644
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
oxygen in milk and the magnitude of the galvanometer deflections is linear. The concentration of oxygen in milk may be determined a t a potential ranging from 0.8 to 1.2 volts. The slight variations in the solids content of normal milks do not introduce significant errors. The statistical analyses of the data on the air-saturated milks show that the method is highly reliable.
Acknowledgment The authors wish t o express their appreciation to the Cambridge Instrument Co., New York, N. Y., for the loan of the instruments used in this study, and to the Federal Work Projects Administration (0. P. 65-1-22-477) for laboratory assistance.
Vol. 14, No. 8
Literature Cited (1)
Baumberger, J. P., Symposia o n Quantitative Biology, 7, 195
(1939). (2) Heyrovsk9, J., Phil. Mag., 45, 303 (1923); Trans. Faraday Soc., 19, 692 (1923). (3) Ingols, R. S., IND.ENG.CHEM.,ANAL.ED., 14, 256 (1942). (4) Ingols, R. S., Sewage W o r k s J . , 13, 1097 (1941). ( 5 ) Kolthoff, I. M., and Laitinen, H. A., “PH and Electro Titrations”, New York, John Wiley & Sons, 1941. (6) Kolthoff, I. M., and Lingane, J. J., Chem. Revs., 24, 1 (1939). (7) Manning, W. M., Ecology, 21, No. 4, 509 (1940). ( 8 ) Petering, H. G., and Daniels, F., J . Am. Chem. Soc., 60, 2796 (1938). (9) Sharp, P. F., Hand, D. B., and Guthrie, E. S., IND.ENCI. CHEM.,ANAL.ED., 13, 593 (1941). (10) Vitek, V., Collection Czechoslov. Chem. Commun., 7, 535 (1935). JOCRNAL series paper of the h’ew Jersey Agricultural Experiment Station, Rutgers University, Department of Dairy Husbandry.
Determination of Calcium in the Presence of Magnesium by Standard Soap Solution A Rapid Titration Method J. W. POLSKY AND E. C. FEDDERN, W.H.& L. D.BETZ, Philadelphia, Penna.
Calcium in water can be determined i n the presence of magnesium by direct titration with Clark’s soap solution with the addition of ammonium chloride and pH adjustment. Ions common t o industrial waters do not interfere. The accuracy and rapidity of this method are equivalent to those of the usual soap titration for total hardness.
I
NDUSTRY has needed a rapid method for the determina-
tion of calcium in the presence of magnesium, but a r e view of the literature failed to yield a simple, convenient, and yet satisfactory method that would give results comparable to those encountered in the total hardness determination recommended by the American Public Health Association (1). Froboese ( 5 ) stated that a separate determination of magnesium could be made in the presence of calcium by precipitation of the calcium as calcium oxalate and titration of the magnesium by potassium palmitate in the presence of the calcium oxalate precipitate, Durovdier (4)separated the calcium oxalate by filtration before titration of the magnesium and claimed a sensitivity of 1.4 mg. of calcium oxide or 1 mg. of magnesium oxide per liter. Using either procedure the calcium content can be obtained indirectslyby subtracting the magnesium content from the total hardness. Breazeale ( 2 ) titrated calcium in the presence of magnesium by employing alkaline tartrate which converts the magnesium into a complex that does not react with soap. I n Langelier’s method ( 7 ) the sample is first neutralized to methyl orange and then the carbon dioxide is removed either by boiling or in his mechanical apparatus. The magnesium is precipitated by the addition of carbonate-free sodium hydroxide, and the calcium is titrated with standard potassium oleate solution in the motorized unit. Of the above methods, none had both the accuracy and speed desired for the authors’ work. Ammonium chloride has long been known in the gravimetric determination of calcium and magnesium as a reagent for eliminating the interference of magnesium during the calcium precipitation with ammonium oxalate.
The procedure described in this paper makes use of the fact that magnesium in the presence of ammonium chloride and within prescribed p H ranges will not react with a standard soap solution, which can therefore be used to titrate calcium directly.
REAGEXTS.Clark’s soap solution (1, 3), 1 ml. = 1 mg. CaCO, equivalent. Ammonium chloride (reagent grade), 10% solution, Phenolphthalein, 1% solution [50% alcoholic, neutralized]. Sodium hydroxide, 0.77 N (carbonate free, 6). Calcium chloride, 1 ml. = 1.084 mg. CaCOs equivalent. Magnesium chloride, 1 ml. = 2.239 mg. CaCOSequivalent.
Experimental Standard solutions of calcium chloride and magnesium chloride were prepared gravimetrically, and from them, seven stock solutions of varying calcium and magnesium content were made. Six 50-ml. samples were taken from each stock solution and placed in 0.24-liter (8 ounces) narrow-necked glass-stoppered shaker bottles and 1 ml. of the ammonium chloride was added to each one. To the samples sufficient sodium hydroxide was added t o bring the pH values to 8.0, 9.0, 10.0, 11.0, 11.7, and 12.0, respectively, using a Beckman pH-meter. Correcting for the sodium ion, the values of the last three are actually 11.1, 12.1, and 12.7. The quantity of sodium hydroxide necessary to adjust to these pH values was determined on separate samples. Standard soap solution was then added from a buret in small portions, approximately 0.2 ml. a t a time, and after each addition the bottle was shaken vigorously and placed in a horizontal position. The end point was considered to have been reached when a lather was formed which covered the entire surface of the liquid and lasted for one minute. The number of milliliters of soap solution required in each titration was recorded in Table I. Table I reveals that a p H of 11.7 is optimum for this procedure. When magnesium is present in the absence of calcium, a minimum p H value of 11.7 is necessary for the titration value to agree with the blank of 0.20 ml. required for distilled water. This p H value also agrees with the fact that in the other calcium and magnesium concentrations a pH value of 11.7 was necessary to obtain a constant relationship between the milligrams of calcium added and the milliliters of soap solution required minus the 0.2-ml. blank, as shown in the lust column of Table I.
ANALYTICAL EDITION
August 15, 1942
z = mg. of calcium present y = ml. of soap solution titrated
where TABLE I. EFFECTOF PH
Mg
.
0 0 0
(Each sample contains 1 ml. of 10% hTHaC1) h l g . Ca Added as CaCOa [Eauivalent) , . M1. of Soap minus Blank Mg Added 0.77 X Under Bt p H 11.7 NaOH as and over Soap p H 11.7 Added CaCOa PH M g.
M1.
0 0 0
0.10 0.80 2.10 2.50 3.30
0
n
0 0
0 0 5.42 5.42 5.42 5.42 5.42 5.42 4.33 4.33 4.33 4.33 4.33 4.33 3.79 3.79 3.79 3.79 3.79 3.79 2.71 2.71 2.71 2.71 2.71 2.71 1.62 1.62 1.62 1.62 1.62 1.62 1 .os 1 .os 1.08 1.08 1.08 1.08
0 0
0 0 0
n
1 os 1 08 1 0s
os 1 os 1 os 1
1 62 1 62 1 62 1
62
1 62
1 62 2 71 2 71 2 71 2 71 2 71 2 71 3 79 3 79 3 79 3 79 3 79 3 79 4 33 4 33 4 33 4 33 4 33 4 33 5 42 5 42 5 42 5 42 5 42 5 42
5.15
.w.
8.0 9.0 10.0
0.10 0.75 2.10 2.60 3.35 5.10 0.10 0.90 2.15 2.60 3.30 5.10 0.10 0.80 2.05 2.50 3.35 5.15 0.10 0.90 2.20 2.70 3.40 5.10 0.10 0.90 2.25 2.70 3.30 5.20 0.10 0.80 2.10 2.50 3.20 5.10 0.10 0.85 2.10 2.55 3.50 5.20
11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0 8.0 9.0 10.0
11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0 8.0 9.0 10.0 11.0 11.7 12.0
0.20 0.20 0.20 0.20 0.20 0.20 6.70 6.15 5.50 1.30 0.20 0.20 3.60 4.90 4.95 1.35 1.20 1,15 4.70 2.00 1.90 2.40 1.65
1.55 5.15 2.80 2.75 2.80 2.60 2.50 3.95 3.85 3.75 3.70 3.50 3.50 4.50 4.15 4 10 4.15 4.10 3.90 5.20 5.00 4.90 4.95 4.90 5.05
..
.. .. .. .. .. .. .. .. .. .. 0:32 0.23 0.23 0.94
....
.. .. .. .. .. .. ..
..
1:09
0:36
.. ..
0.90 0.96 0.74
..
0:i5
1.04 1.06
1.04
..
1:01 1.04 1.07 1.09
..
1:01 1.10 1.11 1.10
..
1:09 1.13 1.15 1.14
.. ..
1.14
i:iz 1.20 .. .. ..
645
IC = constant 0.2 ml. = blank required for distilled water The constant, k , for the above curve was found to be 1.14. A variation of the amount of ammonium chloride added to the sample was found to have little effect on the results, as shown in Table 11. However, as the concentrations of the ammonium chloride were increased the resulting lather of the end point was not so definite as with lower concentrations. In the cases where no ammonium chloride was added to the samples, difficulty mas encountered in obtaining consistent end points. Procedure A 50-ml. sample of water is measured into a 0.24-liter (8ounce) glass-stoppered bottle and neutralized t o the phenolphthalein end point, and 1.0 ml. of the ammonium chloride reagent and 2.7 ml. of 1 N sodium hydroxide are added, bringing the pH of the resulting solution t o approximately 11.7. A variation in the pH value of the solution before titration, from 11.7 to 12.0, is allowable without affecting the stability of the end point or the accuracy of the determination. The soap solution is then added in small portions from a buret. The bottle is shaken vigorously after each addition, and placed
i:i3 1.17
.. .. ..
i:i5 1.15
..
..
TABLE
11. EFFECTO F VARYING AMMONIUM CHLORIDE CONTENT
[Each sample adjusted t o pH 11.7(before titration) with sodium hydroxide] C a as CaCOa Present 107 VHaCl Found Ca as CaCOa M g as CaCOa hded from Figure 1
.. .. ..
i:is 1.12
This being true, a curve was plotted (Figure 1) using the values obtained from the samples titrated at a p H value of 11.7, the total milliliters of soap solution required being plotted against the milligrams of calcium present. This gave a linear function whose equation is x = k ( y - 0.2 ml.)
0
0 0 0 0 0
5.42 5.42 5.42 5.42 5.42 4.33 4.33 4.33 4.33 4.33 3.79 3.79 3.79 3.79 3.79 2.71 2.71 2.71 2.71 2.71 1.62 1.62 1.62 1.62 1.62 1.08 1.08 1.08 1.08 1.08
i:ii 1.17
3
5 0 1 2 3 5
1.0s 1.0s 1.0s 1 .os 1.08 1.62 1.62 1.62 1.62 1.62 2.71 2.71 2.71 2.71 2.71 3.79 3.79 3.79 3.79 3.79 4.33 4.33 4.33 4.33 4.33 5.42 5.42 5.42 5.42 5.42
0
0 0 0 0
6.00 5.35 5.45 5.40 5.35 4.55 4.25 4.30 4.25 4.30 4.00 3.75 3.80 3.85 3.85 3 .OO 2.75 2.75 2.75 2.80 2.05 1.70 1.70 1.70 1.75 1.40 1.20 1.25 1.25
1 2
0
1
2 3 5 0
1 2 3 5 0
1 2
a
5 0
1 2 3 5 0 1 2 3 5
i.ao
0.45 0 0 0 0
TABLE 111. EFFECTO F V.4RIOUS IONS Present M g as Ca as CaCOa CaCOi p.p.m. P.p.m. 31 71 31 71 71 31 71 31 71 31 71 31 71 31 71 31 71 31 71 31 71 31 71 31 31 71 71 31
FIGURE1
71
71
:3 1 Til
71
31
.
Ca a8 Ions Present CaCOa SOI-Si02 HCOaF e + + + Found P.p.m. P.p.m. P.p.m. P.p.m. P.p.m. 71 50 71 100 73 200 72 500 ... ... 70 I000 ... ... 73 .. 5 ... 73 25 ... .. 73 50 ,.. .. 71 .. 100 ,.. 73 50 .. ... 71 100 ... 71 200 ... .. 5n0 n; ,.. 72 ... ...
J
... ...
...
... ... ...
71 70
70
INDUSTRIAL AND ENGINEERING CHEMISTRY
646
on its side, and the formation of a lather is observed. This procedure is continued until a lather is formed which covers the entire surface of the liquid and lasts for 1 minute. If the test requires more than 7 ml. of soap solution, an aliquot portion is diluted to 50 ml. with distilled water so that the final end point will be less than 7 ml.
Calculation of Results
TABLE IV. OPERATOR’S TOLERANCE Present as CaCOa Cs. Mg P.p.m. P.p.m. 86.7 21.7 54.2 54.2 108.4 0
The calcium content of the sample as p. p. m. of calcium carbonate is obtained from the formula [Ml. of soap (titrated)
- 0.20 ml.]
X
KO.
Effect of Ions I n order to determine whether other ions usually found in industrial water interfere with the test, various amounts of silicate, sulfate, bicarbonate, and iron were added to different samples; they did not noticeably affect the accuracy of the method, as shown in Table 111. Since ammonium chloride is added in the determination, chloride can also be regarded as noninterfering.
Industrial and Synthetic Waters A series of synthetic samples was analyzed b y several different operators (Table IV). The maximum error was small and on a par with the standard soap method. A list of industrial waters that have been analyzed is given in Table V, showing that good accuracy can be expected from this method. Conclusions This method gives accurate results for calcium in the presence of magnesium, and is as easily executed as the standard soap method. It is not affected by normal concentrations of ions found in industrial waters. The difference between a total hardness determination b y the usual Clark method and b y the method described reveals the approximate hardness due to magnesium. It is therefore possible to determine distribution of hardness in terms of calcium and magnesium
Ca as CaCOa Found by Operator A B C D P.p.m. P,p.m. P,p.m. P.p.m. 21 24 20 23 51 54 53 50 106 105 106 106
OF INDUSTRIAL WATERS TABLE V. ANALYSIS
Test
1000 X 1.14 = p. p. m. of Ca as CaCOa No. of ml. of sample
Vol. 14, No. 8
1
2 3 4 5
6
7 8 9 10 11
12 13
14 15
Gravimetric Ca as Mg as Dilution CaCOa CaCOs Factor P . p . m . P . p . m. 1 Feed 19.7 ... 1 35.8 ... Raw 1 46.9 Raw ... 1 ... 56.7 Raw 2 171.4 29.4 Well 202 5 268 City 2 Test well 1 5 6 . 5 76 17.2 1 26.1 Well 195 5 Test well 3 7 2 . 2 5 Well 370 176.4 41.7 1 81.7 City 472 242.4 5 Well 83.3 2 Well 183.6 141 5 Well 322.6 497 245 5 Well Source
Ca Found as CaCOa
Total Hardness by Soap
18 35 46 53 168 256 158 26 360 380 SO 465 184 320 485
29 50 73 64 196 480 220 46 570 555 122 730 270 460 730
by this new modified method. Its application t o boiler waters will be the subject of a later paper.
Acknowledgment The authors are indebted to C. A. Koll, chief chemist, for his suggestions and to W. H. &I L. D. Betz for making this investigation possible.
Literature Cited (1) American Public Health Association, “Standard Methods of Water Analysis”, 8 t h ed., p. 59, 1936. (2) Breaseale, E. L., and Greene, R. A., J. Am. Water W o r k s Assoc., 30, 1040 (1938). (3) Clark, T., Chem. Gaz., 5 , 100 (1847). (4) Durovdier, R., Ann. fals.,27, 273 (1934). (5) Froboese, V., 2. anorg. allgem. Chem., 89, 370 (1914). (6) Kellog, Chemist-Analyst, 29, 4 (1940). (7) Langelier, W. F., J . Am. Water Works Assoc., 32, 279 (1940).
PRBSENTED before the Division of Water, Sewage, and Sanitation Chemistry a t the 103rd Meeting of the AMERICAX CHEMICAL SOCIETY, Memphis, Tenn.
Colorimetric Determination of Phenothiazine with Palladous Chloride LYLE G. OVERHOLSER
C
AND
JOHN H. YOE, University of Virginia, Charlottesville, Va.
OSSIDERABLE interest has been manifested in the use of phenothiazine as a n insecticide and in the determination of small amounts found in spray residues. Eddy and D e Eds ( 2 ) determined small amounts of phenothiazine colorimetrically by oxidizing a n alcoholic solution t o a highly colored red compound with bromine water. Recently, Cupples ( I ) reported additional information concerning this reaction. The authors have observed that phenothiazine reacts with a number of inorganic ions. Most of these ions are oxidizing agents and the red or green colored solutions formed are due to an oxidation of phenothiazine. Palladous chloride reacts with phenothiazine, yielding a dark blue colored solution or precipitate which is not a n oxidation product but a complex having the formula Pd(CI2H&S)2C12. A procedure for the colorimetric determination of small
amounts of phenothiazine based on this reaction, methods for the preparation of the complex, and a description of its properties are presented in this paper.
Reagents A compound obtained ffom the Eastman PHENOTHIAZINE. Kodak Co. (P1456) was purified by recrystallization from ethyl alcohol. The purified compound melted a t 182” C. An acetone solution containing 0.05 mg. per ml. was used. (An ethyl alcohol solution of the same concentration may be used.) The solution slowly acquires a pink color; for this reason a fresh solution should be prepared at least once a Fveek. SODIUM ACETATE-HYDROCHLORIC ACID BUFFER. Fifty milliliters of 1 M sodium acetate were added to 50 ml. of 1 M hydrochloric acid and the solution was diluted to 250 ml. with water. This buffer has a pH of 2.6 which increases Bo 2.9 upon dilution of 5 ml. to 25 ml. with water. PALLADOCS CHLORIDE. A standard palladous chloride solution containing 1 mg. of palladium per ml. in 1 M hydrochloric
