Sulfur test strips

Test Strips. Larger batches of direct-substituted sulfur-asphalt paving mixtures were prepared with type IVb aggregate materials. Mixtures containing 0-, 15-, 25-, and 35-vol % sulfur in the asphalt binder were... 

Table VII. Properties of Sulfur Asphalt Paving Test Strips...

A simple test for ether peroxides is to add lOmL of the ether to a stoppered cylinder containing ImL of freshly prepared 10% solution of potassium iodide containing a drop of starch indicator. No colour should develop during one minute if free from peroxides. Alternatively, a 1% solution of ferrous ammonium sulfate, O.IM in sulfuric acid and 0.0IM in potassium thiocyanate should not increase appreciably in red colour when shaken with two volumes of the ether. Merck-Chemicals supply peroxide test kits (Perex Test) which use a colorimetric method with test strips which can be used to estimate the amount of hydrogen peroxide, from as low a concentration as... 

Most known procedures of this group of methods are called oxidation and sulfuration tests. In the former case a metal test specimen wrapped in a VCI film material is placed in a desiccator (about 10 1 in capacity). The internal atmosphere reaches 100% RH using 20 cm of water. The desiccator is blocked up and is placed in a 50° C constant-temperature tank or in normal-temperature room to promote the growth of rust. In sulfuration test the desiccators about 2.5 1 capacity are used. After having adjusted the inside atmosphere to reach 93% RH using 10 cm of a saturated solution of Na2S04, a test metallic strip wrapped in inhibited film material is placed inside. The tests are continued until a corrosive phenomenon is observed. 

If sulfur is a contaminant, its content can be measured, but it may suffice to characterize its effects by the copper strip corrosion test, or by the doctor test". 

The reaction is completed after 6—8 h at 95°C volatiles, water, and some free phenol are removed by vacuum stripping up to 140—170°C. For resins requiring phenol in only trace amounts, such as epoxy hardeners, steam distillation or steam stripping may be used. Both water and free phenol affect the cure and final resin properties, which are monitored in routine quaHty control testing by gc. OxaHc acid (1—2 parts per 100 parts phenol) does not require neutralization because it decomposes to CO, CO2, and water furthermore, it produces milder reactions and low color. Sulfuric and sulfonic acids are strong catalysts and require neutralization with lime 0.1 parts of sulfuric acid per 100 parts of phenol are used. A continuous process for novolak resin production has been described (31,32). An alternative process for making novolaks without acid catalysis has also been reported (33), which uses a... 

Attack on metals can be a function of fuel components as well as of water and oxygen. Organic acids react with cadmium plating and 2inc coatings. Traces of H2S and free sulfur react with silver used in older piston pumps and with copper used in bearings and brass fittings. Specification limits by copper and silver strip corrosion tests are requited for fuels to forestall these reactions. 

The acid wash test consists of shaking a mixture of 96% sulfuric acid with benzene and comparing the color of the (lower) acid layer with a set of color standards. Other quaUtative tests include those for SO2 and H2S determination. The copper strip corrosion test indicates the presence of acidic or corrosive sulfur impurities. The test for thiophene is colorimetric. 

Corrosive sulfnr componnds can be detected by their effect on copper and the form in which the general copper strip corrosion test (ASTM D1838) for petrolenm prodncts is applied to liqnefied petrolenm gas. Hydrogen sulfide can be detected by its action on moist lead acetate paper, and a procedure is also used as a measure of sulfur compounds. The method follows the principle of the standard Doctor test. 

Tests for Identification of Some Synthetic Dyes. Two very simple reactions can confirm the presence of synthetic dyes. In the solvent stripping test, if the ammonia solution is heavily stained and it becomes irreversibly colorless upon the addition of zinc dust even at room temperature, the presence of an azo dye with sulfo group or groups is indicated (an acid or direct dye) (36, 37). The color of the solution in concentrated sulfuric acid can also be an important indication for identifying synthetic dyes. In this test, a few drops of concentrated sulfuric acid are dripped on a small sample of the dyeing, and the color of the sulfuric acid is observed after a few minutes. Intensive magenta red, red-violet, violet, blue, and green solutions indicate the presence of synthetic dyes (36, 37). 

The dye bath is prepared from 50 mg of Orange II or Methyl Orange, 0.5 mL of 10% sodium sulfate solution, 15 mL of water, and 5 drops of 10% sulfuric acid in a 30-mL beaker. Place a piece of test fabric, a strip 3/4-in. wide, in the bath for 5 min at a temperature near the boiling point. Remove the fabric from the dye bath, allow it to cool, and then wash it thoroughly with soap under running water before drying it. 

Control of the total sulfur content, hydrogen sulfide, and mercaptans ensures that the product is not corrosive or nauseating. Stipulating a satisfactory copper strip test further ensures control of corrosion. 

Mercaptan sulfur (R-SH) and hydrogen sulfide (H2S) (ASTM D-1219, IP 103, IP 104) are undesirable contaminants because, apart from their corrosive nature, they possess an extremely unpleasant odor. Such compounds should have been removed completely during refining but their presence and that of free sulfur are detected by application of the Doctor test (ASTM D-4952, IP 30). The action on copper of any free or corrosive sulfur present in gasoline may be estimated by a procedure (ASTM D-130, ASTM D-849, IP 154) in which a strip of polished copper is immersed in the sample, which is heated under specified conditions of temperature and time, and any staining of the copper is subsequently compared with the stains on a set of reference copper strips and thus the degree of corrosivity of the test sample determined. 

Some sulfur compounds can also have a corroding action on the various metals of the engine system, varying according to the chemical type of sulfur compound present. Fuel corrosivity is assessed by its action on copper and is controlled by the copper strip test (ASTM D-130, IP 154), which specifies that not more than a slight stain shall be observed when the polished strip is immersed in fuel heated for 2 h in a bomb at lOO C (212°F). This particular method is not always capable of reflecting fuel corrosivity toward other fuel system metals. For example, service experience with corrosion of silver components in certain engine fuel systems led to the development of a silver corrosion test (IP 227). The mercaptan sulfur content (ASTM D-1219, ASTM D-3227, IP 104, IP 342) of jet fuels is limited because of objectionable odor, adverse effect on certain fuel system elastomers, and... 

Free, or corrosive, sulfur in an appreciable amount could result in corrosive action on the metallic components of an appliance. Corrosive action is of particular significance in the case of pressure burner vaporizing tubes that operate at high temperatures. The usual test applied in this connection is the corrosion (copper strip) test (ASTM D-130, ASTM D-849, IP 154). 

The copper strip test methods are used to determine the corrosiveness to copper of gasoline, diesel fuel, lubricating oil, or other hydrocarbons. Most sulfur compounds in petroleum are removed during refining. However, some residual sulfur compounds can have a corroding action on various metals. This effect is dependent on the types of sulfur compounds present. The copper strip corrosion test measures the relative degree of corrosivity of a petroleum product. 

The copper strip test methods are used to determine the corrosiveness to copper of diesel fuel and are a measure of the relative degree of corrosivity of diesel fuel. Most sulfur compounds in petroleum are removed during refining. However, some residual sulfur compounds can have a corroding action on various metals, and the effect is dependent on the types of sulfur compounds present. One method (ASTM D-130, IP 154) uses a polished copper strip immersed in a given quantity of sample and heated at a temperature for a time period characteristic of the material being tested. At the end of this period the copper strip is removed, washed, and compared with the copper strip corrosion standards (ASTM, 2000). This is a pass/fail test. In another method (ASTM D-849) a polished copper strip is immersed in 200 ml of specimen in a flask with a condenser and placed in boiling water for 30 min. At the end of this period, the copper strip is removed and compared with the ASTM copper strip corrosion standards. This is also a pass/fail test. 

Corrosion of heating equipment can occur if the sulfur oxides formed on combustion of fuel oil are allowed to condense in the presence of moisture on the cooler parts of the flue system. Corrosion of metal parts of the fuel system may also reflect the presence of corrosive sulfur components in the fuel. The corrosive tendencies of the fuel may be detected by the copper strip test (ASTM D-130, ASTM D-849, IP 154), the effect of these sulfur compounds being indicated by discoloration of the copper strip. 

In view of the wide use of copper in electrical equipment, it is essential to ensure that the oil does not corrode this metal. Noncorrosive or corrosive sulfur can be verified by any one of several test methods (ASTM D-130, ASTM D-849, ASTM D-4048, ASTM D-4636, IP 154) in which the oil is heated in the presence of a metallic copper strip for a specified time at a specified temperature after which the strip must be discolored. In addition, corrosiveness toward silver is becoming increasingly important, and a test method (IP 227) has been developed that is closely similar to the copper corrosion test. 

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