METHODS OF ANALYSIS USED. 



17 



SIGNIFICANCE OF ODOR, COLOR REACTIONS, AND BEAD. 



Straight wood turpentines are readily distinguished from gum tur- 

 pentines by their odor, or when they have been very carefully refined, 

 by the odor of the first fraction, or of the residue from fractional dis- 

 tillation. One or both of these portions have the peculiar " sawmill 

 smell," and fche residue has a camphoric and somewhat nauseating 

 odor characteristic of wood turpentine, which is quite different from 

 the mild, sweet fragrance of gum turpentine. 



Destructively distilled wood turpentine and also rosin spirits are 

 more readily distinguished from gum spirits by their odor than is wood 

 turpentine prepared by steam distillation, and they also give distin- 

 guishing color reactions when mixed with sulphurous acid as sug- 

 gested by Hertzfeld or with hydrochloric acid (the presence of tin 

 or zinc is not necessary) as suggested by Grimaldi. When steam- 

 distilled wood turpentine has been carefully refined so that 90 to 95 

 per cent of it distills at from 155 to 170C. (311 to 338 F.), both of 

 these color tests are practically useless. 



Turpentine adulterated with more than 10 to 20 per cent of coal-tar 

 oils, or of gasoline or kerosene which have not been deodorized, may 

 usually be readily detected by the characteristic odor of the mixture. 

 The odor of rosin spirits, while quite distinctive, is difficult to detect 

 in mixtures with turpentine. The presence of petroleum oils is also 

 indicated by bubbles or "beads" persisting for a few moments on 

 the surface of the turpentine shaken in a partly filled bottle. 



The presence of more than about 10 per cent of kerosene or similar 

 mineral oils is readily detected by the spot which a few drops of the 

 sample placed on white paper leaves on drying. Gasoline and other 

 light mineral oils do not leave this spot. 



MINERAL OIL. 



It is possible so to adulterate turpentine that neither the specific 

 gravity, refractive index, or flash point is materially altered. Such 

 careful adulteration is, of course, very rare, but as adulterants can 

 not invariably be detected by making these determinations, and 

 further, as mineral oil is the most probable adulterant, it is more 

 rational to at once polymerize the suspected sample, note the volume, 

 color, and consistency of the unpolymerized residue, and determine 

 its refractive index. 



The detection of mineral oils in turpentine is relatively quite simple, 

 and is accomplished by mixing the turpentine with a certain propor- 

 tion of sulphuric acid of a given strength, in which the turpentine is 

 destroyed and mixes with the acid while most of the mineral oil 

 remains unaffected and separates in a layer on top of the acid. The 

 polymerization or sulphonation of turpentine, as this operation is 

 72457 Bull. 13511 3 



