Detection of Sulfite Waste Liquor in Sea Water H. K. BENSON' AND W. R. BENSON, University of Washington, Seattle, Wash. I n dilute concentrations of sulJite waste liquor ONSIDERABLE w o r k Objection to this method lies h a s been d o n e on t h e in the variation of n a t u r a l l y in sea water, the oxygen consumed and the biooccurring oxidizable organic effect of sulfite pulp mill chemical oxygen demand values, when compared matter in unpolluted sea water effluent on fresh water streams. for an unpolluted sea water with similar values Investigations in Wisconsin ( I d ) d u e to the change of tide or to in the same locality, are useful indicators of its describe various technical land drainage. Another objecpresence. tion consists in the decrease of m e t h o d s which h a v e been developed to measure the effid i s s o l v e d o x y g e n due to the With the aid of a n accurate colorimeter, p H p o l l u t i n g matter. Nevertheciency of p o n d i n g of sulfite values vary in the same manner as the equivalent less, the oxygen balance furnishes wastes. In a recent sanitary acid required to give a constant p H beyond the survey of the Willamette Valley a graphic representation of the buffering range of sea water. in Oregon the measurement of spread of pollution over a given For high concenlralions, the ordinary analytical sulfite pollution is also underarea when sufficient samples are taken (7). Quite generally the taken. determinations, such as dissolved oxygen, sulfates, greatest reliance has been placed and, to some extent, color, may be used to give BIOCHEMICAL OXYGENDEMAND upon the biochemical oxygen of amounts of sulfite approximate indications AND OXYGENCONSUMED d e m a n d and the oxygen conVALUES waste liquor present, if compared with a suitable sumed values as indicators of the reference sample. presence of u n s t a b l e organic T h e s a m e r e s u l t m a y of matter, any. appreciable increase course be obtained by using the __ in the vicinity of pulp mills being attributed to their effluent. oxygen demand itself. When the 5-day demand a t 25' C. is I n some cases use has been made of plants and animals as divided by the sewage factor 0.68, a set of values is obtained indicators (IO) of the nature of polluting matter. which, when plotted against various concentrations of digester The detection of sulfite waste liquor in sea water is compli- liquor in sea water. rather closely parallels that obtained by cated by several factors. The presence of tidal currents and the proposed modification (2) of the permanganate method for eddies and the higher density of sea water in relation to fresh oxygen consumed, A study of Figure 2 together with the close water are liable to make sampling highly erratic unless taken agreement on samples of sea water indicates that both over a long period of time. The organic content of sea water methods are sensitive within the range of one part of digester is also extremely variable, depending upon its relation to the liquor in 5000 to 20,000 parts of sea water. larger ocean waters as well as to the land drainage. It contains both calcium and sulfate ions. The presence of sulfite HYDROGEN-ION CONCENTRATION waste liquor in sea water, unless in great quantity, cannot be Sulfite waste liquor varies considerably with the methods detected, therefore, by simple chemical analysis. I n the absence of a specific test, it is evident that its presence or used for pulp digestion. The method of sampling also has a absence in sea water must be established by a number of marked effect on the analytical constants. If it is taken from corroborative tests rather than by the simpler determinations the blow pit it has been diluted by the cooling showers generused in studies of fresh-water pollution. Therefore, it is of ally employed, and if it is blown hot from the digester it interest to consider the use of various methods which may be suffers loss of SOz. To eliminate these variables and to obapplied to the quantitative estimation of sulfite waste liquor tain maximum pollutional effects, cold-drawn samples from digesters were used. Even so, the liquor from two different in sea water. mills shows variations in composition as given in Table I. OXYGENBALANCE TABLEI. COMPOSITION OF SULFITEWASTELIQUOR I n a previous paper (1) the usual biochemical oxygen deSAMPLE A SAMPLE B % % mand of sea-water samples suspected of containing sulfite 1.11 0.47 Total SO2 waste was substracted from the dissolved oxygen contained in 10.59 11.11 Total solids 9.44 10.17 Volatile solids a sample taken simultaneously. The result obtained was 0.94 1.15 Ash known as the oxygen balance. I n samples of unpolluted sea water the oxygen balance approaches the dissolved oxygen in The acidic nature of digester liquor, due to its slight content value, whereas in polluted water its value is n e g a t i v e 4 e., the of free SO2, will of course reduce the alkalinity of sea water. oxygen required to oxidize the polluting matter is greater than Its pH value should therefore be a measure of its presence, and that contained in the sample as dissolved oxygen. By in fresh water such values are commonly accepted for its calibrating this measure with representative samples of sulfite determination. I n sea water, however, the accuracy of pH waste taken from the digester just prior to the blowing of the values has been questioned. It has been shown by Irvine (5) digester, it was found that a concentration of one part of that bicarbonate ions, as well as minute traces of phosphates, sulfite liquor in 7500 parts of sea water (133 parts per million) borates, silicates, and organic matter, exert a buffering effect will yield negative values. It is still sensitive a t dilutions of and that a relatively large addition of acid is necessary to alter one in 30,000 (33l/9 parts per million). By comparing the materially the pH of such a buffered solution, especially oxygen balance of an unpolluted sea water in the same locality between pH 5.5 and 8. Therefore, various investigators (3, with that of the sample, it is evident that the difference must 8 ) have proposed to set free the COzby adding acid to increase be due to the extraneous or polluting matter. the hydrogen-ion concentration to grams per liter and thus get beyond the range of the buffering effect. By titrat1 Present address, National Research Council, Washington, D. C.
C
'
220
April 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
ing 100 cc. of sea water with 0.01 N hydrochloric acid, using a convenient indicator until the color changes, and expelling the carbon dioxide, it has been found that ocean water requires from 23 to 26 cc. of 0.01 N acid to bring it to a hydrogen-ion Concentration of loT4grams per liter. As an alternative (8) the sea water may be titrated until the color of the indicator is the same as a t the same concentration in distilled water saturated with carbon dioxide. The amount of acid necessary to yield a constant pH of approximately 4.0 should therefore be a measure of other acidic constituents not normally present in ocean water. I n Table I1 are given values obtained by various dilutions of digester liquor in sea water, in distilled water, in distilled water saturated with carbon dioxide, and the amount of acid required to bring the sea water dilutions to a constant pH of 3.7. All determinations were made by means of a Bausch and Lomb hydrogen-ion colorimeter, the dilutions being made by meane of a microburet and kept in Pyrex bottles.
221
I n Table I11are giventhe values obtained on adding one cup of breakfast coffee, sweet cider, fresh milk, and garden compost (leaves, humus), respectively, to a quart of stabilized sea water. The mixture was kept in an open Mason jar a t a temperature of 70" F. for 2 weeks. After filtration, dilutions of 10,000 parts per million of stabilized sea water were made of the respective solutions. It is apparent that old organic matter in sea water such as results from animal and vegetable matter lowers the pH and affects the buffering of sea water to an appreciable degree.
SULFATE-CHLORIDE RATIO The ratio of the sulfate and chloride content of the waters of North Puget Sound has been investigated by Thompson (11) and found to have a constant value of 0.1396. I n the larger bodies of water this value is independent of temperature and dilution variations. Further inland the value is subject to slight changes. If a polluting substance containing sulfur is TABLE11. PE OF DIQESTER LIQUOR DILUTIONS IN STABILIZEDadded to sea water this ratio will be higher, or, if reducing substances are present as in brackish lagoons or over mud SEAWATER 0.01 N DISTILLID flats where anaerobic conditions prevail, its value will be DIQECITER SAMPLE SAMPLE ACIDFOR DISTILLED H2O AND diminished. LIQUOR A B PH 3.7 WATER COn P.p . m.
PH
PH
cc.
PH
PH
10,000 8,000 6,000 4,000 2,000
3.34 3.50 3.86 5.66 6.64
4.97 6.17 6.34 6.72
'*"
5.9 10.3 15.0 16.0 20.9
2.85'3 2.96 3.14 3.65 3.68
2.85a 2.92 3.12 3.24 3.56
1,000 800 600 400 200
6.95 7.05 7.21 7.06 7.37
6.99 7.06 7.07 7.15 7.34
21.5 25.0 25.0 25.0 25.0
4.00 4.17 4.46 4.85 5.43
3.89 3.99 4.11 4.20 4.30
7.60 25.1 7.60 7.61 25.1 7.59 7.68 26.3 7.85 7.79 26.3 25 40 .7.70 7.82 26.3 Blank 7.79 Matched in colorimeter and estimated.
6.23 6.68 6.68 6.68 6.68
4.36 4.43 4.36 4.43 4.40
100 80
These values are plotted in Figure 1 on semi-logarithmic paper. It is noted that in both sea water and distilled water the pH and acid equivalent values are noticeably affected in the dilution of 200 parts per million (one part in 5000 parts) and that the general shape of these curves is the same. Below 100 parts per million changes in pH are apparently within the range of experimental error. I n the higher concentrations, the respective values for pH and equivalent acid show a marked proportionality to the dilution values in sea water. From the similarity of the graphs, there seems to be no necessity for correction of the buffering action of sea water, since the changes in pH are of the same order regardless of its range or the presence or absence of buffering agents. I n sulfite liquor-disposal systems, direct readings of pH should therefore continue to be a very simple and accurate means for the detection of sulfite liquor where it is known to be the polluting agent and where reference values for the unpolluted water of a given locality have been determined simultaneously. TABLE111. BUFFERINQ ACTIONOF ORQANICMATTERIN SEA WATER ORQANIC MATTER
PH
0.1 N HCl ADDED
RESULTANT PH
cc. Blrnk sea water Coffee Compost Cider Milk
7.95 7.55 7.81 6.98 6.06
25.0 25.0 25.0 25.0 20.0
3.69 3.98 3.83 3.74 4.45
It i s of interest to note the effect of organic matter in general upon the buffering action of sea water. For this purpose various organic substances ordinarily associated with the uge of land draining toward the sea, such as orchard and dairy products, vegetable extract, and decaying matter, were added to stabilized sea water and allowed to undergo fermentation.
F~GURE I
The effect of sulfite waste liquor on this ratio may be noted in the dilution studies given in Table IV, in which bromine is used as the oxidizing agent in preparing the samples for precipitation of barium sulfate. SULFURIN MIXTURE OF SULFITE LIQUOR TABLEIV. TOTAL AND SEA WATER COMPOSITION OF SAMPLE 100 100 100 100 100 100 100
cc. blank cc. 0.2 cc. liquor cc. 0.4 cc. liquor ca. 0.8 cc. liquor cc. 1.0 cc. liquor cc. 2.0 cc. liquor cc. 4.0 cc. liquor
++ + ++ +
CHLORIDE Mg./litsr 15,873 15,873 15,873 15,873 15,873 15,873 15,873
RATIO SO1:Cl
Mw./Zitm 0.2237 0.2259 0.2772 0.2324 0.2380 0.2441 0.2586
I n order to check back in these analyses it is necessary to know the sulfur content of the sulfite liquor itself. Unfortunately this varies with each charge in commercial operation, depending upon the manner of blowing and cooling the
ANALYTICAL EDITION
222
Vol. 4, No. 2
TABLEVI. CALCIUM AND MAGNESIUM VALUES SAMPLE
BlOCHrM/CAL
OXYGLN
366.0 372.3 349.5 374.1 392.3
1128.0 1134.7 1068.5 1068.5 1099.2
0.3244 0.3281 0.3270 0.3270 0.3669
Ca
Field sample of pure sea water Stabilized sea water Dilution 1 to 10,000 Dilution 1 to 1000 Dilution 1 to 100
.
RATIO
Mg Mg./liter
CP:Mg
iMg./Zzter
It appears from these determinations that no appreciable effect in ionic distribution can be detected until concentrations of 1 to 100 (10,000 parts per million) are reached.
COLORREACTIONS Many color reactions between wood and various chemical compounds are noted in the literature (4). Some of these are regarded as being specific for lignin and it would seem reasonable that some might also apply to the soluble lignin compounds in sulfite liquor. However, the color reactions in 0 /OW0 20063 30000 40000 50oW almost every case are due to the predominance of a colorD/LUT/ONS OF D/G€STER L/QUOR /N SEd WATER producing aldehyde in the wood. I n sulfite waste liquor, such i Parts of Sea Water fa one Part Oyester- L / p r ] reaction has already taken place in the digester and is indeed FIGURE2. EFFECTOF SULFITEWASTELIQUORON OXYGEN used as a test for the completion of the cooking process. It CONSUMED AND B. 0.D. OF STABILIZED SEA WATER would seem logical to conclude, therefore, that sulfite waste liquor in sea water is itself a color indicator. Hence the sample. Even on a given sample considerable difficulty was encountered in obtaining check results. The following methods were employed: (1) Schreiber's method (9); (2) neutralization with sodium hydroxide, oxidation with bromine, and fusing the residue; (3) the method suggested by the U. S. Forest Products Laboratory, consisting of distillation of sulfur dioxide into standard iodine and precipitation of residual soluble sulfates by barium chloride; (4) the method of A. W. Schorger, suggested in correspondence, consisting of the oxidation of the organic matter by fuming nitric acid; and ( 5 ) a method in which a 10-cc. portion of diluted digester liquor (1 to 10) is taken. In the last method, 100 cc. of bromine water are added and, after diluting to 200 cc., are digested on a steam bath overnight. Five grams of potassium chlorate and 20 cc. of concentrated hydrochloric acid are next added and the chlorine boiled off. After diluting to 400 cc., the barium sulfate is precipitated. Upon evaporating the filtrate to dryness, fusing with sodium, dissolving in hot water, and acidifying, a good test for hydrogen sulfide was obtained in each sample, showing that despite good checks in barium sulfate precipitates the method does not determine total sulfur. The results are given in Table V. TABLEV. SULFURCONTENTOF SULFITEWASTELIQUOR METHOD
Schreiber
SAMPLE TOTALSULFUR Mg./liter 1 10.5 2 , 10.9
Oxidation by bromine
1
8.6
U. 8. Forest, Products Laboratory
1
8.2
Schorger
1 2 3
8.7 8 .'6 8.7
'CALCIUM AND MAGNESIUM VALUES
The determination of calcium and magnesium in sea water reauires mecia1 mecautions because of the DreDonderance of mignesium. T6e results obtained by the aGhirs are given in Table VI.
FIGURE3
standard method for determination of color is probably as sensitive as any other reagent and is not so liable to be confused with other reactions occurring between sea water and such reagents as permanganate, chlorine, nitric acid, and ferric ferricyanide. The color imparted to sea water by sulfite waste liquor can often be noted a t the time of digester discharge for a considerable distance, and in concentrations of 1 part in a thousand (1000 parts per million) or greater it is very pronounced in laboratory samples. Caution must be exercised, however, in the interpretation of color tests in sea water. I n addition to organic coloring matter brought in by stream dilution, striking color mass is often observed, and found due to phytoorganisms, as well as to organic matter from land drainage.
April 15, 1932
INDUSTRIAL AND ENGINEERING
EFFECTOF HIGHCONCENTRATIONS In concentrations of sulfite waste liquor exceeding 1000 parts per million, the values obtained are more marked and a wider range of determinations becomes available. In Table VI1 are given values determined by Standard Methods of Analysis, with the exception that oxygen consumed was made in accordance with the proposed modification. The B. 0. D. was determined a t 25” C. Oxidation with bromine was used for the determination of sulfates. The dilutions of the sulfite waste liquor in stabilized sea water (blank) were prepared with a micropipet. The results are the average of three dilution sets. In Figure 3 these values are plotted on a semi-logarithmic scale and show the same general effect with increasing concentration. By comparing such values with .&milar values obtained from unpolluted sea water in the same locality, it is evident that a measure of the extent of pollution may be obtained.
CHEMISTRY
223
an order of magnitude rather than the correlation of sea water with sulfite waste liquor. Both of these are too variable to permit of quantitative relationships. Nevertheless, the values may be taken as approximations of sulfite waste liquor present, as is obvious from the following table:
1. 2. 3. 4. 5. 8.
SAMPLE Puget Sound surface Puget Sound: 40-ft. depth Inland Bay surface Inland B a i 18-ft. depth Near dispoAal sewer of sulfite mill 1000 parts sulfite waste per million parts of sea water (sample 3)
PH 8.1
8.1 8.1 8.2
&DAY COLOR B.O.D. 13 1.62 0.83 14 1.35 12 1.14 13
OXYGEN CONSUMED 2.15 2.24 2.38 1.94
7.1
90
30.15
177.6
7.2
33
27.1
96.6
By consulting Table VlI, the quantity of sulfite waste liquor in sample 5 ranges from 900 to 1500 parts per million, except that the color is much higher than the color scale of the stabilized sea water for such concentration. TABLBVII. ANALYTICALVALUESOF VARIOUSCONCENTRATIONS OF SULFITE WASTELIQUOR IN STABILIZED SEAWATER LITERATURE CITED DIQEST’ER COLOR
LIQUORI N DISSOLVED& D A Y OXYGEN RATIO PT.CO SEAWATER OXYOENB. 0. D. CONSUMED SULFATES S04:Cl STANDARD Parts Ma./!iter Mg./liter Mg./Ziter Mg./Ziter .. 0.1654 112 1295 0.2791 -34.3 387 10,000 92 0.2697 0.1598 770 -28.5 304 8,000 76 0.2613 0.1549 635 169 6,000 -24.0 46 0.2551 0.1512 551 149 4000 -12.2 25 0.2461 0.1459 219 72.5 2:ooo 0.75 1,000 800 600 400 200
3.90 4.00 4.90 5.87 5.95
32.9 28.6 21.9 14.5 7.8
100 80 40 25 Blank
6.55
3.7 3.1 1.9 0.8
6.70
6.80 6.96 7.10
0.0
106 83.3 62.2 43.8 20.3 14.1 12.1 7.25 7.45 3.8
0.2400 0.2413 0.2398 0.2393 0.2362
0.1426 0.1429 0.1421 0.1406 0.1400
8 7 5 5
0.2363 0.2367 0.2369 0.2372 0.2381
0.1397 0.1403 0.1404 0.1405 0.1406
4 3 3 2 0
4
APPLICATIONOF RESULTSTO FIELDMEASUREMENTS The analytical values reported were obtained on dilutions of sulfite waste liquor in stabilized sea water. They represent
(1) (2) (3) (4) (5) (6) (7)
(8) (9) (10) (11) (12)
Benson, Paper Trade J.,90, No. 24, 69 (1929). ENQ. CHEX.,Anal. E d . , 3, 30 (1931). Benson and Hicks, IND. Bruce, Brit. J. Erptl. Biol., 2, 57-64 (1924). ENG.CHEM.,13, 625 (1921). Crocker, J. IND. Irvine, J. Biol. Chem., 63, 767-81 (1925). McClendon, Ibid., 30, 274 (1917). Oregon State Coll., Engineering Expt. Sta., BUZZ. Series N o . 2. pp. 19-28 (June, 1930). Saunders, Brit. J. ExptZ. Bid., 4, 46-72 (1926). Schreiber, J. Am. Chem. SOC.,32, 978 (1910). Suter and Moore, Rept. N . Y . State Conservation Comm., 1922, 292. Thompson, Pub. Puget Sound B i d . Sta. Univ. Wash., 5, 27792 (1927). Wisconsin S t a t e Board of Health Rept., “Stream Pollution in Wisconsin,” pp. 76-83, Jan., 1927.
RECEIVEDOctober 30, 1931. Presented before the Division of Water, Sewage, and Sanitation Chemistry a t the 81st Meeting of the American Chemical Society, Indianapolis, Ind., March 30 to April 3, 1931.
Slotted Watch Glasses for Use in Electroanalysis EARLER. CALEY,Frick Chemical Laboratory, Princeton University, Princeton, N. J.
F
OR the prevention of loss by spraying or splashing
during electrolytic determinations, the slotted watch glasses shown in the figure have been found to be a decided improvement over the perforated or split watch glasses usually employed for this purpose. Watch glasses with one or more holes drilled in them protect solutions satisfactorily during electrolysis, but the necessity of disconnecting the electrodes each time a watch glass is to be placed on or removed from a vessel renders their use inconvenient, whereas the divided type of watch glass frequently causes difficulty or loss because of its tendency to be easily jarred out of position. The preparation of slotted watch glasses of the types shown, from plain watch glasses, presents no especial difficulty providing there is available a sufficiently thin Carborundum wheel. I n making form A , which is designed for use with stationary electrodes, an ordinary watch glass is simply slotted by means of the grinding wheel. In the preparation of form B, which has been found more satisfactory for use with a rotating anode, the central hole is drilled first in the usual manner before the slotting operation is performed. I n order to minimize the risk of breakage during grinding, it is necessary to select the rather thick variety of plain watch glass in preference to the thin kind.
Several practical precautions must be observed during the grinding operation in order to prepare these slotted watch glasses successfully. I n the first place, the speed of the wheel should be kept low, preferably at about 400 r.p.m., and lubrication with Carborundum powder and water should be generous during the entire operation. It is quite essential to introduce the edge of the glass to the wheel slowly and to maintain a slow rate during grinding. Good technic requires
A
6
TYPESOF SLOTTED WATCHGLASSES
that the wheel be worked back and forth in the partly formed slot following each new advance so that a slight enlargement is continually produced. An average-sized watch glass should
