160 METHODS OF ANALYSTS. 



2. Alcohol. 



Dilute 50 cc of the extract, measured at 15.6 C., to 200 cc, place the flask in a 

 centrifuge and run until the oil separates in a clear layer at the top ; then make 

 up to the mark, using the lower meniscus of the oil. Pour the mixture into a dry 

 Erlenmeyer flask containing 5 grams of light carbonate of magnesia, stopper, 

 shake well, and filter quickly through a large, dry, folded filter. Determine the 

 alcohol in 150 cc of the filtrate as directed under "XV. Distilled Liquors," 

 page 95. 



3. Glycerol. 

 Proceed as directed under " XIII. Wine," on page 83. 



4. Lemon Oil. 

 (a) BY POLARIZATION (MITCHELL). 



Polarize the extract without dilution in a 200-mm tube at a temperature of 

 20 C., using the S. and H. sugar scale. Divide the reading by 3.2 and, in the 

 absence of other optically active substances, the result will be the percentage 

 of lemon oil by volume. 



A small amount of cane sugar is occasionally present, being used to facilitate 

 solution of the oil. In such cases determine it as directed under sucrose and 

 correct the reading accordingly. 



(b) BY PRECIPITATION (MITCHELL). 



Pipette 20 cc of the extract into a Babcock milk bottle ; add 1 cc dilute hydro- 

 chloric acid (1:1); then add from 25 to 28 cc of water previously warna-d at 

 60 C. ; mix and let stand in water at 60 for 5 minutes; whirl in centrifuge 

 for 5 minutes; fill with warm water to bring the oil into the graduated neck 

 of the flask; repeat whirling for 2 minutes; stand the flask in water at 60 C.| 

 for a few minutes and read the per cent of oil by volume. In case oil of lemon 

 is present in amounts over 2 per cent add to the percentage of oil found 0.4 per 

 cent to correct for the oil retained in solution. If less than 2 per cent and 

 more than 1 per cent is present, add 0.3 per cent for correction. 



When the extract is made in accordance with the United States Pharma- 

 copoeia, the results by the two methods just given should agree within 0.2 per 

 cent. 



To obtain per cent by weight from per cent by volume, as found by either of 

 the above methods, multiply the volume percentage by 0.86 and divide tl 

 result by the specific gravity of the original extract. 



Negative results by the above methods are conclusive as to the absence of 

 lemon oil. Positive results, however, should be confirmed by determining the 

 physical constants of the precipitated oil. 



5. Refraction of Precipitated Oil. 



Determine the refractive index of the precipitated oil as directed unil-r 

 -XIX. K.liblr Oils ami Fats/' page 131. 



Limonene and most commercial adulterants give a higher reading than lemon 

 >il. with the exception of citronella aldehyde and oil of turpentine. 



J. Amer. Chem. Soc., 1S99, 21:1132. 



