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relation passes through it and the pure azeotropic agent point, provided there is no association, in which case two points must be known. Consequently, the search for the best azeotropic agent for the separation of the constituents of a mixture is simplified and made less time-consuming. ACKNOWLEDGMEhT
The author wishes to thank A. L. Glasebrook of this laboratory for his interest and helpful cooperation in the preparation of this article. LITERATURE CITED
(1) Atkins, W. R. G., Nature, 151,449 (1943). (2) Birch, S. F., Collis, C. B., and Lom-ry, R. A., Ibid., 158, 60 (1946). (3) Egloff, G., “Physical Constants of Hydrocarbons,” Vol. I, p. 42
Yol. 40, No. 3
(1939), Vol. 111, p. 25 (1946), A.C.S. Monograph 78, 1st ed., New York, Reinhold Pub. Corp. (4) Kolosovskii, N. A., and Alimov, A,, BuTZ. soc. chim., [ 5 ] 2, 686 (1935). (5)
Kolosovskii, N. A , , and Teodorovich, R. L., I b i d . , [ 5 ] 2, 692
(1935). (6) Lecat, R.1. $., Ann. S O C . sci. Bruzelles, 48B ( I ) , 54 (1928). (7) I b i d . , 48B (11),105 (1928). (8) I b i d . , 50B, 21 (1930). (9) Lecat, XI. A,, “L’Azeotropisrne,” Brussels, Maurice Lamertin, 1918. (10) Lecat, 31.A , , Rec. trac. chim., 45, 620 (1926). (11) I b i d . , 47, 13 (1928). (12) Mair, B. J., Glasgow, A. R., Jr., and Rossini, F. D., J . Research ATatLatl. Bur. Standards. 27. 39 (1941). (13) Marschner, R. F., and Cropper, JV. P., IND.ENG.CHEM., 38, 262 (1946).
RECEIVED October 17, 1947.
Chlorine and So ium Pentaehlorohenate as in Sea W. J . TURNER,
JR., D. RI. REYIOLDS, AND A. C. REDFIELD
Woods Hole Oceanographic Institution, Woods Hole, Mass.
Continuous chlorination with residual concentrations as low as 0.25 part per million prevents the attachment and growth of slime bacteria and macroorganisms in sea waEer circulating systems. Some adult mussels and anemones may survive 10 days of intermittent chlorinatien with residual concentrations as high as 10.0 parts per million even when the periods of treatment are as long as 8 hours per day. Sodium pentachlorophenate prevents the attachment and growth of macroorganisms but is ineffective in eliminating slime w-hen concentrations as low as 1.0 part per million are maintained continuously. The relative merits of chlorine and sodium pentachlorophenate are discussed.
and conduits used to transport sea water in ships and P I Pindustrial F S power plants are frequently subject to marine fouling. Such growths reduce the efficiency of cooling systems, and when they occur in fire mains, they create serious hazards. The design of the system must provide for periodic cleaning, and cleaning operations with their attendant shutdowns are themselves expensive. Dobson (1) recently reviewed the various methods which have been tried or suggested for the control of such fouling. He concluded that the most promrsing treatment is the injection of chlorine into the sea water. Such treatment appears to be quite effective against slime-forming organisms which directly interfere with heat transfer in condensers. In somP cases it has given promise of controlling the growth of niacroorganisms in pipe systems. Although a number of installations have been made for the control of fouling by means of chlorine, there appears to be no published record of studies designed t o determine experimentally the concentrations and periods of treatment which are required t o prevent fouling efficiently. Such experiments have been conducted recently by the Woods Hole Oceanographic Institution. The results of these experiments are reported here. They give
some indication of what may be expected from various methods of treatment and also suggest an explanation of failures which sometimes occur in industrial practice. The antifouling properties of an organic toxic, sodium pentachlorophenate, were also investigated t o determine if this material could be used where chlorine might be unsuitable. EXPERIMEYTS WITH CHLORISE
ISTERMITTENT TREATYENT. The first experiment,, performed a t Woods Hole, Mass., determined the killing power of various concentrations of chlorine when applied both intermittently and continuously to adult organisms ( 4 ) . Battery jars containing organisms of representative species were subjected to the following treatment : One jar, serving as a control, was circulated continuously with fresh sea water. Four jars were irrigated periodically with sea water containing chlorine in a residual concentration of 10 parts per million on a schedule of 1, 2, 4, and 8 hours each day. The rest of the time the jars were circulated with untreated sea water. The sixth jar was flushed continuously with the chlorinat,ed water. (Chlorine was applied as a solution of calcium hypochlorite, introduced int,o the sea water main by means of a proportionating pump.) After 10 days of this treatment, the organisms in all six jars were flushed continuously for 10 more days vith unchlorinated sea water to allow for delayed effects t,o develop. The results of this experiment are given in Table I. Intermittent, exposures for periods as long as 8 hours per day with 10 p.p.m. chlorine were ineffective against mussels and ar:emones, and the 4-hour periods did not completely eliminat’eall the barnacles. The tunicates and bryoxoa were all killed by exposure for 1 hour per day. This short treatment was sufficient t o prevent the formation of slime on the sides of the jars. CONTINUOUSTREATMEST. Since int,ermittent treat’ment with daily exposures as long as 8 hours per day was ineffective against some forms, an experiment was performed t o determine
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foot length of 3-inch galvanized iron pipe. A rubber hose dipping below the surface of Biscayne Bay served as an RESIDUAL CHLORINE intake. Sea water was sucked through % Survival after Treatment of Hr. the units by means of gear pumps Treatment/ 1 2 3 4 5 6 7 8 9 10 20 Day Animals day days days days days days days days days days days mounted in the outflow. Glass plates 0 Anemones 100 100 100 100 ,, 100 100 100 100 100 100 were inserted into the pipe t o serve Mussels 100 100 100 ,. ,, 100 100 100 100 100 100 Barnacles 100 100 85 . . 85 .. 85 85 as collectors of fouling. Calcium hypoMolgula 100 . . f00 . . . . . . I00 . . 100 90 . . 75 , , 0 chlorite solution was injected near the Botryllus 100 Bugula 100 . . 100 . . :: 100 .75 . .. , . . . .. 75 50 50 intake by means of a proportjonat1 Anemones 100 100 100 100 100 100 100 100 100 100 100 ing pump, and the residual concenMussels 100 100 100 100 95 95 95 95 95 95 95 Barnacles 100 25 25 10 10 10 10 10 10 10 0 tration was checked a t the outflow. Molgula 75 50 50 5 5 5 5 5 5 0 0 Botryllus 20 20 . . . . 10 10 10 0 0 0 0 The rate of flow was maintained at 2 Bugula 50 . . . . . . 0 0 0 0 0 0 0 gallons per minute with a chlorine 2 Anemones 100 100 100 100 100 100 100 100 100 100 100 Mussels 100 100 100 100 100 100 100 100 100 100 100 residual of 1.0 p.p.m. One untreated Barnacles 100 65 10 10 10 10 10 10 10 . 10 5 unit served as a control. During 2 Molgula 75 20 10 10 0 0 0 0 0 0 0 Botryllus 20 10 . . . . 0 0 0 0 0 0 0. months' operation the glass test plates Bugula 50 . . . . . . 0 0 0 0 0 0 0 inserted into the control system fouled 4 Anemones 100 100 100 100 100 100 100 100 100 100 100 Mussels 100 100 100 100 100 100 100 100 100 100 100 heavily, while those in the treated Barnacles 100 75 50 10 10 10 7 7 7 5 5 10 10 0 0 0 0 0 0 0 system remained ent,irely free of orMolgula 75 20 Botryllus 20 0 0 0 0 0 0 0 0 0 0 ganisms. 10 . . . . . . 0 0 0 0 0 0 0 Bugula 8 Anemones 100 100 100 100 100 100 100 100 100 100 100 Snother experiment designed to de100 100 100 100 100 100 100 100 100 100 100 Mussels termine the minimum concentration 0 0 0 10 0 0 0 0 Barnacles 66 65 50 0 which would be effective was con0 0 0 0 0 0 . Rlolgula 10 75 10 10 Botryllus 20 ,. 0 0 0 0 0 0 0 0 0 ducted a t Kure Beach, N. C. (6). Bugula 10 . . . . . . 0 0 0 0 0 0 0 24 a Anemones 100 . . . . . . 0 lo05 100 100 50 0 .. Six similar units of steel pipe were Mussel6 50 . . . . . . . 0 lo05 90 50 10 2 0 flushed continuously from a common Barnacles 25 . . . . . . 0 50; 10 0 0 0 .. Molgula 10 . . . . . . 0 25 25 0 0 0 .. source of aea wat,er. Each emptied Botryllus 0 .. .. .. .. .. .. 0 106 Bugula 10 0 10" ..10 00 00 00 .. .. into a weir box used to control the rate of circulation. Chlorine gas was ina The population of this jar was renewed on the sixth day after all the dead organisms had been rejected into the sea water so that chlomoved and the jar cleaned. rine residuals of 1.5, 1.0, 0.75, 0.5, and 0.25 p.p.m. weie maintained in ' reTABLE11. PERCENTAGE SURVIVAL OF ORGANISMS AFTER CONTINUOUS TREATMENT spective units of the apparatus. One WITH CHLORQVATED SEA WATER O F VARIOUS STRENGTHS AND FOR V.4RIoUS TIMES unit was untreated as a control. % Survival after Treatment of Chlorine The velocity of flow varied in different Concn 0 1 2 3 4 5 6 7 8 9 1 2 1 5 P.P.M." Animal day day days days days days days days days days days days parts of each unit from 8.6 t o 1.3 feet 10 .4nemones 100 100 100 50 0 0 . . . . . . . . . . . . per second and was lower in the weir Mussels 100 95 65 35 10 0 . . . . . . . . . . . . box. During 3 months' operation Barnacles 90 20 20 0 2 0 . . . . . . . . . . . . iuoigula 0 0 0 . . . . . . . . . . . . abundant fouling occurred on test Bugula 0 0 0 . . . . . . . . . . . . panels in the weir box of the control 2.5 Snemones 100 100 100 100 75 60 50 .. 0 .. ,, ,, Mussels 95 95 85 35 20 0 0 .. 0 .. ,, ,, unit and in all parts of the system Barnacles 100 50 25 5 0 0 2 ., 0 where the velocity of flow was 1.72 feet Molgula 100 0 0 0 0 0 0 ,. 0 ... . ,, ,, ,, ,, Bugula 100 .. 0 0 0 0 0 .. 0 . . . . . . per second or less. No fouling occurred 1 Anemones 100 100 100 100 .. 100 .. 100 ,, 100 100 100 in any of the chlorinated units. This Mussels 100 100 75 65 .. 45 .. 35 .. 50 15 0 50 2 20 indicated that 0.25 p.p.m. was above Barnacles 100 90 90 50 .. 25 ,, 0 ,. hfoigula 100 100 100 o .. o .. o ... o o o the effective minimum, and also showed that attachment and growth'of fouling can be prevented by continuous application of concentrations of chlorine much the killing times of different chlorine concentrations when applied lower than those which permit adults to survive even after a continuously. Three series of jars containing fouling organisms considerable period of exposure. I t also lends support t o the were circulated with sea water containing residual chlorine conbelief that such fouling organisms as mussels are less resistant centrations of 1.0, 2.5, and 10.0 p.p.m., respectively. One jar in the larval stages. from each series was removed each day and supplied with fresh. running sea water. The survival times of the different species EXPERIMENTS WITH SODIUM PENTACIILOROPIIENATE are given in Table 11. The two higher chlorine concentrations were lethal to all organisms in 5 t o 8 days. Anemones, mussels, In a preliminary experiment to determine the general order of and barnacles survived longest. A few mussels survived 12 toxicity of sodium pentachlorophenate a 5 % stock solution of days of treatment with 1.0 p.p.m., and a few barnacles and all sodium pentachlorophenate (Santobrite) in distilled water was the anemones were alive after 15days. added t o sea water in quantities sufficient t o give solutions rangPREVENTION OF ATTACHMENT.Since the larvae are generally ing from 0.1 t o I000 p.p.m. The solutions containing 100 and considered t o be more delicate than adults, it was believed that 1000 p.p.m. formed precipitates and consequently did not retain somewhat lower chlorine concentrations might be effective in the original concentration. Mussels, barnacles, and anemones preventing their attachment. To test the effect of continuous were placed in each solution, and the solutions were changed dosage on attachment and subsequent growth under conditions twice daily t o remove waste materials and maintain the oxygen comparable with industrial practice, experimental pipe systems supply. The condition of the animals a t subsequent times is were set up in Miami, Fla. (6). These units consisted of a 6given in Table 111.
TABLEI. PERCENTAGE OF SURVIVAL OF FOULING ORGANISMS DURING A N D AFTER PERIODIC TREATMENT WITH CHLORINATED SEA WATERCONTAINING 10 P.P.M.
::
4
.
40": 0" 0"
*
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INDUSTRIAL AND ENGINEERING CHEMISTRY
452
parable to chlorine in preventing attachment and growth of
TABLE 111. COXDITION OF ORGAXISMS AFTER VARIOCS TIMES macro-organbms but i s ineffective against slime-forming organOF EXPOSURE TO DILUTIONS OF' SODIEM PENTACHLOROPHENATE isms. IN SEAWATER Conon., P.P.M. 0 0 I 1.0 10
100 1000
Animal Mussels Anemones Barnacles hlussels Anemones Barnacles Mussels Anemones Barnacles Mussels lnemones Barnacles Mussels Anemones Barnacles Mussels Anemones Barnacles
0 hr. x xx xx xx xx x x xx xx x x xx x x x x x
-
Conditiona 1 7 18 22 hr. hr. hr. hr. x xx xx xx xx xx xx xx x x xx xx x xx xx xx xx xx xx xx xx xx xx xx x xx xx x xx xx xx xx xx x x x x x x x x x x x x x x x x x - - x - -x -
-
- -
after 27 hr. xx xx xx xx xx xx x x x
Exposure of 43 53 65 hs. hr. hr. xx xx xx xx xx xx xx xx xx x x x xx xx xx x x xx x x x x x x x -
x - - - - - x x - - - - - - - - - - - - - -
-
-
91 115 hr. hr. xx xx xx xx xx XX xx xx x
xx xx x
- -
- - -- - - - - - - - - - - - - - - - - - - -
a xx = quite active-barnacles filter, anemones yide open, mussels siphon; x = inactive b u t alive-barnacles just "breathe, mussels and anemones shut: - = dead-barnacles rigidly open or shut, mussels wide open, anemones usually decomposing.
The experiment showed that dilutions of 0.1 p.p.m. were ineffective but those of 1.0 p.p.m. killed all the organisms in less than 3 days. Stronger solutions killed in shorter times. To secure a more exact comparison of the toxicity of sodium pentachlorophenate and chlorine, a solution of the former (4) was injected into running sea water a t rates which yielded concentrations of 10 and 1.0 p.p.m. Animals were then exposed t o these concentrations continuously in a manner similar t o that employed in the experiment made a t Woods Hole with various concentrations of chlorine. The percentage of organisms surviving after various intervals is given in Table IV.
TABLE IV. PERCENTAGE SURVIVAL OF ORGAXISYS AFTER CohTINUOUS TREATMENT WITH SEA W.4TER COXTAISISG SODIUM PENTACHLOROPHESATE Concn. Pentachlorophenate P.P.M.' 10
% Survival aftes Treatment of 0 1 2 3 4 5 6 7 Animal day day days days days days dags days Anemone 100 0 0 0 0 0 0 0 Mussel 100 95 50 10 4 0 0 0 Barnacle 75 25 5 0 0 0 0 0 Molgula 100 0 0 0 0 0 0 0 Bugula 100 0 0 0 0 0 0 0
This experiment demonstrated that the toxicity of sodium pentachlorophenate is of the same general order as is that of chlorine, and that it is somewhat more effective against the hardier forms in the concentration of 1 p.p.m. When the experimental pipe system was set up for the experiments with chlorine a t Miami, Fla., the effects of continuous application of sodium peritachlorophenate on the attachment and growth of organisms were tested a t the same time. A solution of sodium pentachlorophenate was injected by one of the pumps of the propoitionator into a unit identical to the control and chlorinated units in an amount calculated t o maintain the concentration in the pipes a t 1.0 p.p.m. n'hen the experiment was terminated after 2 months' operation, no macroscopic fouling had appeared but there was a deposit of slime in the pipes. The experiment indicated that sodium pentachlorophenate is com-
The effective dosage of sodium pentachlorophenate kvas tested further a t Kure Beach simultaneously with the chlorination experiment. By means of Wallace and Tiernan hypochlorinators, two units identical with those used in the chlorination experiment were fed continuously sufficient stock solution of sodium pentachlorophenate (Dowicide G) to result in concentrations of 0.5 and 1.0 p.p.m. The higher concentration satisfactorily inhibited macroscopic fouling, while the lower one permitted a moderate growth. This demonstrated that the minimum lethal dosage lies between those concentrations. In both units there was a considerable accumulation of slime in the pipee and weir boxes and on test plates. CONC I.USI0V s
The experiments indicate that continuous chlorination with residuals as low as 0.25 p.p.m. should give complete control of fouling in sea water circulating systems. Harbor water commonly contains enough organic matter t o produce chlorine demands of 2 or 3 p.p.m., and where pollution is heavy the demand is considerably greater. Consequently it appears that the chlorine requirement is set essentially by the chlorine demand of the water and that a chlorine dosage slightly in excess of this demand may be expected t o control fouling. The minimum dosage of sodium pentachlorophenate which will prevent attachment and growth of marine animals when applied continuously is 1 p.p.m. This is a net figure which presumably does not need to be supplemented by an allowance for organic matter present in the sea water. Pentachlorophenate may consequently be an acceptable substitute for chlorine in preventing the development of clogging growths, especially when the chlorine demand of the water is great. On the other hand, it is inferior to chlorine in controlling the development of slim(, in condenser tubes. Otherwise the relative merits of chlorine and pentachlorophenate will depend on a variety of factors, including cost, the question of corrosion, and the convenience and hazards involved in handling the materials, which depend on the size and nature of the installation in question. Where large volumes of sea water are used, the cost of continuous treatment with chlorine has proved t o be greatcr than the expense of periodic cleaning of the conduits. Attempts t o control fouling more economically by intermittent treatment have succeeded in preventing the formation of bacterial slimes in condenser tubes and appear t o be profitable because of the improved efficiency of heat transfer which results ( 2 ) . Such treatment has Sometimes failed to control the growth of marine animals. Along the Atlantic coast north of Cape Hatteras the most serious fouling in sea water conduits is due t o the mussel, iV1ytiL-i~~ edulis. The experiment with intermittent treatment described here shows that adult mussels are able t o resist relatively heavy daily dosages of chlorine if applied intermittently with a considerable interval without treatment intervening. I t is apparent that if adult mussels are once permitted t o become established, intermittent treatments may be ineffective in dislodging them or preventing their continued growths. Yothing appears t o be known of the susceptibility of m u s d larvae t o intermittent tieatments Kith chlorine. According t o Matthew-s (3) and Field (W), mussels first attach during a stage when the larvae are still equipped with swimming organs but are already enclosed by shells. I t is possible that, by closing the shell, these larvae may protect themselves during intermittmt periods of chlorination as the adults are observed to do. Any attempt t o reduce effectively the expense of chlorination bv intermittent treatment should br based on the determination of the susceptibility of the mussel during the early stages of attach-
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ment to chlorine which is applied in intermittent dosages of various durations and strength.
453
LITERATURE CITED *
(1) Dobson, J. G., Tmns. Am. Soc. Mech. Engrs., 68, 247-65 (April 1946).
S.Bur. Fisheries, 38, 127-259 (1921-22). (3) Matthews, Annie, J . Marine Biol. Assoc. United Kingdom, 9, No. 4, 557-60 (1913). (4) Reynolds, D. M.9 a n d Redfield, A. c., 6th Rept. to B u r . of Ships, Paper 14 (1943), unpublished. ( 5 ) Reynolds, D . M., a n d Redfield, A. C., Interim R e p t . 7 t o Bur. of Ships (1943), unpublished. (6) T u r n e r , H. J., Jr., I n t e r i m R e p t . 11 t o Bur. of Ships (1945), unpublished. (2) Field, I. A,, BUZZ. [J.
ACKNOWLEDGMENT
The pioportionating pump used in the chlorine experiments a t Woods Hole was loaned by % proportioneers, %, providence, I., through the kindness of Jeff CorYdon. The equipment used a t Kure Beach was supplied by Wallace and Tiernan, Inc., through the kindness of R. B. Martin, and consisted of their type MSP chlorinators. The location and facilities were supplied by the Ethyl Dow Corporation and were arranged for by F. L. LaQue of the Interna&nal Nickel Compani The sea water was ~h~ drawn from the intake canal of the Ethyl D~~ Dom7icide Was by John v. Grebe Of the Company.
RECDIVED Ami1 9, 1947. Contrihtion No. 380 of the Woods Hoke Oceanographic Institution. This work was done under a contract between the Institution and the Bureau of Ships, Navy Department. The interest of H. A. Ingram, U.S.N., in initiating the study is gratefully acknowledged. The opinions presented here are those of the authors and do not necessarily reflect the official opinion of the Navy Department or the naval service at large.
Corrosion Prevention by Controlled Calcium Carbonate Scale SHEPPARD T. POWELL, H. E. BACON, AND E. L. KNOEDLER Professional Building, Baltimore 1, M d . T h e use of controlled calcium carbonate scale for corrosion prevention in cooling tower systems serving steel equipment was discussed in an earlier paper. Conditions were described in which rising temperatures caused the actual pH of the water to decrease at the same rate as the calcium carbonate saturation pH; this produced scale of nearly uniform thickness over the entire temperature range. New data for the ionization constants of carbonic acid have been used to recalculate the pH temperature curves shown in the former paper to bring them up to date.
I
N A recent publication (8, 9) the theory and experience in the
formation and control of a calcium carbonate scale to act as a dam between a metal surface and a corrosive medium (water) were discussed. Explanations and corrective measures were suggested for differences between operating experience and theory as formulated in the Langelier saturation index. In particular, it was pointed out that calculation of the true theoretical index over a range of temperature rise required recognition of the decrease in actual pH throughout the same range. Subsequent to publication of the previous discussion (a), Langelier published two papers (6, 6) in which he expanded his original work in this field. He further compared his results with those of the authors and noted that a discrepancy of 0.2 to 0.4 existed between the two sets of data in which corrections were made for change of p H with temperature. Attention has been called to newer values for the ionization constants of carbonic acid published by Harned and Davis ( 3 ) and by Harned and Bonner (2). A review of these data led to the conclusion that the older values used by Amorosi (1) should be replaced by these new constants for purposes of practical application of the Langelier index. The original data presented in the authors' paper, have been recalculated using this latest information, and the results are included in this paper. The purpose of this discussion is not to review the earlier work, but to make available the adjusted data and curves with illustrative problems to meet the demands of a continuing need which exists in this field. More detailed discussions are given in the former paper. Other papers on the subject have also been published (4, 7 , 10).
EFFECT O F TEMPERATURE ON pH
As was explained earlier, the pH value of a water solution varies with temperature, the magnitude of the change depending on the initial alkalinity. Figures 1, 2, 3, 4, and 5 show the variation of actual pH with temperature fqr waters containing 25, 50, 100, 200, and 300 parts per million (p.p.m.) of methyl orange alkalinity. These were calculated according to the method of AmQrosi and McDermet but using the data of Harned and Bonner. To simplify the presentation of this paper, the same examples are employed as were used before (8). The discrepancy between expected performance and actual performance is explained and compensated partially, when the effect of temperature on actual pH is taken into consideration, and when the change in saturation index is plotted over a normal operating range, in this case 80" to 150" F. Such discrepancies were illustrated in Figure 4 of the previous paper. It was observed that a falling index (case A) predicts increased aggressiveness at high temperatures, a rishg index (case B) predicts heavier scale, and a nearly horizontal index (case C) predicts the formation of a uniform protective film throughout the temperature range considered. Also, it was indicated that the conventional saturation index would predict increased scaling in each of these three instances. Figure 0 shows the decrease in saturation p H (pH,) with temperature. This is an expression of the change in constant C of the Langerier index, as illustrated by the difference between the parallel lines of Figure 1 in the previous paper. Figure 7 shows four curves for actual p H (pH,) against temperature at several alkalinities. These are essentially similar t o the curve of Figure 6. As previously explained, waters having these approximate relations will produce a scale of nearly uniform thickness throughout this temperature range. Thus, light scaling on a cold surface will not be accompanied by formation of a thick scale on a hot surface, a condition which occurs often in practice, These data, when plotted as shown in Figure 8, indicate the desirable pH-alkalinity relations to produce a scale relatively uniform in thickness over a temperature range of 80' to 150' F. This graph shows the relations that might be expected to produce a uniform scale, but should not be confused with the saturation index which indicates the rate and amount of scale deposited,
