Apparatus for Determining Moisture by the Dis.tillation Method .4. C. BECKEL, A . G. SHARP, AND R. T. MILNER U. S. Regional Soybean Industrial Prodpcts Laboratory, Urbana, Ill.
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HE continued interest in the distillation method for the determination of moisture (I,%?, 3) in materials containing no low-boiling liquids appreciably miscible with water lies in the fact that it measures only the actual water which is given off a t the boiling temperature of the liquid used, whereas by the oven methods the total loss in weight is obtained. Total loss includes, besides the true moisture content, the weight of other volatile constituents of the material under examination, plus the weight of any water that may be formed from the oxidation of the nonvolatile constituents, minus any gain in weight due to the formation of nonvolatile oxidation products. I n the usual Bidwell-Sterling apparatus, as well as in any modification of which the authors are aware, it is necessary to bring the moisture clinging to the walls of the condenser into the measuring tube either by the use of a buret brush or by the introduction of some substance (1, 1,3) to reduce its tendency to adhere to the glass. Using the apparatus described in this paper, it is unnecessary to resort to such practices. The entire determination mag be completed in less than 2 hours. The general procedure, which can readily be gathered from
the diagram, is as follows: The water and toluene, which are distilled from a flask immersed in an oil bath, pass through a slanted tube and down through a condenser whose outlet is beneath the toluene in the measuring vessel. The advantages of locating the condenser on the downcoming tube are not immediately apparent but become so when compared with the operation of the condenser in other locations. I n the Bidwell-Sterling apparatus the vapors of toluene and water travel up into the reflux condenser, condense, and flow back by gravity. Most of the water condenses above the toluene, and the droplets which cling to the glass can be dislodged only by additional manipulation. In the early forms of the apparatus described in this paper and in an apparatus recently reported by Avellar de Loureiro ( I ) the condenser was placed around the receiver. Under these conditions the distillate tended to form a milky suspension of water in toluene from which the droplets of water were deposited on the cooled walls of the receiver to probably the same degree as with the original Bidwell-Sterling apparatus. It mas not possible for the condensed toluene to flow over these droplets, and some method of bringing the droplets into the measuring tube was necessary. On the other hand, with the condenser on the downcoming tube, all the droplets of water deposited on the cold walls of the condenser are washed by the condensing toluene or are dislodged by the surging toluene mentioned below in connection with the bumping. The milky suspension, which practically always forms except with samples having a very low moisture content, is not circulated past cold walls. Strangely enough, no considerable amount of milky suspension or toluene distillate ever accumulates in the upper part of the receiver. This results from the automatic sucking-back caused by the building up of the column of distilled toluene in the cooled tube leading down from the flask, along with the vigorous surging caused by the bumping in the distillation flask. When the column of toluene builds up to a sufficient height, the surging causes some of the cooled condensate to drop into the distilling flask; and the resultant cooling effect causes the entire liquid, down to the outlet of the condenser, to be sucked back into the distillation flask. The frequency of this operation depends on the rate of distillation; usually it occurs about once every 10 minutes. The bumping is, of course, an almost invariable accompaniment to the determination of moisture in solid foodstuffs by the distillation method. Its violence may be reduced by immersing the distilling flask in a bath to bring about more uniform heating. However, when bumping was entirely eliminated-for example, by placing the sample in a cloth bag and suspending it in the toluene-neither the surging nor the automatic suck-back took place. When distilled water was added to the toluene in order to determine the extent of its recovery, the surging and suck-back were likewise not observed. On adding a small quantity of dry sand to the toluene-water mixture the bumping once more occurred, and the distillation proceeded entirely unaided.
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DIAGRAM OF APPARATUS Dimensions in millimeters
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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The repeated automatic suck-back is important to the determination of the moisture by this method. Careful observation of the progress of the distillation of the water shows that the first port,ionswhich come over condense in large clear drops and quickly sink into the measuring vessel; later, the condensed droplets become very small and the milky suspension results. As a consequence of the repeated suck-back, the fine droplets are repeatedly distilled, and each time this occurs a considerable number of clear droplets sink into the measuring tube, with the final result that the determination is completed with no supernatant suspension. This condition is frequently reached in 1 hour, although in some cases it may require 2 hours or more. Since it is impossible to control the bumping accurately, two other points should be emphasized-namely, the use of an enlarged or bell-shaped end on the condenser tube and an annular ring on the receiver. The function of the enlarged end is to reduce the violence with which the liquid is driven into the receiver. However, in spite of this provision an especially violent bump will occasionally drive the toluene up the sides of the receiving vessel with sufficient velocity to cause a drop or two of liquid to splash out. The insertion of the annular ring eliminated this loss by causing the liquid to be thrown back into the center of the receiver. The mercury leveling bulb connected to the bottom of the graduated receiver proved advantageous at times in collecting droplets clinging to the sides of the measuring tube and in
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leveling the top meniscus of the water layer in order to facilitate reading. A series of moisture determinations was made on ground soybeans with the following results: 6.73, 6.64, 6.71, 6.59, 6.73, and 6.80 per cent. The maximum difference in this series is 0.21 per cent, whereas the maximum difference due to the error in reading the graduated measuring tube, assuming it can be read to *0.01 cc. would be 0.134 per cent, since the total volume of water obtained is about 1.00 cc. The samples used weighed 15 grams to the nearest milligram. The temperature of the oil bath surrounding the distillation flask varied from 110" to 155" C.
Summary An apparatus for the determination of moisture has been devised and has been found to be superior to those of the Bidwell-Sterling type, because the removal of droplets of water forming on the walls of the condenser is accomplished automatically and the milky suspension forming in the receiver is eliminated by automatic redistillation.
Literature Cited (1) Avellar de Loureiro, J., J . Assoc. OficiaZ Agr. Chem., 21, 645 (1938). (2) Calderwood, H. N., and Piechowski, R. J., IND.EA-G.C H E M . , Anal. Ed., 9, 520 (1937). (3) Langeland, E. E., and Pratt, R. W., Ibid., 10, 400-2 (1938).
Determination of Neutral Oil and Tar Acids
in Phenolic Compounds EDWARD FIELD
AND
LOUIS STEUERWALD, Standard Oil Company of California, San Francisco, Calif.
Improved methods of testing for neutral oil and tar acids in phenolic compounds have been worked out in the authors' laboratories on the basis of known blends and pure compounds. The adoption of these improved methods will result in more accurate analysis, the sum of the percentages of neutral oil, tar acids, and water not exceeding 100, as is frequently the case with existing methods. Specifications formulated on the basis of these analytical procedures will represent quality which is at once rigid and dependable.
P
HENOLIC compounds or cresylic acids obtained from such sources as petroleum, coal tar, and low- and hightemperature carbonization processes are known to contain varying amounts of neutral oil and tar acids. The neutral oil has been found to be a hydrocarbon mixture of boiling range similar to the acids from which they were extracted, while the acids consist exclusively of phenol, cresols, xylenols, and higher pheno!ic homologs. Since the amount of neutral oil and tar acids present is a prime consideration in specifications for phenols covering a wide field of industrial usefulness, it is important to determine these constituents with a high degree of accuracy and reproducibility.
Neutral Oil The official method for unsaponifiable residue (8) was tried on several samples but without success, the oil being incompletely recovered. The Standardization of Tar Products Test Committee of London has published a method, Serial No. CC.5-38 (4, for the determination of neutral oil. The sample is distilled with aqueous sodium hydroxide solution and water, the oil being collected in a graduated separating funnel receiver, the graduated portion of the stem being either 1- or 3-ml. capacity. After allowing for complete separation of oil and water in the receiver, the water is drawn off and the oil volume is read within the graduations and calculated t o percentage of the sample. A method published by Allen (1) also uses steam-distillation, but removes phenols and nitrogen bases from the ether extract of the oil before evaporation and weighing. This method has one possible disadvantage in that some cresylic acids may be lost on evaporation of the ether.
A new method has been developed by the writers which uses a 100-ml. sample and measures the volume of separated oil in a standardized Babcock cream bottle. APPARATUS. Graduated cylinder of 100-ml. capacity. Round short ring-necked flask of I-liter capacity. Water-cooled condenser. Balloon separatory funnel of 1-liter capacity. Funnel, 10-cm. (finch) size. Small funnel with stem drawn to near capillary size (approximately 1 to 2 mm.). Babcock bottle, 9-inch, g-gram, 50 per cent ,X I/$. Beaker of 600-ml. capacity. Burner and shield. Boiling beads and Alundum chips.
