FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICA TION
(See section 10, rule 13)
1. Title of the invention
A METHOD OF MARKING A PETROLEUM FUEL
2. Applicant(s)
Name Nationality Address
TATA CHEMICALS LTD. INDIA BOMBAY HOUSE, 24 HOMI MODI STREET,
MUMBAI-400001
3. Preamble to the description
COMPLETE SPECIFICA TION
The following specification particularly describes the invention and the manner in which it is
to be performed.

The disclosure relates to a method for marking a petroleum fuel. The disclosure also relates to a method for detecting adulteration in a petroleum fuel. BACKGROUND
Petrol and diesel constitute important fuel chemicals used extensively worldwide. The annual consumption of these materials in India alone is about 9 million tonnes, making it as one of the most consumed chemical. Petrol and Diesel are obtained by refining crude petroleum. During the refining process crude petroleum is separated into different fractions, each used for a particular function. While petrol (or gasoline) comprises of lower chain hydrocarbons (bulk of them in the region of 4-12 carbon atoms), diesel, the other main consumable petroleum fraction, comprises chiefly of hydrocarbons containing 8-21 carbon atoms. These hydrocarbons may be either linear or branched and may be saturated or unsaturated. The third most consumed fraction of petroleum is kerosene that typically contains between 6 and 16 carbon atoms per molecule.
Markers are often used to tag these and other petroleum fuels. Dyes or markers may be added to fuels to distinguish fuels of various brands or grades for commercial and safety reasons. Another reason for adding markers or dyes to fuels is for identifying particular batches of bulk fuels for protecting them against theft, particularly for fuel that is owned by government, military or large commercial consumers.
Moreover, certain fuels are dyed or tagged to deter fraudulent adulteration of premium grade fuels with lower grade fuels, such as by blending kerosene, stove oil or diesel fuel into petrol or blending lower grade petrol into premium grade petrol.
In India, kerosene is largely subsidized in order to provide cheaper cooking fuel for the economically backward category and to prevent cutting of forest wood for cooking purpose. Due to a huge subsidy provided on kerosene it is often added to petrol and diesel. In

India in order to prevent adulteration of fuels with kerosene a marker is added to the kerosene.
The markers at present used for petrol, diesel and kerosene are dyes of suitable and acceptable colors. These are materials that show powerful absorbance in the visible region. However, these dye molecules are easily separated from the fuel based on their physical and chemical properties. This therefore defeats the main purpose of deterring adulteration.
Moreover, the combustion of these dyes along with the fuel often results in the production of different compounds that may be environmentally unfriendly.
Therefore, there is a need for a method of marking petroleum fuels that is simple and uses a marker that cannot be easily separated from the petroleum fuel in which it is added. The methods by which the presence of marker is detected in the fuel should be simple. Moreover the marker should be such that its presence in the fuel may even be detected in very minute quantities. Additionally the marker should be environmentally friendly and should be obtained from renewable sources.
SUMMARY
The disclosure relates to a method of marking a petroleum fuel. The method includes adding a marker to the petroleum fuel, the marker comprising a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
The disclosure also relates to a marker for petroleum fuels. The marker comprises a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
The disclosure also relates to a method for determining adulteration of a petroleum fuel. The method comprises detecting the presence of a marker in the petroleum fuel by adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer. The marker is a salicylic acid

having a linear hydrocarbon chain substitution that results in a change in colour in the organic layer. The change in colour of the organic layer indicates the presence of an adulterant in the petroleum fuel.
The disclosure also relates to a kit for determining adulteration of a petroleum fuel by a fuel to which a salicylic acid having a linear hydrocarbon chain substitution is added as a fuel marker. The kit includes a transition metal acetate; and a set of instructions for detecting the presence of the fuel to which the fuel marker has been added. The instructions include adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer. The marker is a salicylic acid having a linear hydrocarbon chain substitution that results in a change in colour in the organic layer. The change in. colour of the organic layer indicates the presence of an adulterant in. the petroleum fuel.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the described method, and such further applications of the principles of the invention as described therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
A method for marking a petroleum fuel by addition of a marker is disclosed. The marker is a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain (R) as illustrated below:


R may be a saturated or an unsaturated side chain having 6 to 23 carbon atom.
In accordance with an aspect, the marker is any one of cashew nut shell liquid, saturated anacardic acid, anacardic acid enes or their mixtures.
Saturated anacardic acid is a molecule having a salicylic acid unit linked to a saturated linear alkyl chain (R). The alkyl chain may have any number of carbon atoms, depending upon the source of the saturated anacardic acid. By way of an example, in the saturated anacardic acid obtained from cashew nut shell, the alkyl chain (R) is a saturated I5-carbon long alkyl chain represented as 1R below. The molecular structure of the saturated anacardic acid obtained from cashew nut shell liquid is illustrated below:

Anacardic acid enes are unsaturated anacardic acids having various degrees of unsaturation in the side chain. In accordance with aspect, the anacardic acid enes obtained from cashew nut shell liquid have 1 to 3 double bonds. The anacardic acid enes obtained from cashew nut shell liquid may be an 8'Z -monoene (2R); 8'Z, 11 'Z-diene (3R) and 8'Z, 11 'Z, 14'-triene (4R) anacardic acid enes having the following molecular structures:


In accordance with an aspect the marker may be a metal derivative of substituted salicylic acid, wherein the salicylic acid is substituted with a linear hydrocarbon chain,
Metal derivative of substituted salicylic acid may be a 1:1 derivative having one metal ion bonded with one molecule of substituted salicylic acid. The metal derivative of substituted salicylic acid may also be a 2:1 derivative having one metal ion bonded with two molecules of saturated anacardic acid or anacardic acid enes.
The 1:1 metal derivative of substituted salicylic acid has one metal ion (M) bonded with one molecule of the substituted salicylic acid. The molecular structure of the 1:1 metal derivative of substituted salicylic acid is illustrated below:

The salicylic acid is substituted with a linear hydrocarbon chain (R). R may be a saturated or an unsaturated side chain. By way of an example the alkyl chain (R) is saturated 15-carbon long alkyl chain represented as 1R above or unsaturated 15-carbon long chain having 1 to 3 double bonds represented as 2R, 3R and 4R above.

In the 2:1 metal derivative of substituted salicylic acid, one metal ion (M) is bonded with two molecules of substituted salicylic acid. The molecular structure of the 2:1 derivative of substituted salicylic acid is illustrated below:

R may be a saturated or an unsaturated liner side chain. By way of an example the linear side chain (R) is saturated 15-carbon long alkyl chain represented as 1R above or unsaturated 15-carbon long chain having 1 to 3 double bonds represented as 2R, 3R and 4R above.
In accordance with an embodiment the marker comprises of metal derivative of substituted salicylic acid having a linear hydrocarbon chain substitution and substituted salicylic acid having a linear hydrocarbon chain substitution such that the ratio of substituted salicylic acid to metal ions in the range of 2:1 to 10:1.
In accordance with an aspect, the metal derivative of substituted salicylic acid may be any transition metal derivative. In accordance with an aspect the transition metal derivative of

substituted salicylic acid is a transition metal derivative of any one of transition metal salt including iron, cobalt or copper.
In accordance with an aspect the marker is any one of transition metal derivatives of saturated anacardic acid or anacardic acid enes or their mixtures.
In accordance with an aspect the saturated anacardic acid or anacardic acid enes are obtained from natural cashew nut shell liquid.
Natural cashew nut shell liquid may be obtained by any known method. By way of an example, fresh cashew nuts are broken and the kernels along the pericarp are removed. The shells are treated with organic solvent, which may be hexane, ether, ethyl acetate, chlorinated solvents or hydroxylated solvents, to extract the lipophilic phenols referred to as natural cashew nut shell liquid. The natural cashew nut shell liquid thus obtained is nearly 34% yield of the nut, in the form of a light brown coloured viscous liquid containing anacardic acid enes (as much as 75%) as the chief ingredient.
Natural cashew nut shell liquid may also be obtained from the cashew nut shell by cold pressing the shells.
The anacardic acid enes may be separated from the natural cashew nut shell liquid by any known method. By way of a specific example, the natural cashew nut shell liquid is subjected to column purification to separate the components of the natural cashew nut shell liquid as various fractions. The factions containing anacardic acid enes are pooled together to obtain a mixture of anacardic acid enes in the form of a pale yellow viscous liquid.
By way of another example the anacardic acid enes may also separated from the natural cashew nut shell liquid by treating the natural cashew nut shell liquid with calcium salts

Further, the anacardic acid enes may be converted to their saturated analog form to obtain saturated anacardic acid. Saturation of anacardic acid enes may be carried out by any known method including but not limited to catalytic hydrogenation using Pt/C catalyst.
In accordance with an aspect at least l0ppm of marker is added to the fuel. The amount of marker that may be added to the fuel is in the range of 10 to 5000ppm.
In accordance with an aspect the petroleum fuel is any one of kerosene, petrol or diesel.
A method for determining adulteration of a petroleum fuel is also disclosed. The method comprises detecting the presence of a marker in the petroleum fuel, where the marker indicates the presence of an adulterant fuel.
In accordance with an aspect, the method of detecting the presence of marker in the petroleum fuel comprises of adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer. The presence of an adulterant in the petroleum fuel is indicated by a change in the colour of the organic layer. The marker is a salicylic acid having a linear hydrocarbon chain substitution.
In accordance with an aspect, the method further comprises of mixing or shaking the reaction mixture after adding the aqueous solution of the transition metal acetate to the petroleum fuel.
In accordance with an aspect the marker may be any one of cashew nut shell liquid, saturated anacardic acid or anacardic acid enes.
The transition metal acetate that may be added to the fuel is a transition metal (II) acetate. In accordance with an aspect the transition metal acetate that may be added to the fuel is any one of iron acetate, cobalt acetate or copper acetate.
In accordance with an aspect, the amount of transition metal acetate that is added to the fuel is in the range of 20 to 5000 mg per liter of fuel.

In accordance with an aspect, the presence of a marker in the petroleum fuel may also be detected by methods including but not limited to spectral methods and chromatographic techniques.
The marker may be detected by checking the UV absorbance typical of it in the λmax at 280 and 310 nm. The marker may also be detected by Infra-red and Nuclear Magnetic Resonance (NMR) spectral characterization. The marker may be detected by High Performance Liquid Chromatography. The High Performance Liquid Chromatography may be conducted using a reverse phase column using a mixture of acetonitrile, water and acetic acid as a solvent system.
A kit for determining adulteration of a petroleum fuel by a fuel to which a salicylic acid having a linear hydrocarbon chain substitution is added as a fuel marker is also disclosed. The kit comprises a transition metal acetate; and a set of instructions for detecting the presence of the fuel to which the fuel marker has been added. The instruction comprises adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer. The presence of an adulterant in the petroleum fuel is indicated by a change in the colour of the organic layer.
Specific embodiments are described below:
A method of marking a petroleum fuel comprising adding a marker to the petroleum fuel, the marker comprising a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
Such method(s), wherein the marker is a transition metal derivative of the substituted salicylic acid, the metal derivative being a 1:1 derivative having one molecule of the substituted salicylic acid bonded with one transition metal ion or a 2:1 derivative having two molecules of the substituted salicylic acid bonded with one transition metal ion wherein the salicylic acid is substituted with a linear hydrocarbon chain.

Such method(s), wherein the marker further comprises of substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain such that the ratio of substituted salicylic acid to transition metal ions in the range of 2:1 to 10:1.
Such method(s), wherein the linear hydrocarbon chain is a C6 to C23 hydrocarbon chain.
Such method(s), wherein the linear hydrocarbon chain is unsaturated with the degree of unsaturation between 1 and 3.
Such method(s), wherein the marker is any one of cashewnut shell liquid, saturated anacardic acid, anacardic acid enes, transition metal derivatives of saturated anacardic acid or anacardic acid enes or their mixtures.
Such meihod(s), wherein the saturated anacardic acid and anacardic acid enes is obtained from natural cashew nut shell liquid.
Such method(s) wherein the petroleum fuel is kerosene, petrol or diesel.
Such method(s), wherein at least 10 ppm of the marker is added to the fuel.
A marker for petroleum fuels comprising a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
Such marker(s) for petroleum fuels, wherein the marker is a transition metal derivative of the substituted salicylic acid, the transition metal derivative being a 1:1 derivative having one molecule of the substituted salicylic acid bonded with one transition metal ion or a 2:1 derivative having two molecules of the substituted salicylic acid bonded with one transition metal ion wherein the salicylic acid is substituted with a linear hydrocarbon chain.
Such marker(s) for petroleum fuels,, further comprising of a substituted salicylic acid such that the ratio of substituted salicylic acid to transition metal ions in the range of 2:1 to 10:1.

A method for determining adulteration of a petroleum fuel comprising detecting the presence of a marker in the petroleum fuel by adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer; the marker a salicylic acid having a linear hydrocarbon chain substitution resulting in a change in colour in the organic layer, the change in colour of the organic layer indicating the presence of an adulterant in the petroleum fuel.
Such method(s), wherein the marker is any one of natural cashew nut shell liquid, saturated anacardic acid, anacardic acid ene, or their mixture.
Such method(s), wherein the transition metal acetate is any one of iron acetate, copper , acetate or cobalt acetate.
Such method(s), wherein the amount of transition metal acetate added per liter of petroleum fuel is in the range of 20 to 5000 mg.
A kit for determining adulteration of a petroleum fuel by a fuel to which a salicylic acid having a linear hydrocarbon chain substitution is added as a fuel marker comprising a transition metal acetate; and a set of instructions for detecting the presence of the fuel to which the fuel marker has been added; the instructions comprising adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer; the marker a salicylic acid having a linear hydrocarbon chain substitution resulting in a change in colour in the organic layer, the change in colour of the organic layer indicating the presence of an adulterant in the petroleum fuel.
Such kit(s), wherein the marker is any one of cashewnut shell liquid, saturated anacardic acid, or anacardic acid enes or their mixtures.
Such kit(s), wherein anacardic acid or anacardic acid enes is obtained from natural cashew nut shell liquid.

Such kit(s), wherein the transition metal acetate is any one of iron acetate, copper acetate or cobalt acetate.
Examples:
The following examples are provided to explain and illustrate certain preferred embodiments of the process of the invention.
Example 1:
Cashew nut shell liquid (CNSL) (500 mg) containing about 80 wt% of anacardic acid ene mixtures was added dropwise to kerosene (100 ml). The cashew nut shell liquid was completely miscible in kerosene generating a homogeneous mass. The presence of cashew nut shell liquid in kerosene was monitored by spotting the kerosene without cashew nut shell liquid, kerosene with cashew nut shell liquid and cashew nut shell liquid dissolved in hexane on a Thin Layer Chromatography plate and observing them under Ultra Violet radiation at 254 nm and 355 nm. Dark brown spot under 254 nm and a bright blue coloration at 365 nm are a clear indication of the presence of marker (phenolic especially anacardic acid) in the sample. Similar experiments were tried by using anacardic acid ene mixtures. Experiments involving addition of the cashew nut shell liquid to petrol and diesel also resulted in a homogeneous mixture.
Presence of maker was also tested using High Performance Liquid Chromatography. The High Performance Liquid Chromatography was tried using acetonitrile : water : acetic acid as a solvent in the ratio of 80:20:1 volume/volume with UV detection at 280 and 310 nm. Example 2:
Anacardic acid ene mixtures were hydrogenated using hydrogen on a 10 weight % Pd/C catalyst. The isolated saturated anacardic acid was further purified by recrystalization using hexane-ethyl acetate. Resulting white solid was dried and checked for its physical properties. This saturated anacardic acid was converted into metal derivatives by dissolving anacardic acid in an organic solvent and shaking them with a solution of transition metal acetate including

copper acetate and cobalt acetate in an aqueous solution. Copper derivative of the saturated anacardic acid or anacardic acid enes are dark green in colour while cobalt derivatives of saturated anacardic acid or anacardic acid enes was purple in colour.
Addition of these saturated and metal derivatives of anacardic acid to kerosene resulted in a homogeneous solution. Further, saturated anacardic acid, anacardic acid enes and their metal derivative could be dissolved in an organic solvent (eg., xylene, ethyl acetate) and then can be blended with kerosene resulting in a homogeneous solution.
Example 3:
50 mg each of cashew nut shell liquid, saturated anacardic acid or anacardic acid enes were blended with 30 millilitre of kerosene. The mixtures were stirred for 2 minutes to get a homogeneous mass. The marker-kerosene blends were washed with 30 millilitres of 5% wt./vol dilute hydrochloric acid (HC1) solution. The organic layer and aqueous layer were tested for the presence of the marker molecule by thin layer chromatography. The presence of marker was only observed in the organic layer and not in the aqueous layer. This indicates there is no loss of the marker even by acid treatment.
20 milligrams of copper derivative of anacardic acid in 1 mille liter of ethyl acetate was added to 50 millilitres of kerosene. This resulted in a pale green solution. To this, pale green solution 30 millilitres of 5% (w/v) Hydrochloric acid was added and the mixture was vigorously stirred for 5 minutes. It was observed that the kerosene layer became colourless since the complex in the kerosene was broke by the addition of the acid. The kerosene layer was then separated from the aqueous layer, washed with 20 mille liter of water and was treated with 50 mille grams of copper acetate dissolved in 10 mille liter of water. The green colouration reappeared in the kerosene layer indicating the presence of anacardic acid in the kerosene layer and re-formation of the copper complex,

Example 4
50 millegrams of marker (saturated anacardic acid, anacardic acid enes mixture or cashew nut shell liquid) was blended with 50 millilitre of kerosene. The mixture was passed over a cartridge of activated charcoal (5 gram). The effluent of the cartridge was tested for the presence of anacardic acid. There was no detectable loss of cashew nut shell liquid, anacardic acid or anacardic acid enes due to this treatment. However, under similar experiments conducted with silica gel a decrease in the concentration of cashew nut shell liquid in kerosene was observed.
Example 5:
Marker -kerosene blend as described in Example 3 were kept exposed to sun light and air for 24 hours. No observable change was observed. The marker molecule could be easily detected by Thin Layer Chromatography, High Performance Liquid Chromatography and by UV-Vis spectral spectroscopy.
Example 6:
Marker- kerosene blend as described in Example 3 was treated with 5% (wt./vol) NaOH solution in a ratio of 1:1 by volume by volume. It was found that an emulsion formed which was difficult to break. This was because of anacardic acid forming mono and di-sodium salts which have a partitioning between organic and aqueous phase. Addition of bases to a copper derivative of saturated anacardic acid or anacardic acid enes used as marker in kerosene resulted in a yellow coloration of the kerosene layer. This was hard to remove from the organic phase since it formed a fine suspension.
INDUSTRIAL APPLICABILITY
The marker as disclosed above may be used for tagging or marking any petroleum fuel including petrol, diesel or kerosene. As it forms a homogenous mixture with these fuels it may be added in any proportion to these fuels. The marker may be added in higher parts per million

levels to the fuel since its calorific value is similar to that of the fuel component and does not cause any problems. Moreover, as the marker molecule is structurally very similar to these fuels and also has similar chemical and physical properties it is very difficult to remove this marker from the fuel once it has been added to the fuel.
Moreover, the presence of theses markers may be detected using simple and routine tests. Further, even very minor quantities (upto ppm levels) are detectable.
Moreover the marker molecule disclosed above is obtained by renewable source and is biodegradable is therefore environmentally friendly.

WE CLAIM:
1. A method of marking a petroleum fuel comprising:
adding a marker to the petroleum fuel, the marker comprising a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
2. A method as claimed in claim 1, wherein the marker is a transition metal derivative of the substituted salicylic acid, the metal derivative being a 1:1 derivative having one molecule of the substituted salicylic acid bonded with one transition metal ion or a 2:1 derivative having two molecules of the substituted salicylic acid bonded with one transition metal ion wherein the salicylic acid is substituted with a linear hydrocarbon chain.
3. A method as claimed in claim 2, wherein the marker further comprises of substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain such that the ratio of substituted salicylic acid to transition metal ions in the range of 2:1 to 10:1.
4. A method as claimed in any preceding claim, wherein the linear hydrocarbon chain is a C6 to C23 hydrocarbon chain.
5. A method as claimed in any preceding claim, wherein the linear hydrocarbon chain is unsaturated with the degree of unsaturation between 1 and 3.

o. A method as claimed in claim 1 or 2 wherein the marker is any one of cashewnut shell liquid, saturated anacardic acid, anacardic acid enes, transition metal derivatives of saturated anacardic acid or anacardic acid enes or their mixtures.
7. A method as claimed in claim 5, wherein the saturated anacardic acid and anacardic acid enes is obtained from natural cashew nut shell liquid.
8. A method as claimed in any preceding claim wherein the petroleum fuel is kerosene, petrol or diesel.
9. A method as claimed in any preceding claim, wherein at least 10 ppm of the marker is added to the fuel.
10. A marker for petroleum fuels comprising:
a substituted salicylic acid wherein the salicylic acid is substituted with a linear hydrocarbon chain.
11. A marker for petroleum fuels as claimed in claim 10, wherein the marker is a
transition metal derivative of the substituted salicylic acid, the transition metal
derivative being a 1:1 derivative having one molecule of the substituted salicylic acid
bonded with one transition metal ion or a 2:1 derivative having two molecules of the
substituted salicylic acid bonded with one transition metal ion wherein the salicylic
acid is substituted with a linear hydrocarbon chain.

12. A marker for petroleum fuels as claimed in claim 11, further comprising of a substituted salicylic acid such that the ratio of substituted salicylic acid to transition metal ions in the range of 2:1 to 10:1.
13. A method for determining adulteration of a petroleum fuel comprising:
detecting the presence of a marker in the petroleum fuel by adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer; the marker a salicylic acid having a linear hydrocarbon chain substitution resulting in a change in colour in the organic layer, the change in colour of the organic layer indicating the presence of an adulterant in the petroleum fuel.
14. A method for detecting adulteration as claimed in claim 13, wherein the marker is any one of natural cashew nut shell liquid, saturated anacardic acid, anacardic acid ene, or their mixture.
15. A method for detecting adulteration as claimed in claim 13 wherein the transition metal acetate is any one of iron acetate, copper acetate or cobalt acetate.
16. A method for detecting adulteration as claimed in claim 13, wherein the amount of transition metal acetate added per liter of petroleum fuel is in the range of 20 to 5000 mg.

17. A kit for determining adulteration of a petroleum fuel by a fuel to which a salicylic
acid having a linear hydrocarbon chain substitution is added as a fuel marker
comprising:
a transition metal acetate; and
a set of instructions for detecting the presence of the fuel to which the fuel marker has been added; the instructions comprising:
adding an aqueous solution of a transition metal acetate to the petroleum fuel to obtain a reaction mixture having an aqueous layer and an organic layer; the marker a salicylic acid having a linear hydrocarbon chain substitution resulting in a change in colour in the organic layer, the change in colour of the organic layer indicating the presence of an adulterant in the petroleum fuel.
18. A kit as claimed in claim 17, wherein the marker is any one of cashewnut shell liquid, saturated anacardic acid, or anacardic acid enes or their mixtures.
19. A kit as claimed in claim 17, wherein anacardic acid or anacardic acid enes is obtained from natural cashew nut shell liquid.
20. A kit as claimed in claim 14, wherein the transition metal acetate is any one of iron acetate, copper acetate or cobalt acetate.
21. A method of marking a petroleum fuel substantially as herein described.
22. A marker for petroleum fuels substantially as herein described.

23. A method for determining adulteration of a petroleum fuel substantially as herein described.