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INDUSTRIAL AND ENGINEERING CHEMISTRY
produced by yeast fermentation, and b y the Sichert and Bleyer chemical method. Both methods gave satisfactory results in determining dextrose, but only the biological method, because of its high specificity, could be relied upon in analyzing for maltose. The chemical method is unreliable for the determination of maltose in the presence of the reducing dextrins which occur in both acid and enzymehydrolyzed starch products. P-rlrnylase can be used to give an indication of the amount of such reducing dextrins. The two methods applied to the analysis of the course of acid hydrolysis of starch showed that the longstanding work of Rolfe and Defren is in error, owing to the lack of specificity of Fehling’s solution for the determination of maltose in the presence of reducing dextrin.
Vol. 15, No. 8
Literature Cited (1) Barfoed, c,, z,
Chem., 12, 27 (1873),
(2) Browne, C. 8., and Zerban, F. W., “Sugar Analysis”, 3rd ed., New York, John Wiley & Sons. 1941. (3) Harding, V. J., and Nicholson, T . F., B i o c h m . J.. 27, 1082 (1933). (4) Nanji, D. R., and Beaaeley, R. G. L., J . Soc. Chem. Ind., 45, 215T (1926). ( 5 ) Rolfe, G. W., and nefren, G., J . Am. Chem. Soc., 18, 869 (1896). (6) Schultz, A. S., Atkin, L., and Frey, C. N., IND. ENC.CHEM., ANAL.ED.,14, 35 (1942). (7) Schultz, A. S., and Kirby, G. W., Cereal Chem., 10, 149 (1933). (8) &chert, K., and Bleyer, B.. 2. anal. Chem., 107,328 (1936). (9) Somogyi M., J . Bioi. Chem., 119, 741 (1937). (10) Steinhoff,G., 2. Spiritusind., 56, 64 (1933). (11) Voorst, F. T . van, Chem Wsekblad, 35, 338 (1938).
Gas-Absorption Apparatus LUTHER BOLSTAD AND RALPH E. DUNBAR, N o r t h Dakota Agricultural College, Fargo,
D
U R I S G a series of acetylation studies with ketene it became necessary to devise a compact, flexible, and efficient type of absorption apparatus that would provide intimate and prolonged contact of the gas with the liquid reactant. After testing several arrangements of the traditional absorption equipment, the piece of apparatus shown in Figure 1 was constructed and has been found to be thoroughly satisfactory. The arrangement can be used for the absorption of other gases under similar conditions. The use of the glass-bead column was suggested by Sham ( I ) but this equipment is sufficiently different to justify description. -4 6-cm. piece of 6-mm. glass tubing, A , is sealed endwise to a 10-cm. piece of 12-mm. glass tubing, B. Four small oblong holes, C , of approximately 4-mm. diameter, are blown in the larger tube just above the point of sealing. A 6-cm. length of 20-mm. glass tubing, D, is then sealed t o B , just above the four openings. D should not reach to the lower level of A bv some 1 or 2”cm., in order to provide the correct circulating operation when the completed equipment is in use. This arrangement provides two concentric tubes, A and D, with B extending above the other t w o as shown. The upper end of R should be attached to an efficient reflux condenser during operation, by means of a rubber or g r o und-glass connection. The space between A and D is then nearly filled with FIC~T-RE 1 solid glass beads
Pi. Dak.
and enough constrictions are formed at the lower end of D to hold. the glass beads in place. B is inserted through the opening of a, one-hole stopper that closes a 125-ml. filtering flask, E . The accompanying illustration shows all these essential features. Proportionate changes in dimensions may be made, so that this equipment can be used with any available size or type of filtering flask. The gas to be absorbed is then introduced through the side arm, F , of the filtering flask. The lower end of D should dip just below the surface of the liauid absorbent. As the Dressure within the flask increases, the liquid is forced up A and-D, until a few bubbles enter the glass-bead column. Here a percolating effect is produced, as gas and liquid ascend through the glass beads. A large portion of the resulting solution returns through A . As the volume of the liquid increases, owing to the absorption of gas, the same relative positions of liquid to absorption apparatus may be maintained by raising the glass tubes through the supporting stopper. This piece of equipment differs materially from that designed by Shaw ( 1 ) in the following major respects. It was constructed to handle relatively large volumes of liquids or solutions and highly concentrated gases in small volumes, rather than small volumes of liquids and large volumes of dilute gases. It has been employed in the preparation of numerous organic acetates in yields of better than 90 per cent of the theory, and in quantities of better than 40 grams of the final acetate. The absorption apparatus has operated continuously for 20 hours or more without further adjustment, except the raising of the absorption tube in relation to the liquid in the filtering flask. The rate of flow of ketene was 0.07 mole per hour (3 to 4 liters of mixed pyrolysis gases), although any slower perceptible rate of flow would be absorbed with the same quantitative efficiency. The average back pressure during operation is 50 to 60 mm. of mater, which is readily counterbalanced by any closed traditional gas generator. -4further advantage of this equipment is that precipitates, produced by reaction between gas and liquid, do not clog or hinder the operation, since there are no small openings to become clogged. I n case the gases employed are less soluble than ketene, the length of the glass-bead column may be extended to permit longer contact between the gas and liquid solvent. The entire piece of equipment is relatively cheap and can be constructed by any efficient glass blower from materials readily available in any laboratory.
Literature Cited (1) Shaw, J. A,, IND.EKG.CHEM., ANAL.ED.,6,479 (1934).
