ASTM_D_2385_-_81_1990_scan.pdf

ASTM DE!385 BL m 0759530 0078497 7 m 4lb Designation:D 2385-81(Reapproved 1990)An Am&can National Standard Standard Test Method for Hydrogen Sulfide and Mercaptan Sulfur in Natural Gas(Cadmium Sulfate lodometric Titration Method)This standard is issued under the fixed designation D 2385;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.A superscript epsilon(t)indicates an editorial change since the last revision or reapproval.1.Scope 1.1 This test method covers the determination of hy-drogen sulfide and mercaptan sulfur in natural gas.It is applicable over the concentration range from 0 to 5 grains of hydrogen sulfide(about 11 mg/m3)and 0 to 1 grain of mercaptan sulfur/100 ft3(2.832 m3)of natural gas.1.2 This standard does not purport to address all of the safety problems,tf any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Document 2.1 ASTM Standard:D 1193 Specification for Reagent Water2 3.Summary of Test Method 3.1 A measured volume of natural gas is bubbled through neutral cadmium sulfate solution to remove hydrogen sul-fide,and then through basic cadmium sulfate to scrub out the mercaptans.The amounts of hydrogen sulfide and mercaptan sulfur in the absorbers are then determined iodometrically.4.Significance and Use 4.1 Natural gas and its products of combustion must not be unduly corrosive to the materials with which they come in contact and the measure of hydrogen sulfide and other sulfur compounds is important.In addition,in some cases the odor of the gas must not be objectionable and from this stand-point the measurement of mercaptan sulfur is significant.5.Apparatus 5.1 Gas Washing Bottle-A bottle with side inlet,coarse-porosity fiitted disk(40 to 60 pm maximum pore size),and 24/40 outer joint at the outlet.The diameter of the fritted disk is 60 mm,and the approximate outside diameter and height are 70 and 280 mm,respectively.3 5.2 Spray Traps,with 20140 inner joint,for use on the t This test method is under the jurisdiction of ASTM Committee D-3 on Gaseous Fuels and is the direct responsibility of Subcommittee DO3.05 on Determination of Special Constituents of Gaseous Fuels.Current edition approved Aug.28,1981.Published October 1981.Originally published as D 2385-65 T.Last previous edition D 2385-66(1976).2 Annual Book of ASTM Standards,Vol 11.O I.3The bottle available under Coming catalog No.31750 has been found satisfactory for this purpose.outlet side of the gas washing bottle.4 5.3 Test Meter,with dial divisions graduated to 0.01 ft3(28 cm)and accurate to 0.5 percent when measuring gas volumes from 2 to 10 fi3(0.06 to 0.28 m3).The meter should be calibrated before use and should be a type that is usable in the field.5.4 Thermometer,graduated in 1F(0.5”C)divisions.5.5 Aspirator Bulb,with a short piece of gum rubber tubing attached to the pressure end.5.6 Barometer.5.7 Stop Watch.5.8 Tubing and Connections-Glass,aluminum,or stain-less steel is satisfactory.Connections between tubing and apparatus should be made with gum rubber tubing,with a minimum amount of rubber exposed to the gas sample.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 reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chem-ical Society,where such specifications are available.5 Other grades may be used,provided it is fast ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.6.2 Purity of Water-Unless otherwise indicated,refer-ences to water shall be understood to mean reagent water conforming to Specification D 1193.6.3 Cadmium Sulfate Solution A-Dissolve 10 g of cad-mium sulfate hydrate(3CdS04.8H20)(Danger-Poison.May be fatal if swallowed or inhaled)in water and dilute to 1 L.6.4 Cadmium&Kate Solution B-Dissolve 140 g of 3CdS04*8H,0(Danger-Poison.May be fatal if swallowed or inhaled.See Annex All)in water and dilute to 1 L.6.5 Hydrochloric Acid(sp gr 1.19)-Concentrated hydro-chloric acid(HCI).6.6 Iodine Standard Solution(0.1 N&Weigh 13.0 g of resublimed iodine into a 250-mL beaker.Add 22 g of potassium iodide(RI)and 100 mL of water.Stir until solution is complete,dilute to 1 L,mix thoroughly,and store in an amber,glass-stoppered bottle.Standardize this solution 4 The spray trap available under Coming Catalog No.37723(specify spray trap only)has been found satisfactory for this purpose.s Reagent Chemicals,American Chemical Society Specifications,”Am.Chem-ical Sot.,Washington,D.C.For suggestions on the testing of reagents not listed by the American Chemical Society,see-Reagent Chemica