ANALYTICAL EDITION
296
free sea water, which in the Puget Sound region is most apt to be found in the surface waters. LITERATURECITED (1) Am. Pub. Health Assoc. N. Y., Standard Methods of Water Analysis, 7th ed., 1933. (2) Braarud, T., and Klem, A., Hvalradets Skrifter Norska Viden8 k ~ p s - A k ~ Oslo, d. 1, 50 (1931). (3) Buch, K., Rapp. proc. verb. reunion. conseil perm. intern. explor. mer., 53, 36 (1929).
Vol. 5 , No. 5
(4) Cooper, L. H. N., J . Murine Biol. Assoc. United Kingdom, 18, No. 2, 719 (1933). ( 5 ) Robinson, R. J., and Wirth, H. E., J. conseil intern. exploration mer. . Accepted for publication. (6) Trcadwell and Hall, “Analytical Chemistry,” 6th ed., Vol. I, Wiley, 1927. (7) Urbach, C., Mikrochemie, 11, 50 (1932). (8) Wattenberg, H., Ann. der Hydrog. Murit. Meteorol., 59, 95 (1931). (9) Wattenberg, H., Rapp. proc. verb. reunion. conseil perm. intern. ezplor. mer., 53, 108 (1929). RWEIVDDJuly 3, 1933.
X-Ray Method for Quantitative Comparison of Crystallite Orientation in Cellulose Fibers WAYNEA. SISSON~ AND GEORGEL. CLARK,Department of Chemistry, University of Illinois, Urbana, Ill.
T
HAT the orientation of Since these planes are parallel to The relation between orientation of the crystalthe cellulose structural the long axis of the crystallites lites or micelles and various properties of cellulose units varies w i d e l y in ($4, 66), each plane a t angle 0 fibers is pointed out and a n x-ray method for different fibers and in the same to the x-ray beam (fulfilling the quantitatively comparing the orientation is fiber (1, 8) is well known, and its conditions of the Bragg equation described. The method is based upon the asinfluence upon the physical and nX = 2d sin 0) w i l l d i f f r a c t chemical properties of the fiber x-rays in the limiting case, upon sumption that the distribution of the crystallites has been discussed by many 002 diffraction ring a t right the around the pencil of x-rays is proportional to investigators (Ic5, 23), particuangles to the long axis of the the distribution of intensity around the 002 larly with reference to the degree crystallite. The diffraction ring diffraction ring. Intensity measurements are of m e r c e r i z a t i o n , t e n s i l e registered on the photographic made with a microdensitometer equipped with a s t r e n g t h , classification, elasfilm is thus a summation of the ticity, and dyeing properties of individual diffractions from all rotating stage. cotton ( 5 , 6 , 1 9 , 3 1 ) ; the swellthe diffracting crystallites, and a The distribution of the crystallites is calculated comparison of the intensity dising, elasticity, tensile strength, from the intensity values and the orientation is tribution around this ring gives ability to take dyes, resistance expressed by distribution curves which may be to e n z y m a t i c decomposition, a measure of the distribution of differentiated from one another by statistical the crystallites around the pencil gloss, creasing resistance, refractiveindex, and extension of rayon of x-rays. For a complete picmethods. The data obtained may be used to (3, 5 , 7 , 9,11,18,19, 21,22,28); ture of the orientation in any study the structure of the fiber or to predict sample it is necessary to obtain and the density, tensile strength, physical and chemical properties which are an x-ray pattern with the sample e x p a n s i o n , and shrinkage of anisotropic. Typical data for three grades inclined at various angles wood ( I , 17, 32). of cotton are presented to show the sensitiveness The use of x-rays in studying to the x-ray beam. However, this orientation and differentifor comparing the orientation of the method. of different fibers, one pattern ating b e t w e e n the v a r i o u s taken w i t h t h e x - r a v b e a m textce fibers, especially rayon, has been described by Clark ( 5 ) , Mark (20), and others. perpendicular to the fiber axis is sufficient. A perfectly uniThese investigators, however, used a visual method of com- formly intense 002 diffraction ring, such as that obtained with paring the x-ray patterns which is essentially qualitative in the x-ray beam perpendicular to the cellulose sheet, implies nature. It is the purpose of this paper to describe briefly that the long axes of the crystallites have a random orientaan improvement over the visual method, which enables a tion in the plane of the sheet. If the intensity is concenquantitative comparison to be made, and to point out the trated into localized maxima, as is the case for the x-ray beam perpendicular to the ramie fibers, then the crystallites appossible applications of the method. The improved method is based on a comparison, for differ- proach a parallel arrangement along the fiber axis. ent samples, of the relative intensity distribution along the EXPERIMENTAL circle on which the 002 interference maxima are localized. Although the significance of cellulose fiber diagrams has been The intensity measurements are made on a microdensitomedeveloped by Polanyi and Weissenberg (26, 27) and the rela- ter of the “photograph wedge” type, the principle of which tion between crystal orientation and sharpness of the localized was first described by Hartman (14) and more recently by maxima is explained in textbooks on x-rays (2, 4), the basis Vasil’ev (36). It is manufactured by the Gaertner Scientific of the method may be explained briefly as follows: Corporation and involves some novel features. The wedge Figure 1 shows typical x-ray patterns of a cellulose sheet used is not strictly a photographic wedge but a dyed gelatin and a bundle of ramie fibers. I n both patterns the most wedge between glass plates. This is essential in order to give intense interference ( A ) line) is due to the 002 planes (2.4). the necessary linear relation between density and scale readings. To make up for the lack of grain of this type wedge a 1 Senior Textile Foundation Fellow.
September15,1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
grain plate is placed a t the focus of the comparison microscope which makes it unnecessary to defocus the microscope viewing the spectrum line. The shifting of the cube which was present in the original Hartman microdensitometer has been eliminated by utilizing a short vertical slit a t the silvered horizontal strip of the dividing surface. The readings, which are read from a scale dividing arbitary units from 0 to
0
29'7
0
30 0
26
(3
0
0
0 0
Cellulose Sheet
Ramie Fibers I
ILLUSTRATING RANDOM AND PREFIGURE 1. X-RAYPATTERN FERRED ORIENTATION
0 V
V
100, are proportional to the densities and consequently to the logarithm of the reciprocal of that portion of the light transmitted. The wedge type is more satisfactory than the registering type of microphotometer ( l . Z , l S , SS), since it gives definite, duplicable values for the intensity which may be used as the basis of calculations. A special calibrated rotating stage was constructed which allows the film to be rotated through 360 " with the microdensitometer focused on the 002 line. The area included in the measurement is about 0.05 mm. wide and 0.8 mm. long, the long dimension being across the diffraction ring and including about one-half to two-thirds the width of the ring. The position of the film in focus may be read directly from the stage. Figure 2 shows the microdensitometer equipped with the rotating stage. Although the planes which are parallel t o the fiber axis diffract on the "equator line," a t right angles to the fiber, the equator line will be referred to as the 0" position in order to avoid confusion in this discussion. Readings may be made every 2", So,or lo", depending upon the accuracy desired.
80
FIGURE3.
MEASURED
(X-ray photographs represent times of exposure corresponding to curves)
are averaged. If more accurate data are desired four readings for each 5" angle should be averaged. TABLEI. TYPICAL DATASHEET ANGLE 0
Readings every 5" are satisfactory for most purposes and the number of these made in each quadrant will depend also upon the accuracy desired. I n order to eliminate errors due to failure to mount the film and sample perpendicular to the x-ray beam, uneven scattering, or the slightly off-center position of the film on the stage, readings should be made over a 360" range in every case. A typical data sheet is shown in Table I. In this table, and also in data given elsewhere, the angles ending in 0 are read in two quadrants and those ending in 5 in opposite quadrants. This gives two readings every 5" which
40 PO 0 PO 40 60 8C NW TO P/B.R AXIS EFFECTOF TIME OF EXPOSURE ON
INTENSITY CURVES
5 10 15 20 25 30 35 40 46 50 55 60 65 70 75 80 85 90
FIGURE 2. MICRODENSITOMETER EQUIPPED WITH ROTATING STAGE
60
Sample 351 (cotton) READINGS (QUADRANT) 1 2 3 4 AYERAQX! CORRECTED % 42.6 42.0 34.0 42.3 12.00 33.5 11.90 4i:8 4i:s 41.8 33.1 4i:4 4i:4 11.70 41.4 32.3 11.40 40.6 40:2 4i:o 30.0 3810 38:6 10.60 38.3 27.7 3516 36:4 9.80 36.0 22.0 3010 30:6 7.80 30.3 18.7 2715 28:6 6.63 27.0 13.3 2116 2i:s 4.71 21.6 10.3 3.65 18.6 l8:2 19:o 15:2 13:8 2.20 6.2 14.5 1.77 5.0 13.3 13:s 13:2 3.6 ii:6 i i : ~ 1.27 11.9 2.9 1.03 ii:o ii:s 11.3 1.9 10:2 10:4 0.67 10.2 2.8 11.1 0.99 ii:2 ii:o 1.7 0.60 1014 9:6 10.1 1.6 0.57 9.9 9:6 10:2 1.7 10:o 1o:o 10.0 0.60 ..
..
Correctlon = 8*5
-
+ 8'o + 4
Total 282.3 8'5 8'2 83
+
A correction for the scattered radiation must be subtracted from the average reading, and this may be obtained by reading the intensity on the lightest portion of the film between the 002 line and the next line of larger diameter for each quadrant and taking the average as the correction factor. The corrected readings are then converted to a percentage basis. Representing the data on a percentage basis eliminates the necessity of carefully controlling such experimental variables as time of exposure, intensity of the x-ray beam, thickness of sample, as well as the temperature and time of developing. These factors, however, should be held constant for accurate work.
ANALYTICAL EDITION
298
Vol. 5 , No. 5
Several experimental faccentage values by dividing tors must be controlled. For each reading by the total and example, the fiber axis of the multiplying by 100. Each s a m p l e and a flat p h o t o c u r v e p l o t t e d from these graphic plate should be pervalues has a constant area pendicular to a small parallel and the height of the curve a t pencil of x-rays. Best results any angle to the fiber axis is 0 0 are o b t a i n e d with filtered b8 + proportional to the relative B B copper radiation and a sample number of crystallites a t that O B to film distance of 5 em. The a n g l e . The value a t each photographic plate must be point on the curve is desigcarefully shielded from outnated as the relative per cent side scattered radiation. The of the total crystallites over a fibers should be arranged sym5"angularrangeatthatpoint. metrically in the path of the The curves may be designated x-ray b e a m , a n d in photoas an "empirical measuring a , w u ro NBLR AXIS graphing fibers such as cotton, stick" by which the relative ON MEASURED orientation of different fibers it is imperative that they be FIGURE4. EFFECTOF TIMEOF EXPOSURE INTENSITYCURVES arranged in a parallel condimay be compared. For ex(Same data as Figure 3 corrected to percentage basis) tion. A s p e c i a l apparatus a m p l e , examination of the for preparing specimens of data in Table I shows that cotton meeting these requirements has been constructed and about 9.8 per cent of the crystallites for that sample are will be described elsewhere in connection with the applica- orientated between 22.5" and 27.5" to the fiber axis. This tion of this method to cotton fibers. The center of the is not an absolute value, but a relative value which may be diffraction rings and the 90" and 0" positions of the film compared with that obtained from another sample. Plotting should coincide with the corresponding positions on the the data to the scale of 10" = 1per cent gives standard curves rotating stage. If this condition is fulfilled, readings made a t which may be compared directly. How the measured inequal angles on both sides of the 0" position will be identical, tensity curves are transposed to relative intensity curves and plotted in terms of crystallite orientation is illustrated in INTERPRETATION OF CURVES Figures 3 and 4. Figure 3 shows observed intensity values So far, readings have been obtained which give intensity for 0.5, 1, 2, and 4-hour exposures of the same material. distribution curves. Before these curves can be defined or Figure 4 shows the same data after being corrected to a interpreted in terms of crystallite orientation they must be put on a strictly comparable basis. This is accomplished by converting the observed intensity values to relative or per-
I
-:So
u 80
60
20 0 Po 40 AWL6 TO fI6ER A.YI.7 40
60
81
FIGURE6. TYPICAL ORIENTATION CURVESFOR COTTONMERFIGURE 5. TYPICAL ORTENTATION CURVESFOR COMPRESSION CERIZED WITH AND WITHOUT TENSION WOOD AND RAMIE (Upper, mercerized with tension. Center, mercerized without tension. (Upper, ramie. Lower, compression wood)
Lower, unmercerized)
.
September15,1933
INDUSTRIAL AND EXGINEERING CHEMISTRY
percentage basis and plotted in terms of crystallite orientation. The curves obtained by this method give a measure of the average orientation of a number of fibers, since the diffraction pattern is usually made from a bundle of a thousand or more fibers. All fibers do not give normal distribution curves corresponding to an irregular arrangement of the crystallites such as found in rayon (6) and to a more or less degree in cotton (IO). In some fibers the crystallites have a degree of regularity in their inclination to the fiber axis. This is especially true in certain types of wood known as compression wood (SO) such as shown in Figure 5 . This is contrasted with ramie which has a majority of crystallites oriented parallel to the fiber axis. Figures 6 and 7 show the type of curves obtained for several other different materials. As a rule the curves do not fit any simple mathematical equation, but correspond to normal frequency curves which are most satisfactorily differentiated from one another by statistical methods (26, 29, S 7 ) . The exact method of treatment depends upon the type of curve and the nature of the information desired. Preliminary results indicate that many properties are proportional to the sine or cosine of the mean, median, or standard deviation of the crystallites. The curves may also be expressed in terms of per cent orientation (25). Another method is that of obtaining a factor which represents a summation of the behavior of groups of crystallites over the whole angular range. If the relative number of crystallites over each 5" angular range is multiplied by the sine or cosine of the average angle, the product is proportional to the behavior of this group and the summation of all the groups gives a factor which represents the general behavior of the fibers. For cosine values this gives a factor which varies from 100, when the crystallites are all parallel t o the fiber axis, to 50 when they have random arrangement. This method works satisfactorily for the correlation of properties which are anisotropic and consequently proportional to the sine or cosine of their angle to the fiber axis. Figure 8 shows the orientation curves for three commercial
299
grades of cotton which differ in physical and niicroscopic properties. The application of the various methods mentioned above for differentiating between the orientation of these samples is illustrated in Table 11. TABLE11. METHODSFOR EXPRESSING DIFFERENCES IN ORIENTATION OF COTTONS
--
METEOD Tensile strength of cord Height of mode Per cent orientation Cosine summation factor Median Mean Standard deviation
Irrigated cotton 17.6 11.40 45.06 85.38 17.83; 27.27 32.40"
VALUES
Eastern cotton 18.3 12.00 49.94 87.79 16.41' 25.50' 29.30'
Egyptian cotton 20.0 13.35 52.86 88.58 14.38O 24.10' 2S.4Oo
DISCUSSION The work now in progress employing this method is of a twofold nature: First, the orientation of the crystallites is being correlated with the orientation of the gross configurations of the fiber as revealed under the microscope with ordinary and polarized light (8), and by such a study it is hoped to obtain fundamental information regarding the arrangement of the cellulose units in the cell walls of fibers. The results obtained by this method are also being compared with those obtained by optical methods (25). The second application is concerned with a study of the relation between orientation and the various physical and chemical properties of the cellulose fiber. The experimental data thus far obtained indicate a functional relationship between the orientation of the crystallites and many physical properties, and it is possible that with the compilation of further data a definite mathematical relationship may be found in many cases. It is obvious, however, that other factors such as the nature of the wall configurations in certain fibers ( I ) , the arrangement of the crystallites in these larger structural
2ot
2 0
I
80
l
l
l
l
l
l
l
l
l
l
'
l
'
l
'
6 0 4 0 2 0 0.2040 6 0 @ ANGU To f/5&R AX/S
l
FIGURE 7 TYPICAL ORIENTATION CURVES FOR Two TYPES OF
RAYON
(Upper, cuprammonium rayon.
Lower, viscose rayon)
m 6 0 M 2 Q
0804O6080 AN6U TO FIB€,? AXIS
FIGURE8. ORIENTATION OF CRYSTALLITES IN THREETYPES OF COTTON (Upper, Egyptian cotton.
Center, eastern cotton. Lower, irrigated cotton)
ANALYTICAL EDITION
300
units (34,’35),the shape and size of the crystallites as well as the attraction forces between them, and the nature and the amount of the intercrystalline material will also have considerable influence upon the properties of the fiber. This will necessitate a consideration of the chemical constitution and microscopic structure of the fiber in connection with x-ray studies in order properly to interpret the x-ray results. Such studies are in progress and the modifications and limitations of the above general method when applied to specific fibers will be described in future publications concerning the application of this method to different types of fibers and to specific problems relating to these fibers. It is obvious that the method described in this paper is not limited to cellulose fibers but may be applied equally well to protein fibers, regenerated cellulose sheets, cold-worked metals, or any other material having a fiber structure. LITERATURE CITED Anderson, D. C., Ohio J . Sei., 28, 299 (1928). Bragg, Sir Wm., “Introduction to Crystal Analysis,” Van Nostrand, 1929. Chaumeton, P., and Yardsley, V. E., Brit. Plastics, 2,452 (1931). Clark. G. L.. “Auulied X-Raw.” McGraw-Hill, 1932. Clark; G. L., IND.~ENO.CKEM.,22, 474 (1930). Clark, G. L., Pickett, L. W., and Farr, W. K., Science, 71, 293 (1929). Eckling, K., and Kratky, O., A~aturwissenschaften,18, 461 (1930). Farr, W. K., and Clark, G. L., Contrib. Boyce Thompson Inst., 4, 273 (1932). Fiers-David, H. E., and Brunner, A,, Helv. Chim. Acta, 13, 47 (1930). Frey, A., Naturwissenschaften, 15, 760 (1927). Hall, A. J., Textile Colorist, 53, 520 (1931). Harrington, E. A., J . Optical Soc. Am., 16, 211 (1,928). Harrison, G. R., Ibid., 10, 157 (1925).
Vol. 5, No. 5
(14) Hartman, 2. Instrumentenk., 19, 97 (1899). (15) Hess, K., and Kate, J. R., “Chemie der Zellulose und ihrer Begleiter,” Akademische Verlagsgesellschaft, Leipsig, 1928. (16) Kelley, T. L., “Statistical Method,” Macmillan, 1923. (17) Koehler, A,, Trans. Am. SOC.Mech. Engrs., 53, 17 (1931). (18) Levin, E., and Rowe, F. M., Rayon Record, 4,1283 (1930). (19) Mark, H., J. Sac. Dyers Colourists, 48, 53 (1932). (20) Mark, H., Kunstseide, 12, 214 (1930). (21) Mark, H., Rayon Record, 7,165 (1933). (22) Mark, H., Trans. Faraday Soc., 29, 6 (1933). (23) Meyer, K. H., and Mark, H., “Aufbau der hochpolymeren organisohen Naturstoffe,” Akademisohe Verlagsgesellschaft, Leipzig, 1930. (24) Meyer, K., and Mark, H., Ber., 61B, 593 (1928); 2. physik. Chem., 2B, 115 (1929). (25) Morey, D. R., Textile Research, 3, 325 (1933). (26) Polanyi, M., 2. Physik, 7, 149 (1920) ; Naturwissenschafton, 9, 337 (1921). (27) Polanyi, M., and Weissenberg, K., 2. Physik, 9, 123 (1922); 10, 44 (1922). (28) Preston, J. M., Trans. Faraday Soc., 29, 65 (1933). (29) Riets, H. L., “Handbook of Mathematical Statistics,” Houghton Mifflin. 1917. (30) Ritter, G. J., Sisson, W. A., and Clark, G. L., IND.ENG.CHEM., 22, 495 (1930). (31) Schiamek, W., 2.physik. Chern., 13B, 462 (1931). (32) Schmidt, B., 2. Phzlsik., 71. 696 (1931). (33) Siegbahn, M., Phii. Mag., 48, 217 (1924). (34) Sponsler, 0. L., Protoplasma, 12, 241 (1931); Nature, 125, 634 (1930). (35) Sponsler, 0. L., and Dore, W. H., Fourth Colloid Symposium Monograph, Chemical Catalog, p. 174 (1926). (36) Vasil’ev, K. V., Trans. Inst. Econ. Mineral. Met. (Moscow), 34, 16 (1928). [C. A., 22, 4012 (1928)l. (37) Yule, G. U., “Introduction to the Theory of Statistics,” Griffin, London, 1922. RECEIVEDApril 15, 1933. Presented before the Division of Cellulose Chemistry a t the 85th Meeting of the American Chemical Society, Washington, D. C., March 26 t o 31, 1933.
Colorimetric Determination of Fluorine W. D. ARMSTRONG, Laboratory of Physiological Chemistry, University of Minnesota, Minneapolis, Minn. HE d e t e r m i n a t i o n of Fluorine in solution is determined by its these e x p e r i m e n t s were pubfluorine in silicon tetrafading action on the color of ferric acetylacetone. l i s h e d @), F o s t e r (4) has refrom ported a procedure developed fluoride The influence of the acidity of the solution and of on somewhat similar principles, a highly simplified apparatus (1) the presence of certain impurities 3 eliminakd using t h i o c y a n a t e as color required the development of a by determination of the fading caused by the reagent for iron. However, the method with which sulfatesand colored compounds formed by salts of volatile acids would not fluorine in a n aliquot of the solution, followed by a iron and its color reagents preinterfere. Soluble fluorides in measurement of the fading produced by an equal viously listed, with the exception Or slightly acid aliquot to which has been added a known quantity of acetylacetone, fade apprecireact with ferric iron to form a Of Jluorine. The fluorine content Of the aliquots ably in a short time. Furthercomplex which does not develop is calculated from the ratio of the fading of the more, the degree of fading caused s, color with the various reagents by a u n i t a m o u n t of fluorine for iron. The colorimetric titraunknown to that of the known, multiplied by the on all of the colored iron comtion r i ~ t J ~ based ~ d On this fact, quantity offluorine added in the second case. Dounds is markedlv altered bv as developed by Guyot (6) and ;light c h a n g e s i n - t h e acidity Greef (5); has undergone considerable modification, chiefly by Treadwell and Kohl @), and of the solution. It is very difficult to adjust the acidities by Fairchild (3). The procedure to be reported is an applica- of different solutions with sufficient exactness to permit tion of the same principle, but it allows the determination of reproducible results to he obtained with small amounts of microquantities of fluorine in the presence of substances which fluorine. A buffer with a pH slightly under 7 which did not itself affect the colored iron compound was not found. interfere with other methods. Attempts were made to adapt the principle directly to While the method already outlined and as reported by Foster colorimetric procedure. Solutions of ferric thiocyanate, can be applied with fairly accurate results when the necessary partially faded by various amounts of fluorine, were compared factors can be controlled, in the procedure here reported with similar solutions containing standard amounts of fluorine there is no necessity for observing these difficult precautions. or no fluorine a t all. Similar trials were made in which The color developed by ferric iron and acetylacetone has salicylic acid, 8-hydroxy quinoline, and acetylacetone were been made the basis of a colorimetric method for iron desubstituted for thiocyanate as color reagents for iron. Since termination by Pulsifer ( 7 ) . The stability of the compound
