 3, 138-60 (1910); J. So?. Chem. Ind., 29, 217 (1910). (27) Villavecchia, “Applied Analytical Chemistry,” pp. 272-3, 1918. RICEWEDJanuary 12, 1932.
Mineral Composition of Dates M. M. CLEVELAND AND C. R. FELLERS, Massachusetts State College, Amherst, Mass. HE chemical composition of the date is of interest because of the widespread use of this fruit as a human food. I n the date-producing countries of the Orient and northern Africa it is a principal component of the diet. France and Italy import many dates from their colonies across the Mediterranean. In England the annual consumption is 3 pounds per capita, whereas in Canada and the United States it is respectively 1 pound and 0.43 pound. The date industry in California and Arizona is important and is growing rapidly, the present production being over 3,000,000 pounds per year. The American-grown dates, however, furnish only a small fraction of those consumed, for approximately 54,000,000 pounds of dates are imported annually, principally from Iraq. Although there are many varieties of dates, only a few are of commercial importance. The Deglet Noor is the principal American-grown variety, while the Hallowi, Sayer, and Khadrawi comprise the greater part of the annual import. The present paper is concerned particularly with the more important imported varieties, Hallowi and Sayer.
PROXIMATE COMPOSITION Numerous proximate analyses of dates have been reported in the literature. However, to show the general composition
of dates, proximate analyses of packaged samples of Hallowi and Sayer varieties purchased on the market were made and are presented in Table I. These samples were grown in Iraq and were packed by the Hills Brothers Company of New York. TABLEI. PROXIMATE COMPOSITION OF EDIBLE PORTION OF IRAQ DATES HALLOWI SAYER
% Moisture Ash Protein (N X 6.25) Fat (ether extract) Reducing sugars as invert Total carbohydrate6 other than crude fiber Crude fiber Sucrose
19.0
2.22 1.72
1.90
73.50
73.67 2.17 None
% 18.0 1.69 2.16 0.31 76:i4
1.90
The moisture content of bulk dates varies from 12 to 21 per cent, about 17 t o 20 per cent being that of a palatable date. It may become considerably less in storage. As the date dries out, the dextrose crystallizes. Sugared dates are considered inferior both by the trade and by the public, but they can be restored to a suitable moisture content by treatment with moist steam. Dates with a moisture content below 23 per cent will keep satisfactorily, because the high sugar concentration inhibits the growth of microorganisms.
