ASTM D2784 Test Method for Sulfur in Liquefied Petroleum Gases (Oxy-Hydrogen Burner or Lamp)
5. Apparatus
5.1 Oxy-Hydrogen Combustion Assembly - The two types listed below are recommended. Any combustion apparatus giving equivalent results, however, is satisfactory.
5.1.1 Wickbold-Type Combustion Apparatus, as shown in Fig. 1.
5.1.2 Modified Beckman Burner-Type Apparatus, as shown in Fig. 2. Each of the above types of apparatus shall consist of three parts: atomizer-burner, combustion chamber, and absorber with spray trap. A blowout safety port in the combustion chamber is desirable. The remainder of the apparatus shall consist of a suitable support stand with the necessary needle valves and flow meters for precise control of oxygen, hydrogen, and vacuum.
5.1.3 Safety Shield - A transparent shield shall be used to protect the operator in the event an explosive mixture is formed in the combustion chamber.
5.2 Apparatus for Lamp Combustion:
5.2.1 Absorbers, Chimneys, and Spray Traps, as required are described in detail in Annex A3 of Test Method D1266.
5.2.2 Manifold System, consisting of a vacuum manifold with regulating device, valves, etc. (Fig. 2 of Test Method D1266) and a dual manifold (burner and chimney) supplying a gas mixture of approximately 70 % carbon dioxide (CO2) and 30 % oxygen (O2) at regulated pressures. The gas mixture in the chimney manifold shall be maintained at a nearly constant pressure of 1 to 2 cm of water and the burner manifold at approximately 20 cm of water. A suitable arrangement is shown in Fig. 2 of Test Method D1266 and described in A3.6 of Annex A3 of Test Method D1266, but any other similar system giving equivalent results can be used.
5.2.3 Blast Type Gas Burner, having dimensions given in Fig. 3.
5.3 Vacuum Source, having a capacity of at least 1200 L/h. If a vacuum pump is used, it should be protected by a suitable trap.
5.4 Corrosion-Resistant Metal Cylinder, 75-mL - It shall be tested at a pressure of 600 psig (4.14 MPa gage) and shall show no leaks when filled with air or nitrogen to this pressure and submerged in water. It shall be fitted with a needle valve for connection to the burner assembly.
5.5 Variable Transformer, 0 - 120 V, 750-W.
5.6 Carbon Dioxide Pressure Regulator - This regulator should be of a type that eliminates the refrigeration difficulties occurring with the pressure reduction of carbon dioxide.
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 Chemical Society, where such specifications are available. Other grades may be used, provided it is first 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, references to water shall be understood to mean reagent water as defined by Types II or III of Specification D1193. Water conforming to the following specification is required. Sulfate-free deionized water prepared by percolation of water through a column of mixed anion and cation exchange resins.
NOTE 1 - A means for determining when to replace the exchange resins should be provided. Use of a simple electrical conductivity meter has been found satisfactory for this purpose.
6.3 Standard Sulfate Solution (1 mL = 100 µg S) - Dilute 6.24 +/- 0.01 mL of 1 N sulfuric acid (H2SO4) with water to exactly 1 L. Check the dilution by titration against standard NaOH solution of about the same normality and adjust the concentration, if necessary, so that each millilitre of this solution is equivalent to 100 µg of sulfur.
6.4 Hydrogen (Warning - Extremely flammable), Carbon Dioxide (Warning - Gas may reduce oxygen available for breathing), and Oxygen (Warning - Oxygen accelerates combustion), meeting the requirement in Note 13.
6.5 Scavenger-Rinse - Mix equal volumes of low-sulfur acetone and isopropanol.
6.6 Hydrogen Peroxide Solution (1.5 %) (1 + 19) - Mix 1 volume of concentrated hydrogen peroxide (H2O2 = 30 %) with 19 volumes of water. Store in a dark-colored, glass-stoppered bottle.
6.7 Quality Control (QC) Sample(s), preferably are portions of one or more liquefied petroleum gas materials or product standards of known sulfur content that were not used in the generation of the instrument calibration curve. These (QC) samples are to be used to check the validity of the testing process as described in Section 16. An ample supply of QC sample material shall be available for the intended period of use, and must be homogeneous and stable under the anticipated storage conditions.
