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THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
which in passing through collects some of the liquid on its surface. The material which so adheres is continuously scraped o f fin the form of a dry ribbon. One of the Passburg types provides that the drum dip into the liquor supply, whereas in another type the drum is not in contact with the main body of liquid, but the solution is conveyed to the drum surface from the liquor supply tank by a small roll situated parallel to and directly under the drum. I n the double drum type the liquid or semiliquid is applied between heated drums revolving in opposite directions. The solution is forced between the rolls, and the material which adheres is scraped o f f in the upper quarter of the revolution. The Buflovak type utilizes a circulating device for applying the liquid. The main body of the liquid is held in a large reservoir in the bottom of the casing, from which it is continuously pumped to a pan directly below and close to the drum. A slight pressure is maintained in this pan which tends to force the liquid against the drum surface and to compel it to adhere to the drum as it passes through the pan. This method gives a uniform coating, which, combined with the control obtained by an adjustable spreader bar, makes possible an accurate regulation of the film thickness. The overflowing liquid from the pan drops back into the tank and is recirculated.
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The running expense of drying sulfite waste liquor by t h continuous process is as follows: Size of drum Steam pressure Vscuum Speed of drum
5 x 1 2 ft. 39 lbs. 2 7 . 8 in. 8 . 2 5 r. p. m. 7 . 2 7 sec. time of test Duration 4 hrs. Weight of liquor, 31 . g o BC. at 60" F. 8011.00 lhs. weight of dry material 4483.00 lbs. Weight of.dry mqterial per hr. 1120.75 lhs. Moisture in solution 4 7 . 8 3 per cent Moisture in dry material 6 . 7 6 per cent Steam consumption per Ib. water evaporated 1 . 1 6 5 lbs. Steam consumption per Ib. dry material 0 . 9 1 7 lh. H. p of drum, pumps, and conveyor 30.16 lhs. Supervision 1 man Floor space of equipment including working space 797 sq. f t . COST 4112 lhs. of steam for drying at 40 cts per 1000 Ihs. $1.6448 4102 lhs of steam for power at 40 cts. per 1000 lbs. 1 .I3408 12,700 gal. water for condenser a t 6 cts. per 1000 gal. 0.7620 hrs, at 4o cts. per hr. 1.6000
-
TOTAL 56476 Cost per pound of dry material $ Cost per ton of dry material Using motor driven equipment the cost would he: 4112 lbs. of steam at 40 cts. per 1000 lbs. 12,700 gal. water at 6 cts. per 1000 gal, 90 k.w. hrs. at 1 . 5 cts. per k.w. br. 4 hrs. labor at 40 cts. per hr. TOTAL Cost per lh. of dry material Cost per ton of dry material
0.001259 2.518 1.6448 0.7620 1.3500 1.6000 5.3568
-
0.001195 2.390
Potash from Kelp. IV-Continuous Countercurrent Lixiviation of Charred Kelp 1 ~ ? , 3 By J. W. Turrentine and Paul S. Shoaff EXPERIMENTAL KELPPOTASH PLANT,BUREAUOF
SOILS,
DEPARTMENT OF AGRICULTURE, SUMMERLAND. CALIFORNIA
I n a chemical process involving the extraction of water- ties, and particularly where a completely extracted solid and soluble constituents from solids and the recovery of the a concentrated filtrate are desired simultaneously. The solution or of the solid residue or both, the ultimate object apparatus has been successfully operated for about two Years, is the complete removal of soluble matter; and in cases in and its efficiency and low cost of operation are thoroughly which the solution is to be processed, the coincident aim is established. the production of a solution as highly concentrated with I n the washing of a precipitate, it is recalled, one is taught respect to the solute as is practicably and economically that the most complete extraction of the things whose reallowable under the specific conditions. moval is sought is accomplished by transferring the precipiThis frequently encountered problem arose in the deter- tate from the filter to a container and stirring it thoroughly. mination of an efficient and economical method for extracting with the quantity of wash water to be used in each indithe potash salts from charred kelp. Its solution is described vidual application and returning the mixture to the filter; but since this is scarcely practicable, one is taGght to stir in the following paragraphs. Nearly all of the material extracted is "activated" char, the precipitate on the filter with a stream of the wash water. which is the product of the reduction of the giant Pacific To add water without stirring washes imperfectly, since the kelp, Macrocystis pyriferu, by a process consisting, briefly, wash water merely establishes channels through the solids. of drying the wet kelp in direct-heat, rotary dryers, charring For that reason, washing solids as filter cake on continuous the dried material by destructive distillation in retorts or in vacuum filters removes impurities only imperfectly and, other manner, and activating the charcoal by subjecting it where a concentrated filtrate is desired, a t a rate which may to a special heat treatment. From the activated char preclude the subsequent use of the washings. are recovered potassium chloride, iodine, and decolorizing In the large-scale washing of a precipitate or extraction carbon. This process has been described in a general way of a solid in the lixiviator herein described, it is practicable to in a previous article. remove the solids from the filter and transfer to a container, The activated char averages 75 per cent total water- there to be stirred with the water or brine being built up. soluble constituents and 52 per cent potassium chloride, and This is repeated as desired, the number of washings being will yield an amount of decolorizing carbon depending, among determined by the number of filter units comprising the other things, on the manner and degree of activation. The Iixiviator. That number may be multiplied to suit the greater part of the water-soluble matter other than potassium problem in hand, the multiplication of the number of units chloride is sodium chloride. The manner in which the char but very slightly increasing the difficulties or expenses is extracted for potash values is of interest not only in con- involved. nection with the recovery of potash and by-products from The system here described may properly be termed counterkelp, but has wide adaptation in other fields, where materials current lixiviation. The material to be leached is fed in a are to be completely washed free from values or from impuri- continuous stream into one end of the apparatus and passes 1 Received April 25, 1921. out of the other end as a satisfactorily washed and largely * Puhlished with the permission of the Secretary of Agriculture. t Part I, b y j .w. Turrentine and Paul s. Shoaff, THISJOURNAL, 11 dewatered filter cake, the while advancing against a stream of water which enters a t one end as fresh water and emerges w i g ) , 864; Parts 11 and 111, by G. c. Spencer, Ibid., 12 (1920). 082.786.
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52.0y. X C I AGITAroR N o I
._._
MoIsrURE
TRAP
D R Y VACUUMP U M P
FIG.]-FLOW SHEETO F CONTINUOUS COUNTERCURRENT LIXIVIATION OF ACTIVATED CHARREDKELP
a t the other as a highly concentrated brine. This is accomplished in a lixiviator of only three units, a unit being a container wherein the solid is stirred with its quota of water, and a filter, with accessory apparatus. For materials less easily extracted, more units would be required. Each, unit accordingly represents a stage in the complete extraction, and each stage represents an application of the extracting agent and a filtration. The units comprising such a lixiviator are made up of a leaching tank, a rotary vacuum filter, with vacuum receiver, and brine pump.
DESCRIPTION OF APPARATUS The leaching tank, which we shall hereafter designate as an agitator, is made of 2-in. redwood, 14 in. x 14 in. x 7 ft. 6 in. inside, and is of standard construction. It has a removable cover of 2-in. redwood, with suitable openings for the entrance of filter cake, brine, etc. In each tank is a 12-in. steel screw conveyor with specially constructed flights by means of which the contents are thoroughly mixed and simultaneously conveyed. The shafts of the agitating screw run out through the ends of the tanks through cast-iron stuffing boxes, and one shaft in each case is extended to run in a journal and to receive a sprocket wheel for driving. Steam heating coils are placed in the bottom of the tanks. At the discharge end of the agitator tank there is an opening on one side a t the top, 3 in. deep and 4 in. wide, from which a 4-in. open trough leads to the tank of the appropriate rotary filter, the trough having a slight fall. This delivers the mixture of solid and liquid in the form of a sludge into the tank of the filter.
The continuous, rotary, vacuum filters may be any of the well-known multiple compartment types, although the one here employed is the one known as the American disk continuous suction fdter. Each filter has one 4-ft. diameter disk, of an approximate filter area of 21 sq. ft. It is made u p of eight removable filter-leaf segments clamped to a central shaft by rods extending radially from this shaft. The shaft is subdivided into eight longitudinal pipe compartments, each leaf segment being connected to one compartment. On one end of the central shaft is a worm gear driving mechanism for rotating the entire disk. At the other end is an automatic distributing valve with eight ports connecting the pipe compartments of the shaft to the solution suction lines and to a back pressure air line for inflating the filter bags and discharging the cake. The disk is mounted in a tank into which flows the sludge to be filtered. The sludge is maintained a t such a level as to cover the leaf segments of the lowest section of the disk. In operation the sludge flows continuously into the tank, and as the disk rotates, the filtering surface passes through the sludge. As each segment under vacuum is immersed, SL cake begins to build and continues to build until the segment emerges above the sludge level. The liquid passes through the filter cloth and vacuum pipes to the automatic valve, while the solids adhere to the fdter surface on both sides of the disk in a cake from 0.26 to 0.5 in. thick. The segments bearing the cake enter the drying area, where the moisture content is reduced by reason of the continuous suction, and then successively move into the discharge zone comprising an arc of l6O, where the vacuum
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is cut off and air a t 15 to 20 lbs. pressure is automatically admitted through one valve port to the segment in this zone to loosen the cake from the filter cloth. The cake is scraped off by a metallic scraper and drops into the agitator of the following unit. The disk rotates a t a speed of one r. p. m. The vacuum receiver is a steel cylinder, insulated, 16 in. in diameter by 5 ft. high. It serves to separate the air from the solution drawn over from the filter to which it is connected. As is the usual arrangement, the solution line from the filter enters on the side of the receiver, a drain line passes from the bottom to the solution pump, and the vacuum line enters a t the top. The solution from each filter is drained from the receiver by an individual pump which conveys it to the proper agitator or storage tank, as the case may be. The receiver from each unit is connected to a common vacuum line running to a single vacuum pump. The moisture trap is a steel cylinder, 16 in. diameter by 3 ft. high, with internal baffles. The condensate from water vapor or entrained solution runs to a seal and is returned to the system. The dry vacuum pump has a capacity equivalent to a displacement of 153 cu. ft. of free air per min. a t 350 revolutions. I n addition to this, a low pressure air compressor is provided to furnish air a t 15 lbs. per sq. in. to the automatic valves of the fiIters for loosening the filter cake before it reaches the scrapers. Steam may be substituted for air a t any time for cleaning the filter cloths of particles tending to clog the pores. The three units are arranged in series in echelon order, so that the filter cake from the filter of one unit falls by gravity into the agitator of the next. The brine from the filter of one unit is delivered by the appropriate pump into the agitator of the preceding one. Thus, the solids pass through the system by gravity flow, while the brine is passed through by the aid of pumps. The total fall from end to end is 28 in. The concentrated brine from the first unit is discharged by its pump into the so-called hot storage tank for strong brine, from which it is drawn off as desired into the evaporating and crystallizing system, and the filter cake from the last unit is discharged into a conveyor for transference to the carbon refining department. Fresh water is added to the last agitator. Brines of three concentrations-weak, intermediate, and strong-are received from the respective units; and solids of four degrees of extraction-the raw material and the filter cake from the respective three filters-are handled. OPERATION The operation of the apparatus is illustrated diagrammatically by Fig. 1, which is a flow sheet of the system. The ground charred kelp, as a dry powder, is fed continuously into Agitator 1 and the solution or filtrate from Filter 2 is constantly delivered to the same point. The sludge resulting from this mixture of fresh char and brine, after thorough agitation, flows by gravity into the tank of Filter 1. The solution from Filter 1 is drawn into its individual vacuum receiver from which it is pumped to storage tanks. This No. 1 solution, or "strong brine," as it is termed in the plant, is the highly concentrated solution from which potassium chloride and iodine are ultimately recovered. The cake from Filter 1 is discharged into Agitator 2, together with the solution from Filter 3. The resulting sludge flows to Filter 2 , which produces the No. 2 solution sent to the first unit, and which discharges a cake into Agitator 3. Hot fresh water flows into this last agitator with the No. is filtered in Filter 3. filter is the No. 3 solution referred to as going to Agitator 2. The cake from the last
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filter, after its third extraction, contains an amount of potash approximately equal to that contained in the weak brine which it carries. Thus its potash seems to be in solution. The normal operating conditions as indicated by the flow sheet may be summarized as follows: Original Activated Char: Total water-soluble solids, per c e n t , . . KC1, per cent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..
......................
75.0 52.0 94.0
Temperature, C ...................... Gravity, BC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KCl by volume (g, per cc.), per cent.. . . . . . . . . . . . . . . . . Filter Cake 1: KC1 (wet basis) per cent ...................... Sludge from Agitat:; 2: Temperature, C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solution 2 : Temperature, C . . , ...................... Gravity, B e . , . . . . . ...................... KC1,per cent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Filter Cake 2: KC1 (wet basis), per cent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sludge from Agitator 3 : Temperature, C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solution 3: Temperature, C . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gravity, Be .......... .......... KC1, per cent .......... .......... Final Filter Cake, 3: Moisture, per cent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KC1 (wet basis), per c e n t . . ...........................
65.0 24.0 25.8
20.0 66.0 56.0 7.5 9.0
7.1 55.0 50.0 0.5 1.4 70.0 1.2
The normal capacity and extraction efficiency may be summarized as follows: Activated char lixiviated per h r . . . . . . . . . . . . . . . . . . . . . . 1100 lbs. Eauivalent KC1 enterine svstem Der hr.. . . . . . . . . . . . . 572 lhs. Stiong brine (Solution fi 6roduc;d per hr.. . . . . . . . . . . . 260 gals. Equivalent KCl extracted per h r . . . . . . . . . . . . . . . . . . . . . 560 lbs. Final filter cake (No. 3) discharged per h r . . . . . . . . . . . . 990 lbs. Equivalent KCl discharged per hr.. . . . . . . . . . . . . . . . . . . 12 lbs. 97.9 Average extraction efficiency, per cent. . . . . . . . . . . . . . . The average vacuum on the filter system is 18 in. The extraction efficiency and the capacity would be increased if the capacity of the vacuum pump were sufficient to maintain a vacuum of 22 to 25 in. on the system. The strong brine (Solution 1) is normally a t a concentration approaching the practical operating limit. The brine of 24" BB. a t 65" C. is equivalent to a slightly supersaturated solution a t 15' C. If cooled to 15" C., accordingly, some potassium chloride crystallizes out, but to an extent reduced through the mutual influence of the salts in solution. However, there is a separation of potassium chloride in small amounts in storage tanks, where no inconvenience results. A more nearly saturated solution at a higher temperaturewhich would represent a higher rate of extraction and likewise a reduced volume of water to be evaporated in the crystallization of potash salts-could be obtained, but it would involve the necessity of more thorough insulation and care in operation to prevent crystallization of salts in the lines and pumps and consequent plugging. The rapid increase in the solubility of potassium chloride in water with increase in temperature makes the use of hot water highly advantageous. The average amount of fresh hot water added to the agitator of the third unit is 345 gal. per hr., which is about 630 gal. per ton of char. This is admitted a t a temperature of 82 C. The drop in temperature may be prevented by the use of more heating coils in the agitators or of higher temperature steam. The progress of the extraction is further illustrated by the curves in Fig. 2 . ~
O
COST O F OPERATION
The entire apparatus is controlled by one man, who regulates the operations by observing the gravity of the solution. With a uniform feed of char the conditions are determined by the amount of fresh water allowed to enter the last unit of the system. Since the capacity of the apparatus operating 8 hrs. is equal to the total daily output of char, the labor cost is that for one man working 8 hrs. per day.
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The apparatus here in operation is the smallest that could be constructed with standard rotary filters. Average operating costs per ton of char lixiviated are as follows:
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nals, one end extending past the journal to receive a sprocket wheel or gear for driving the device. An agitator of the standard type with a round vertical tank and vertically hung stirring device would also be suitable, Labor @ $5.50 per d a y . . .......................... $1.25 provided the arms of the stirrer could be raised when the Electric power, @ $0.025 per k. w.hr. ..............1 . 6 2 Steam ........................................... .I1 apparatus was shut down for any length of time. Unless the Water, 628 gal. @ $0.205 per 1000 gal.. ............ . I 2 8 latter could be done, the settlement of solids from the sludge Miscellaneous supplies.. ........................ , ...53 .. would make starting the agitator a difficult and a t times a GROSSCOST PER T O N ,.............. . $3.638 I n estimating the cost of operating larger apparatus, it nearly impossible matter. For gravity flow of solids, however, should be remembered that no more labor will be required to the height of such tanks would make this use objectionable operate a large extractor than the small one here described; because of the difficulty of installing the units on such widely that the power required will be somewhat greater; that the varying levels. The horizontal agitator can be started operating a t once, even after a prolonged shut-down, so that the system can be stopped “loaded” a t any time and started up a t will. This type also simplifies the transfer of cake from the filters. CONTINUOUS ROTARY VACUUM FILTERS-The filters may be of the drum or disk type. If drum type, the heads should be enclosed. The tanks of the filters should be of wood, as in the usual “acid-proof” construction. Each tank should be provided with a compressed air or mechanical agitating device. The screen on the filters should be of monel metal or wood, and if the drum type is employed, the wire winding over the cloth should be monel metal wire. The valve housings of the automatic valves may be cast iron, but the other wearing parts should be monel metal. The scrapers, likewise, should have contact edges of monel metal. Cotton filter cloth of fairly open weave is satisfactory. On account of the free filtering nature of the sludge, each filter should have a filter area of approximately 2 sq. ft. per 100 Ibs. char per hr. entering the system, with a vacuum of 22 to 25 in. The last filter should have a spray wash sufficient to displace steam and water consumption will be proportional to the .the most of the solution in the cake. This added amount of increase in capacity, and that the cost of all these items will water will not disturb the volume balances in the system bevary with location. cause there is a reduction in sludge volume as the char proSUGGESTIONS FOR A N IMPROVED INSTALLATION gresses through the apparatus. The filtrate and wash of the Experience gained in the design, installation, and operation last filter should be combined. In every case, a steam line besides the usual compressed air of the initial lixiviator in use in this plant suggests modifications which might profitably be observed in its future appli- line should be connected t o the blow-ports of the automatic valves. Air will ordinarily be used to loosen the cake just cation. Materials of construction should be employed which will before reaching the scrapers, but it will be found advantageous insure a long life for the apparatus. The aqueous solutions at times to cut off the air and blow the cloths with steam to from charred kelp, although alkaline in nature, have a corro- clear them of fine solids. The cake from the last filter may be conveyed by a cast-iron sive action upon steel; cast iron is also attacked, but less actively. Copper and brass are attacked by the ammonia in screw running in a wooden box or by a belt conveyor. Prefsolution, and these metals in contact with iron or steel set erence will depend upon the method of final treatment of the cake. up serious electrolytic action. VACUUM RECEIVERS-The vacuum receivers for separation I n certain instances parts of equipment may be of ordinary iron or steel as, for example, parts that are especially of air from the solution drawn through the filters may be of heavy and will function properly when somewhat corroded, 0.25-in. steel or heavier. They may be of the usual design or where they are not subject to erosion, or when not directly employed in such systems. Cylindrical receivers 2 ft. in diameter x 5 ft. to 6 ft. high, with conical bottoms, are suitable exposed to the atmosphere. AGITATORS-The agitator tanks should be of redwood, for quite a range in filter capacities. They should have cypress, or pine, which will last for years, and are flanged connections on top, side, and bottom to the vacuum self-insulating and easy to instal, and represent a low initial line, solution line from filter, and to solution pump, respeccost. A good construction is a tank that is rectangular in tively. It is desirable to equip all receivers with vacuum horizontal section, with a half-round bottom to conform release valves actuated by floats, to prevent solutions from with the sweep of the agitating device. They should be being carried over into the vacuum pump in case of the failcovered with removable wooden covers. Steam heating ure of a solution pump to operate properly. Their elevapipes should be run lengthwise in the tanks close to the tion should be such that the solution inlets are about on a sides. The troughs carrying the sludge from the agitators level with, or lower than the automatic valves of the filters. All the receivers and the pipe lines carrying solutions to and to the filters should also be made of wood. For agitating devices, the standard cast-iron screw conveyor from them should be well insulated. on which the flights are cast as paddles will serve admirably. SOLUTION PUMPS-For removing the solutions from the The shaft of the screw should extend through the ends of the receivers and conveying them to their respective agitators or tank through cast-iron stuffing boxes, and should run in jour- storage tanks, well-designed centrifugal pumps should be pro-
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vided. The casings and runners of these pumps may be cast iron, but the shafts should be monel metal or steel with monel metal sleeves. Unless otherwise provided for, self-priming of the pumps should be insured by a by-pass from the impeller “eyes” to the respective vacuum receivers. The vertical distance from the solution pumps to the receivers should be as great as possible; the nearer the distance approaches 30 ft., the simpler the pump requirements become. A steam line should be connected to the strong brine line just beyond the outlet from Pump 1 to be used to clear the line in case of clogging with crystallized salts. VACUTJM PuMp-The vacuum on the system should be maintained by a dry vacuum pump. I t s capacity should be approximately equivalent to a displacement of 4 cu. ft. of free air per min. for each sq. ft. of‘fdter area. COMBINED MOISTURE TRAP AND CONDENSER-Between the vacuum receivers and the vacuum pump there should be interposed a simple, vertical condenser, which will serve the double purpose of catching any entrained solution and condensing the vapors from the hot solution coming into the receivers. This will not only protect the pump, but will increase the efficiency of the vacuum system. Sea water will usually be available for the condenser. The condensate should pass through a “barometric leg” to a seal tank and be discarded. PIPES AND VALVES-Standard galvanized pipe may be used throughout the system, though cast-iron pipe would represent an ultimate saving in certain instances. I n any of the solution lines, the all-iron lubricated plug valve will give excellent service, also all-iron plug cocks of some designs and monel metal fitted valves can be used. RELATIVE POSITION O F APPARATUS-An ideal arrangement of the different apparatus would be such that the agitators, rotary filters, and vacuum receivers would all be on one floor level; for example, on the upper floor of a 2-story building. The solution pumps should be placed on the lower floor. The combined moisture trap and condenser should be a t such a height that the drain line from it to a seal tank located on the lower floor would be a “barometric leg.” The dry vacuum pump would be placed in any location desired and a t any convenient elevation.
EXTRACTION The minimum amount of water or other solvent which may be used in such a lixiviator is that which will hold as a saturated solution the amount of solute to be extracted; or else the amount of solvent which, mixed with the solids to be extracted, forms a sludge which will flow from the agitator to the tank of the filter. Where the solute is slowly soluble, the time of contact with solvent may be increased by increasing the length of the agitator. To the same end, more violent agitation therein may be obtained by the simple device of increasing the speed of rotation of the agitating paddles. More complete extraction is obtainable by increasing the number of stages or units; likewise by more completely dewatering the filter cake. OTHERAPPLICATIONS It is obvious that, where only extraction without the countercurrent feature is desired, it is necessary only to add fresh volumes of the extracting agent to each agitator and to discharge the filtrate wherever desired. This can be done without impairing the multiple stage and automatic feature of the apparatus. The principle and apparatus here described are applicable conversely to the purification of solutions with some solid adsorbing agent, such as bleaching or decolorizing carbon. I n the application of these materials, an excessive amount of the adsorbent must be used with a single application to
secure a complete bleaching or purification, while much smaller quantities may be used with the same purification if the material is applied countercurrentwise. This partially spent carbon can be induced to take up more impurities from a fresh portion of the solution to be purified; which is to say, that carbon which has lost its power to absorb impurities from a partially purified solution is still capable of taking up some impurities from an untreated solution. In such an apparatus as here described, the solution to be purified would take the place of the fresh water, and the fresh carbon, the unextracted kelp charcoal. Thus, the nearly spent carbon would be used finally to treat the crude solution entering the apparatus, and the fresh carbon, the almost completely extracted solution. The number of applications would be determined by the number of units, and time, temperature, and rate would all be easily adjusted over a wide range. The spent carbon finally would pass from the last filter to the reactivating apparatus. A limiting feature would be encountered in the treatment of solutions whose viscosities would preclude their filtration in vacuum filters. A similar apparatus likewise may be employed in the reactivation of carbon by the wet methods.
SUMMARY A continuous, automatic, countercurrent, multiple stage lixiviator is described, which is based on the employment of any one of the standard continuous rotary filters. The solids to be extracted are alternately extracted and filtered. They flow through the apparatus countercurrentwise against a stream of the leaching agent. The apparatus, developed for the extraction of potash salts and other values from kelp charcoal, is applicable to the washing or extraction of any materials that can be filtered on the standard vacuum filters. The efficiencies obtained and costs of operation are shown. Suggestions for various improvements are given.
National Research Council Research facilities of American industries are to be described in the forthcoming revision of Bulletin of the National Research Council, Number 2, “Research Laboratories in Industrial Establishments of the United States of America.” It is hoped that several hundred new names will appear in the revision. The demand for the first edition shows the wide interest in this subject, and the importance of having every laboratory which devotes even a portion of its time to research properly listed. The Council requests information from directors of research who have not already supplied it. The following data are wanted: name and address of firm and address of laboratory; name of director of research; number on laboratory staff (classified as chemists, engineers, bacteriologists, etc.) ; approximate proportion of time spent on research; chief lines of research: unusual features of equipment; research laboratory space; date of organization of research laboratory and annual expenditure for research. Confidential information is not desired. This material should be furnished as promptly as possible to the Research Information Service, National Research Council, 1701 Massachusetts Avenue, Washington, D. C. The fifth annual report of the Council has recently appeared. The program laid out a t the time of its reorganization from a wartime to peacetime organization in 1918-19 has so far been followed along its essential lines, the principal changes being ones of extension. During 1920 the Council has been an organization controlled by its own membership and supported by other than government aid. The Council, however, maintains close contact with government departments through its division of Federal relations.
