Ethanol Testing Methods
| Test | Method | Min. Volume Required |
|---|---|---|
| Ethanol & Methanol | ASTM D5501 | 5 mL |
| Solvent-Washed Gum | ASTM D381 | 100 mL |
| Acidity | ASTM D1613 | 100 mL |
| Specific Gravity | ASTM D4052 | 20 mL |
| Proof | ASTM D4052 | 20 mL |
| Density | ASTM D4052 | 20 mL |
| pHe | ASTM D6423 | 100 mL |
| Visual Inspection | ASTM D4176 | 500 mL |
| Total Sulfur | ASTM D5453 | 5 mL |
| Inorganic Sulfate | ASTM D7319 | 25 mL |
| Chloride | ASTM D7319 | 25 mL |
| Copper by ICP | ASTM D1688-Mod | 50 mL |
| Denaturant Content | Calculation | 0 mL |
| Water by Coulometric KF | ASTM E1064 | 10 mL |
Ethanol & Methanol
Federal regulations require fuel ethanol to be made unfit for human consumption. However, the fuel ethanol must contain a minimum concentration of ethanol and a minimum concentration of other organic oxygen compounds to protect the properties of ethanol/gasoline blends. ASTM D4806 Requirement: a minimum ethanol concentration of 92.1% by volume and a maximum methanol concentration of 0.5% by volume.
solvent-washed gum
The solvent-washed gum content test gravimetrically measures the amount of residue after evaporation of the fuel and subsequent heptane wash. Solvent-washed gum measures gums that are both fuel-soluble and fuel-insoluble. The fuel-insoluble gums can clog fuel filters. Both types of gum can be deposited on surfaces upon evaporation of the fuel. ASTM D4806 Requirement: a maximum solvent-washed gum content of 5.0mg/100mL.
Acidity
Low molecular weight organic acids such as acetic acid are corrosive to many metals. It is necessary to limit the concentration of these acids in the fuel ethanol to minimize damage to metal engine components. ASTM D4806 Requirement: a maximum acidity of 0.007% mass, as acetic acid.
Specific Gravity
Specific Gravity (now more commonly called Relative Density) is required for the conversion of measured volumes to volumes at 15 degrees C (the standard temperature). The specific gravity of an ethanol product may be an indicator of contamination. There is no ASTM D4806 requirement for Specific Gravity.
Proof
Proof is a measure of the ethanol content and is calculated as 2 times the ethanol concentration by volume. Proofs of denatured ethanol commonly exceed 200 due to the addition of denaturants which have a different density than the ethanol. There is no ASTM D4806 requirement for Proof.
Density
Density is a fundamental physical property. It is a required measurement to convert measurements from mass % to volume % to report values in accordance with ASTM D4806. There is no ASTM D4806 requirement for Density.
pHe
The pHe is a measure of the acid strength of a fuel ethanol and is a predictor of the fuel ethanol's corrosion potential. Low pHe fuel ethanol can cause corrosive wear in fuel injectors and engine cylinders. High pHe fuel ethanol can cause fuel pump plastic parts to fail. ASTM D4806 Requirement: pHe 6.5 - 9.0.
Visual Inspection
Fuel ethanol must be free of suspended matter and sediment. Turbidity or suspended matter generally indicate major contamination. ASTM D4806 Requirement: the fuel ethanol must be clear and bright at indoor ambient temperatures.
Total Sulfur
Sulfur contaminates the catalytic converter which is used to reduce environmental pollutants such as hydrocarbons, carbon monoxide, and nitrogen oxides. The Environmental Protection Agency (EPA) has established gasoline sulfur limits in support of vehicle emission standards. ASTM D4806 Requirement: a maximum of 30ppm by mass.
Inorganic Sulfate
Small quantities of inorganic sulfates can cause deposits in metering devices and plugging in fuel dispensing pump filters. Inorganic sulfates have also been shown to cause fuel injector sticking in automobiles which results in engine misfiring and poor driveability. ASTM D4806 Requirement: a maximum total sulfate concentration of 4ppm by mass.
Chloride
Chloride ions are corrosive to many metals and may cause premature engine wear. Chloride salts can also cause filter plugging and deposits in fuel injectors. ASTM D4806 Requirement: a maximum of 10ppm by mass.
Copper
Copper actively catalyzes low-temperature oxidation of hydrocarbons. If present in concentrations greater than approximately 12 parts per billion (ppb) by mass, significant increases in the rate of gum formation can occur. ASTM D4806 Requirement: a maximum of 0.1ppm by mass.
Denaturant Content
Denaturant is added to fuel ethanol as required by federal regulations to ensure that the ethanol is made unfit for human consumption. The only denaturants allowable under the ASTM D4806 specification are natural gasoline, gasoline components, or unleaded gasoline. ASTM D4806 Requirement: 1.96 - 5.0% by volume.
Water by Coulometric KF
Water contamination can cause serious operating problems in normal spark-ignition engines. Water contamination is typically encountered during fuel transportation and storage. Additionally, gasoline-ethanol blends tend to absorb moisture from the air. For these reasons, it is important to limit the water concentration of the ethanol intended for blending in order to reduce the risk of phase separation. ASTM D4806 Requirement: a maximum of 1.0% by volume.