Tests for Oil: The simplest test for suspected oil stains in a rock is by 

 fluorescence under ultraviolet light, provided, of course, that a fluoroscope is 

 available. If fluorescence is not obtained with a dry chip, it should be immersed 

 in ether or carbon tetrachloride for a few minutes and re-examined in the 

 ultraviolet light. Some minerals have characteristic fluorescence under ultra- 

 violet light. One must be sure that the fluorescence observed is actually from 

 the oil stains and not from certain minerals. Chips having no visible stains 

 should be compared with those that are stained. 



A delicate test for soluble hydrocarbons is as follows (C.P. acetone and 

 distilled water are the reagents) : 



Select a few stained chips and mash them to about match-head size. Blow 

 the dust away so that it will not interfere with the test. Place the broken chips 

 in a small test tube half filled with acetone, and shake the tube for a few 

 minutes. Filter into a clean tube. Add a few drops of distilled water and shake 

 again until thoroughly mixed. If hydrocarbons are present, even in very small 

 quantity, the solution will become milky, and the density of the cloudiness is 

 an indication of the amount of hydrocarbon present. 



In cases of very faint cloudiness, compare the test solution with a similar 

 tube containing only acetone. Hold the two tubes side by side against a dark 

 background. 



Hydrocarbons are more soluble in one solvent than another, depending on 

 the nature of the hydrocarbon. When ether or carbon tetrachloride is used, the 

 following procedure is recommended: 



In addition to the solvents, only chemical watch glasses are needed. Make 

 certain that the watch glasses are completely free of oil or grease by cleaning 

 them with the solvent and paper cleansing tissue. 



Place a few stained chips on the watch glass and add sufficient solvent to 

 cover the chips. Stir the chips with a glass rod or needle to agitate the solvent. 

 Do not use a match stick for this purpose; it may contain some oil. Allow the 

 solvent to evaporate completely. Now examine the watch glass under the 

 microscope for residual oil rings on the glass. Weak stains leave only a ring 

 of oil film; strong stains leave rings composed of minute globules of oil. 



It is difficult to detect light-colored oil stains in similarly colored dolomites, 

 and solvents may not reaily remove the oil from impermeable rocks of this 

 type. If the solvent tests fail to give a satisfactory answer to the problem, 

 proceed as follows: 



Break or grind the rock into fine particles and dissolve in pure, dilute 

 hydrochloric acid in a clean dish. When the material is completely in solution 

 and the reaction has ceased, examine the acid under the microscope. If oil is 

 present in appreciable quantity, a residue film will accumulate on the surface 

 of the acid. 



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