ASTM D1541 Test Method for Total Iodine Value of Drying Oils and Their Derivatives
5. Apparatus
5.1 Iodine Flasks, glass-stoppered, of 250-mL capacity.

NOTE 2 - The test may be run either in a photographic-type darkroom under red safelight illumination5 or in a darkened laboratory in which the light intensity is adjusted to 0.5 footcandle (5.4 1x) or less. The darkroom with red safelights permits the use of clear flasks. If the test shall be run in a darkened laboratory, low-actinic (amber) flasks, or clear flasks protected from light by covering as described below, must be used. Alternative modes of using clear flasks in a darkened laboratory are described as follows. The type of covering is left to the discretion of the analyst:
(1) Place the clear iodine flask in a suitable metal can so that the neck of the flask is level with the can rim. Over the top of the can, place a piece of heavy cardboard, with a hole precut in the center to just fit over the neck of the flask; the top of the flask should just protrude out of the hole in the cardboard cover. Then run the analysis as usual in a darkened laboratory.

(2) Wrap heavy aluminum foil around the iodine flasks so as to cover all but the top rim. The foil can be then removed at the latter stage of titration. Run the analysis in a darkened laboratory.

(3) Place the flask in an opaque bag that has a drawstring neck. The rim of the iodine flask should just protrude from the bag to allow addition of reagent.

5.2 Graduates, 5, 25, and 50-mL capacity.

5.3 Volumetric Pipets, 10, 20, and 50-mL capacity.

NOTE 3 - The bulb of the 50-mL pipet should be covered with aluminum foil.

5.4 Buret, 50-mL capacity graduated in 0.1-mL divisions.

5.5 Weighing Device for Sample - A small, wide-mouth vial, fitted with a cork stopper and medicine dropper, may be used to weigh the sample by difference. Alternatively, the sample may be weighed directly into a 1-mL microbeaker, and carefully dropped into the iodine flask.

5.6 Photoelectric Light Meter - Any suitable meter for measuring room illumination in footcandles. If a darkroom and red safelight illumination are to be used, a meter is not required.

5.7 Erlenmeyer Flasks, three, 250-mL.

5.8 Volumetric Flasks, four, 1-L, glass-stoppered.

5.9 Bottle, Amber, one, 4-L, glass-stoppered.

6. Reagents
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 conforming to Type I of Specification D1193.

6.3 Solvents: isooctane or fresh cyclohexane to replace long used carbon tetrachloride now banned as hazardous (Precaution - See 7.1).

6.4 Carbon Tetrachloride (CCl4) - (Precaution - See 7.1)

6.5 Mercuric Acetate Solution - Dissolve 25 g of mercuric acetate (Hg(C2H3O2)2) (Precaution - See 7.2) in glacial acetic acid (CH3COOH) and dilute to 1 L with glacial acetic acid. (Precaution - See 7.3)

6.6 Potassium Iodide Solution (150 g/L) - Dissolve 150 g of potassium iodide (KI) in water and dilute to 1 L.

6.7 Rosenmund-Kuhnhenn Reagent - Place 40 mL of glacial acetic acid (CH3COOH) in each of three 250-mL Erlenmeyer flasks. To the first, add slowly 28.4 more or ess 0.2 g of pyridine, (Precaution - See 7.4) with cooling in an ice bath. To the second flask, add slowly 35.5 more or less 0.2 g of concentrated sulfuric acid (H2SO4, sp gr 1.84) with cooling as above. When cool, add the contents of the second flask to the contents of the first flask, with further cooling. To the third flask, add the contents of a 1-oz (28.4-g) bottle (or ampule) of bromine. Add the bromine solution to the mixture of the first two solutions. Transfer to a 1-L volumetric flask with the aid of glacial acetic acid, and make up to 1 L with glacial acetic acid. Mix thoroughly and transfer to a 4-L, amber, glass-stoppered bottle. Add an additional 2.5 L of glacial acetic acid, making a total of 3.5 L of reagent. In this way, the weighing or measuring of bromine is eliminated. The reagent is approximately 0.1 N with respect to bromine. Fresh reagent should be prepared if the bromine concentration drops below 0.99 N. The normality of the reagent can be checked by running a reagent blank titration as described in 8.4, but eliminating the 1-h standing time.

NOTE 4 - The stock bottle containing the Rosenmund-Kuhnhenn reagent should be kept stoppered when it is not in use to minimize loss of bromine.

6.8 Sodium Thiosulfate, Standard Solution (0.1 N) (Precaution - See 7.1-7.7) - Dissolve 24.8 g of sodium thiosulfate (Na2S2O3•5H2O) in water and dilute to 1 L. Add 0.5 g of sodium carbonate (Na2CO3) and a few drops of chloroform, as a preservative. Standardize against potassium iodate (KIO3) primary standard as follows: Weigh, to the nearest 0.1 mg, into a 250-mL Erlenmeyer flask about 0.12 to 0.17 g of the KIO3 and dissolve in 50 mL of water. Add 2 g of KI, and as soon as this is dissolved, 1 mL of concentrated hydrochloric acid (HCl, sp gr 1.19) diluted to 10 mL. Titrate the liberated iodine immediately with the Na2S2O3 solution, using starch indicator near the end point. Calculate the normality of the Na2S2O3 solution as follows:
Normality = W/(0.03567 x V)
where:
W = KIO3 used, g, and
V = Na2S2O3 solution required for titration of the KIO3, mL.

NOTE 5 - The Na2S2O3 may be standardized against potassium dichromate (K2Cr2O7), if desired, as described in Test Method D1959.

6.9 Starch Indicator Solution - Make a paste with 10 g of starch in cold water. Add to this 1 L of boiling water, stir rapidly, and cool. Salicylic acid (1.25 g/L) may be added as a preservative. If long storage is required, keep the solution in a refrigerator at 40 to 50°F (4 to 10°C). Prepare fresh indicator when the end point of the titration from blue to colorless fails to be sharp.

7. Hazards
7.1 Carbon Tetrachloride is a very hazardous liquid. It is absorbed by the skin. Its vapor is hazardous through inhalation. It is an irritant to skin and eyes; avoid breathing (TLV-10 ppm). It causes liver and kidney damage and has cumulative effects. Use with adequate ventilation (in a hood) and wear rubber gloves. See supplier's Material Safety Data Sheet.

7.2 Mercuric Acetate - Mercuric acetate and other organic mercury compounds are poisonous by oral ingestion and can be absorbed by the skin. Overheating results in decomposition. Do not flush mercuric acetate and its solutions down a drain but disposed of as hazardous wastes. See supplier's Material Safety Data Sheet.

7.3 Acetic Acid, Glacial, is corrosive and may cause burns to the skin and eyes. See supplier's Material Safety Data Sheet.

7.4 Pyridine is a flammable liquid and hazardous by inhalation. It is an eye, skin and respiratory irritant (TLV-5 ppm). May cause liver and kidney damage. Use with adequate ventilation; perform all operations in a hood. See supplier's Material Safety Data Sheet.

7.5 Sulfuric Acid is corrosive to skin, eyes, and mucous membranes in form of liquid, mist or fumes. It causes severe burn. Take care to prevent the contact of the acid with eyes, skin, or on clothing. In making dilute solutions, always add the acid to water with care. See supplier's Material Safety Data Sheet.

7.6 Bromine is a powerful oxidizer and may cause fire on contact with organic matter. Liquid and vapor may cause severe burns. The gas is toxic (TLV-0.1 ppm) and, as such, is a serious respiratory irritant. Use with adequate ventilation (in a hood); avoid contact with skin and eyes. Handle bromine with rubber gloves. See supplier's Material Safety Data Sheet.

7.7 Chloroform is a hazardous liquid that can be absorbed through the skin. Its vapor is hazardous through inhalation. It is a narcotic. Use only with adequate ventilation (in a hood). It is also extremely flammable. See supplier's Material Safety Data Sheet.