Pipet Method of Sedimentation Analysis Rapid Determination of Distribution of Particle Size V. V. DESHPANDE A N D M. S. TELANG Laxminarayan Institute of Technology, Nagpur University, Nagpur, India
T H E pipet method of sedimentation analysis is well known Table I.
(1-5). In a critical study of sedimentation methods Schweyer (6, 7) and Work (8) showed the advantages of Andreasen's pipet method (1, 2 ) . Schweyer attempted (6) to reduce the duration of experiment by using a special kind of tap, but the equipment has t o be specifically made, i t involves complicated glass blowing, the depths a t which the pipets can be immersed in the suspension cannot be altered a t will, and the pipets cannot be operated simultaneously. In the changeover from one pipet to another, the distribution function of the particles that have passed the tip of the shorter pipet and still lie above the tip of the longer pipet cannot be determined with certainty.
Experiment with Single Pipet of Andreasen Type Particle Size (Diameter, Microns)
Time, Min.
Table 11.
%
Undersize
Experiment with Double Pipet
4.75 11 35 60 120 240 360 480
Particle Sjee (Diameter, Microna) Short Long pipet pipet A, First Experiment 20.41 16.03' ... 13.18 5.56 7.25 4.14 ... 2.85 1.95 2.82 1.64 2.11 1.28 1.80
3 10 30 60 125 240 360 480
B, Duplicate Experiment 26.47 19.91 95.28 ... 90.42 13.71 7.78 5.94 82.22 5.42 4.09 65.09 4.13 2.74 55.94 2.61 1.91 36.04 2.09 ... 26.57 1.78 1.26 21.10
Time Min.
...
% Undersize Long pipet
Short pipet
98.35 93.99 73.21
88.74 70:ig 56.54 43.46 26.61 20.81 15.65
...
36 76 23.33 22.14
80.19
137:is 58.51 38.95 23 57 16:63
two of the holes into the suspension in the cylindrical graduate a t two different predetermined depths. The capillaries are joined to two independent 10-ml. pipets by means of threeway taps. The to s of the two pipets are connected to a Y-tube, by means of whicg samples can be withdrawn simultaneously. Through the third hole, a bent tube with a bulb containing some water (medium) immersed in the thermostatic bath is fitted to minimize evaporation losses. The experimental procedure is a8 usual. China clay passing through a 200-mesh screen (Tyler) was used in water throughout the investigation. Tables I and I1 shorn the results of B single-pipet experiment in comparison with the double-pipet method.
J Figure 1. Graduate
I00
The present work was undertaken to minimize the time required. The apparatus was designed to withdraw samples a t two different depths simultaneously and not consecutively as was done by Schweyer. Theoretically, the whole size range may be obtained by analysis of samples a t different depths a t one and the same time, but experimental difficulties prevent such a determination. However, by using two or three pipets operating simultaneously at two or three different depths, the time of observations can be considerably shortened. The time necessary for the operation of the experiment will obviously depend on the smallest particle size desired.
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EXPERIMENTAL
A 1000-ml. cylindrical graduate (Figure 1) is fitted with a rubber bung with three holes. Two capillary tubes pass through
t
6 a RADIUS, MICRONS 4
Figure 2
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IP
14
V O L U M E 2 2 , N O . 6, J U N E 1 9 5 0
841
As a further test of validity and reproducibility of this method, Austin's (3) suggestion of plotting particle size on a logarithmic scale and cumulative percentages on an integrated probability scale has been adopted in Figure 3. The tog-probability graph is linear, as anticipated. However, a point or two a t the commencement of the experiment is off the linear graph. This may be due to inaccuracy in recording the zero time and initial sedimentation. The time of 1130 minutes required for obtaining the per cent undersize of particles of 1.23 p diameter with a single pipet (Andreasen type) has been reduced to 480 minutes to obtain nearly the same particle size. Obviously, the saving of time effected depends upon the depth a t which the short pipet is located. The apparatus is easily assembled.
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0.2 0.6 PARTICLE SIZE, LOG
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LITERATURE CITED
1 .o 1.4 DIAMETER, M I C R O N S
OF
Figure 3 DISCUSSION
I n Figure 2, the results in Table I have been plotted with those of Table II,B, to give a common cumulative percentage curve. The duplicate experiment with double pipet was made to indicate that the agreement between the single pipet and the proposed double-pipet method is decisive and not accidental.
Andreasen, A. H. M., Kolloid Beihefle, 27,349 (1928). Andreasen, A. H. M., a n d Berg, S., Angew. Chem., 48, 283-5 (1935). Austin, J. B., IND.ENG.CHEM.,ANAL.ED.,11,334-9 (1939). O d h , S., "Alexander's Colloid Chemistry," Vol. I, p. 861, New York. Chemical Catalog Co., 1926. Robinson, G. W., J . Agr. Sci., 12,306-21 (1922). Schweyer. H.E.,IND.ENG.CHEM.,ANAL.ED.,14, 622-7 (1942). Schweyer, H.E.,a n d Work, L. T., Am. SOC.Testing Materials, Symposium on New Methods for Particle Size Detn. in Subsieue Range. 1941, 1-23. Work, L.T., Proc. Am. SOC.Testing Matetinls, 28 11,771 (1928).
RECEIVED June 28, 1949.
Infrared Absorption Band of "=Butyl Group STEPHEN E. WIBERLEY A N D LEWIS G. BASSETT Rensselaer Polytechnic Institute, Troy, N . Y .
N RUNNING the infrared spectra of a series of ethers i t was Istrong noted that all the ethers containing an n-butyl group showed a absorption band a t approximately 739 cm.-l which was lacking in the other ethers. This band is in the region of 720 to 760 cm.-1, suggested by Sheppard and Sutherland (b,3) as being a reasonable range within which one can expect the occurrence of the CH2 rocking modes. I n further agreement with the assignment of this absorption to the CH, rocking mode, Vallance-Jones and Sutherland ( 7 )showed by use of polarized infrared radiation on an orientated polyethylene sample that the change in electric moment occurring during this vibration at approximately 720 cm. -1 was perpendicular to the carbon chain. Sheppard and Sutherland (3)state that any molecule containing (CHz),CH$, in which n is equal to or greater than 3, possesses a band in this region of 720 to 760 cm. -1 This would include the n-butyl group. Tuot and Lecomte ( 6 ) have reported that, in a study of the infrared spectra between 700 and 800 cm.-1 of a series of approximately 30 alcohols, indications can be obtained regarding the length and branching of the carbon chain. They find for alcohols, in which the n-butyl group is the longest unbroken chain present without substitutions, a band a t approximately 274 cm. -'-for
H example, for 2-hexanol
CH~-C-CHZ-CH~-CHZ-CH,,
a
I
OH maximum absorption band at 724 cm.-l port for Poctanol H
However, they also re-
I
CH~-CH~-CH~-C-CHZ-CH,-CH~-CHZ-CH~
OH a maximum absorption band a t 735 cm.-I
Recent articles by Barnes, Gore, Stafford, and Williams ( 1 )and by Thompson (6) contain tables listing functional group absorption frequencies but do not specifically include the n-butyl group. From the chart in Thompson's article the following approximate ranges can be obtained.
One methylene group Two methylene groups Four methylene groups
CHI-CHaCHI-CHz-CHz--CH-CH:-CH~-CHz-
Cm.-1 (Estimated from Chart) 760-780 730-750 715-730
The information on these three groups is based on work done on the spectra of hydrocarbons a t Oxford and Cambridge. Because the work of Sheppard also referred to hydrocarbons and that of Tuot and Lecomte to alcohols, it was considered worth while to investigate the position of this band in various types of organic compounds containing the n-butyl group. It is of qualitative value to establish the approximate location of the n-butyl group and the variation in the range of frequency that may be expected for a given series of n-butyl compounds. EXPERIMENTAL PROCEDURES
The or anic compounds used were Eastman Kodak (White label gracfe), except for diethyl Cellosolve, butyl Cello:olve, dibutyl Cellosolve, and dibutyl Carbitol, which were obtained from the Carbide and Carbon Chemicals Corporation. The compounds were purified by distillation immediately prior to use and a sample boilin4 within * 0.1 ' C. of the literature value was used for the absorption measurement. In the case of the ethers and alcohols, distlllation over calcium hydride was employed to remove all traces of water, inasmuch as sodium chloride windows were used in the 0.025-mm. sample holder. The measurements were made with a Perkin-Elpler infrared recording spectrometer Model 12B, using a sodium chloride prism. The prism was calibrated with ammonia gm, carbon dioxide vapor, atmospheric water vapor, and benzene vapor using a 10cm. gas cell.
