SEPTEMBER 15, 1940
a large part of the expressed fluid escaped between the piston and the cylinder and flowed down the sides of the cylinder during the pressing operation. Ordinarily, the liquid expressed in this manner can be collected as it flows from the drain hole in the platform of the press, but in the authors' case means for making a more quantitative collection of the fluid and for avoiding its contamination were desired. By placing the test cylinder in the metal pan provided as part of the Carver equipment, losses can be largely avoided, but even this procedure is not entirely satisfactory or convenient, especially in the treatment of small amounts of tissue. To answer their needs in this respect the authors have devised a modified juice extractor (in cooperation with the American Instrument Company, 8010 Georgia Ave., Silver Spring, Md. The equipment is designed for use with the usual type of hydraulic laboratory press.). The new extractor is well adapted to laboratory pressing operations where relatively small amounts of material must be handled and where both the press cake and the press liquid must be carefully collected with a minimum of loss and contamination.
A cross-sectional diagram of the improved extractor is shown in Figure 1. The apparatus is constructed of steel and consists of four separate parts : base, perforated plate, cylinder, and piston. To operate, the base, perforated plate, and cylinder are assembled as shown in the diagram and a circular felt disk is placed on top of the plate. The cylinder is filled to a suitable depth (found by trial) with the material to be pressed and the material is covered by a second felt disk. The piston is placed in the cylinder and the entire extractor is placed on the platform of a Carver laboratory press where pressures up to 20,000 pounds can be applied. During the pressing operation most of the expressed fluid passes through the perforated plate a t the bottom of the cylinder and is expelled through the spout. Any fluid which is forced between the piston and the cylinder, or through the joint between the cylinder and the base, is collected in the channels provided and eventually flows out through the spout. After the fluid has been completely expressed, the cylinder is simply lifted from the base, the press cake is ejected by means of the piston, and the apparatus is ready for use with a second lot of material. For best results the felt filter disks should be renewed frequently. A hole through the top of the piston handle, in which a metal rod may be inserted, facilitates removal of the piston.
A Versatile Gas Saturator WILLIAM R. RINELLI AND KARL S. WILLSON Ansul Chemical Company, Marinette, Wis.
ARKHAM ( I ) has described a gas saturator claimed to
be more satisfactory than the commercial Friedrichs or Milligan gas-washing bottles. Equipment of this type can be used t o saturate a gas with the wash liquid, or scrub out one or more constituents of a gas stream, using a n appropriate liquid. Perhaps less well known is the possibility of removing undesirable dissolved gas from a liquid by bubbling another noninterfering gas through it. A wash tower, which is based on a somewhat different principle than that of Xarkham, in several modifications has proved highly satisfactory in the authors' laboratory during the past few years.
Basically, the tower is designed to pass the liquid-gas mixture through beads, helices, rings, or irregular fragments of suitable material held in place, for example, by indentations made by pressing the end of a file into the heated glass wall. Greater agitation is secured than in the spiral bottles referred to above. Liquid is circulated in both types, but in the authors' tower, if rubber tubing connections are satisfactory, several reservoirs such as R (Figure 1, A , B ) may be used to provide any desired total volume of wash liquid. The path of circulation of the liquid is indicated by arrows. A bottle of any required size can be readily connected to replace the reservoir, as shown in C. The apparatus may be easily cleaned without dismantling by filling with water and draining as often as necessary.
Where glass-blowing facilities are limited or where i t is necessary to thermostat the tower, the modified form shown in Figure 2 has proved satisfactory. Glass seals may replace the rubber stoppers where desired. The entire unit may be placed in a larger tube, through which a constant-temperature liquid is circulated, or the entire tower could be placed in a tall thermostated bath. The tower may be readily modified to fit specific needs. Recently it became necessary to wash large quantities of a n
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
VOL. 12, NO. 9
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.
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.