October 15, 1943
ANALYTICAL EDITION
Literature Cited (1) Anderson, C.W.,IND. ENQ.CHEM.,ANAL. ED.,9, 569 (1937). (2) Blumenthal, H., 2.anal. Chern., 74, 33 (1928). (3) Clark, S. G.,Analyst, 56, 82 (1931). ENQ. (4) Clarke, B. L., Wooten, L. A., and Struthers, J. D., IND. CHEM..ANAL.ED., 9, 349 (1937). (5) Evans, B.9..Analyst, 54, 523 (1929). (6) Fainberg, 8. Yu., Zavodskaya Lab., 7 , 405 (1938). (7) Gangl, J., and Vazques Sanchez, J., Z . anal. Chem., 98, 81 (1934). (8) Gybry, G., Zbid., 32, 415 (1893). (9) Hillebrand, W. F.,and Lundell, G. E. F., “Applied Inorganic Analysis”, p. 238,New York, John Wiley & Sons, 1929. (10) Jarvinen, K . , - Z .anal. Chem., 62, 184 (1923). (11) Kallman, S.. and Pristera, F.. IND. ENQ.CHEM..ANAL.ED.,13, 8 (1941). \----,-
629
(12) King, B. W., and Brown, F. E., J. Am. Chem. Soc., 61, 968 (1939). (13) Kolthoff, I. M., and Amdur, E., IND.ENQ.CHEM.,ANAL.ED., 12, 177 (1940). (14) Kurtenacker, A., and Fiirstenau, E., 2. anorg. allgem. Chem., 212, 289 (1933). (15) McCay, L.W.,IND. ENQ.CHEM.,ANAL.ED.,5, 1 (1933). (16) Robinson, R.G., Analyst, 65, 159 (1940). (17) Scherrer, J. A., J. Research Natl. BUT.Standards, 21, 95 (1938). (18) Schulek, E., and Villecz, P. v., 2.a d . Chem., 76, 81 (1929). (19) Sloviter, H. A., McNabb, W. M., and Wagner, E. C., IND. ENQ.CHEM.,ANAL.ED., 14, 516 (1942). (20) Wolbling, N.,“Die Bestimmungsmethoden des Arsens, Anti-
mons, und Zinns und ihre Trennung von anderen Elementen”, Stuttgart, F. Enke. 1914. (21) Wooten, L. A., and Luke, C. L., IND.ENO.CHEM.,ANAL.ED., 13, 771 (1941).
Fixing and Determining Oil in Feed Water and Boiler Water C . A. NOLL m D W. J. TOMLINSONI W. € t I. L. D. Betz, Phdadelphia, Penna.
The two sources of error encountered in the determination of oil in water samples are: (1) the presence in the oil residue after evaporation of substances other than oil, such as the inorganic salta, sodium sulfate, and sodium chloride. These substances increase the apparent oil cantent of the water sample and produce high results. (2) The separation of oil from the water sample on standing. This oil may separate onto the sides of the container, from which it may be incompletely removed even by rinsing the container with a solvent.
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I L is both undesirable and dangerous in a boiler water, particularly under modern operating conditions. The presence of even a very small quantity of oil may lead to foaming and priming of the boiler water, corrosion of the boiler metal, and overheating of boiler tubes, resulting in possible failure. The overheating of the tubes may be due either to the heat-insulating properties of a layer of oil or to the effects of oil on scale formation. Oil absorbed by suspended solids in the boiler water may adversely affect the ability of such solids to remain in suspension. Oil is considered such an important factor in the production of pure steam that the American Boiler Manufacturers’ Association, in its guarantees of steam purity, stipulates a n oil content of the concentrated boiler water not exceeding 7 p. p. m. Methods for the removal of oil from boiler feed water or returned condensate range from mechanical baffle-type separators to complete chemical coagulation and filtration systems. Since a guarantee on the purity of steam from a given boiler may definitely hinge on the oil content of that boiler water, oil determinations of the boiler water must be made as accurately as possible. There are admitted difficulties in securing a representative sample of a boiler water for oil, as the oil may partially be found on the metal or absorbed by solid matter, such as sludge. In many cases (given as a n alternate by the A. B. M. A. speciha1 Present address, Betz Laboratory Division. Wood Industry Supply Co., Ltd., Canada.
This loss of oil from the water sample itself yields a lower apparent oil content and gives low results. Data are presented on the magnitude of the error involved, using present methods. A new procedure is recommended for fixing the sample at its source by adsorbing oil in a ferrid hydroxide precipitate and subsequently extracting the oil from the washed and dried floc. It is possible by this method to avoid both of the above sources of error and to obtain consistent, accurate results.
tions) the practice has been to secure a sample of the boiler feed water and first concentrate it a t low temperature and pressure to the same number of cycles of concentration as the boiler water before making the oil analysis. Inasmuch as 5.0 per cent of blowdown, equivalent to 20 cycles of concentration, may be considered an average case, if the boiler water is not to exceed 7 p. p. m. of oil, the feed water should contain no more than 0.35 p. p. m. of oil. Water samples lose their oil content on standing as the oil separates from the water and adheres to tht. sides of the container or stopper. Such oil may be incompletely removed, even by rinsing the container with a solvent. Concentrating the sample prior to analysis is undesirable, owing to the separation of the oil which may take place during concentration: on the other hand, analysis of the unconcentrated feed water requires a minimum of errors, because of the small quantities involved. A truly comprehensive study of boiler feed water for oil would require spot samples, taken a t sufficiently frequent intervals to detect suspected variations in oil content. Obviously, a continuous sample will be subject to some oil separation, owing to the time required for collection, before the sample can be &xed or analyzed. An investigation by the authors has shown errors in the methods for oil determination now available. The following methods have been considered: ( a ) standard method (2), (b) technical method (3),(c) ether extraction method, ( d ) A. B. M. A. method ( I ) , and (e) Scott’s method (6).
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Vol. 15, No. 10
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Preparation of Oil Standards OF METHODS ON OIL-DISTILLED WATER TABLE I. COMPARISON
SOLUTION
Ether-extraction method
Oil Values Technical method
P. p. m.
P. p .
c
Sample 1 2 3 4 5 6
0.0 4.4 11.4 22.6
380:O
m.
0.0 4.8 12.4 21.0 42.6 374.8
Authors' procedure
P. p .
m.
0.0 5,6 12.4 21.5 42.2 362.2
Paraffin oil was selected for these studies because of its inertness and low volatility. The latter is important, particularly in view of the fact that the oil samples after their extraction from water are placed in an oven to dry. The loss in weight, due to the volatility of the p a r a 5 oil employed, was 0.012 per cent after drying a t 105" C. for 15 minutes and 0.26 per cent after drying for 30 minutes. Oils normally encountered in water have low volatility. Considerable difficulty waa experienced in preparing a standard water-oil solution. Oil separated rapidly from the water in a simple mixture of oil with distilled water, even with the most vigorous stirring. Unlike Pringle (4),the author did not find it possible to add a definite weight of oil to a water sample and to check the addition of weight on aliquot samples. The method finally adopted was to mix a small amount of paraffin oil intimately with distilled water, employing a laboratory hand homogenizer and then thoroughly mixing this solution with a larger volume of distilled water. This latter solution exhibited a milky appearance, similar to the appearance of samples drawn from oilcontaminated return condensate systems. Even with this homogenization, however, small oil droplets separated from the body of the solution and gradually floated to the top. Changes in the concentration of oil in the mixture from time to time necessitated siphoning of the sample from beneath the surface and the simultaneous securing of the duplicate samples for the test by the different methods. In each case, 500 ml. of the water-oil solution were taken. Even using this procedure it was not possible to check the amount of oil originally added to the water
The standard method ( 2 ) is described as a rough, quantitative method in which 2 to 4 liters of the water are evaporated to dryness a t a temperature below 100" C. The residue is taken up with petroleum ether, or high-test (oil-free) gasoline in a tared, platinum dish, or small light beaker, and evaporated to dryness on a steam bath. This reference cites "the technical method" (3) as more precise. The technical method ( 3 ) involves transferring a water sample to a separatory funnel and shaking with redistilled chloroform. The water and chloroform layers are separated and the latter is evaporated in a weighed flask and dried to constant weight at 100" C. This method is subject to an error, due to the fact that some of the dissolved salts in the water, such as sodium chloride, sodium sulfate, etc., are taken up by the chloroform and finally weighed as oil. The ether-extraction method is the same as the technical method, except that ether is used instead of chloroform, and is subject to the same error. The A. B. M. A. standard contract ( 1 ) states, "The total quantity of oil, or grease, or substances which are extractable either by sulfuric ether or by chloroform, shall not exceed 7 p. p. m. in the boiler water when the sample being tested is acidified TABLE 11. SOLVENT EFFECTOF DIFFERENTMETHODS ON OIL-FREESAMPLES to 1 per cent hydrochloric acid, c or 7 p. p. m. in the feed water Apparent Oil Content, P. P. M. 100 200 when the sample being tested 1000 5000 1000 5000 1000 5000 1000 5000 P . P . ~ . p. p. m. is first concentrated a t low Solutions "$ac?. yss; gpClg* Fj p. m, P.P.m. p m. tannic tannic stC0: NaOH %*OH acid acid temperature and pressure to the same p. p. m. total solids E t h e r Extraction hlethod as the boiler water." The 5o m,, of ether 0.8 5.6 0.6 3.6 0.8 5.4 0.6 5.2 1.0 0.8 hydrochloric acid is used to ml. of ether 2.0 7.6 2.2 7.0 2.2 9.4 3.0 11.2 1.2 2.2 remove from the water solution 150 ml. of ether 2.0 11.6 2.2 10.2 4.0 14.6 3.2 15.8 1.4 3.0 any saponifiable oil. This Technical Method method also yields high results 50ml.ofchloroform0.2 0.6 0.0 1.0 0.2 1.8 0.8 1.0 0.6 duetothesolublesalttakenup 100ml.ofchloroform 0.4 0.8 0.2 1.2 0.4 3.0 1.0 1.6 1.2 by the chloroform. 150ml.ofohloroform 0 . 6 1.0 0.4 2.0 0.6 3.4 1.4 1.8 1.0 a Scott's method (6) uses Authors' Method ferric hydroxide to absorb the oil from a sample and subse1-hour reflux 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 quently extracts the oil. This 2-hour reflux 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 method is essentially the same A. B. M. A. Method as that used by the authors, 50 ml. of ether 0.6 4.0 0.6 5.8 1.4 3.8 2.4 1.0 1.5 2.0 except in the matter of fixing ml, of ether 2.8 10.0 2.8 15.8 6.6 10.6 4.8 16.2 5.4 6.2 the. Sam le a t its source. Its 150 ml. of ether 2.9 10.0 4.4 15.8 11.4 7.0 14.6 7.6 19.8 10.6 malor xisadvantage is that a Too much foam developed for good separation. oil which has separated from the sample on standing is not absorbed.
E&$;
Inaccuracies involved in all the above mentioned methods may be from one or both the following sources of error: 1. The presence in the oil residue after evaporation, of sub-
~~~~d~!'~~~~d''il, ~ ~ ~ e a content of the water sample and produce high results. 2. The separation of oil from the water sample on standing. This oil may separate onto the sides of the container, from which it may be incompletely removed, even by rinsing the container with a solvent. This loss of oil from the actual water sample itself yields a lower apparent oil content and gives low results.
This paper presents a method of fixing the sample at its source, so that an accurate result may be obtained later in the laboratory by a method similar to Scott's (6). Data are Presented to show the errors inherent in the other methods.
,
sample, although it was possible to duplicate oil values on samples simultaneously siphoned off and immediately analyzed. In an attempt to check the oil content of the oil-water solution, portions were siphoned and evaporated to dryness. Separation of oil on the sides of the tared container during evaporation exposed this oil to prolonged heating and resulted in volatilization of the oil and erratic results.
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~
~
~
t
~
~
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Authors' Procedure PREPARATION OF FERR.IC CHLORIDE SOLUTION.Ten erams of ether-washed iron by hydrogen are placed in a 600-ml. bUeaker to which are added 400 ml. of distilled water, followed by 30 ml. of concentrated C . p. hydrochloric acid. After solution is complete, c. P. concentrated nitric acid is added until the ferrous chloride is completely oxidized and a deep, amber color per-
~
~
ANALYTICAL EDITION
October 15, 1943
sists. This solution is stirred constantly during the addition of the nitric acid. It is boiled for approximately 0.5 hour, cooled, and made up in volume to 1 liter with distilled water. PREPARATION OF AMMONIUM HYDROXIDE SOLUTION.Concentrated ammonium hydroxide (360 ml., specific gravity 0.9) is made up to 1.0 liter with distilled water. ETHER. Anhydrous ethyl ether (fat-free). PROCEDURE FOR TEST. Five hundred milliliters of the sample are treated with 10 ml. of the ferric chloridc solution, and stirred well, and then 10 ml. of the ammonium hydroxide solution are added and stirred. The solution, now fixed, is brought to a boil for approximately 1 minute, cooled to room temperature, and filtered by gentle suction through an Alundum thimble, which has previously been ignited. The thimble containing the ferric hydroxide is washed free from chloride with distilled water, dried a t 105” C. for 1.5 hours, and cooled to room temperature, and the oil is extracted in a Soxhlet apparatus in the usual manner for 1 hour. It was found necessary to use an Alundum thimble instead of filter paper, because of ether- and chloroform-extractable matter in the filter paper.
EFFECTOF DIFFERENT METHODS ON OILTABLE 111. SOLVENT WATERSAMPLES CONTAINING SODIUMCHLORIDE Method Ether extraction Technical Authors’
Apparent Oil Content, P. P. hi. Sample 1, Sample 2, Sample 3, Sample 4, 1000 p. p. m. 2000 p. p. m. 3000 p. p. m. 5000 p. p. m. NaCl NaCl NaCl NaCl 77.0 19.2 20.0 47.2 46.2 73.0 18.4 20.1 70.2 18.0 19.5 45.6
Experimental Data Table I illustrates the values secured by three different methods for determining the oil content of oil-distilled water solutions, and indicates that in distilled water solutions the technical method and the authors’ method compare very favorably. There is no essential difference between these methods on distilled water solutions free from dissolved salts and on samples simultaneously obtained and immediately analyzed. Using the authors’ method, the dried ferric hydroxide containing no oil gave no measurable increase in weight after being refluxed for 2 hours with ether. I n order to illustrate the increase in weight and apparent oil content found by the various methods, due to the presence of different salts dissolved in the water sample, solutions containing 1000 and 5000 p. p. m. of sodium chloride, sodium sulfate, sodium carbonate, and sodium hydroxide and solutiom containing 100 and 200 p. p. m. of C. P. tannic acid were prepared with oilfree distilled water. Oil determinations were made on each sample in accordance with the procedures described. Table I1 illustrates the apparent oil content of these solutions. With the ether-extraction method, particularly with the sample containing 5000 p. p. m. of these salts, the apparent oil content increased with the use of increasing quantities of ether employed in the extraction. This is apparent to a lesser extent with the solutions of lower concentration. With the technical method, the apparent oil content also increased with increase in the quantity of chloroform employed in the extraction. With both of these methods, and to a greater extent with the A. B. M. A. me hod, this increase in weight with greater volume of solvent can be ascribed to the increased quantity of water dissolved in the solvent, with accompanying increased quantity of dissolved salt. The authors’ method illustrates that it is possible to avoid the error due to the presence of dissolved salts in the solvent residue after evaporation, inasmuch as the ferric hydroxide precipitate containing the oil is washed free from solids by distilled water before it comes in contact with the solvent in the Soxhlet apparatus. To determine the solvent effect when oil is actually present in water samples, sodium chloride was used in concentrations of 1O00, 2000, 3000, and 5000 p. p. m. These solutions were made in homogenized oil-distilled water samples, collected, and meas-
631
ured in the manner previously described. The results are illustrated by Table 111. The lowest oil values were consistently shown with the authors’ procedure, and the ether extraction and technical methods were consistently higher in apparent oil content. This is due to the residue of sodium chloride remaining on evaporation of the solvent, as illustrated by Table 11. The increase in apparent weight of oil with the ether extra-tion and technical methods, compared with the authors’ method, closely checks the solubility of sodium chloride in these solvents shown by the first column of Table I1 with the use of the same volume of solvent. For all the results shown by Table 111, 50 ml. of chloroform were used with the technical method and 100 ml. of ether with the ether extraction method. While the results obtained by the three methods do not vary to a great extent, these values were obtained on freshly prepared oil samples which were immediately analyzed. I n order to illustrate the loss of oil resulting from the separation of oil from the water on standing, samples of oil-contaminated boiler feed water from nearby industrial plants were obtained through a cooling coil and collected in a 5-gallon bottle. The individual samples were siphoned into 500-ml. volumetric flasks and placed in Pyrex bottles. The samples which were to be determined with the use of the authors’ procedure were all fixed a t the time of sampling. Results shown in Table IV are for oil determinations made immediately after collection and then a t intervals of 2, 4, and 6 days. A definite decrease in the oil content of the unfixed samples can be noted after 2 and 4 days, when the analysis was made by the ether extraction or technical method. I n each case the bottle was rinsed with a portion of the solvent to attempt to collect oil clinging to the sides of the container. Employing the authors’ procedure for fixing and determining the oil content, no drop in oil content was noted. Drop in oil content, because of oil separating from solution and clinging to sides of container, is apparently prevented by the adsorption of the oil in the ferric hydroxide precipitate using the authors’ procedure. Table IV shows clearly that it is necessary to fix the samples for oil determination in order to secure an accurate result. The low solids content of these feed-water samples did not affect the final result to any great extent. The residue left after the oil contamination gave a slight test for sulfate and chloride on the samples analyzed by the ether extraction and technical methods. No sulfate or chloride was found in the residue using the authors’ procedure. 1
TABLE IV. SEPARATION OF OIL FROM WATERSAMPLES ON STANDING Sample
A B
---_-Oil Content, P. P. M. Immediately T w o days Four days Six days after after after after collection collection collection collection Ether Extraction Method 2.4 1.0 10.4 8.8
A B
Technical Method 2.3 0.8 9.9 8.5
A B
Authors’ Method 2.2 2.3 10.0 10.1
Mineral Analyses of Feed Water” Sample A Total hardness 88 CaCOs 16 Bulfate a8 so4 4 Chloride as C1 1 Iron aa Fe 0.0 P alkalinity 88 CaCOa 0 M alkalinity aa CaCOs 22 Total solids 45 7.1 PH a
Values in p. p. m. with exception of pH.
0.8 5.9
i:8
0.5 5.5
4:4
2.2 1;:2
9.9
Sample B 6
48 3.6
Trace 0
16 108 7.1
INDUSTRIAL AND ENGINEERING CHEMISTRY
632
In order to show the solvent effect on actual boiler water, boiler waters having different oil contents were secured from industrial planta and the oil was determined immediately after their collection (Table V). The consistent check values obtained by means of the authors’ procedure compare very favorably with those previously secured from synthetic oil-water samples. Close checks were obtained in each case with the use. of the authors’ procedure, while the other three methods showed wide variation on check samples. The residues were tested in each case for the presence of sulfate and chloride. Sulfate and chloride were present except in samdes determined by the authors’ procedure. I n the case of the A. B. M. A. method, the residue also showed the presence of iron. The consistent checks obtained with the use of the authors’ method and the absence of chlorides, sulfate, etc., in the residue illustrate the importance of fixing a sample for oil prior to its determination in order to avoid erratic results.
OF METHODS ON BOILER WATER TABLE V. COMPARISON
SAMPLES
Sample 1 Ether-extraction method Technical method
A. B. M.A. method Authors’ procedure
33.5 28.5 43.3 28.7 52.0 48.8 26.2 26.0
Oil Content, P. P. XI. Sample Sample Sample
2 33.5 20.1 23.3 22.0 20.5 24.0 18.2 18.2
3 58.0 56.7 55.0 42.5 95.5 72.4 47.0 47.4
Mineral Analyses of Boiler Watera“ 0 0 0 Total hardness as CaCOt 272 304 260 Sulfate as SO, 44 168 100 Chloride as C1 0.0 0.0 0.0 Iron as Fe 124 154 102 P alkalinity as CaC& 270 310 264 hl alkalinity as CaCOi 1408 1730 1786 Total solids
10.2 25
0
10.2 30
10.1 25
4 374.0 356.0 365.0 450.0 328.0
382.2 383.0 26 352 60 0.0
124 344 3336 10.1
..
Sample 5
62.5 58.6 55.1 49.3 71.0 33.0 57.2 56.8 100 144 168 0.0 120 400 4321 10.1
Values in p. p. m. with exception of pH.
Recommended Procedure for Fixing and Determining Oil Content of Water Samples COLLECTING THE SAMPLE. Wash a 500-ml. volumetric flask with a small amount of 95 per cent alcohol, rinse out the alcohol with a small amount of ethyl ether, and dry the inside of the flask with a stream of air. mash a 500-ml. bottle and cork stopper in the same fashion. Measure 500 ml. of the water sample into the volumetric flask a t the sampling point. Pour the contents of the flask into the bottle and rinse the flask with a small amount of oil-free distilled water which is also added to the 500-ml. bott e. By means of a graduate, add 10 ml. of the ferric chloride solution, stopper, and shake well. Then add 10 ml. of the ammonium droxide solution, stopper, and shake well. The sample is now zxed”. Set up a filtc r flask and insert an Alundum DETERMINATION. thimble in the filter tube, fastening by means of a wide rubber band. The Alundum thimble should first be ignited in a Bunsen flame for ap roximately 5 minutes. Add the L e d sample to a 1-liter beaker (ether-washed) and rinse the bottle well with oil-free distilled water, bring the sample just to a boil on a hot plate, and let stand until cool (below 40’ C.). Filter the fixed sample through the Alundum thimble, using a gentle suction. Wash the beaker well, making certain that all of the ferric hydroxide floc is washed into the thimble. l h e n wash the thimble with distjlled water, testing the filtrate from time to time with 0.1 N silver nitrate solution until no further opalescence appears. Let the thimble dry with gentle suction and then place the thimble in an oven a t a temperature of 105 * 1” C. for 1.5 hours. Remove and let cool in a desiccator. Weigh a Soxhlet flask which has been previously ether-washed and dried a t 100’ C. for one hour and cooled in a desiccator and add a p roximately 75 m1. of ethyl ether. Extract the cooled thimble an8floc in the Soxhlet apparatus for one hour on a steam
Vol. 15, No. 10
bath. Evaporate the ether. Dry the outside of the flask, place in an oven a t 100” C. for 15 minutes, cool, and weigh. The increased weight of the Soxhlet flask in milligrams, multiplied by 2, equals p. p. m. of oil.
Discussion and Conclusions One source of error involved in the various methods for determining oil in water is the presence of inorganic salts in the oil residue when weighed. In certain instances, this error may be appreciable. The error due to inorganic salts is most noticeable on water samples containing high dissolved solids content, such &B boiler water. Since the specification limit on oil in a boiler water is only 7 p. p m., it is necessary to employ a method of oil analysis that will not register erroneously high simply because of inorganic salts such as sodium sulfate and sodium chloride in the oil residue. A second and more important source of error is due to the loss of oil from the water sample on standing. It is seldom convenient to run oil samples immediately at their source. The authors’ method of “fixing” the sample, immediately upon collection satisfactorily maintains the original oil content even after prolonged standing. The difficulty in preparing standard oil-water solutions made it necessary to prove the accuracy of the proposed method by indirect means. Had it been possible to add a definite amount of oil to a water sample and then to check this addition by determination of the oil on aliquot portions, the percenbage adsorption of oil could have been proved by the ferric hydroxide preripitate. No method employed, even direct evaporation of an oil-water sample, checked the initial addition of oil to a water sample. However, on oil-distilled water samples, freshly prepared and immediately analyzed, check results were obtained by the technical method, ether extraction method, and the authors’ procedure, indicating complete adsorption of oil by the ferric hydroxide precipitate within the limits of error of thesr tests. The authors’ procedure does not determine saponifiable oil. However, lubricating oil a8 usually employed throughout the power plant cyrle contains only a small percentage of saponifiable oil. While the method recommended by the American Boiler Manufacturers’ Association, acidification to 1 per cent hydrochloric acid. can determine the saponifiable oil, this slight advantage is overweighed by the inrrease in solids content due to the presence of inorganic ealts and to the change in oil content from time of sampling to time of analysis. This recommended procedure has been employed i n the laboratories of W. H. & L. D. Betz for the past four years, during which time between four and five thousand determinations of the oil content of water samples have been made. The method haa been found satisfactory in practice. The authors suggest its use for fixing and determining oil content of feed water and boiler water samples as a referee method.
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Acknowledgments The authors wish to thank J. J. Maguire, director, Technical Division, H. L. Kahler, director of research, E. C. Feddern, research chemist, and other members of the staff of W. H. & L. D. Bet2 for their valuable suggestions and to acknowledge grate fully the generous aid of W. €I. & L. D. Betz and their permiasion to present these data.
Literature Cited American Boiler and Affiliated Industries, “Manual of Industry Standards and Engineering Information”, pp. 2 - 4 , 1942. (2) American Public Health Association. “Standard Methods of Water Analysis”, 8th ed., p. 117, 1938. (3) G r S n , R. C., “Technical Methods of Analysis”, 2nd ed., p. 702, New York, McGraw-Hill Book Co., 1937. (4) Pringle, C. P., J . SOC.Chem. Ind., 60, 173 (1941). (6) Scott, W. W., “Standard Methods of Chemical Analysia”, Vol. 11, 5th ed., p. 2078, New York, D. Van Nostrand Co., 1939.
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