Analysis of lubricating oils for iron content

Claim 1

A method for determining the amount of iron present in a used lubricating oil which comprises the following steps: a. adding a solution of concentrated sulfuric acid in distilled water and ethanol to a sample of the lubricating oil in an amount sufficient to extract iron from the oil; b. adding isoamyl alcohol to the solution formed in step a in an amount sufficient to prevent formation of emulsions; c. adding a solution of a buffering amount of sodium acetate in distilled water and a solution of a reducing amount of hydroxylamine hydrochloride in distilled water to the solution formed in step b; d. adding a solution of a complexing amount of bathophenanthroline disulfonic acid or an alkali metal salt thereof in distilled water to the solution formed in step c; e. adding distilled water to the solution formed in step d in an amount sufficient to dilute the color; f. allowing the solution of step e to separate into an oil phase and a colored aqueous phase; and g. determining from the color intensity of the aqueous phase the iron content of the lubricating oil.

Claim 2

A method for determining the amount of iron present in a used lubricating oil which comprises the following steps: a. adding a solution of concentrated sulfuric acid in distilled water and ethanol to a sample of the lubricating oil in an amount sufficient to extract iron from the oil; b. adding isoamyl alcohol to the solution formed in step a in an amount sufficient to prevent formation of emulsions; c. adding a solution of a buffering amount of sodium acetate in distilled water and a solution of a reducing amount of hydroxylamine hydrochloride in distilled water to the solution formed in step b; d. adding a solution of a complexing amount of bathophenanthroline disulfonic acid or an alkali metal salt thereof in distilled water to the solution formed in step c; e. adding distilled water to the solution formed in step d in an amount sufficient to dilute the color; f. allowing the solution of step e to separate into an oil phase and a colored aqueous phase; and g. determining from the color intensity of the aqueous phase the iron content of the lubricating oil.

Claim 5

A method for determining the amount of iron present in a used lubricating oil which comprises the following steps: a. placing in a reaction vessel one milliliter of the used lubricating oil; b. adding one milliliter of a 2 to 8 N concentrated sulfuric acid solution in distilled water and ethanol to the reaction vessel; c. shaking the reaction vessel to ensure thorough mixing of the ingredients therein; d. adding 2 milliliters of isoamyl alcohol to the reaction vessel; e. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; f. adding one milliliter of a solution of sodium acetate dissolved in 100 milliliters of distilled water, the amount of sodium acetate being sufficient to provide a pH of 1 to 7; g. adding one milliliter of a solution of hydroxylamine hydrochloride dissolved in 100 milliliters of distilled water, the amount of hydroxylamine hydrochloride being sufficient to reduce trivalent iron to divalent iron; h. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; i. adding 0.5 milliliter of a stock solution of bathophenanthroline disulfonic acid or sodium salt thereof ranging from about 0.05 to 0.5 gram dissolved in 10 milliliters of distilled water; j. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; k. allowing an oil phase and a colored aqueous phase to separate in the reaction vessel; l. withdrawing one milliliter aliquot of the colored aqueous phase from the reaction vessel; m. introducing the one milliliter aliquot into a test cell; n. adding 5 milliliters of distilled water to the test cell; o. mixing the distilled water and colored liquid in the test cell; and p. measuring color intensity of the colored liquid in the test cell as an indication of the amount of iron contained in the lubricating oil.

Claim 6

A method for determining the amount of iron present in a used lubricating oil which comprises the following steps: a. placing in a reaction vessel one milliliter of the used lubricating oil; b. adding one milliliter of a 2 to 8 N concentrated sulfuric acid solution in distilled water and ethanol to the reaction vessel; c. shaking the reaction vessel to ensure thorough mixing of the ingredients therein; d. adding 2 milliliters of isoamyl alcohol to the reaction vessel; e. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; f. adding one milliliter of a solution of sodium acetate dissolved in 100 milliliters of distilled water, the amount of sodium acetate being sufficient to provide a pH of 1 to 7; g. adding one milliliter of a solution of hydroxylamine hydrochloride dissolved in 100 milliliters of distilled water, the amount of hydroxylamine hydrochloride being sufficient to reduce trivalent iron to divalent iron; h. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; i. adding 0.5 milliliter of a stock solution of bathophenanthroline disulfonic acid or sodium salt thereof ranging from about 0.05 to 0.5 gram dissolved in 10 milliliters of distilled water; j. shaking the reaction vessel so as to ensure thorough mixing of the ingredients therein; k. allowing an oil phase and a colored aqueous phase to separate in the reaction vessel; l. withdrawing one milliliter aliquot of the colored aqueous phase from the reaction vessel; m. introducing the one milliliter aliquot into a test cell; n. adding 5 milliliters of distilled water to the test cell; o. mixing the distilled water and colored liquid in the test cell; and p. measuring color intensity of the colored liquid in the test cell as an indication of the amount of iron contained in the lubricating oil.