ASTM_D_992_-_71_1978_scan.pdf

1 Designation:D 992-71(Reapproved 1978)An American National Standarc Standard Test Method for NITRATE ION IN WATER1 This standard is issued under the fued designation D 992;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.This method has been approved for use by agencies of the Department of Defense and for listing in the DoD Index of Specifications and Standards.1.Scope and Application 1.1 This method2 covers the determination of nitrate ion in water.1.2 Samples containing l to 50 mg/liter of nitrate,as N03,may be analyzed by this method.The concentration range may be ex-tended by dilution of an appropriate aliquot.2.Summary of Method 2.1 Nit rate ion reacts with brucine in strong sulfuric acid solution to develop a yellow color.The color does not follow the Beer-Lambert relationship.However,a plot of absorbance versus concentration produces a smooth curve.It is necessary to develop a series of standards simultaneously with the samples.The color is measured at 410 nm.2.2 The rate of color development varies directly with the temperature and the intensity varies inversely with the temperature.3.Definitions 3.l For definitions of terms used in this method refer to ASTM Definitions D 1129,Terms Relating to Water.3 4.Interferences 4.1 Strong oxidizing or reducing agents interfere.Oxidizing agents may be determined with orthotolidine.Chlorine interference up to 5 mg/liter may be eliminated by the addition of sodium arsenite.4.2 High content of organic matter may interfere by increasing the absorbance read-ings at 410 nm and also because of the pos-sible charring effects from the concentrated sulfuric acid(H 2SO.).This can be minimized by pretreatment with aluminum hydroxide and specially treated activated carbon.4.3 Nitrite interference up to 7 mg/liter is eliminated by the sulfanilic acid in the brucine reagent solution.4.4 Table 1 shows the amount of various other substances commonly found in water that can be present without causing interfer-ence in this test.S.Apparatus 5.1 Photometer-A spectrophotometer or filter photometer suitable for measurements at 410 nm with a light path of I to 5 em.Pho-tometers and photometric practice described in this method shall conform to ASTM Rec-ommended Practice E 60,Photometric Methods for the Chemical Analysis of Metals;spectrophotometers shall conform to ASTM Recommended Practice E 275,for Describing and Measuring Performance of Spectrophotometers.6.Reagents and Materials 6.1 Purity of Reagents-Reagent grade chemicals shall be used in all tests.Unless otherwise indicated,it is intended that all re-agents shall conform to the specifications of the Committee on Analytical Reagents of the This method is under the jurisdiction of ASTM Com-mittee D-19 on Water.Current edition effective Oct.22,1971.Originally is-sued 1948.Replaces D 992 52(1965).A method similar to this appears in Standard Methods for the Examination of Water and Wastewater,12th edi-tion,American Public Health Association.3 1983 Annual Book of ASTM Standards,Vol 11.01.1982 Annual Book of ASTM Standards,Part 12.1983 Annual Book of ASTM Standards,Voll4.01.Reagent Chemicals,American Chemical Soc1ety Specifications,Am.Chemical Soc.,Washington,D.C.For suggestions on the testing of reagents not listed by the American Chemical Society,see Reagent Chemicals and Standards,by Joseph Rosin,D.Van Nostrand Co.,Inc;:New York,N.Y.,and the United States Pharmacopeia.542 NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.chemical Society,where such specifications are available.6 Other grades may be used,pro-vided it is Jirst itscertained that the reagent is of sufficiently high purity to permit its use without lssening the accuracy of the deter-mination.6.2 Purity of Water-Unless otherwise in-dicated,references to water shall be under-stood to mean reagent water conforming to Type I of ASTM Specification D 1193,for Reagent Water.6.3 Activated Carbon-Heat fine grain(0.2 to 0.5-mm diameter)activated carbon to red heat in an atmosphere of carbon dioxide,cool,extract with n-hexane,and wash with water at 80 C.6.4 Aluminum Hydroxide Cream-Diss-olve 124 g of potassium or ammonium alum in I liter of water.Heat to 50 C and slowly add with stirring 55 ml of ammonium hy-droxide(NH.OH,sp gr 0.90).Let stand 1 h,and then wash the precipitate with water by mixing and decanting until free from ammo-nia,chloride,nitrate,and nitrite ions.6.5 Brucine-Sulfanilic Acid Solution-Dissolve 1 g of brucine sulfate(Caution:Note 1)and 0.1 g of sulfanilic acid in approxi-mately 70 ml of hot water.Add 3 ml of hy-drochloric acid(HCI,sp gr 1.19),cool,and dilute to 100 ml with water.This solution is stable for several months.The pink color that develops slowly does not affect its usefulness.NOTE 1:Ca