Acid field test kit for refrigeration oils containing a leak detector

A field test kit which uses a single vial is useful in testing acidity in refrigeration oils contaminated with a colored leak detector. This vial contains a pre-measured indicator solution and has sufficient additional volume that the test oil can be added directly to the indicator solution and accurately measured within the vial. After shaking, the mixture quickly separates into two phases. The color of the bottom phase indicates whether or not the acidity of the refrigeration oil exceeds 0.05 acid number.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to test kits for detecting acidity in oils and 
particularly relates to field test kits for detecting acidity in 
refrigeration oils which are contaminated with a leak detecting component. 
2. Review of Prior Art 
In the refrigeration industry, lubricating oils are tested for acidity as 
an indication of suitability for continued use and as a means for 
detecting contamination of the entire refrigeration system. Such tests are 
set forth in ASTM D664-58 and ASTM D974-64, but the requirements of 
D664-58 for laboratory equipment makes this procedure unsuitable for field 
testing, and testing according to D974-64 is not satisfactory with dark 
colored samples of refrigeration oils because the color changes that are 
produced by a color indicator such as p-naphtholbenzein solution are 
obscured by the color of the sample, making it difficult to estimate color 
changes with sufficient precision. 
Acid field test kits for use on refrigeration and airconditioning systems 
have been developed to meet this need and are currently designed to show 
whether or not the acidity of the refrigeration oil is above an acid 
number of 0.045 to 0.05, as determined by the color produced by an 
acid/base indicator in the test kit. New refrigeration oils intended for 
use in refrigeration systems generally have an acid number of from 0.01 
to 0.02 when tested according to conventional ASTM test methods. Such an 
acid number represents the quantity of base, expressed in milligrams of 
potassium hydroxide, that is required to titrate all acidic materials in a 
1 -gram sample of the oil that are dissociated sufficiently to react to 
the KOH. According to experience, when a refrigeration oil develops an 
acid content which corresponds to an acid number of from 0.05 to 0.07, it 
should be replaced with new oil. 
There are four acid field test kits which are now in popular use for 
testing refrigeration and air-conditioning systems. Two of these four 
field test kits produce a homogeneous mixture after shaking, and two 
produce a mixture that separates into two phases, the aqueous bottom phase 
containing the telltale color. The two-phase kits are based upon the 
method disclosed in U.S. Pat. No. 3,510,260 for forming an aqueous acid 
solution as an immiscible bottom phase, in which the acidic components are 
dissolved, with the oil as the top phase. When testing dark oils with a 
homogeneous-type kit, the color change is obviously likely to be masked. 
When using the two-phase method, the color change of an indicator 
solution, such as a one percent solution of phenolphthalein in ethanol, 
can become easily observable even with a dark oil when the aqueous phase 
turns from colorless to pink or red. However, if a red-colored leak 
detector is present as a component of the oil, the color change can be 
entirely obscured. 
For example, when the refrigeration oil is contaminated with a leak 
detector such as the highly colored additive marketed by E. I. Dupont de 
Nemours and Company as Dytel, the color of the homogeneous mixture is 
distorted and the test results are no longer reliable. It is believed that 
the alkylanilino-substituted anthraquinone dyes in U.S. Pat. No. 3,770,640 
are sold under the mark, Dytel. Other leak detectors are disclosed in U.S. 
Pat. No. 3,370,013 as organic dye compounds such as methyl derivatives of 
azobenzene-4-azo-2-naphthol, phenyl-azo-2-naphthol and methyl derivatives 
of azo-benzene-4-azo-2-naphthol, phenyl-azo-2-naphthol, and 
p-diethylaminoazobenzene. 
One homogeneous-type device, identified as "TKO ACID TEST KIT," is simplest 
to use. It employs a single vial, having a capacity of two fluid ounces, 
containing a purple mixture of alcoholic potassium hydroxide, an acid-base 
indicator and a solvent mixture comprising benzene and ethyl alcohol or, 
preferably toluene and isopropanol. By adding refrigeration oil to the 
mold line on the neck of the test vial, the correct amount of oil that 
corresponds to the amount of potassium hydroxide is obtained. The vial 
need be shaken for only a few seconds after addition of the refrigeration 
oil sample to produce a homogeneous mixture, with no transfers and no 
delay for separation into distinct phases. If the test sample has an acid 
number less than 0.045, the color of the mixture in the shaken vial 
remains purple. If the oil sample has a borderline acidity, the color 
becomes orange, indicating that changing the oil is desirable. If the oil 
is definitely too acidic, the color becomes yellow, indicating that the 
oil must be changed. Unfortunately, if a red leak detector is present as a 
component of the refrigeration oil, the results are unreliable. 
Another test kit of the homogeneous type is identified "as `ONE TIME ACID 
TEST KIT` and consists of a two-fluid ounce vial containing an acid-base 
indicator in a benzene-ethyl alcohol media (reddish-orange in color). A 
second vial of approximately 0.5 fluid oz., with a capacity for 15.5 g of 
fresh refrigeration oil, contains an alcoholic potassium hydroxide 
solution in benzene. According to the test procedure, the contents of the 
small vial are emptied into the larger vial producing a violet color. The 
small vial, which also serves as the measuring vial, is then filled with 
the test oil and finally emptied into the larger vial. If after shaking 
for fifteen seconds the color of the resulting homogeneous mixture remains 
purple-red, the oil is considered to be satisfactory". However, if the 
refrigeration oil contains a highly colored leak detector, the homogeneous 
mixture does not produce the expected test colors so that the kit is not 
suitable for such contaminated oils. 
A field test kit of the two-phase type, identified as "UNI-KIT", consists 
of three vials and a glass ampoule containing potassium hydroxide 
solution. The largest vial has a capacity of approximately one fluid ounce 
and contains dried crystals of phenolphthalein indicator. When the ampoule 
is broken and its colorless contents emptied into the large vial with the 
aid of a small piece of rubber tubing for venting the ampoule and 
obtaining better drainage into the vial, as described in U.S. Pat. No. 
3,653,839, the contents become pink. A second vial, containing isopropyl 
alcohol and toluene, is emptied into the mixture. Using the third vial for 
measurement, a sample of the refrigeration oil is then poured into the 
pink mixture, and the large vial is shaken vigorously. The resulting 
heterogeneous mixture frequently must stand for one to five minutes so 
that the partially emulsified layers can be separated sufficiently for an 
accurate color determination. Any pink color remaining in the bottom 
layer, even very light pink, signifies satisfactory oil. Therefore, if the 
oil in the top layer contains a leak detector, such as Dytel, which is 
even slightly miscible with or emulsified in the bottom layer, a slightly 
pinkish color is observed which could lead to an erroneous pass for an 
acidic refrigeration oil which is contaminated with the leak detector. 
The fourth test kit, also of the two-phase type, is marketed as "PHASE II" 
and consists of a two-fluid ounce bottle, which is partially filled with a 
solvent solution consisting of benzene, methanol, and toluene, and a 
0.5-fluid ounce bottle of neutralization solution. When the contents of 
the smaller bottle are poured into the large bottle, a purple-colored 
bottom layer is formed. The smaller bottle is then filled completely with 
oil to be tested and emptied into the larger bottle. After capping and 
shaking the larger bottle well, the mixture separates into two phases upon 
standing for two to three minutes. If the bottom layer loses its purple 
color, the sample has an acid number of 0.05 or more so that the oil 
should be replaced. This field test kit is probably the most convenient 
test kit which is now available for testing refrigeration oil taken from a 
system contaminated with a leak detector, even though it is subject to 
some interference from the dye. However, there are several practical 
drawbacks in that the kit requires the use of two bottles instead of only 
one bottle, considerable time is lost while waiting for phase separation, 
and benzene as one component of the solvent mixture is now a suspected 
carcinogen. 
Other test kits of interest are described in U.S. Pat. No. 3,528,775 for 
determining the water content of water-immiscible petroleum products, U.S. 
Pat. No. 3,449,081 for performing blood tests, and U.S. Pat. No. 1,674,416 
for testing alcohol. 
In the refrigeration and air conditioning fields, no simple and quickly 
operated field test kit is known that is not obscured by a leak detector 
in the oil to be tested. Accordingly, an acid field test kit is needed 
that provides acidity indications that cannot be obscured by a leak 
detector in oil contaminated therewith, that requires minimum time for 
field testing, that requires only a single vial so that transferring 
liquids is not necessary, and that preferably contains no benzene. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide an acid field test 
kit that is operable within a single bottle or vial for measuring a sample 
of a refrigeration oil, for carrying out the test precedure, and for 
obtaining reliable test results as to acidity of the oil. 
It is also an object to provide an acid field test kit of the two-phase 
type wherein the phases separate with exceptional rapidity and without 
emulsification. 
It is further an object to provide an acid field test kit having components 
that permit an acidity-related color change to be observed without 
interference from the color of a leak-detecting component of a 
refrigeration oil. 
Therefore, in accordance with the objects and principles of this invention, 
an acid field test kit of the two-phase type is herein provided which 
comprises a single vial for storage of the testing solution, for 
measurement of the oil sample, and for carrying out the test procedure. 
The testing solution comprises an aqueous bottom layer, which includes a 
color indicator and which is highly ionic in nature, and a solvent top 
layer which preferably includes no benzene. In operation, this field test 
kit requires only one vial, provides fast phase separation, produces 
distinct colors, and utilizes cyclohexane as the preferred solvent. Fast 
phase separation into two distinct layers is effected by the highly ionic 
nature of the aqueous layer. With the test kit of this invention, the 
single vial is merely filled to the line on its neck and shaken. The 
layers separate almost immediately, and in a very short time the operator 
can detect the color of the bottom phase. If its color is blue to 
blue-green, the oil is satisfactory for further service. If its color is 
green to yellow-green, the oil is marginal for further use. If its color 
is distinctly yellow, the oil is bad and unquestionably should be changed. 
The highly ionic nature of the aqueous layer is principally imparted by a 
water-soluble inorganic salt as a major component of the testing solution. 
This salt is preferably sodium chloride at 6-12% of an indicator stock 
solution by weight. 
DESCRIPTION OF THE INVENTION 
The method of preparing acid field test kits in general comprises the 
preparation of an indicator stock solution according to the following 
steps which are defined for an indicator, such as thymol blue, which 
changes color over a pH range of 8.0 to 9.6: 
A. preparing a concentrated aqueous indicator solution; 
B. preparing an indicator mixture comprising 20-28 percent by weight of a 
lower alcohol, 56-79 percent by weight of distilled water, 6-12 percent by 
weight of a water-soluble inorganic salt, and 0.2-0.3 percent by weight of 
the concentrated aqueous indicator solution; 
C. adjusting the pH of the indicator mixture to 9.5 with 1.0 N alkaline 
hydroxide, preferably as a solution, to form an adjusted mixture; 
D. adding to the adjusted mixture, to form the indicator stock solution, 
exactly the amount by weight of additional alkaline hydroxide solution so 
that the weight ratio of oil to be tested to one milliequivalent of the 
additional alkaline hydroxide is 1122; and 
E. protecting the indicator stock solution with nitrogen. 
Other materials producing an equivalent result can be substituted for the 
preferred materials. Indicators having a pH range of 8-10, such as 
phenolphthalein and phenol red, can be substituted for thymol blue to 
produce different colors. The term, alkaline hydroxide, includes potassium 
hydroxide, sodium hydroxide, and lithium hydroxide; potassium hydroxide is 
preferred. The term, water-soluble inorganic salt, includes sodium 
chloride, calcium chloride, magnesium chloride, sodium bromide, and like 
materials; sodium chloride is preferred. 
Using KOH as the alkaline hydroxide in steps C and D on a gram basis, for 
example, so that one milliequivalent (meq.) is 0.0561 gram, the quantities 
used in step B are: 600 ml-900 ml of alcohol/meq. KOH, 1400-1950 ml of 
water/meq. KOH, 135-275 g NaCl/meq. KOH, and 5-7 ml of concentrated 
aqueous indicator solution/meq. KOH. The preferred levels, as outlined in 
Example 1 hereinafter, are 751 ml of alcohol/meq. KOH, 1690 ml of 
water/meq. KOH, 201 g of NaCl/meq. KOH and 6.4 ml of indicator 
solution/meq. KOH. 
When KOH is used as a 1.000 N solution in step D, exactly 0.04018 percent 
by weight is added to the adjusted mixture to form the indicator stock 
solution. 
Step C is necessary to neutralize any acidic components arising from the 
raw materials and to establish a baseline for the indicator which changes 
from yellow to blue over a pH range of 8.0 to 9.6. By setting the baseline 
at a pH of 9.5, the color is unmistakably blue. If an indicator such as 
phenol red had been chosen, the baseline would have been set at pH 8 since 
it changes from yellow to red over a range of 6.8 to 8.0. 
The alkaline hydroxide added in step D is critical because the final kit 
should contain 0.775 mg KOH if KOH is the selected alkaline hydroxide. 
This amount represents the alkalinity consumed by 15.5 g of test oil with 
an acid number of 0.05. When properly filled with test solution and test 
oil, the weight of oil corresponds to 15.5 g. If the test oil is more 
acidic (acid number &gt;0.05), the KOH is consumed and the kit changes color. 
If the oil has an acid number below 0.05, the oil does not consume all of 
the KOH and the kit remains blue. 
In order to prepare kits of another size and be able to use larger or 
smaller oil samples, the amount of KOH in the kit would have to be 
adjusted so as to maintain a level of 20 g of oil/mg of KOH or 14.3 g of 
oil/mg of NaOH, for example. Whether the potassium hydroxide is added as a 
1.0 N solution, or 2.0 N, etc., is not critical so long as the ratios are 
properly maintained. 
The method further comprises the preparation of a plurality of test vials, 
each having a mark thereon to indicate a selected internal volume, 
according to the following steps: 
A. adding to each test vial, while protecting its contents with nitrogen, a 
quantity of a waterimmiscible solvent equalling 22.7 percent of the 
volume, preferably principally comprising cyclic carbon compounds having 
no carboxyl groups, alcohol groups, or ether linkages in its side chains, 
such compounds including benzene, toluene, the xylenes, mesitylene, 
isopropyl benzene, and cyclohexane, and mixtures thereof; and 
B. adding to each test vial, while continuing to protect its contents with 
an inert gas such as nitrogen, a quantity of the indicator stock solution 
equalling 51.4 percent of the selected internal volume. The remaining 
capacity of each field test vial equals 25.9% of its total volumetric 
capacity up to the mark. One or more test vials are included in a field 
test kit to be used by automobile mechanics and air conditioning and 
refrigeration servicemen. When carrying out the test procedure in the 
field, the oil to be tested is filled to this mark, shaken, and allowed to 
settle and separate into two distinct phases. The color of the aqueous 
bottom phase is then examined to obtain the test results. 
This procedure is illustrated with the following examples in which 
preferred materials and preferred quantities are used.

EXAMPLE 1 
A plurality of acid field test kits were made according to the following 
preferred procedure, in which all bottles and vials were clean and dry and 
all vials had a capacity of two fluid ounces up to a mark thereon, as 
follows: 
(1) a concentrated aqueous indicator solution was prepared by dissolving 
2.0 g of thymol blue indicator, in two hundred ml. of distilled water; 
(2) an indicator mixture was prepared under a nitrogen atmosphere by mixing 
14.1 liters of isopropyl alcohol, 31.5 liters of distilled water, 3.175 
kilograms of sodium chloride, and 120 ml. of the concentrated indicator 
solution; 
(3) using a pH meter, the pH of the indicator mixture was adjusted to 9.5 
with 1.0 N potassium hydroxide solution, using approximately 2.0-2.3 ml. 
of the KOH solution; 
(4) 18.64 ml. of 1.000 N KOH was added to the indicator mixture to form the 
indicator stock solution which was thereafter protected with nitrogen; 
(5) exactly 13.4 ml. of cyclohexane was charged to each field test kit 
vial; 
(6) while protecting with nitrogen, exactly 30.4 ml. of the indicator stock 
solution was added to each vial containing cyclohexane, forming two phases 
of which the bottom layer of each kit was blue with the top layer varying 
from a slight yellow tint to clear; and 
(7) each vial was very carefully sealed. 
EXAMPLE 2 
Five samples of Suniso 3GS refrigeration oil were treated with oleic acid 
(Wilmar 110) to produce acid numbers of 0.02, 0.04 and 0.06. Dytel II leak 
detector was added in normal commercial quantities to each sample. (Suniso 
refrigeration oils, such as Suniso 3GS, 4 GS, and 5GS refrigeration oils, 
are naphthenic oils manufactured by the Sun Oil Co.). Five vials made 
according to Example 1 were filled with the oil samples. The test oil at 
acid number 0.02 produced a blue bottom layer, the test oil at 0.04 acid 
number produced a green bottom layer, and the test oil at 0.06 acid 
number, in triplicate, produced distinctly yellow bottom layers. 
Other materials producing an equivalent result can be substituted for the 
preferred materials, such as toluene, benzene, and the xylenes being 
substituted for cyclohexane, and ethyl alcohol, n-propyl alcohol, and 
tert-butyl alcohol being substituted for isopropyl alcohol. The volumes 
and weight ratios of the water, cyclohexane, alcohol, and inorganic salt 
can be altered from the preferred amounts given hereinbefore without 
seriously affecting the test results. 
Because it will be readily apparent to those skilled in the art that 
innumerable variations, modifications, applications, and extensions of 
these embodiments and principles can be made without departing from the 
spirit and scope of the invention, what is herein defined as such scope 
and is desired to be protected should be measured, and the invention 
should be limited, only by the following claims.