ANALYTICAL EDITION
30
Vol. 3, No. 1
Proposed Modification of Oxygen Consumed Method for Determination of Sea Water Pollution' H. K. Benson and J. F. G. Hicks, Jr. UNIVERSITY OF WASHINGTON, SEATTLE, WASH.
By applying the Zimmerman-Reinhardt reaction to ion by the permanganate ion N USING the standard alkaline permanganate consumption, an easy and in acid solution occurs to a method (2) for the deterreliable method for the estimation of pollution in sea variable degree d e p e n d e n t mination of pollution in water is obtained. upon time, temperature, and briny w a t e r s , considerable Each set of determinations must be calibrated concentration factors. Howdifficulty was experienced in against the blank sample of the purest sea water in the ever, at times it was found this laboratory in obtaining locality of the pollution. possible to check aliquot a sharp end point. Also reThe method may be correlated with other means for parts of the same s a m p l e sults were not consistent with the detection of pollution such as the biochemical within 2 or 3 p, p. m. of the known pollution in given oxygen demand, bacteria, and plankton. oxygen by allowing an samDles and the values a r i r t r a r f length of -time were*several fold too high. Table I shows the variations obtained in samples of sea (20 seconds) from the addition of a single drop of permanwater from several bays of Puget Sound. These samples ganate (in back titrating) until the disappearance of its were all taken by means of a deep sea tester at a uniform color. Even so, the values obtained for oxygen consumed depth of 10 feet. The biochemical oxygen demand was appear much too large. I n order to enable the accurate reproduction of results determined after 5 days' incubation in a thermostat a t 25" C., and computed to a 20-day basis by use of the sewage in a given sample and to limit the reaction more nearly to the oxidizable organic matter contained in sea water, use is factor 0.68. made of the Zimmerman-Reinhardt (6) method for the Table I-Variations in Pollution Data titration of permanganate in the presence of hydrochloric acid. OXYGENCONSUMED
I
'
SAMPLE
B. 0. D. Mn./liter -.
Mg./liter 18.54 17.89 20.29 17.45 14 76 29,34 13.13 19.60
1.82 3.49 0.87 2.75 2.21 4.15 1.82 5.88
Table 11-Comparison SAMPLE
CHLORIDES Mg./litcr 14,750 14,200 14,184 15,905 15,975 16,110 16 075 153160
KMnO4
BY
of Results by Old a n d New Methods NEWMETHOD OLD METHOD Mg./liter
Mg./liter
Proposed Procedure
The digestion is carried out in exactly the same manner as in the standard method ( 2 ) . The modification lies in the determination of unconsumed permanganate. After digestion, the sample is acidified with 25 ml. of the preventative solution containing manganous sulfate, sulfuric acid, and phosphoric acid. Immediately thereafter 10 ml. of standard ferrous sulfate solutions are added. The sample
BLANK SEA WATER BEFORE INCUBATION
37.4 46.4 45.0 49.0 40.5 43.7
13.0 12.8 12.7 12.5 12.7 12.7
Av.
AFTER INCUBATION FOR 98 HOURS AT 28'
6.8 6.7 6.7 7.0 6.8 6.8
Av.
c.
33.0
DIGESTER LIQUOR DILUTIONS AFTER 98 HOURS' INCUBATION AT 2s'
RATIOLIQUORTO
C.
SEA WATER
1: 1000
1 :5000 1 :10000 1 :50000
74.5 73.8 21.7 20.7 14.6 13.8 7.2 7.2
80.9 81.9 40.1 23.2 34.3 30.8 40.3 26.3
DIGESTER LIQUOR DILUTIONS AFTER 24 HOURS' INCUBATION AT 21' C.
1 :7500
1 :30000
25.2 25.2 16.1 15.9
38.2 36.2 36.2 37,.2 3
It is evident that no correlation exists between the organic content of these samples as measured by the biologic and permanganate oxygen consumptions, respectively. The differences are rather suggestive of slight variations in technic which would permit other reactions than the oxidation of organic matter to proceed. I n the presence of iron as ti catalyzer it seems probable that the oxidation of the chloride 1 Received
September 10, 1930.
is brought to room temperature and standard permanganate added until the addition of one drop changes the solution from colorless to light pink. This end point is sharp enough so that two identical samples may be checked within 0.02 ml. Tenth normal permanganate standardized against either
INDUSTRIAL A N D ENGINEERING CHEMISTRY
January 15, 1931
iron wire or sodium oxalate is used. The iron solution contains ferrous ammonium sulfate and sulfuric acid in concentrations of 0.1 N and 0.3 N , respectively. The preventative solution contained 67 grams of MnS04.4Hz0, 138 ml. of 85 per cent phosphoric acid, and 130 ml. of sulfuric acid (concd.) diluted to the volume of 1 liter. The comparison of this method with the standard method is given in the determinations, used in Table 11,which utilized various dilutions of waste liquor from sulfite digesters in sea water obtained from Seattle harbor. With this constancy of results it is obvious that the oxygenconsumed values may be used to indicate the concentrations of sulfite liquor when it is known that it is the polluting agent in sea water. By making up the various dilutions and taking the mean of five determinations on each dilution the results used in Table I11 were obtained. Table 111-Oxygen Consumed with Sulfite Liquor as Polluting Agent DILUTION OF LIQUOR IN OXYGEN CONSUMED OXYGEN CONSUMED BY SEA WATER BY MIXTURE DIGESTER LIQUOR Mdliter M ~_. /.l i l e r Blank 11.3 0.0 73.7 1 : 1000 62.4 32.8 21.5 1: 5000 12.4 23.7 1 :7500 18.3 1 : 10,000 7.0 13.7 2.4 1 : 30,000 11.5 0.2 1 : 50,000 11.3 1: 100,000 0.0
When these values are plotted against concentrations the resulting curve (Figure 1) is either identical or nearly so with that obtained by dividing the 5-day biochemical oxygen demand (3’) by the sewage factor 0.68 commonly used to express complete biological oxygen consumption. Inasmuch as Rudolfs (4) has shown that there is a direct relation between the biochemical oxygen demand, bacteria, and plankton, it would seem that the oxygen consumed as determined by this modified method correlates with the other factors ordinarily used for detection of pollution. Abbot (1) has proposed a modified acid dichromate absorp-
31
tion test as a more sensitive index of oxidizable matter than the permanganate absorption test, His values of the percentage oxidation of various organic substances range from 98 per cent in the case of sodium oxalate to 66 per cent for gelatin. To ascertain the degree of completion of oxidation of organic substances somewhat similar to lignin and the other components of digester liquor, the following compounds were submitted to the modified permanganate consumed test: vanillin, tannic acid, starch, sucrose, and pyrogallol. Complete oxidation is defined according to the following reactions : Vanillin: Tannic acid: Starch: Sucrose: Pyrogallol:
++ ++ +
++ + +
CsH& 17 (0)+8COs HzO C14HloOg 24 (O)---t14cO~ ~HzO C6Hlo05 12 (0)+6C02 5H20 C l z H ~ ~ O+24 l l (0)+12C02 1lHzO C6He03 12 (0)+6C01 3Hz0
After making correction for the oxygen consumed by the blank, the results given in Table IV were obtained by the modified method. Table IV-Modified Permanaanate Consumed Tests WEIGHT O F OXYGEN REQUIRED COMPLETE SUBSTANCE SAMPLE Theoretical Actual OXIDATION Gram Gram G7am % Vanillin 0.0159 0.0285 99.0 0 0282 Tannic acid 0.0056 0.0067 65.5 0.0044 Starch 0.0527 0.0626 72.0 0.0451 Sucrose 0.0408 0.0446 0.0372 83.5 Pyrogallol 0.0130 0.0196 77.5 0.0152 I
From the similarity of these substances to those present in digester liquor it would be reasonable to expect that their oxidation is from 85 to 90 per cent complete. Literature Cited (1) Abbot, IND. END. CHEM.,19, 919 (1927). (2) American Public Health Assocn., “Standard Methods for Examination of Water and Sewage,” 6th ed., p. 24, footnote. (3) Benson, Paper Trade J., 90, No. 24, 69 (1930). (4) Rudolfs, IND. END. CHEM.,21, 256 (1929). (5) Treadwell and Hall, “Analytical Chemistry,” Vol. 11, pp. 515-8, footnote 2.
Modified Ford-Williams Method’ L. H. James REOMOTORCo., LANSING,MICH.
T
HE following procedure is applicable to the determination of manganese in high chrome-nickel alloys which are practically insoluble in nitric acid. Such alloys are, however, soluble in nitro-hydrochloric acid. If either the persulfate or bismuthate method is used for determining the manganese in nickel-chrome alloys soluble only in nitro-hydrochloric acid, i t is necessary to remove the hydrochloric acid by fuming with sulfuric acid and the chromium with ainc oxide. The only difficulty encountered in this procedure arises from the fact that the complex SUIfates formed often dissolve very slowly after dilution with water. The insolubility of these chromium sulfates probably increases with the temperature and time of fuming, although rather startling variations have been met with in regard to the time required to dissolve the sulfates formed, while working with the same alloy under like conditions. The Ford-Williams method is the O d Y other Practical alternative method used to determine the manganese in such alloys. It is not necessary to separate the chromium in this method, but the hydrochloric acid must be removed by at least two evaporations with nitric acid to a sirupy COnSiStenCy. Received September 3, 1930.
Evaporations of this kind are always somewhat troublesome and time-consuming, The proposed method eliminates the objectionable features of the above-mentioned procedures if the alloy is insoluble in nitric acid, as it is easily carried out, reasonably accurate, and much faster than the methods usually employed. However, if the material to be analyzed is soluble in nitric acid, obviously the following modification cannot be used to any advantage as the Ford-Williams method in its present form has always been recognized as entirely reliable. Method
Weigh 2 grams of sample into a 5 0 0 - ~ tall ~ . form beaker, Add 15 CC. of hydrochloric acid (SP. gr. 1.19), 5 CC. of nitric acid (sp. gr. 1-42), and 20 cc. of water. Boil until dissolved and add 20 cc. of perchloric acid (60 per cent). Continue to boil until the perchloric acid fumes and insoluble salts start to separate. cool, dissolve in 30 CC. of nitric acid (SP. gr. I & ? ) ,and heat just to boiling. Add a few crystals of sodium chlorate in order to avoid excessive foaming and then precipitate with four additions of 2 grams each of sodium chlorate adding each portion after the effervescence produced
