ANALYTICAL EDITION
56
assistance rendered by E. N. Geddings of the Mallinckrodt Company.
Vol. 4, No. 1
(4) Holde, D., “The Examination of Hydrocarbon Oils and Saponi-
LITERATURE CITED
fiable Fats and Waxes,” translation from the German of E. Mueller, p. 69, Wiley, 1922. (5) Seltz, H., and McKinney, D. S., IND. ENG.CHEM.,20, 542 (1928).
(1) Am. .Sot. Testing Materials, Rept. of Sub.-Com. I X of Committee D-1, Vol. 26, 1926. (2) Britton, H. T. S., “Hydrogen Ions,” Van Nostrand, 1929. (3) Gardner, W. H., and Whitmore, W. F., IND.ENG. CHEM.,Anal. Ed., 1, 205 (1929).
RECEIVEDSeptember 10, 1931. Presented before the Division of Paint and Varnish Chemistry a t the 82nd Meeting of the American Chemical Society, Buffalo, N. Y.,August 31 to September 4, 1931. From a portion of a thesis submitted by Mr. Mattiello for the degree of master of science a t the Polytechnic Institute of Brooklyn, 1931.
Elimination of Corrections for Nitrites in Nitrate Determinations G. H. NELSON, MAXLEVINE,AND J. H. BUCHANAN, Iowa Engineering Experiment Station, Ames, Iowa THE LIMITING reactions at which nitrites and nitrates are decomposed on evaporation to dryness have been determined. Nitrites are decomposed at pH 3 and nitrates at pH 2 when acidified with acetic acid. It has been observed that nitrites are destroyed by evaporation to dryness in the presence of ammonium chloride or ammonium sulfate from acid or moderately alkaline solution, but at pH 11 none of the nitrite was lost. Ammonium hydroxide and ammonium carbonate did not serve to decompose the nitrite on evaporation. The elimination of the troublesome correction f o r nitrites in the determination of nitrates by evaporation of a neutral solution in the presence of ammonium chloride or ammonium sulfate, and the possibility of utilizing REACTION LIMITSIN EVAPORAa solution made acid (PH 3), with acetic acid for TION TO DRYNESS this purpose, is suggested.
I
N A p r e v i o u s report (2) it was suggested t h a t nitrite n i t r o g e n could be completely eliminated without affecting the nitrate nitrogen by evaporation of a neutral solution to dryness in the presence of an excess of ammonium chloride. This was s u g g e s t e d for the reduction method for the purpose of eliminating the troublesome correction for nitrites. The following report deals with the influence of reaction and certain a m m o n i u m s a l t s on the success of the proposed method.
Portions of solution (50 cc.) containing various a u a n t i t i e s of nitrites-and nitraces acidified with acetic acid, as shown in Table I, were evaporated to dryness on a water bath, and the residue dissolved in 100 cc. of nitrogen-free water. Fifty cubic centimeters were then tested for nitrites with naphthylamine acetate, and the nitrogen in the remaining 50 cc. was determined by the reduction method. To bring the reaction to a pH of 1.9 it was necessary to add some hydrochloric acid. It is evident that a t this reaction both nitrite and nitrate were decomposed on evaporation. At reactions of pH 3.0 to 3.2, nitrites up to 9.20 parts per million were decomposed completely, whereas nitrates were not affected, the latter being quantitatively recovered. At reactions of pH 4.0 or more alkaline (observations were made up to pH 7.9), neither nitrites nor nitrates were lost. These results indicated the possibility of eliminating the corrections necessitated through the presence of nitrites by the simple process of adjusting the reaction to a pH of 3.0 and evaporating to dryness. A series of observations was therefore undertaken with other acids to ascertain whether this limiting reaction was applicable when employing hydrochloric, sulfuric, or phosphoric acids. The results for these three inorganic acids are summarized in Table 11. It appears that, as was observed with acetic acid, the nitrites were destroyed when evaporated to dryness from solutions made up to a pH of 3.0 with sulfuric or phos-
p h o r i c a c i d s , but with hydrochloric a reaction of pH 2.7 was required. With respect to the stability of nitrates, however, the results (Figure 1) were quite different from those observed with acetic acid. Thus, with hydrochloric a c i d t h e r e was no loss of nitrates a t pH 3.0. At this reaction, however, nitrite was not always completely d e s t r o y e d . At a r e a c t i o n of pH 2.8 with hydrochloric acid, there was a loss of over 13 per cent of nitrates, and at pH 2.7, which was found necessary to destroy nitrites, there was a loss of over 50 per cent of nitrates. With sulfuric acid, the results were even more discouraging. It was f o u n d t h a t a t pH 3.2, there was a loss of 16 Der cent. and a t pH 3.1 over 70 per cent of nitrates were desiroyed o n evaporation to dryness. TABLE I. EFFECTOF ACETICACIDON RECOVERY OF NITRITE AND
NITRATEAFTER EVAPORATION TO DRYNESS
QUAL. TEST NITROQIN INITIALNITROGEN ADDED FOR RncovREACTIONNitrite Nitrate NITRITE ERED pH P.p . m. P. p. m. P.p . m. 1.9a 4.39 1.05 1.9“ 4:iO 4.61 1.60 3.0 4.59 4.60 3.0 41:tO 3.1 1.84 3.2 9.20 3.1 4.60 4.‘61 4 ,’$3
....
..
4.0 4.1 4.0 4.0
1.84 9.20 4.60
4:59 4.61
5.4
4.60
4.61
..
....
4-k
+ +
.. 4:?4 9.29 9.28
A small quantity of hydrochlorio acid aotion to p H 1.9. (I
REMARKS
Nitrate destroyed Nitrate destroyed Nitrate recovered Nitrite destroyed Nitrite destroyed Nitr,ite destroyed Nitrite destroyed, nitrate recovered Nitrite present Nitrite present All nitrate recovered Both nitrite and nitrate recovered Both nitrite and nitrate recovered had to be added to bring re-
The results with phosphoric acid showed losses of 98 per cent a t pH 2.8, 73 per cent at pH 3.0, 34 per cent at pH 3.2, and about 4 per cent a t pH 3.4. In general there was an overlapping of the reaction a t which nitrites and nitrates were destroyed on evaporation from solutions made acid with these
January 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
57
the reaction be properly adjusted, but as the range suitable for the purpose is very wide (pH 3.0 to about pH 8.0),the adjustment need not be very delicate.
RELATIVE EFFICIENCIES OF VARIOUS AMMONIUM COMPOUNDS FOR ELIMINATION OF NITRITES
8 6 $ Q
A series of ammonia compounds was tested to determine the effect on recovery of nitrites and nitrates after evaporation. Samples were prepared by making up solutions of 4a nitrites and nitrates to 50 cc. The desired quantities of ammonium compounds were then added, and the mixture !iC evaporated to dryness in casseroles on a steam bath. The casseroles were washed down with water and again evaporated. The residue was taken up in 100 cc. of nitrogen-free water. Fifty cubic centimeters were tested for nitrites and LO 55 3.0 the remainder was made alkaline, reduced, etc., as recompH &/ma mended in standard methods for nitrate determination. The FIGURE 1. RECOVERY OF NITRATES FROM VARIOUS ACID results given in Table IV show clearly that ammonium chloSOLUTIONS ride and ammonium sulfate, the salts of strong acids, were satisfactory, whereas ammonium hydroxide and ammonium mineral acids. The reaction was quite in marked contrast a salt of a weak acid, were not suitable for the to that observed with acetic acid, where PH 3.0 was found to. destruction of nitrites. with ammonium the form a sharp line of demarcation a t which nitrites were com- chloride at different hydrogen-ion concentrations, it was found pletely destroyed while nitrates were not affected. It is that the reaction had to be more acid than pH 9.0 in order to therefore suggested that acidification with acetic acid to pH eliminate nitrites on evaporation. The failure of the hy3.0 (avoiding too large an excess of the acid) and evaporation droxide and carbonate is attributed to the high initial alkato dryness may be employed for elimination of nitrites in linity of the solutions. the determination of nitrates. It was found on further study that this method could not be safely employed if the initial TABLE 111. EFFECT OF REACTION ON RECOVERY OF NITRITES AND concentration of nitrites was over 20 parts per million, because NITRATES AFTER EVAPORATION TO DRYNESS IN PRESENCE OF of-an apparent oxidation of some of the nitrites to nitrates. AMMONIUM CHLORIDE TABLE11. EFFECT OF MINERAL ACIDSON RECOVERY OF NITRITES AND NITRATES AFTER EVAPORATION TO DRYNESS HYDROCHLORIC ACID SULFURIC ACID INITIAL Amt. Qual. Amt. Qual. REACTIOX added test added test P. p . m. pH P. p . m.
PHORPHORIC ACID Arnt. Qual. added test
P.p . m.
EXPERIMENTS WITH NITRITPS
2.7 2.7 2.7 2.7 3.1 3.1 3.3 3.3 3.3 3.6 3.7
9.2 19.7 27.2 47.2 9.1 27.2 8.8 9.2 16.6 9.2 9.2
Traoe Trace
+
++ +
8.9 42.4
9.21 9.21
8.9 8.9
++
9.21 9.21
+4-
EXPERIMENTS WITH NITRATEB
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.6 3.6 3.7 3.8 3.9
8.78 8.97 8.98 8.98 8.97
Nitrogen recovered 4.29 7.78 8.70 8.98 8.97
8.97
8.97
8.97
8.97
Nitrogen recovered
9.13
9.12
8.92 8.92 8.92 8.92 8.92 8.92 8.92 8.92 8.92 8.92 8.92
9.13
9.12
8.92
9.13 9.13
2.69 7.63
9.13
S.63
Nitrogen recovered 0.15 0.42 2.38 3.68 5.88 7.75 8.58 8.75 8.75 8.92 8.90
AMMONIUMCHLORIDE AT DIFFERENT ACIDITIES
A number of determinations were made on the influence of reaction on the recovery of nitrites and nitrates after evaporation to dryness in the presence of ammonium chloride. The reactions were adjusted with acetic acid in the acid range and sodium carbonate in the alkaline range, and 1000 parts per million ammonium as chloride were employed in all tests. The results are summarized in Table 111, from which it is seen that a t initial reactions of pH 2.0 nitrates were destroyed, and between the range pH 3.0 to pH 7.7 the nitrites only were destroyed. It is therefore important that
NITEOQEN QUAL.RECOVNITROGEN ADDED TEST ERED INITIAL IN As FOR AS RENiNiNINIACTION trites trate TRITES TRATEB
PH
P. P. m. P.P. w.
REMARKS
P. p . m.
2.0 2.1 3.0
4.60 4.60 4.60
4.59 4.69 4.61
2.15 1.60 4.68
3.1
None
4.69
4.56
3.9
4.60
4.61
4.43
4.1
4.60
4.69
4.15
4.1 6,4
None 4.60
4.59 4.61
4.60 4.53
5.4 6.1
None 4.60
4.59 4.61
4.70 4.52
6.6
4.60
4.59
4.30
6.9 7.0 7.2
None 4.60 4.60
4.59 None 4.61
4.53
7.6
4.60
4.61
4.52
7.7
4.60
4,61
4.62
11.2 11.2
4.60 4.60
None 4.61
4: 42
$
9:25
Nitritesand nitrates destroyed Nitritesand nitrates destroyed Nitrites deatroyed Nitrates recovered Nitrites destroyed, nitrates reoovered Nitrites destroyed. nitrates reoovered Nitrites destroyed, nitrates reoovered Nitrates recovered Nitrites deatroyed, nitrates recovered Nitrates recovered Nitrites destroyed. nitrates recovered Nitrites destroyed, nitrates recovered Nitntes destroyed Nitrites destroyed, nitrates recovered Nitrites destroyed. nitrates recovered Nitrites destroyed, nitrates recovered Nitrites not destroyed Both nitrites and nitrates recovered
PROCEDURE FOR DETERMINATION OF NITRATES IN SEWAQE The following method of determination of nitrates is suggested: 1. Adjust reaction t o about pH 7.5. A reaction which is acid to phenolphthalein and alkaline to phenol red will be found satisfactory. 2. Add about 2000 parts per million ammonium as chloride. 3. Evaporate in casserole to dryness on the steam bath. Wash down with distilled water and again evaporate to dryness. 4. Take up the residue in about 100 cc. of distilled water. Add 5 cc. of 40 per cent sodium hydroxide and boil mixture down to about 25 cc. to expel ammonia. 5. Reduce with aluminum foil, distil over the ammonia thus produced, and record as nitrates.
ANALYTICAL EDITION
58
TABLEIV. EFFECT OF DIFFERENT AMMONIUM SALTSON RECOVERY OF NITRITES AND NITRATES QrAL. NITROQEN NITROQEN ADDED TESTFOR RECOVADDED Nitrites Nitrates NITRITES ERED P p.m. P. p . m. P. p . m. P. p . m.
AMMONIUM
REMARK8
AMMONIUM CHLORIDE
2,000
44.0
8.8
Traoe
9.0
2,000
44.7
44.7
Trace
44.7
4,000
47.2
9.4
Trace
9.7
,000
7.2
47.2
Trace
47.2
Nitrites qestroyed Nitrates recovered Nitrites destroyed Nitrates reoovered Nitrites destroyed Nitrates recovered Nitrites destroyed Nitrates reoovered
AMMONIUM SULFATE
44.7
8.9
Traoe
9.7
4,000
44.7
44.7
Trace
44.7
2 000 2:ooo 4 000 4:OOO 10.000 10,000
44.0 44.0 47.2 47.2 44.7 44.7
2,000 2,000 4,000 4,000 10,000 10,000
44.0 44.0 47.2 47.2 44.7 44.7
4,000
Nitrites destroyed Nitrates reoovered Nitrites destroyed Nitrates recovered
AYMONIUM HYDROXIDE
Nitrites Nitrites Nitrites Nitrites Nitrites Nitrites
not not not not not not
eliminated eliminated eliminated eliminated eliminated eliminated
Nitrites Nitrites Nitrites Nitrites Nitrites Nitrites
not not not not not not
eliminated eliminated eliminated eliminated eliminated eliminated
AMMONIUM CARBONATE
8.8 44.0 9.4 47.2 8.9 44.7
Strong Strong Strong Strong Strong Strong
49.0 79.0 49.7 79.7 47.2 79.3
The foregoing method was tried on a number of sewage samples, including creamery and packing-house wastes and domestic sewage. Various quantities of nitrites and nitrates mere added to these wastes, which were then treated as described above for recovery of nitrates. The results for a number of tests are summarized in Table V. The method proved to be suitable with the wastes and quantities of nitrites and nitrates employed.
Vol. 4, No. 1
BIBLIOGRAPHY (1) Bartow, E., and Rogers, J. S., Pub. Health Repts. and Paper of the Am. Pub. Health Assom., 34, 228 (1910). (2) Burke, G. W., Levine, M., and Nelson, G. H., J . Am. Wafer Works Assocn., 22, 679-85 (1930). (3) Chamot, E. M., Pratt, D. S., and Redfield, H. W., J. A m . Chem. SOC.,33, 366 (1911). (4) Copeland, W. R., and Soper, G. A., Orig. Com. 8th Intern. Congr. Appl. Chem. (Appendix), 26, 211-3 (1913). (5) Curtman, L. J., and Lebowitz, S. H., Chem. News, 132, 293-5 (1926). (6) Hazen, A,, and Clark, H. W., Ibid., 64, 121 (1891). (7) Hazen, A., and Clark, H. W., Ibid., 64, 162 (1891). (8) Lampe, B., Wochschr. Brau., 39, 303-4 (1922). (9) Liebennann, yon, L., and A d , D., J. Chem. SOC.,110, 11. 342 (1916). (10) Pouget, L., Bull. SOC. chim., 7 , 449-52 (1910). (11) Rockwood, E. W., “An Introduction t o Chemical Analysis,” p. 190, Blakiston, 1913. (12) Steward, R., and Greaves, J. E., J. Am. Chem. SOC.,35, 579 (1913). (13) Streaker, W., Be?., 51, 997 (1918). RECEIVED July 13, 1931. Presented before the Division of Water, Sewage, and Sanitation Chemiatry at the Slat Meeting of the Amerioan Chemioal Sooiety, Indianapolis, Ind., March 30 to April 3, 1931. This study was ‘assisted by a oontribution from the Chemical Foundation.
Removal of Bromide and Iodide for Detection of Nitrate M. J. MURRAY AND A. w. A V E N S , Cornell University, Ithaca, N . Y .
T
0 DETECT nitrate by the so-called brown ring test, OF NITRITE ELIMINATION PROCEDURE TABLE V. DEPENDABILITY bromide and iodide must first be removed. These halide IN DETERMINATION OF NITRATES IN SEWAGE ions are frequently precipitated by means of saturated NITROQEN ADDBD NITROQEN FOUND No. OF AS NITRATES Nitrites Nitrates DETNI. silver sulfate or silver acetate solutions and the test made P. p. m. P. 8. m. P. p . m. on the filtrate. Since water solutions of these salts are very MADRID RAW SEWAQE 0.0 9.6 9.2 dilute even when saturated, large volumes must be used if 3 0.6 9.4 9.2 3 much bromide or iodide is present. It seemed reasonable 9.6 9.6 19.7 3 9.3 27.2 9.6 3 to expect that a more concentrated solution, made by dis47.2 9.6 9.4 3 solving the silver salt in ammonium hydroxide, might be AMER T A N K EFFLUENT employed in this removal. The literature shows no reference 9.35 9.20 4 0.0 9.2 9.35 9.30 4 to such a method. 9.40 19.7 9.36 4 9.35 9.60 27.2 A solution 0.5 N with respect to silver sulfate was pre4 4 47.2 9.36 9.30 pared by dissolving 7.8 grams of the salt (Merck c. p.) in CREAMERY WASTE 25 cc. of 4 N ammonium hydroxide and diluting to 100 cc. 11.86 11.98 4 9.2 30.20 30.16 3 9.4 The solutions tested for nitrate contained 250 mg. of iodide, 45.20 44.70 3 9.4 100 mg. of bromide, and 70 mg. of chloride per cubic centi19.7 11.86 11.98 4 12.23 4 27.2 11.86 meter. The quantity of nitrate was varied from 0 to 1 mg. 47 2 11.86 11.98 4 21.45 21.60 40.2 4 per cubic centimeter. To 1 cc. of each of these solutions, 30.20 32.20 46 2 4 4 46.2 46.20 44.80 3 cc. of 6 N sulfuric acid and a slight excess of ammoniacal M A D R I D TANK EFFLUENT silver sulfate solution were added. Approximately 12 cc. 0.0 9.45 9.40 4 of the silver sulfate solution were necessary for complete 9.20 9.2 9.46 4 19.7 9.46 9.60 precipitation of the halides. One cubic centimeter of the 4 9.40 4 27.2 9.46 filtrate was then mixed with 5 cc. of concentrated sulfuric 4 47.2 9.46 9.60 acid and the mixture cooled and overlaid with a little freshly A W E S FINAL EFFLUENT 0.0 11.8 11.7 6 prepared ferrous sulfate solution. At the end of 5 minutes, 11.7 5 9.2 11.8 solutions containing 0.5 mg. or more of nitrate per original 19.7 11.8 11.7 6 11.9 27.2 11.8 5 cubic centimeter showed a definite brown ring at the junc11.7 5 47.2 11.8 tion of the two layers. Solutions containing less nitrate PACKING-HOUSE WASTE 9.34 9.4 failed to give satisfactory tests. 0.0 9.88 9.76 0.0 By this method it is possible to detect a small amount 9.48 9.34 9.2 9.75 9.76 9.2 of nitrate in a solution from which large quantities of bromide 9.43 9.48 19.7 9.75 and iodide have been removed. Chloride was included, 9.76 19.7 9.60 9.48 27.2 since, if present, it is also removed by the silver ions. 9.88 9.75 27.2 4 4 4
47.2 47.2
9.48 9.75
9.66 10.38
RECEIVED August 12, 1931.
