Document 9JoZo8Z7gzX6eqOevnqvrLRYV

--/ Monsanto Chemicals-Plastics ___V/rf__ AN INDIRECT AROCLOR HEATER for UNIT CHEMICAL OPERATIONS Monsanto Technical Bulletin No. P-130 September, 1949 Monsanto Chemical Company St. Louis (4), Missouri Aroclor* 1248 (chlorinated biphenyl) is an ideal nonflammable liquid phase heat-transfer medium for temperatures up to 300C. This bulletin describes the physical properties of Aroclor 1248 and illustrates the design and operation of heaters that have been used successfully by Monsanto plants during the past seven years. The units described are gas fired and the capacities are in the range of 200,000 to 400,000 B.t.u. per hour. Other larger commercial installations using Aroclor 1248 have capac ities ranging up to 2,000,000 B.t.u. per hour. Also small electrically heated stationary and portable units with capac ities around 40,000 B.t.u. per hour,using Aroclor 1248 as the heattransfer medium,are in service. Several leading manufacturers of heating equipment are in position to build or offer Aroclor heating units to meet specific requirements. > z c z z o jo 0m 1n m :E n > 73 > r no o TJ r o m 73 ;o X >m > oH zm 73 ~n O 73 Monsanto Technical B u lle tin No. P-130 September, 1949 Reg. U. S. Pet. Office The tniormelion contained in thi bulletin la, to our beet knowledge, true end accurate, but all recommendation* or euggeatlona are made without guarantee, eince the conditions of uaa are beyond our control. Tha Monearuo Chemical Company dleclelmi any liability incurred In connection with th* uaa of thee* data or auggetUon*. Furthermore, nothing contained herein ahall be conetrued at a recommendation to use any product in conflict with emitting patent* covering any malarial or ita uaa. 0558214 Y. TOWOLDMONOQ36712 Reprinted from INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 41, Page 1341, July 1940 Copyright 1949 by the American Chemical Society and reprinted by permission of the copyright owner An Indirect Aroclor Heater for Unit Chemical Operations MEADE McARDLE1, L. C. GARRETT, AND P. G. BENIGNUS' Monsanto Chemical Company, Anniston, Ala. The characteristics of Aroclor 1248 indicate that it Sprat Flammabilitt. When a tube ruptures in a liquid heat- is an ideal liqiiic' phase heat-exchange medium for transfer system under high pressure, a spray or miat forms. temperatures up to 300 C. This article discusses its The possible fire hazard under these conditions requires considera properties and illustrates the design and operation of tions not covered by the foregoing discussions relative to the ma heaters that have been used successfully by Monsanto terial in the liquid form. In their comprehensive study of plants during the past seven years. flammability of the higher boiling liquids and tbeir mists, Sulli van, Wolfe, and Zisman {0) determined the spray flammability IN CERTAIN manufacturing processes of the Monsanto limit of numerous materials in accordance with the percentage of Chemical Company, it was necessary to employ a noncom- oxygen required for combustion. This value was then correlated buslible heat-transfer medium at pressures of 30 pounds per with the results of incendiary firing tests of the fluids conducted 6quareinch or less and temperatures up to 300 C. The following at the Naval Proving Ground, Dahlgren, Va. The oxygen re general properties of a heat-exchange medium were required: quirement for Aroclor 1218 combustion in the spray flammability Freedom from fire hazards. Viscosities to permit pumping at room temperatures. Boiling point sufficiently above 300 C. to assure a liquid con dition at all times. Stability against heat, with enough safety factor to accommo date accidental overheating. Controllable vaporization losses. Freedom from corrosive action against valves, piping, tank jackets, etc., made of cast iron and steels, bronze, and stainless steel, Freedom from toxicity hazard. limit studies was found to be 04%. Fluids requiring over 45 to 50% oxygen in the spray test failed to cause a fire in the incendi ary test. These results establish the nonflammable and noncom bustible qualities of Aroclor 1248. VISCOSITY CONSIDERATIONS Cold Flow. For most inside installations centrifugal pumps will handle Aroclor at reduced rates without preheating. Experi ence confirms this. Outside installations have been started at Aroclor, chlorinated biphenyl (registered in U. S. Patent 0 C. by heating the pump and feed line until circulation through Office), was selected, The pertinent physical characteristics relalive to its use as a heat-transfer medium are given in Table I. Table I. Physical Properties of Aroclor 1248 FREEDOM FROM FIRE HAZARDS Flash Point. Limitations of this test for the prediction of the fire hazard of relatively nonvolatile organic fluids have been recognized by the Aaxcrican Society for Testing Materials com mittee (fl, 4). Fikk Point is a more significant measurement. The Under writers' Laboratories {10) state that fire tests more truly reflect the (lack of) fire hazard of Aroclor. Spontaneous Ignition Temperature. The combustion- Appearance Absolute density, g./m). Absolute viscosity, centipoisca Practically colorlcsa mobile liquid C. C T.) 1.44 1.41 1.37 1 27 1.17 30 <80> 60 (140> 100 (212) 200 (392) 300 (572) 112 17.5 4.2 0.99 0.47 30 (86) GO (140) 100 (212) 200 (392) 300 (572) resisting qualities of Aroclor 1248 are indicated by its high spon taneous ignition temperature of 704 C. (1299 F.) determined by Sullivan, Wolfe, and Zisman (#), using the convenient apparatus described by Sortman, Beatty, and Heron (5). Under conditions of industrial use the spontaneous ignition Thermal conductivity, B.t.u./hour/sq. foot/ 0 F./foot Distillation range, A.S.T.M. D-20, 0 C. Flash point, Cleveland open cup, A.S.T.M, D 92-45, 6 C. 0.0613 0.0698 0 0800 340-375 193-190 30 (80) 60 (140) 100 (212) temperature will be determined by factors including the nature of the hot surface, the amount oT liquid impinging on it, the volume of enclosed space, and the ventilation. An accidental failure in a heating system demonstrated the nonflammability of Aroclor 1248 and its freedom from the hazard of fire propagation. An operator's failure to start the circulation of the heat^tranefer medium when the gas heater was on resulted in excessive coil temperatures and caused the lower coil to soften and sag into the fire chamber. A weld ruptured and Aroclor 1248 poured into the red-hot fire chamber in contact with the flame. Dense smoke aroBe from the heater but there was no external fire. After the gas flame was cut off, the smoking stopped. 1 Prcacnt address, Monsanto Chemical Company, Organic Chemicals Division, 8t. Louis, Mo. ' Present address, Monsanto Chemical Company, Phosphate Division, Fire point, Cleveland open cup, A.S.T.M. D 92-45 Pour point, A.S.T.M. D-7, e C. Coefficient of expansion, ml./ml./0 C. (25- 65 C.) Specific volume, ml./g. Specific heat, oal./g./e C. Vapor pressure, mm. Ilg None -7 0 000702 0.696 0.709 0.728 0.787 0.800 30 60 100 200 300 0.313 0.337 0.326 0.355 50 too 200 300 0.00037 0.16 2.9 18.0 360.0 37.8 100 150 200 300 (86) (140) 212) (392) (572) 1122) (212) 1302) (5721 (100) 212) (302) (393) (672) Bt. Louis, Mo. ju~ 05582X5 TOWOLDMONOQ36713 1342 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Table II. Stability of Aroclor 1248 Heated for 30 Hours Temperature 2B0 300 310 320 830 Mg. of HCI per Gram of Aroclor Table III. Stability of Aroclor 1248 Continuously Heated AT 280 AND 330 C. Hour* Mb of HC'l per Gram of Aroclor 280 C 330 C. 30 0 070 0.248 60 0 116 0.510 BO 0.16W 0023 120 0.104 1.141 160 0.2G1 1.3G2 Table IV. Gas Analysis of Aroclor 1248 Heated 4 Hours at 260 C. and 210 Pounds per Square Inch Pressure Gae % Carbon dioxide Carbon monoxide Oxygen (derived from air) Methane Hydrogen chloride Chlorine Acidity {% by weight HCI) Prior to exposure After exposure 20O12 N.2 0 0076 0.0076 the heater had been effected so that the system could operate normally. BOILING POINT Operating experience has shown that the boiling point of Aro clor 1248 (3406 C. at 760 mm.) is enough above the 300 C'. operating limit to prevent trouble from this cause. At the maxi mum operating temperature the vapor pressure is less than 0.5 atmosphere. HEAT STABILITY In order to establish a maximum practical operating tempera ture, the (-lability of the material when heated to elevated tem peratures in the presence of iron was noted. A slow, stream of nitrogen was passed over the hot Aroclor to sweep the decom position products into a caustic trap. The amount of acidic material was determined and calculated as hydrochloric ncid. The results given in Table II indicate the stability of Aroclor 1248 wlien individual samples were healed for 30 hours at the given 4**tnpcraturcv The decom position is very low at temperatures up to 300 C. ' The stability of Aruelor 1218 in contact with L iron continuously healed at 28(1 and 330 C. is indicated by Tublc 111. These test results indi cate that Aroclor 1248 in con tact with iron can lie used satisfactorily at temperatures up to 300c C. The Notional Hoard of Fire Underwriters (lO)reported that "decomposition of the product [Aroclor 124S j was not appreci able at temperatures below 400" C., but became increas ingly apparent at higher tem peratures." at. 340 C. fitted with an internal gas burner so that the gas flame impinged directly on the surface of the Aroclor. Analysis of the gases produced under these conditions included 0.6% carbon monoxide, 0.17% oxygen (derived from the air). 0.99% hydrogen chloride, 2.1% combustible gas calculated as methane, 0.002% chlorine, and no phosgene. The same workers studied the stability ot Aroclor when heated for 4 hours in an iron pipe at 260 C. under an internal pressure of 210 pounds per Bquare inch, resulting from the introduction of compressed air. Following this treatment and cooling, the cases removed from the system were analyzed. The acidity of the Aroclor was determined prior to and after exposure to these con ditions. The results given in Table IV reflect an extremely small amount of decomposition under conditions similar to those selected for the practical use of Aroclor 1248 as a heat-transfer medium. In actual practice using the type of heating unit described below there has been no evidence of hydrochloric acid effect and no car bon deposits have been noted in the heater, pipes, or valves. The heaters have been operated successfully with combustion gases at approximately 600 C. in contact with the coils. At one time, a spiral coil type of heater was built and through faulty design a burner tunnel was located 1.5 inches from the 2inch steel pipe coil. The radiation from the white-hot refractory tunnel and the direct impingement of the flame on the pipe caused the pipe to glow a dark rea for a space of about 2 inches. This unit was operated almost 3 months before a circulation stoppage occurred. When the line was opened lumps of carbon were found to have come loose and moved forward to lodge in the glebe valves. The lumps measured about 1 X 2.5 cm. and one fare was formed to fit the pipe curvature. No hydrochloric acid effect was Doted and the system was put back into operation after the burner location was changed. CONTROLLABLE VAPORIZATION LOSSES The heating systems in which Aroclor 1248 is used are seaied except for the expansion tank, which has a loose cover or a vent pipe. Because this tank is separated from the stream by a sub stantial length of pipe, the temperature in tlie lank remain? low. In the light, of the relatively low vapor pressure valuer for Aroclor 1248 (7), and us it is unlikely that the expansion tank will ever reach even the 1-inin. state (130 C.), there should not be a measurable loss of Aroclor from the system. Actual experience bears out this contention. Other Losses. Although Aroclor darkens on use, its charac teristics remain the same and replacement has not been found necessary after 7 years of continuous use. Accidental leaks or spills constitute the only observed losses. Plan and ART srC'iON B-0 J Their workers analyzed the decomposition products of Aroclor 1248 heated in the pres ence of hot Iron at 459' C. and also heated in an iron cylinder Figure 1. Heater 0558216 < TOWOLDMONOQ36714 uly 1949 INDUSTRIAL AND ENGINEERING CHEMISTRY 1343 TaHI.K V. ReSISTANCF. OF StRECTI'RAI. Materials to Aiioclor Metals Alumiinitu ( MkllCCIUM Niflkel Silver Tin Metal* Zinc MiM j-U-cl j<0(i brass Yellow bia.-s HR. Lxcclleut reMimitice, less lli&n 10 X 10 cm. per dn.v penetration or 0.00014 incli per year. K. Good resistance, penetration between 1,0 X 10 ' and 10 X 10"* cm. per day or between 0.00014 and 0.0014 inch per year. D. Doubtful raaistunee, penetration between 10 X 10~* cm. per day and 100 X KM* cm. pet day or between 0.0014 and 0.014 inch per year. e. Following letter iridioatitiR reriattmee, sicnifies material may be b-'lWr than indicated if totally immersed, as weiirbt loss is believed to conic fiom oxidation of part of OM strip exposed to air. design ami gonstki ction Heati.no System. The heating system required to utilize Aroclor 124S as the exchange medium includes a heater (Figure 1), cooler, pump, and expansion tank (Figure 2), and control and safety circuits (Figure 3). FREEDOM FROM CORROtMt E ACTION The resistance ol various metals (? j al 25e and 12oc C. is given iu Table Y. 8in)ilnr studies made at 325c' ('. (o') indicate that the penetra tion, in inches per year, for mild .steel is O.OOL'n; for yellow lira--, 0.00047; for copper, 0.001 15. Many years of practical operating experience will) Aroclor 124S as a heut-transfci mediuni have shown that the material is prac tically iionenrrosivc tit valves, piping, tank jackets, etc., mad*' of caat iron and steel?, bronze, and stainless si eel. FllKFIOM FROM TOXICITY HAZARD Aroclor 1248 is a very stable, unreactive liquid. If the materia! is spilled on the skin, there are no noticeable ill effects; however, it is well to wash the skin with soap and water after contact. A akin burn resulting fiom accidental contact with hot Aroclor should be treated in the normal procedure um-J mt hot oil burns. Aroclot adhering to the burned area need no1 be removed im mediately unless treatment of the burn demands it: in this case HOap and water or repealed washing.- with a vegetable oil (linseed oil) should lie IPod. The vapor- ,i,.;Mc<] In Arocloi J21S heated to elevated tem peratures atr injurious I" the liver on prolonged exposure and ehould hot be bio::',bed. Drinker (o' indicated that 0.5 mg. of Aroclot J 2IN per cm 'ic nio! < r of nii n :1c maxi mum safe amount piMuissii.il- iii w arki "cm. In commercial l.eal-l ianslcr installation.-, the presumption ithat the Aloclov i~ 111 a i lo-ed sy-lem flee from leaks. Accord ingly, tie tc sliouM I" no opportunity for workers to come in con tact with vapor- lomi the ho! heat-t:ansh: medium. Figure 3. Control anil Safety Circuit Heater Design. The general requirements of the heater are compactness, ease of construction and service, and avoidance of direct flame impingement on the tula--. Direct flame impingement is prevented bv direcling the gas flame through an enclosed channel with halt-thickness fire brick protecting the tubes above until the high temperature of the flame is reduced by heat cojulucted through these bricks and radial.al to the two bottom coils. The size of the healer is reduced to a minimum by using m>lv 4.5 in.-lies of insulating fire brick in the hottest areas and 2 incho- ot Magi'1 Yu 00 insulation oil the cooler spm -. 'J wm mm - o, :i:11:nr usi d: < bn has a maximum capacity of 2(H),(KID H.t.u. pi t bom, a- shown in Figure 1. The larger has a nuuw of 2''(i.ODit o> tou.uno p.t.u. J lio sm-dl size consi-ts o> 00 ;,vt of ]-in.-h standard weight steel pipe ni.'eh in'o three oils of six piprs eaeli and connected in serio--. in.- lai'ii' i -i/o eoiisists of 144 feet of 1.5-incli standard wvjghi .-toe) pipe arranged in the same lashimi. Results of on tlie smnli-sizv heater covering temperatures, from 150` to 300: show teiuperattnv rises to 10; to 20r' in the Aroclor whih- ei:i-ulating m a rate of 15 to 20 gallons per minute. The "Utht L-i- icmpo-aiim- M eon-i-ion]v within 75' C. of tic- outh-t Aroclor touipomtun . Mi- "|,.,,.nv,] p.m tin- Is'Mom two coils Hh- sorh Mie ina.iot pari <>: u,e boat. TJie small unit indicates 50 to 1,0'( e'hri.lor eapaeities up to 21KI.000 H.t .u. pr lmur n hen a natural gn- of K)()0 1`, t.u. p< r cubic foot is bunnd. A Nirfiue ('oiuh.istii.a ( high prv-'uv inspirator and tunnel bui'iiei sot is us..,| u, tj.is itistallaliou. _ <'vor-:ih lieai-ev-l.a t.;* -oef!n-], n:- (/') mr tie- fiirnac.- nro in tile rnijgo ol 7 1" lu |l t i). p. [ ;,oi!i pci s.piaro foot per degree Fahrem.-r . < )yer-all hem\cuang <']!; -amts for \roclmJ24S to wat," in a 11': 1,]. pip,, h,i -- Aci.angm m;u|e from 1.25-nu'h pipe Will, a 2-mch pip. jack, t an- m -w 12n h> 1 NO range. I hoe figure- mo caieii'at d `ion- t,-t results on this HEATER PIPING Figure 2. Cottier, Pump, and Expansion Tank Cooler. A very useful adjunct to tiit? system is a double pipe cooler on the outlet ot the heater shown in Figuie 2. Hy turning water into the j *1 *11, o11 tlie Aroclot ran be fouled and M.e icniperatuic ui tin sy.-tem lowered Tibs is hc-lpiul when it is necessary to coni a hutch before removing it or when an exothermic reaction itarl# to get out of control. The pump for circulating the Aroclor 124S may be any one of a number of standard centrifugal units designed for hot liquid service. 0558217 TOWOLDMONOQ36715 1344 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 I'll**' Construction Table VI. Piping Detail (Dimensions in inches) l/< through >/ 1 throueh fi '/, through '/ 1 throng' 6 Schedule SO. A.S.T.M. A53 Schedule 40, A.S.T.M. A53 Screwed Flanged Bend in shop and field where pos sible. Must be rleuned to remove Fils, redi ) lungoi Unite am) V, through I through 0 1 through fl Forged steel screwed. Crane 300d Welded fittings. Crane 300e Series 3U (to match valves) Machine bolts A.S.A. H-18.2 with hex agonal nuts (or servire below 500 F. Above use allov steel. Crane tri plex A.S.T.M. A90 Crane 2`i2h forged stee Gaskets Shut-off valves V< through */< C:ig< and gins.- Fi gagi peraluie thread compound Soft iron ring flat or ctirntRuted Crane 300!i\Y, screwed, gate C lane 301MV, ilange, gate Cram- 33XR. flange, gate t rane 3M0 Mi, screwed, globe Ctani 3(in0 XR, flange, globe Ciane 1M XR. flange, globe Ciuni 3uT4 X. screwed < ra in- 30Se X . flanged ( i.tlie l.'iO X. flanged ( (iiiMilulated 11,70 H'V screwed Coien:u!,ite:| 1012 \V. flanged Il.icte ;)40il or Dmaiuetaliie It. 1 HI Tyi-' 100 PCl'R Marsh 0-100 lb./Mp inch gage siphon with Crane 22211 bar stock valve, lerguson Series R20 )iefle\ type ii |1 .id level gage 821 i unviiy thread; d S2 2 Vnru ay flanged The Daylt'ii Dowd Type C pump is an example of the type vetpiived. It should he nihde of cast steel and have a water(doled Mulling lio\ nmi water-cooled hearings. The stuffing hox should have room for at least six rings of packing and a lantern ring. Duriuneiallie Xu. D-110 or Oarlock Xo. 234 may he used for packing the pump. An open impeller is desirable, as it will handle t lj< n"'l. more viscous liquid on starling the system better than will a closed impeller. Enough horsepower for the most viseou* conditions is required. Piping ftvs'i i:m and Expansion Tank. The detail of the piping system h>v Aroelor 124ft used up to temperatures of 300 C. (572 " F.) and 100 pounds per square inch pressure is given in Table V], The valves and specialties given indicate the type re quired. All piping larger than 0.7o inch is flanged or welded; ex perience has shown that lmt Aroclor penetrates screwed joints of tiie larger size.-. Steel and cast steel are used throughout. The system requires an expansion tank located at the highest level of the installation. The size of this tank is normally about 2ort; of the capacity of the Aroclor system. Connections with valves, made on either side of the pump, enable the operator to connect a flexible hose and to pump in or out as required. 1 or operation in location.- where the Aroclor temperature may chop to where the attendant viscosities may make pumping im practical in the system us designed, it may he desirable to steamjacket the Aroclor circulating lines to facilitate rapid start-up. .Suitable safety provisions, such as .safety' pop-off valves, must be installed in the steam jacket system to prevent pressure ruptures which would develop if any condensate remained in a closed sys tem during high temperature operation. In order to establish operating conditions and to check the operation of the heater itself, it is often desirable to measure the temperatures of the Aroclor in and out of the heater and cooler. Items 1), 10, and ]) (Figure 2) provide for this. They may be dial thermometers or mercury bulb thermometers of any commercially available type recommended for the service. Table VII. Safety and Control Equipment High pressure alarm Mercoid DA-31, open oircuit on high pressure. (detects stoppage Actual settings depend on individual layout of pipe) 2. Low pressure alarm Mercoid DA-31-3, open circuit on low pressure. (detects stoppage Actual settings depend on individual layout of pump) 3. Thermostat (detects Fenwal 18002. Contacts open on temperature excessive heating increase hence obstruction Float switch (detects Mercoid Figure 40. S.P. switch. Open at low leakage from sys level 5. Combustion Control Corp. Fireye FF6. Flame tems off gas if failure control for manual ignition gas burner pilot flame goes systems. (F Gas valve (cuts off General Control Corp. K-10-2. Closes with in case preceding current off devices act) 7. Red light (alarm) Killark VA-1 -60 W, or Beniamin 7013-V 8. Horn (sounds alarm' Edwards 312 Alarm relay Type C-1104 1-NO, 1-NC watertight (/) Stop horn relay Tyne C-1104 1-NO, 1-NC. watertight (/) Slop horn button l-NA-4 it) Thermometer wcl I 0-3si0 C. mercury bulb thermometer (visual check of heater perform- 10. Thermometer well 0 3G03 O. mercury bulb thermometer (visual check of heater perform ance) 11. Thermometer well 0-3(10'' C. mercury bulb thermometer (visual check of * 12. Solenoid valve General Control K-10-2. Controls Aroclor temperature to meet demands of system For automatic temperature control a solenoid valve, item 12, is indicated in a by-pass arrangementwith a manually operated needle valve. The needle valve is adjusted to give almost enough heat to meet the requirements and the actual control is carried on by the solenoid valve, which opens and closes as directed by a tem perature-control instrument connected to the equipment being heated. One unit was set up with temperature control using a Leeds & Northrop Model S all-electric control with droop corrector. Very close control over a wide range of heat demand resulted, when a throttling range adjustment of 4 was used on this control device. Safety Circuit. Figure 3 shows a safety circuit which auto matically protects the system by closing off the gas supply in the event of faulty operating conditions. Provision is made for shutting off the warning horn while the system is being put back into operation after a safety shutdown. A detailed list of the safety and control equipment is given in Table. VII. The equipment named indicates the type required. ACKNOWLEDGMENTS The authors are grateful to A. M. Ellenburg of Monsanto's Re search Laboratory at Anniston, Ala., for furnishing many of the technical data about Aroclor 1248 and for assistance in preparing the manuscript. LITERATURE CITED O) Allen Bradlev Co., Milwaukee. Wis., Bull. 700. (2) Ibid.. Bull. 800. (3) Am. Soc. Testing Materials, Proc. Am. Soc. Tetling Material*, 34,53 (1934). . (4) Ain. Soc. Testing Materials. "Standards on Petroleum Prod ucts and Lubricants," 1945. (5) Drinker, C. K., J. Ind. Hy0. Toxicol. 21, 155 (1939). (6) Monsanto Chemical Co., Anniston, Ala., private communica tion. April 13, 1944. (7) Monsanto Chemical Co., St. Louis. Mo., Montanto Tech. Bull. P-115 (August 1947). (8) Sortman, C., Beatty, H., and Heron, S., Ind. Eng. Chem., 33, 357 (1941). (9) Sullivan. M. V,, Wolfe, J. K., and Zisman, W. A..Ibid., 39, 1607 (1947). (10) Underwriters' Laboratories, Chicago, 111., "Miscellaneous Hazards," No. 2498,1934. Rkceived August 27. 1048. Presented before the MeetiDg-ia-Mioisture, Alabama Section, American Chemical Society. December 8. 1946. # 'll " 0558218 L TOWOLDMONOQ36716 MONSANTO CHEMICAL COMPANY ST. LOUIS AKRON BIRMINGHAM BOSTON CHARLOTTE CHICAGO CINCINNATI CLEVELAND DETROIT HOUSTON . LOS ANGELES NEW YORK PHILADELPHIA SAN FRANCISCO SEATTLE MONSANTO (CANADA) LTD. MONSANTO (AUSTRALIA) PTY LTD. Montreol Toronto Vancouver Melbourne MONSANTO CHEMICALS LTD. London Representatives in the Principal Cities of the World PGB:UAOUDI*-9-49 Printed in U.S.A. 0558219 TOWOLDMONOQ36717