XX] FLAVORING EXTRACTS 265 



standard laevo-rotatory quartz plates, or by the use of a 25 mm. tube. The true 

 rotation cannot be obtained by diluting the oil with alcohol and correcting the 

 rotation in proportion to the dilution. 



CITRAL. 



Kleher Method^. — Tentative. 



35 REAGENTS. 



(a) Phenylhydrazin solution. — Prepare a 10% solution in absolute alcohol. A 

 sufficiently pure product can be obtained by distilling the commercial article, 

 rejecting the first portions coming over which contain ammonia. 



(b) N/2 hydrochloric acid. 



DETERMINATION. 



36 



Weigh 15 grams of the sample into a small, glass-stoppered flask; add 10 cc. of the 

 phenylhydrazin solution. Allow to stand 30 minutes at room temperature, titrate 

 with N/2 hydrochloric acid, using either methyl or ethyl orange as an indicator. 

 Titrate similarly 10 cc. of the phenylhydrazin solution. The difference in the num- 

 ber of cc. of N/2 acid used in these 2 titrations, multiplied by the factor 0.076, gives 

 the weight of citral in the sample. If difficulty is experienced in detecting the end 

 point of the reaction, titrate until the solution is distinctly acid, transfer to a sepa- 

 ratory funnel, and draw off the alcoholic portion. Wash the oil with water, adding 

 the washings to the alcoholic solution, titrate back with N/2 alkali and make the 

 necessary corrections. 



37 Hiltner Method^.— Tentative. 



Weigh 2 grams of lemon oil or 8 grams of orange oil into a 100 cc. graduated flask, 

 dilute to the mark with 95% alcohol by volume and proceed as under 25, using 

 2 cc. of the dilute solution for the comparison. 



TOTAL ALDEHYDES. 



38 Chace Method. — Tentative. 



Weigh a small quantity of the sample into a small, stoppered flask and dilute 

 with aldehyde-free alcohol in the proportion of 2 grams of lemon oil or 4 grams of 

 orange oil to 100 cc. of solution. Determine the total aldehydes as directed under 

 23, expressing the result as citral. 



39 PHYSICAL CONSTANTS OF THE 10 PER CENT DISTILL ATE". -TENTATIVE. 



Place 50 cc. of the sample in a 3-bulb Ladenburg flask having the main bulb 6 

 cm. in diameter and of 120 cc. capacity and the condensing bulbs of the following 

 dimensions: 3.5 cm., 3 cm., 2.5 cm.; the distance from the bottom of the flask to 

 the opening of the side arm should be 20 cm. Distil the oil at the rate of 2 cc. per 

 minute until 5 cc. have been distilled. Determine the refractive index and rotation 

 of this distillate as directed in 33 and 34. 



40 PINENE. 



Chace Method^. — Tentative. 



Mix the 10% distillate, obtained in 39, with 5 cc. of glacial acetic acid; cool the 

 mixture thoroughly in a freezing bath and add 10 cc. of ethyl nitrite. Then add 



