Method of determining salt water in oils

The presence of salt water in marine oils is determined aboard ship by using a unique combination of reagents comprising a halogenated hydrocarbon, an inorganic salt solution and an alcohol to efficiently separate the water and then using a salt-impregnated gel to determine the chloride content.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a method for determining the nature and amount of 
salt water held in used oils, especially marine oils. In particular, the 
method is designed for use on board ship to avoid any delay that is caused 
when necessary to reach a land-based laboratory for the determination. 
2. Discussion of the Prior Art 
Various methods have been used to detect the presence of sea water in 
lubricating oil, particularly marine oils. Generally, such methods are 
based on the determination of chloride in a sample of the oil. In testing 
for chlorides by an early method, samples of the used marine lubricating 
oil were diluted with a suitable light solvent, centrifuged, and the 
separated water phase at the bottom of the centrifuge tube was removed for 
chloride analysis. The analysis was carried out by adding silver nitrate 
to the separated water phase. The formation of insoluble silver chloride 
in the form of a white precipitate denoted a positive test for the 
presence of the chloride ion. This test was found to be far from 
satisfactory in laboratory use, and it was practically unworkable in the 
field, for example, in marine ports or emergency ports, where laboratory 
facilities are not available. If, after centrifuging of the lubricating 
oil, a water phase is not formed, no test can be made for chloride ion, 
although the oil may actually have chloride contamination. In addition, 
such tests require, by necessity, a centrifuge and various assorted 
glassware apparatus, a delicate manipulation to remove water from the 
centrifuge tube, personal safety considerations in handling of strong 
acids, relatively easy contamination of chemicals in a marine atmosphere, 
and the possibility of inaccurate conclusions by reason of the 
precipitation of organic acids in a manner similar to that of the 
chlorides. 
An improvement to the above-described method is taught in U.S. Pat. No. 
3,202,483. In carrying out the chloride determination as described in the 
patent, a hydrocarbon, water and an emulsion breaker are used to extract 
the chloride. The chloride containing aqueous solution is then brought 
into contact with a composite of silver chromate deposited on an 
absorbent, e.g. silica gel contained in a glass tube. However, the 
emulsion-breaking action was erratic. Also, the water extract lay below 
the oil phase so that when the tube containing the silver chromate and 
absorbent was pushed through the oil phase, the tube picked up oil. Both 
these difficulties often led to erroneously low chloride values. The 
present invention relates to an improved system for extracting the 
chloride. 
SUMMARY OF THE INVENTION 
In accordance with the invention, there is provided an improved method for 
determining the presence of salt water in a lubricating oil which 
comprises the steps of extracting the oil with an aqueous medium and 
contacting said aqueous medium containing chloride ion with a composite 
comprising silver chromate deposited on an absorbent, the improvement 
whereby the aqueous medium used to extract the chloride ion is a 
combination of aqueous alkali metal or ammonium salt, an aliphatic 
monohydric alcohol and a halohydrocarbon or mixed halohydrocarbon. 
Preferably, the combination comprises aqueous sodium sulfate, 
1,1,2-trichlorotrifluoroethane and 1-butanol. 
DESCRIPTION OF SPECIFIC EMBODIMENTS 
The improved method of the present invention provides a simple, accurate 
and efficient method of separating water and chloride from oil emulsions, 
especially marine oil emulsions, so that the chloride in the separated 
water may subsequently be determined using tubes filled with silver 
chromate-impregnated silica gel. Thereby the possible contamination of the 
oil with salt water, e.g., sea-water, may be determined at the source, as 
for example, onboard ships. 
This test is based upon the fact that when the chloride in the oil is 
transferred to an aqueous medium by an improved combination of reagents, 
and this aqueous medium is brought into contact with a composite 
comprising silver chromate deposited on an absorbent, the composite, which 
normally has a brownish appearance, is changed to a lighter color, varying 
from a yellowish to a whitish appearance. This color variance results from 
the formation of relatively insoluble silver chloride from the silver 
chromate. When this principle is utilized in one of its more practical 
applications, the quantity of chloride ion present in an aqueous solution 
can be measured by the relative quantity of silver chromate which is 
converted to the silver chloride. Thus, when a dry, brown-colored 
composite of silver chromate deposited on an absorbent, such as silica 
gel, is packed in a glass tube, an aqueous solution containing chloride 
ion coming into contact with this composition causes at least a portion of 
the composite to turn lighter, from a yellowish to a whitish appearance, 
due to the conversion of the brown silver chromate to the whitish silver 
chloride. A definite color change is observed, with a sharp line 
indicating reacted and unreacted silver chromate. The linear length of the 
reacted portion of the composite (i.e., that portion which has been 
converted to silver chloride) is proportional to the amount of chloride 
ion present in the aqueous solution. This length can, therefore, be 
measured, and to facilitate such measurement, the tube may be suitably 
calibrated. 
When aqueous solutions which are strongly acidic or strongly alkaline are 
tested by the method of the present invention, the silver chromate in the 
composite may be dissolved and be converted from the aforementioned 
brownish color to lighter yellowish or whitish appearance, even though no 
actual chloride ion is present. On the other hand, where the pH value of 
the aqueous solution is maintained between about 6 and about 10, the 
aforementioned color change only occurs when chloride ion is actually 
present. Therefore, where the aqueous solution to be tested has a pH value 
outside the aforementioned range, suitable buffering agents may be added 
to adjust the pH to a value between about 6 and about 10. 
While the composite of silver chromate deposited on the absorbent is 
prepared in such manner that a sufficient quantity of silver chromate is 
present to react with all of the chloride ion, it varies to a high degree 
with respect to the quantity of absorbent present in the composite. Thus, 
composites are generally employed which comprise silver chromate in an 
amount between 0.25 percent and about 5 percent, and, correspondingly, an 
absorbent in an amount between about 99.75 percent and about 95 percent, 
by weight. Composites comprising silver chromate in an amount between 
about 0.25 percent and about 0.5 percent, and, correspondingly, absorbent 
in an amount between about 99.75 percent and about 99.5 percent, by 
weight, are preferred. 
The preparation of the composite is carried out by wetting a predetermined 
amount of the absorbent with an aqueous silver nitrate solution, and then 
evaporating the absorbent to dryness. The dried absorbent is then reacted 
with an aqueous solution of sodium chromate and the resulting composite is 
then evaporated to dryness. The composite is then ready for use in the 
improved method of the present invention. As a more specific example of 
the application of the method for preparing the aforementioned silver 
chromate-absorbent composite, 100 grams of silica gel are wetted with 100 
ml. of a 0.02 M aqueous solution of silver nitrate. As indicated above, 
the silica gel is evaporated to dryness. The dried gel is then contacted 
with 100 ml. of a 0.03 M aqueous solution of sodium chromate, and the 
resulting composite is evaporated and ready for use as a chloride ion 
indicator. In one of the more practical applications of the apparatus 
suitable for carrying out the improved method of the present invention, a 
small plug of cotton, or other suitable porous material, is placed in one 
end of a length of small-bore transparent glass tubing. The dried 
composite is then packed into the tubing, followed by the insertion of a 
second plug, so the composite is held firmly in place by the two plugs. 
Placing an open end of the tube into an aqueous solution containing 
dissolved chloride ion, will cause the solution to rise up the tube by 
capillary action, wetting the composite, and affecting the aforementioned 
color change from a brown to a yellowish or whitish appearance of such 
linear length of the composite as is proportional to the quantity of 
chloride ion present in the solution being tested. 
While silica gel has been indicated as a suitable absorbent material upon 
which the silver chromate may be deposited or dispersed, various other 
materials may also be employed, including silica, silica-alumina, 
silica-alumina gel, silica-magnesia, glass particles, various vitreous 
materials, various clays, diatomaceous earth, kieselguhr, pumice, 
magnesia, alumina-gel, zinc aluminate, zinc alumina, zinc spinel, titania, 
thoria, zirconia, fuller's earth, "Superfiltrol," sawdust, wood-flour, and 
any other materials which are capable of absorbing and distributing the 
silver-chromate in a homogeneous manner. Suitable binders may also be 
employed in combination with the absorbent material. Preferably, the 
absorbent employed is a light-colored material to facilitate the 
observance of subsequent color change in the presence of chloride ion. 
As was mentioned hereinabove, the prior art used a hydrocarbon, such as 
kerosine, an emulsion breaker and water to extract the chloride from the 
used oil, i.e. marine oil. It is this aspect of the method that the 
present invention improves. An improved combination of reagents comprising 
water, a liquid halogenated hydrocarbon that is heavier than water, an 
alcohol and an inorganic salt is used. The halohydrocarbon or mixed 
halohydrocarbons may be, among others, trichloroethylene, 
1,1,2-trichlorotrifluoroethane, tribromomethane, carbon tetrachloride, 
o-dichlorobenzene, bromochloroethane, chloroform, dibromopropane, 
1,2-dichloroethane, 1-bromonaphthalene and dichloropropane. It should be 
noted that the effective halohydrocarbons will produce an aqueous medium 
that will float atop the oil sample, allowing easy contact with such 
aqueous medium without having to pass the sample probe through the oil 
layer. 
The alcohol may be a liquid monohydroxy alcohol such as 1-butanol, 
1-hexanol, propanol, isopropanol, isobutanol, pentyl alcohol or isopentyl 
alcohol. 
The inorganic salt may be one containing a metallic or non-metallic cation 
and a mono-, or divalent anion. Examples of such cations may be ammonium, 
or the alkali metal cations. Examples of such anions are fluoride, 
nitrate, perchlorate and sulfate. Salt anions that cannot be used because 
they interfere are bromide, iodide, thiocyanate and, of course, chloride. 
Effective combinations of reagents in this invention will be in the 
following ranges. The values are the parts by volume of each reagent 
required for use with one part by volume of used oil, e.g., marine oil. 
The 1,1,2-trichlorotrifluoroethane or other halohydrocarbon or combination 
thereof will range from about 0.7 to about 4.0 parts, preferably about 2.0 
parts to about 3.0 parts, the alcohol from about 0.2 to about 1.0 parts, 
preferably about 0.33 parts to about 0.7 parts, the aqueous solution of 
inorganic salt from about 0.2 to about 1.0 parts, preferably about 0.33 
parts to 0.75 parts. The concentration of the inorganic salt in the 
aqueous solution will range from about 2% weight to about 12% weight, 
preferably about 4% to about 8%. The preferred inorganic salt is anhydrous 
sodium sulfate.

Having described the invention in general terms, the following will 
illustrate it specifically. It is to be understood that the example below 
is not intended to limit the scope of the invention. 
EXAMPLE 
As an example of the method for preparing the aforementioned indicator 
tubes for chloride ion determination, the composite is first prepared in 
the following manner: 
A silver nitrate solution is prepared by dissolving 3.4 grams of reagent 
grade silver nitrate (AgNO.sub.3) in 50 ml. of distilled water, to which 
is added an amount of a mixture comprising approximately 90 percent ethyl 
alcohol and 10 percent methyl alcohol, by volume, sufficient to make one 
liter of solution. The combined components are then thoroughly mixed. A 
sodium chromate solution is then prepared by dissolving 4.7 grams of 
reagent grade sodium chromate (Na.sub.2 CrO.sub.4) in 100 ml. of distilled 
water, to which is added an amount of a mixture comprising approximately 
90 percent ethyl alcohol and 10 percent methyl alcohol, by volume, 
sufficient to make one liter of solution. The combined components are 
thoroughly mixed. 
100 grams of silica gel, having a particle size of 100 to 200 mesh, are 
placed into a 600 ml. beaker. 100 ml. of the aforementioned prepared 
silver nitrate solution are added and thoroughly mixed with the silica 
gel. The silica gel must be completely wetted by the silver nitrate 
solution. If necessary, additional quantities of the aforementioned 
alcohol mixture may be added to effect complete wetting of the silica gel. 
The beaker and its contents are then placed on a hot plate and evaporated 
to complete dryness. To the thus-dried silica gel are added 100 ml. of the 
aforementioned sodium chromate solution. The components are then 
thoroughly mixed in the beaker. The beaker is again placed on a hot plate 
and the contents are evaporated to complete dryness, with occasional 
stirring to prevent spattering. The last traces of water are removed by 
placing the beaker in a drying oven maintained at 110.degree. C. 
A small plug of cotton is next placed into one end of a glass indicator 
tube, and the tube is then filled with the dried silver chromate-silica 
gel composite to a height of 4 inches. Approximately 0.3 gram of the 
composite is required to fill the tube to the aforementioned height of 4 
inches. Thereafter another plug of cotton is inserted into the tube and 
forced down over the composite so that the latter is retained tightly 
between the two plugs. The indicator tube is now ready for use. 
An extractant mixture was prepared by mixing 5 ml. of an 8% solution of 
sodium sulfate with 35 ml. of a mixture containing 1 part of n-butanol to 
each 6 parts of 1,1,2-trichlorotrifluoroethane. 
Ten samples of used marine oil from various ships were tested for the 
presence of sea water. 15 ml. of each of these was shaken with the above 
extractant mixture for 2 minutes. The mixture was allowed to settle for 1 
hour and was then shaken for another two minutes. After further settling 
the aqueous layer containing the extracted chloride separated and floated 
above the oil- 1,1,2-trichlorotritrifluoroethane-butanol solution. The 
glass tube containing the silver chromate composite was inserted into the 
aqueous layer containing the extracted chloride. The aqueous solution 
rises by capillary action up the tube to the top of the composite, 
effecting a color change from brown to whitish or yellowish if chloride is 
present. From the linear length of the yellowish zone and conversion data, 
Table 1, the sea water content of the oil may be obtained. 
TABLE 1 
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Sea Water Content of Whole Sample vs 
Height of Indicator Tube Color Change 
Grams of Grams of 
Height Sea Water per Height Sea Water per 
mm 100 g sample mm 100 g sample 
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5 0.03 76 4.3 
10 0.13 77 4.5 
15 0.28 78 4.8 
20 0.43 79 5.0 
25 0.56 80 5.3 
30 0.71 81 5.5 
35 0.86 82 5.8 
40 1.03 83 6.2 
45 1.2 84 6.5 
50 1.5 85 6.9 
55 1.8 86 7.3 
60 2.2 87 7.8 
62 2.4 88 8.3 
64 2.6 89 8.8 
66 2.8 90 9.4 
68 3.0 91 10.1 
70 3.3 92 10.9 
72 3.6 93 12.0 
74 3.9 94 14.6 
75 4.1 
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The following Table 2 summarizes the results, which include the times 
needed for a clear sample of water to settle following the second shaking. 
TABLE 2 
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Settling Time 
Percent 
Sample Hours Seawater 
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1 6 0.62 
2 15 0.0 
3 5 0.09 
4 4 2.4 
5 4 0.96 
6 11 1.6 
7 11 0.40 
8 4 0.02 
9 4 0.34 
10 6 0.16 
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