INDUSTRIAL AND ENGINEERING CHEMISTRY acid-containing gas with a caustic solution and yet keep the solution highly diluted a t all times in order to prevent plugging of the inlet through deposition of the slightly soluble salt formed. The problem further required a moderate vacuum on the inlet side; hence the head of liquid in the tower shown in Figure 1, for example, would be insufficient to permit draining off portions of the liquid while the tower was in operation. Gas flowage varied considerably. -411 these difficulties have been satisfactorily handled by using a tower as shown in Figure 3. With this tower, the elbow a t A , acting as a gas lift as in the spiral wash bottles, guarantees positive circulation of the liquid even a t extremely slow gas rates. Use of the auxiliary reservoir, B , attached t o the main tower by rubber tubing at C and C’, permits addition of any large volume of wash liquid desired through the inlet at D without interrupting the action of the tower. Thus, added liquid causes liquid to overflow into B until the reservoir becomes filled to the lower connection. Then by placing clamps a t C and C’, the liquid may be drained at E , with F actin as a vent. If desired, a bottle suitable size could be used directly as this auxiliary reservoir. If there is danger of plugging of the FIGURE 2 inlet tube through deposition of salt, a T-connection a t the top of the inlet, as shown. allows a glass or metal rod to be inserted to break up the plug: If desirable, a metal or carbon tube may replace the glass inlet tube. Likewise, if an inert liquid is available (mercury, for example) plugging can be minimized or entirely eliminated by modifying the lower part of the apparatus as shown in detail at right. While towers of any volume, height, and dimensions are possible for ordinary work the authors have standardized largely on a tower made of standard Pyrex glass tubing of the type shown in Figure 1, the two reservoirs being 28 mm. in outside diameter with connecting tubes 7 mm. in outside diameter. A packed section about 30 cm. long has proved satisfactory when 3-mm. glass beads or fragments of glass not over 5 mm. in longest dimension are used. Such a tower has a capacity of
07
-
VOL. 12, NO. 9
GUJ
t n
F
L i90
FIGURE 3
about 300 cc. Adequate headroom above the packed section (at least 15 cm.) should be provided to prevent carry-over of liquid in case of excessive gas flowage, and a longer head section or auxiliary trap may prove desirable for high flowage rates or where foaming may occur. Although no comprehensive tests have been made with this type of tower, continued use in this laboratory has demonstrated its high efficiency and versatility.
Literature Cited (1) Markham, IND.ENO.C H m r . , Anal. Ed., 12, 112 (1940).
Use of Wetting Agents in Glass Apparatus WILFRED H. WHITE, 131 Euclid Ave., Jamestown, N. Y.
T
HE problem of eliminating errors due to the accumula-
tion of dirt or grease which prevents the free flow of solutions through glassware is usually solved by frequent cleaning. This often involves considerable time and the hazard of expensive breakage. This was found unusually true in the use of the gas buret in the apparatus for the determination of carbon in iron by the volumetric gas method (carbon determinator, Laboratory Equipment Company). Grease from the large stopcock above continually fouled the buret, causing drops of the confining aqueous liquid to form on the sides of the tube. It was found that the use of 0.5 per cent of a wetting agent
(Tergitol KO.4, Carbide and Carbon Chemicals Corporation) allowed the liquid to flow uniformly down the tube and practically eliminated the necessity of cleaning. During the past year, since the m-etting agent was added, it has not been necessary to clean the apparatus nor to add more wetting agent. Wider application of this to other apparatus is indicated by its use in the gas buret of a n Orsat gas analysis apparatus m d in water gages. One field for further investigation might be the development of wetting agents which could be added to volumetric solutions. This would give accurate readings of the buret in spite of grease on the inner surface.
