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.
'VIOI,
1 .o
8 I
t
I
I
0.2 0.6 PARTICLE SIZE, LOG
))
I
I
IJI
LO".WT
I
I
LITERATURE CITED
1 .o 1.4 DIAMETER, M I C R O N S
OF
Andreasen, A. H. M., Kolloid Beihefle, 27,349 (1928). Andreasen, A. H. M., a n d Berg, S., Angew. Chem., 48, 283-5
Figure 3
(1935).
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.
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 it 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. Cm.-1 (Estimated from Chart) One methylene group Two methylene groups Four methylene groups
CHI-CHaCHI-CHz-CHz--CH-CH:-CH~-CHz-
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.
A N A L Y T I C A L CHEMISTRY
842
Table I. Absorption Bands Compound
Frequency, Cm.-i
Compound
Frequency, Cm.-I
In n-Butyl Compounda Ethers n-Butyl Dibutyl Carbito1 Butyl Cellosolve Dibutyl Cellosolve
739 739 738 739
Eaters n-Butyl acetate n-Butyl lactate n-Butyl propionate Di-n-butyl oxalate Di-n-butyl tartrate Di-n-butyl succinate
739 739 739 740 740 740
Alcohols n-Butyl
Amides Di-n-butylc yanamide
730
Amines Di-n-butylamine Tributylamine n-Butylaniline
737 734 740
Nitriles n-Valeronitrile
740
Halide8 n-Butyl Prqmide n-Butyl iodide
742 730
738 In Compounds withtout n-Butyl Group in Region of 720-750 om. - 1
Ethers Diethyl Diethyl Celloaolve IsODroDYl ~. Aloohola Methyl Ethyl n-ProuY1 n-Amy1 Isobutyl tort-Amyl
None None None None None
753 730
Esters n-Prop 1 acetate n-Arnyrscetate Amines Diethylamine Halides n-Prowl bromide
721, 759 721 None
740
None
727
DATA AND DISCUSSION
Eighteen available compounds of varying types, all containing one or more n-butyl groups, were measured over the region of 720 to 750 cm.-' To show that the appearance of a band a t approximately 739 cm.-l is reasonably indicative of the presence of the n-butyl group in the compounds under consideration, a few alcohols, esters, ethers, amines, and halidehot containing an n-butyl group were also run in this narrow region. Table I lists the results obtained. The data present strong evidence that an absorption band in the region 734 to 742 cm.-i is indicative of the presence of the nbutyl group, in the compounds listed. This band is of moderate intensity, being slightly stronger in compounds containing two butyl groups as compared to those containing only one. It is especially significant in the case of the ethers and esters. Smith ( 4 ) has pointed out the following, based on a survey of the first 700 of the 800 spectrograms of the A.P.I. series.
Of these, 220 had a band between 725 and 750 cm.-i, and 34 of the 220 had a band of medium or strong'intensity between 734 and 742 cm.-l Of the 34, only 6 contained n-butyl groups; 17 had n-propyl groups, and the remainder were a variety of compounds such as toluene, l12-dimethylbenzene, n-hexadecylbenrene, hexachlorothiolane, 1,2-dicyclohexylethane, 2-acetyl-3methylthiophene, 8-methylstyrene, and 2,2 4trimethylhexane. Six compounds containing n-butyl groups had strong bands from 728 to 730 cm.-' If the range is broadened to include them, such compounds as I-heptene, 2,3-dimethylbutane, 3-ethylpentane1 and I-cyclohexyl-3-cyclopentylpropanealso will be included. A similar situation exists at the upper end of the range above 742 cm.-l That the n-propyl and n-amyl compounds have absorption bands in this region is also to be expected from the references p r e viously cited. I n Table I the presence of the n-propyl bromide absorption band at 740 cm.-1 illustrates the fact that an absorp tion band between 734 and 742 cm.-' indicates only that the nbutyl group may be present and by no means constitutes conclusive evidence, because, as further emphasized by Smith, this region is overlapped by the propyl group. All the n-butyl compounds used in this study except for nvaleronitrile have the n-butyl group separated from the rest of the molecule by a functional group containing either oxygen or nitrogen. In such cases the absorption band attributed to the n-butyl group would be expected to be more specific than in a group that is simply a part of along straight or branched carbon chain, as in the case of the hydrocarbons mentioned by Smith or the alcohols studied by Lecomte. It would seem, therefore, that this absorp tion band in the region 734 to 742 cm.-i should be restricted to compounds containing n-butyl groups attached to a functional group. Moreover, this absorption band for the above butyl Compounds which contain three methylene groups fits well with the previously cited data of Thompson. LITERATURE CITED
(1) Barnes, R. B., Gore, R. C., Stafford, R. W., and Williams, V. Z., ANAL.CREM.,20, 402 (1948). (2) Sheppard, N.,J. Chem. Phys., 16, 690 (1948). (3) Sheppard, N.,and Sutherland, G. B. B. M.,Nature, 159. 739 (1947). (4)
Smith. F. A,, private communication to authora.
(5) Thompson, H. W., J. Chem. Soc., 1948, 328-31. (6) Tuot, M.,and Lecomte. J., Compt. rend., 216, 339 (1943). (7) Vallance-Jones, A,, and Sutherland, G. B. B. M., Nature, 160, 567 (1947). RECEIVED July 9, 1949.
Comparison of Melting Point Methods for Wax A. W. MARSHALL Petrolite Corporation, Ltd., Kilgore, Tex.
HERE are numerous methods for the determination of the T"melting point" of waxes. Many of these methods do not agree on the melting point value of the same wax, and many are affected by the type of wax. For this reason an investigation has been made of a number of melting point determination methods as applied to various waxes, ranging from the paraffins of low melting point, through the plastic microcrystalline and high melting paraffins or microcrystalline waxes, and including three representative oxidized hydrocarbon waxes. The purpose was not primarily a comparison of methods on the basis of their individual reproducibility, but rather a comparison of the average melting points as shown by them. The softer, lower melting point microcrystalline waxes of the type obtained from lubricating oil residue are referred to as "plastic microcrystalline."
The methods used were those most generally encountered in the trade. They are listed below with an abstracted outline of procedure and a reference to the more complete description in the literature. METHODS INVESTIGATED
Melting Point of Petrolatum. Briefly, this method (2) consists of lightly coating the bulb of a special A.S.T.M. thermometer by dipping it into the wax. The thermometer is then placed in an air bath on which the temperature is raised at a specified rate of 2' F.per minute until the wax drips from the thermometer. Melting Point of Paraffin Wax (I).. A molten sample of wax is placed in a specified apparatus consisting of a tubular container together with a thermometer and stirrin device. The container is then placed in an air bath so controllef as to permit lowering of the temperature a t a specific rate. Time VI. temperature read-
