Toxicity of Sodium Pentachlorophenate and Pentachlorophenol to Fish d
C. J. GOODNIGHT', University of
Illinois,
Urbana, Ill.
Above 10 p. p. m. fish can detect the presence of sodiumpentachlorophenatebnt not below 5.0p.p.m. Eggs of lake trout are very resistant to these compounds. Lake trout are most sensitive to pentachlorophenol in the yolk sac stage immediately after hatching. Invertebrates such as are used by fish as food are relatively insensitive to pentachlorophenol and sodium pentachlorophenate. The most sensitive invertebrates will live a t concentrations a t which fish will survive. Adsorption by activated carbon, exposure to light in ponds or reservoirs, and natural dilution in flowing water are suggested as alternative solutions to t h e practical problem of stream pollution by waste waters bearing sodium pentachlorophenate.
Pentachlorophenol and sodium pentachlorophenate are fatal to t h e more sensitive species of fish in concentrations above 0.2 p. p. m. although hardier species will survive a t 0.4 or 0.6 p. p. m. In lethal concentrations they increase the metabolism of fish, as evidenced by increased respiratory movements; bleeding results from capillary rupture. Silver-mouthed minnows are the most sensitive of t h e fish used in the experiments. The toxicity of pentachlorophenol and sodium pentachlorophenate to fish is increased by lowering t h e pH of t h e water. Within reasonable limits t h e size of the fish, t h e temperature of t h e water, and its character do not greatly affect the toxicity of the compounds. The number of fish i n a solution of given volume does not affect their survival time.
cold-blooded animals having gills for respiratory organs. Accordingly, a n investigation was begun on a number of our common sensitive fish.
ODIUM pentachloroplienate is becoming increasingly
S
important comniercially as a preservative for paper and wood pulp (6). I n using this compound a certain amount escapes into the streams with the mill waste, and some concern has been felt over the possibility of creating a new danger to our already depleted fish populations ( 7 ) . The toxicity to fish of a great number of different substances has been investigated experimentally. Schaut ( I S ) tested over sixty chemicals which might occur in industrial wastes in an effort to determine the cause of mass destruction of fish life during droughts. Phenol, C6HjOH, a compound closely related to pentachlorophenol, has been studied extensively. Shelford (14) found that 70-75 p. p. m. of phenol in tap mater killed the orange-spotted sunfish, Lepomis humilis, in one hour; while inxrestigating this same compound, Powers (12)found that 51 p. p. m. in distilled water killed goldfish in 11/*to 2l/3 hours. Other worker&, including Dem'panenko (8), Alexander, Southgate, and Bassindale ( 2 ) , and Adams (1) were also impressed by the sensitiveness of aquatic organisms to phenol. Gersdorff and Smith (IO)studied the effect of introducing halogens into the phenol molecule, and demonstrated that the monochlorophenols have appreciably greater toxicity to goldfish than phenol. The results of investigations on a number of other compounds are summarized by Ellis (9). However, the toxicity to fish of pentachlorophenol or its salts has not been previously reported. The effect of pentachlorophenol on rabbits was studied by Kehoe, Deichmann-Gruebler, and Kitzmiller (11). TT7e cannot, however, make deductions from experimental work on warm-blooded animals and apply them to fish, which are 1
Methods of Study STANDING WATEREXPERIMENTS. The various concentrations of sodium pentachlorophenate tested were diluted from a 10 per cent stock solution made on a weight per volume basis (10 grams of sodium pentachlorophenat'e dissolved in 100 cc. of water). Pentachlorophenol was diluted from a 10 p. p. m. stock solution. Keutral sodium pentachlorophenate which assayed 90.5 per cent was used. Impurities consist of the sodium salts of other phenolic bodies, neutral salts, and moisture. Tests were conducted in open-top battery jars in a constanttemperature bath (16). Two liters of solution and three to five fish were used in each battery jar. The time to the death of each fish was recorded, and the results were plotted as a survival time curve. Salt composition of the water, pH, and oxygen content were checked regularly, and later these variables were investigated. pH was determined by a Welch quinhydrone pH apparatus. Oxy en content was checked by the Rideal-Stewart modification o f the Winkler method (4). For all species of fish studied, observations were made at 5.0, 4.0, 3.0, 2.0, 1.5, 1.0, 0.8, 0.6, 0.4, and 0.2 p. p. m. of sodium pentachlorophenate. The eggs and young of lake trout, Cristivomar namaycush (Walbaum), and healthy fish collected from local st'reams were used in the experiments. The fish were subjected to test only after several days in the laboratory, and were not used after being in captivity two weeks. All results were checked and rechecked from 5 to 250 times, using more than 25,000 fish and often 200 or more in a single test. Controls consisted of the same number of fish as in the test jars, placed in water from the same source but containing no sodium pentachlorophenate. Some tests were made on invertebrates. No significant decrease in the concentration of test solutions was found when checked after different periods to determine if the fish had extracted pentachlorophenol. The concentration was checked biologically by transferring half of the fish t o a fresh solution and comparing their survival time t o that of the ones left
Piesent address, Brooklyn College, Biooklyn, N. Y.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
in the original solution. Chemically it was checked by acidifying the solution, extracting the pentachlorophenol with ether, precipitating as mercuric pentachlorophenate, centrifuging, and comparing with a fresh solution treated in the same manner. RUNNING WATEREXPERIMENTS. As a further check on the standing water expkriments, many fish were tested in running water. Large quantities of solutions of sodium pentachlorophenate were made up and stored in tanks. The tests were then run in a long narrow trough of flowing solution, simulating stream conditions. In a gradient tank similar to GRADIENT TANKEXPERIMENTS. the one described by Wells ( l y ) , fresh water was admitted in one end and sodium entachlorophenate solution in the other. The two liquids mixefin the middle of the tank. Fish reactions were studied in this concentration gradient.
Effect of Sodium Pentachlorophenate The external effects of sodium pentachlorophenate and pentachlorophenol on fish are obvious. A fish introduced into a 5 p. p. m. solution, for example, immediately shows discomfiture. I n a few minutes it darts about rapidly as if trying to escape. Then it begins to jump violently out of the water, and bleeding occurs about the gills, mouth, and pectoral regions. The fish comes to the surface, gasping for air, and in five or ten minutes turns upside down, breathing rapidly. It dies in a short time. Post-mortem examination shows the ruptured capillaries that caused bleeding. I n less concentrated solutions above a tolerated concentration the reaction of the fish is less violent but results fatally. The toxic effects are apparently due t o penetration of the tissues and entrance into the blood stream. Here, due to an upset in the metabolic rate, blood pressure is increased, and rupture of the smaller capillaries and bleeding result. Increase in oxygen consumption is indicated by a large increase in respiratory rate with every addition of a small amount of sodium pentachlorophenate. Such an increase, in the case of larval amphibia, amphibian eggs, and muscle tissue, has been shown in numerous instances by means of the Warburg respiratory apparatus (16).
Survival of Various Species Eight common species of fish were studied in great detail. The approximate number of individuals of each species used, as well as the number of lots, are listed in Table I. OF FISHSTUDIED TABLEI. SPECIES
Approx. No. of
Species Individuals Silver-mouthed minnow Ericymba buccata Cope 10,000 Blackfin minnow, Notro& umbratizis (Jordan) 5,000 Blunt-nosed minnow, Pimephales notatus (Raf.) 6,000 Doughbelly Campostoma anomalum (Raf.) 1,000 Steel-ooloreb. minnow Notropis whipplii (Girard) 1,000 Horned dace, S e m o t i l h atromaculatus (Mitchill) 1,000 Top minnow, Fundulus notatus (Raf.) 500 Orange-spotted sunfish, Lepomis humilis (Girard) 200
No. of Lots
2500 1250 1500 250 250 250 125 50
The term ‘riot" refers to the three to five fish used in each battery jar test. The battery jar is considered to be the statistical unit in this study. Some tests were made on several other common fish, including the following species: Rainbow darter, Etheostmna coeruleum Storer Johnny darter, Boleosoma nigrum (Raf.) Carp, Cyprinus carpio Linnaeus Quillback, Carpiodes cyprinus (Le Sueur) Black bullhead, Ameiurus melas (Raf.) Channel cat, Ictalurus punctatus (Raf.) Green sunfish, Lepomis cyanellus Raf. Straw-colored minnow, Hybopsis volucellus (Cope) Common sucker, Catostmus commersonii (LacBpBde) Hog sucker, H y entelium nigricans (Le Sueur) Small-mouthed{uffalo, Ictiobus bubalus (Raf.)
869
None proved to be significantly more or less sensitive than the eight species studied in detail. Of all species investigated, the silver-mouthed minnow appeared to be the most sensitive to sodium pentachlorophenate and, therefore, the best indicator of pollution danger. It did not survive a t any concentration higher than 0.2 p. p. m. Fortunately this test fish was easy to obtain and stood handling very well, since for conclusive results it was often necessary to use as many as several thousand a week. Other species studied, including the young delicate stages of important food and game fish, were found to be able to survive the effect of sodium pentachlorophenate as well as or better than the silver-mouthed minnow. The maximum concentration a t which 011 species would survive, therefore, was considered t o be 0.2 p. p. m. of sodium pentachlorophenate. All tests were conducted in University of Illinois tap water, dechlorinated by means of activated carbon filters. An analysis of this water by the Illinois State Water Survey follows : ,-Determinations, P. P. M.Manganese 0.0 Silica, 9.0 Turbidity 0.0 Calcium 58.6 Magnesium 26.2 Ammonium 2.4 Sodium 37.5 Sulfate 2.1 Nitrate 1.1 Chloride 0.0 Alkalinity as CaCOs Phenol hthalein 0.0 Methyforange 340.0 Residue 336,O Total hardness 254.6
--Hypothetical
Cc,mbinations Parts Grains per m8Ln oallon Sodium nitrate 1.7 0.10 Sodium sulfate 2.8 0.I6 Sodium carbonate 83.2 4.85 Ammonium carbonate 0.39 6.7 Magnesium carbonate 91.0 5.30, Calcium carbonate 146.0 8.54 Ferric oxide 0.12 2.0 Silica 9.0 0.52 Total
7
-
342.4
19.98
The pH of the water was 7.6 and its temperature 16’ C., although these conditions were varied for certain tests a s described below. Table I1 gives the survival times of the species tested at various concentrations of sodium pentachlorophenate. The values for each concentration were obtained by averaging the times until death of the last fish in each lot tested at that concentration. The time required to kill the last fish was chosen as a criterion for convenience, since in a given lot the variation from first to last fish was small compared t o the observed survival time. Table 111 illustrates for the silvermouthed minnow, on which the largest number of tests was run, the extent of variation within single lots between the survival times of the first and last fish (column 1). Column 2 indicates the range of actual last-fish survival times among the various lots tested a t each concentration. Table IV gives the survival time data of Table I1 in reciprocal form (velocity of fatality). In addition, values for the theoretical threshold of toxicity concentration and the relative sensitivity for each species are included. Figure 1 represents graphically the data in Table IV. These results, obtained in standing water, were checked by running water experiments as outlined. No difference in the survival times of the fish was found between the standing and flowing solutions of the same concentrations. The different species, ages, and sizes of fresh water fish may differ greatly in sensitivity. The young of game fish are in the class of the doughbelly, steel-colored minnow, and blacktin minnow. The orange-spotted sunfish, tadpole, and top minnow are among the hardy species. The primary purpose of these experiments was to determine the toxicity of sodium pentachlorophenate to fish, not to construct theoretical velocity of fatality curves justifying mathematical analysis. To construct such curves would have required testing a larger number of concentrations, particularly in the lower part of the concentration range. However, the theoretical curves for the nine species tested were approximated, according to the general principles estab-
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870
lished by Powers ( I d ) for certain other toxic substances, to make ‘clear t h e wide range of difference which exists in the fish population of any stream. Powers ( l a ) demonstrated that t h e v e l o c i t y of fatality (as measured by the rec i p r o c a l of t h e survival time) of the goldfish (Ca-
FIGURE 1. VELOCITY OF TOTALITY AT VARIOUS CONCENTRATIONS OF SODIUM PENTACHLOROPHENATE
rassius carassius L.) has a definite relation to the concentration of the toxic solution used. He tested a large series of inorganic salts, several alcohoIs, phenol, and a number of other compounds. The typical velocity of fatality curve, obtained by plotting the reciprocals of the survival times a s ordinates against the concentration of the solution a s abs c i s s a , approximates an S-curve. The initial portion or toe of the TIMEIX MINUTES curve: representing the lower concenTABLE11. SURVIVAL P. P. M. of trations, rises slowly. A central porOrangeBlackSteelBluntSilverSodium Pentachloro- Mouthed fin Dough- Colored Nosed Horned Spotted TadTop tion, representing medial concentrabelly Minnow Minnow Dace Sunfish polea Minnow Minnow Minnow Dhenate tions, rises a t a more rapid rate and 42 30 75 90 15 13 16 5.0 105 100 approximates a straight line. The 47 50 25 20 18 4.0 150 135 65 55 35 30 23 3.0 upper portion, representing very high 225 170 72 60 28 45 40 2.0 285 70 255 107 33 55 60 1.5 concentrations, rises more slowly again, 435 375 105 65 147 58 100 1.0 and tends to flatten out and become 140 5zO 5 ! 192 135 93 125 0.8 2t5 267 138 160 160 0.6 parallel to the abscissa. c e 427 3615 s : 2 0.4 c D c The central straight-line portion of 0.2 the velocity of fatality curve,prolonged Wt. av., grams 2 2 10 2 3 12 2 ~ * . 3 to cut the x or concentration axis, is a Ran5 pipiens Sohieber. called the “theoretical velocity of b A few died hut the majority survived after 3 days. Alive after three days. fatality” curve. Its x intercept (a) is called the “theoretical threshold of toxicity concentration”. TABLE 111. VARIATIONS IN SURVIVAL TIMEWITHIN AND AMONQ Powers suggested that the relative toxicities of substances LOTSOF SILVER-MOUTHED MINNOWS be expressed by the equation
.
0
Q
Survival Time Variation Actual Survival Times p. P. M. of Sodium within Lotso, Min. among Lotsb, Min. Pentaohlorophenate 21-24 5.0 1-3 28-32 4.0 1-3 36-44 3.0 1-3 55-65 2.0 1-3 80-90 1.5 1-3 1.0 1-3 99-110 0.8 5-8 130-150 0.6 5-8 190-230 0.4 19-16e 360-390 0.2 Lived Livede a Time intervals from death of first to death of last fish in lot. b Minimum and maximum survival times of last fish in lots tested at each concentration. e Alive after 3 days.
T
=
dE cy
where T = toxicity 8 = angle made by theoretical velocity of fatality curve with 1: axis u = x intercept This formula can be used equally well to express the relative sensitivities, R, of different species of fish to the same toxic
July, 1942
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
87 1
TEMPERATURE. Within ordinary limits, as in the range of 9-24' C., temperature did not appear to have a P. P. M. of SteelBluntOrangeSodium SilverBlackmarked influence on the toxicity to Pentaohloro- Mouthed fin Dough- Colored Nosed Horned 8 otted TadTop phenate Minnow Minnow belly Minnow Minnow Daoe &fish pole Minnow fish of sodium pentachlorophenate. 5.0 4.34 6.25 7.69 6.67 2.38 3.33 4.00 1.33 1.11 At 28-30' C. the high temperature 1.00 2.85 0.95 2.00 4.00 2.12 5.55 5.00 3.33 4.0 itself, together with the resultant lower 0.74 0.66 1.81 1.81 2.85 1.54 3.33 4.34 2.50 3.0 2.0 1.66 2.50 3.57 2.22 1.38 1.66 1.11 0.59 0.44 oxygen content of the water, affected 0.35 0.63 0.39 1.42 1.81 0.93 3.03 2.00 1.17 1.6 the fish and caused them to succumb 0.60 0.27 0.23 0.68 0.95 1.72 1.53 1.00 0.95 1.0 0.8 0.68 0.80 1.07 0.74 0.52 0.71 0.67 0.17 0.17 more rapidly. 0.47 0;62 0.72 0.63 0.37 0.42 0.27 b 0.6 b pH OF WATER. The normal p H of 0.25 b 0.38 0.32 0.22 0.4 0.26 b b b 0.2 the water used, characteristic of many 0.10 0.15 0.35 0.35 0.15 0.25 0.46d 0.15 0.30 a R 3.00 2.86 2.72 2.32 2.32 2.26 1.96 1.55 0.94 of the streams from which the fish came, was 7.6 (6). This was varied in the 100 divided by the survival time in minutes. b Alive after 3 days. range of p H 5.0-8.0 by addition of soc A few died but the majority survived after 3 days. d Data insufficient to draw definite conclusions. dium hydroxide or hydrochloric acid. Fish survived longer a t pH 7.6 than a t 6.6 or lower. The difference a t lower concentrations of sodium pentachlorosubstance, since the sensitivity of the various species will phenate ( 0 . 4 ~p.m.) . was as much as several hours in some cases. OXYGEN CONTENT. The oxygen content of the water likewise vary directly with the slope of the theoretical velocity of fatality curve (tan 0) and inversely with the theoretical remained constant a t 4 p. p. m. throughout the test in both treated and control lots. Above the subsistence level (2 threshold of toxicity concentration (a). The location of these theoretical curves was established by p. p. m. for most fish), variation in the oxygen content had observation from the plotted data, noting the z intercepts no effect on the survival time of the fish. CHARACTER OF WATER. The variation in water from (a)and the angle each curve made with the z axis (e). From these values the relative sensitivities ( R ) were calculated by dzerent natural sources did not, in general, have much effect the formula on the toxicity of sodium pentachlorophenate. However, survival time of fish in a distilled water, containing 20-30 p. p. m. of salts, was decreased. R = SIZE. Within ordinary limits. size is not an imoortant factor in the effect of sodium pentachlorophenate on fish. I n each case the silver-mouthed minnow was found to be the However, extremely large fish (weighing ten times as much most sensitive fish, while the other species fell in the order as the average specimen of the species concerned) did survive given in Table IV. slightly longer on the average than the smaller ones. This The straight-line portion of the fatality curve for the did not hold true in all individualxcases. doughbelly (Figure 1) is drawn as a dotted line extended a t NUMBEROF FISH. The survival times were recorded for both ends to show the form of the theoretical velocity of a series of tests conducted with one to seven fish in the same fatality curve of Powers. I n general, the velocity of fatality amount of solution. No difference in toxicity was noted so curves for sodium pentachlorophenate shows the characterlong as there was sufficient oxygen to supply all the fish. It istic, approximately straight line in the medial concentrations was observed, for example, that one fish in the 2 liters of and no noteworthy peculiarities at high or low concentrations. solution ordinarily used would survive for the same length of time as five to seven fish in the same container. Reactions of Fish to Gradient of Sodium PentaI n connection with this work on aggregate protection, it chlorophenate was noted that the slime exuded by certain Siluridae had little or no effect of decreasing the toxicity. Sodium pentaI n practical problems dealing with pollution it is extremely chlorophenate did not seem to be removed by the slime, as important to know if the fish will be attracted or repelled by are certain other salts in solution (3). the particular poison as it enters the stream. To test this, a gradient tank was set up as described above, and solutions of Effect of Sodium Pentachlorophenate on Invertevarious concentrations of sodium pentachlorophenate were brates admitted into one end and fresh water into the other. Various Standing water experiments similar to those used for fish minnows (especially silver-mouthed and blunt-nosed) were were set up, and a number of invertebrates important as fish used in these experiments. food were studied. They consisted of: Above 10 p. p. m. the fish were able to detect the sodium Crayfish, Cambarus virilis Hagen pentachlorophenate and avoid it. Fish could not even be Am hipods, Hyalella knickerbockeri (Bate) driven into the toxic waters a t these concentrations. HowClaxoooera, Da hnia pulex DeGeer ever, concentrations between 10 and 5 p. p. m. were not so Bloodworms, Jhironomidae Dragonfl nymphs, Epieordulia sp. easily detected, while below 5 p. p. m. fish seemed unable to Damsel ify n mphs, Ischnura sp. detect the sodium pentachlorophenate in the water. Here Isopods, A s e l u s communis Say it seemed merely a matter of chance if the fish swam into the These invertebrates (with the exception of the Chironomifatal solution. Once they began to succumb to the effects of dae) were extremely resistant to sodium pentachlorophesodium pentachlorophenate, however, they swam about nate. At 5 p. p. m. all but the Chironomidae survived easily. wildly and even entered the stronger concentrations. The Chironomidae were relatively sensitive to the compound but survived a t concentrations tolerated by fish. Since the Effect of Various Factors invertebrate food of fish will survive a t any concentration of Studies were made to determine the inffuence of each factor sodium pentachlorophenate a t which the fish themselves will live, it may be concluded that destruction of fish food by this which might modify the toxic action of sodium pentachlorophenate. chemical does not constitute a problem. TABLE Iv,
VELOCITY OF
dF
FATALITY'
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Effect of Pentachlorophenol on Eggs and Young of Lake Trout Eggs of lake trout, Cristicomer namaycush (Walbaum), were found to be extremely resistant t o pentachlorophenol. The newly hatched young in the yolk sac stage were found t o be more sensitive than either the eggs or the more mature fish. Even in this sensitive stage, however, the young trout were hardier than silver-mouthed minnows, having longer survival times a t fatal concentrations. The observations a t different periods of growth indicated that sensitivity decreased as the trout advanced in age.
Toxicity of Pentachlorophenol The insolubility of pentachlorophenol in water imposes experimental difficulties. Since preliminary studies indicated that its action is similar t o that of sodium pentachlorophenate, most of the experimental data, with the exception of the work on the eggs and young of lake trout, have been obtained on She sodium salt.
Practical Aspects of Pollution Problem Sodium pentachlorophenate may be removed from mater by passing it through activated carbon. Extended exposure to light will also destroy the toxic chemical either by oxidation or by the action of algae and bacteria. A third method is to permit the sodium-pentachlorophenate-bearingwaste waters to flow into the streams and become diluted t o safe concentrations naturally. The use of fences to exclude fish from locnl areas of high concentration may be of value. Recommendation of the most practical means of control in individual cases is outside the scope of this paper. The alternatives above are merely suggested, and the choice will be governed by the conditions inherent to a particular mill.
Acknowledgment This research was made possible by a grant from the Nonsanto Chemical Company. The writer wishes to thank L. A. Watt, J. D. Fleming, and H. L. Morrill of Monsanto for advice and cooperation. He is further indebted t o V. E Shelford under whose direction this work was conducted and t o B. A. Wright who assisted in the investigation. Equipment workini space were furnished by the graduaie school the Zoology Department of the University of Illinois.
Literature Cited Adams, B. A , W a t e r W o r k s Eng., 29, 361-3 (1927). Alexander, W. B., Southgate, B. A., and Bassindale, R., Water Pollution Research Board (England), Tech. Paper 5 (1935). Allee, K. C., “Animal Aggregations”, pp. 201-21, Chicago, Univ. of Chicago Press, 1931. Am. Pub. Health Assoc. and Am. Water Works Assoc., Standard Methods for Examination of Water and Sewage, 8th ed., pp. 139-54 (1936). Birge, E . A , and Juday, C., B u l l . W i s c o n s i n Geol. N a t . Hist. Survey, 22, 1-259 (1911). Carswell, T. S., and Nason, H . K., IND.EUG.CHEM.,30, 622 (1938). Cole, A. E., Sewage W o r k s J.,7, 280-302 (1936). Dem’yanenko, V., Hig. i. Z p i d e m . (U. S . S . R ), 10, No. 6/7, 13 (1931); Dept. Sci. Ind. Research (Brit.), Water Pollution Research, S u m m a r y of Current Lit.,6, 35 (1931). Ellis, M.M., U. S. Bur. Fisheries, B u l l . 48, 365-437 (1937). Gersdorff, W. A., and Smith, L. E., Am. J. P h a r m . , 112, 197-204 (1940). and Kitzmiller, K. V., Kehoe, R. A,, Deichmann-Gruebler, W., J . Ind. H y g . Toricol., 21, 160-72 (1939). Powers, E . B., Illinois Biol. Monographs, 4 ( 2 ) , 1-73 (1917). Schaut, G. G., J . Am. W a t e r W o r k s Assoc., 31, 771-822 (1939). Shelford, V. E., B u l l . Ill. State L a b . X a t . Hist., 11, 381 (1917). Shelford, V. E., “Laboratory and Field Ecology”, p , 522, Baltimore, Williams and Wilkins Co., 1930. Warburg, O., “Uber die katalytischen Wirkungen der Lebendigen Substanz”, Berlin, Julius Springer, 1928. Wells, M. &I., Bid. B u l l . , 29, 221-57 (1915).
Graphical Method for Interconversion of Ternary Compositions ICUAN HAN SUAT AND ALEXANDER SILVERMAPI University of P i t t s b u r g h , P i t t s b u r g h , P e n n a .
N A RECENT paper‘ two simple graphical methods were proposed for the interconversion of binary compositions. ’CT’ith the help of one of these, a graphical method for the interconversion of ternary compositions has been developed. Assuming W A ,W B ,and W c are percentages by weight of the three components A , B , and C in a ternary system A-B-C, respectively, it is desired to convert them into their respective mole percentages, X A , X B , and X C . The method consists of t w o steps:
I
Step 1. The system is separated into two binary systems, A-B and A-C. Then W Aand W B ,and W Aand Wc will represent parts by weight of components A and B in system 1
Sun and Silverman, IND.ENC.CWE&Z., 34, 682 (1942).
A-B, and A and C in system A-C, respectively. By applying graphical method I of the previous paper’, the mole percentages, a and b, and a’ and e’, of these two systems A-B and A-C are obtained, respectively: System Composition Parts by weight Xole per cent
A-B
.4-c
V v A : m’B
W A : ??C
a. b
a‘:e
Step 2. On a triangular coordinate paper (Figure l), plot points D and E so that BD = a , AD = 6, CE = a’, and AE = e’. Join BE and CD. The intercepting point, 0, furnishes the desired ternary composition in mole per centnamely, X A , X B , and X c . The proof is simple. From geometry it is easy to see that any point on line CD of Figure 1 will represent a fixed moleou-
