Unworked penetrations often appear In specifi-
cations and in grease product data, but are of
limited practical value. No significance can be
cations and in grease product data, but are of
limited practical value. No significance can be
attached to the difference between unworked
and worked penetration. Undisturbed penetra-
tion is useful mainly in quality control.
and worked penetration. Undisturbed penetra-
tion is useful mainly in quality control.
NEUTRALIZATION NUMBER
ASTM D 664 and D 974
Depending on its source, additive content, re-
fining procedure, or deterioration in service, a
petroleum oil may exhibit certain acid or alkaline
(base) characteristics. Data on the nature and
extent of these characteristics may be derived
from the product's neutralization number, or
"neut number," as it is commonly known. The
two principal methods for evaluating neut num-
ber are ASTM D 664 and ASTM D 974.
Although respective test results are similar, they
are not identical, and any reporting of results
should Include the method by which they are
obtained.
fining procedure, or deterioration in service, a
petroleum oil may exhibit certain acid or alkaline
(base) characteristics. Data on the nature and
extent of these characteristics may be derived
from the product's neutralization number, or
"neut number," as it is commonly known. The
two principal methods for evaluating neut num-
ber are ASTM D 664 and ASTM D 974.
Although respective test results are similar, they
are not identical, and any reporting of results
should Include the method by which they are
obtained.
Acidity and Alkalinity: Acidity and alkalinity are
terms related to dissociation, a phenomenon of
aqueous solutions. Dissociation is a form of
ionization, the natural breaking up of some of
the molecules into positive and negative ions. If
the chemical composition of the aqueous
solution is such that it yields more hydrogen Ions
(positive) than hydroxyl ions (negative), the
solution is considered acid: an excess of
hydroxyl ions on the other hand results in a
solution that is considered to be basic or
alkaline. The greater the excess, the more acid
or alkaline the solution, as the case may be. If
the hydrogen and hydroxyl ions are in equal
concentration, the solution is, by definition, neu-
tral.
terms related to dissociation, a phenomenon of
aqueous solutions. Dissociation is a form of
ionization, the natural breaking up of some of
the molecules into positive and negative ions. If
the chemical composition of the aqueous
solution is such that it yields more hydrogen Ions
(positive) than hydroxyl ions (negative), the
solution is considered acid: an excess of
hydroxyl ions on the other hand results in a
solution that is considered to be basic or
alkaline. The greater the excess, the more acid
or alkaline the solution, as the case may be. If
the hydrogen and hydroxyl ions are in equal
concentration, the solution is, by definition, neu-
tral.
Titration: Since acidity and alkalinity are op-
posing characteristics, an acid solution can be
neutralized (or even made alkaline) by the addi-
tion Of a base. The converse is also true. In
either case, neutralization can be accomplished
by titration, the gradual addition of a reagent
until a specified end point is reached. The
posing characteristics, an acid solution can be
neutralized (or even made alkaline) by the addi-
tion Of a base. The converse is also true. In
either case, neutralization can be accomplished
by titration, the gradual addition of a reagent
until a specified end point is reached. The
amount of acid or base materials in a solution
can thus be measured in terms of the quantity of
added reagent. Being non-aqueous, however,
petroleum oils cannot truly be said to be acid or
alkaline. Nevertheless, they can be modified to
exhibit these properties by addition of water--
plus alcohol to extract oil-soluble acid or alkaline
compounds from the sample, and to dissolve
them in the water. This principle is utilized in the
determination of neutralization number.
can thus be measured in terms of the quantity of
added reagent. Being non-aqueous, however,
petroleum oils cannot truly be said to be acid or
alkaline. Nevertheless, they can be modified to
exhibit these properties by addition of water--
plus alcohol to extract oil-soluble acid or alkaline
compounds from the sample, and to dissolve
them in the water. This principle is utilized in the
determination of neutralization number.
pH: Actual acidity or alkalinity, on the other
hand, can be expressed in accordance with the
pH scale, where zero represents maximum
acidity, 14 maximum alkalinity, and 7 neutrality.
The pH value of a solution can be determined
electrolytically. When two electrodes of different
materials are immersed In the solution, a small
electric potential (voltage) is generated between
them, and the magnitude and polarity of this
potential can be related directly to pH value.
hand, can be expressed in accordance with the
pH scale, where zero represents maximum
acidity, 14 maximum alkalinity, and 7 neutrality.
The pH value of a solution can be determined
electrolytically. When two electrodes of different
materials are immersed In the solution, a small
electric potential (voltage) is generated between
them, and the magnitude and polarity of this
potential can be related directly to pH value.
Potentiometric Method: The potentiometrlc
method for determining neut number (ASTM D
664) is based on the electrolytic principle, pH, as
indicated potentiometrically, is recorded against
added reagent. If the Initial pH reading of the
specially prepared sample lies between 4 and 11
(approximately), the sample may contain weak
acids, weak bases, or an equilibrium
combination of the two. It may be titrated to one
end point with base to yield a total acid number,
and then may be titrated to another end point
with acid to yield a total base number.
method for determining neut number (ASTM D
664) is based on the electrolytic principle, pH, as
indicated potentiometrically, is recorded against
added reagent. If the Initial pH reading of the
specially prepared sample lies between 4 and 11
(approximately), the sample may contain weak
acids, weak bases, or an equilibrium
combination of the two. It may be titrated to one
end point with base to yield a total acid number,
and then may be titrated to another end point
with acid to yield a total base number.
If. on the other hand, the initial pH reading lies
below 4 (approximately), the sample may be
below 4 (approximately), the sample may be
(FIST 2-4 11/90)
A-10