B= normality of potassium ferricyanide solution.
Report results to 2 significant figures.
NR 252.035(4)(a)(a) Each laboratory that uses this method is required to operate a formal quality control program. The minimum requirements of this program consist of an initial demonstration of laboratory capability and the analysis of replicate and spiked samples as a continuing check on performance. The laboratory is required to maintain performance records to define the quality of data that is generated. Ongoing performance checks shall be compared with established performance criteria to determine if the results of analyses are within precision and accuracy limits expected of the method. NR 252.035(4)(b)(b) Before performing any analyses, the analyst shall demonstrate the ability to generate acceptable precision and accuracy with this method by performing the following operations. NR 252.035(4)(b)1.1. Perform 4 replicate analyses of a 20 mg/l sulfide standard prepared in distilled water. See sub. (2) (f). NR 252.035(4)(b)2.a.a. Calculate clean water precision and accuracy in accordance with standard statistical procedures. Clean water acceptance limits are presented in subd. 2. b. These criteria shall be met or exceeded before sample analyses can be initiated. A clean water standard shall be analyzed with each sample set and the established criteria met for the analysis to be considered under control. NR 252.035(4)(b)2.b.b. Clean water precision and accuracy acceptance limits: for distilled water samples containing from 5 mg/l. to 50 mg/l. sulfide, the mean concentration from 4 replicate analyses shall be within the range of 50 to 110% of the true value. NR 252.035(4)(c)(c) The method detection limits or MDL may be determined periodically by each participating laboratory in accordance with the procedures specified in ”Methods for Chemical Analysis of Municipal and Industrial Wastewater,” EPA- 660/4-82-057, July 1982, EMSL, Cincinnati, OH 45268. For the convenience of the user, these procedures are contained in s. NR 252.0365. NR 252.035(4)(d)(d) A minimum of one spiked and one duplicate sample shall be performed for each analytical event, or 5% spikes and 5% duplicates when the number of samples per event exceeds 20. Spike levels are to be at the MDL and at x where x is the concentration found if in excess of the MDL. See par. (c) for MDL samples. Spike recovery shall be 40 to 120% for the analysis of a particular matrix type to be considered valid. If a sample or matrix type provides performance outside these acceptance limits, the analyses shall be repeated using the modified Monier-Williams procedures described in s. NR 252.036. NR 252.035(4)(e)(e) Report results in mg/liter. When duplicate and spiked samples are analyzed, report all data with the sample results. NR 252.035 HistoryHistory: Cr. Register, May, 2001, No. 545, eff. 6-1-01. NR 252.036NR 252.036 Modified Monier-Williams method. NR 252.036(1)(a)(a) Hydrogen sulfide is liberated from an acidified sample by distillation and purging with nitrogen gas (N2). Sulfur dioxide interference is removed by scrubbing the nitrogen gas stream in a pH 7 buffer solution. The sulfide gas is collected by passage through an alkaline hydrogen peroxide scrubbing solution in which it is oxidized to sulfate. Sulfate concentration in the scrubbing solution is determined by either EPA gravimetric test procedure 375.3 or EPA turbidimetric test procedure 375.4 (see 40 CFR 136.3, Table IB, parameter 65 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)). NR 252.036(1)(b)(b) (apparatus see figure 1.) Catalogue numbers are given only to provide a more complete description of the equipment necessary, and do not constitute a manufacturer or vendor endorsement. Heating mantel and control (VWR Cat. No. 33752-464)
1000 ml. distilling flask with three 24/40 joints (VWR Cat. No. 29280-215)
Friedricks condenser with two 24/40 joints (VWR Cat. No. 23161-009)
125 ml. separatory funnel with 24/40 joint (VWR Cat. No. 30357-102)
Inlet tube with 24/40 joint (VWR Cat. No. 33057-105)
Adapter joint 24/40 to 19/38 (VWR Cat. No. 62905-26)
Adsorber head (2 required) (Thomas Cat. No. 9849-R29)
Adsorber body (2 required) (Thomas Cat. No. 9849-R32)
Laboratory vacuum pump or water aspirator
NR 252.036(2)(a)(a) Potassium hydroxide, 6N: Dissolve 340 g. of analytical reagent grade KOH in one liter distilled water.