ORANGE. 441 



devise such a process, the vahie of the oil depending exchisively 

 upon the proportion of citral present in it. Although the aroma 

 of citral appears (in consequence of its enormous concentration) to 

 vary somewhat from that of Lemon oil, it will be found, on diluting 

 it to its corresponding strength, that there is no longer any 

 difference between it and Lemon oil, either in odour or in taste. 

 The action of concentrated sulphuric acid on " citrene " lias been 

 studied by Bouchardat and Lafont.* 



It is greatly to the interest of consumers to secure the oils 

 which are jprejpared during the first two months of the harvest, 

 i.e., November and December, experience having shown that the 

 first oils of the season are of a better quality than those obtained 

 from later-matured fruit. Also the fruit itself which is gathered 

 in November and December is preferred in commerce to that which 

 is collected later on. 



Vol. I., p. 76. 

 Orange oil, sweet. As this oil consists chiefly of the 

 strongly dextrogyre limonenes, and the adulterations are chiefly 

 practised wdth turpentine oil, the method of examination in this 

 case also is based upon the determination of the two important 

 physical properties — specific rotatory power and specific gravity- 

 The rotatory power of pure oils has been determined as + 97^20' 

 or at least + 95*^ in a 100 m. m. tube, and their sp. gr. 

 0"850 at 15^ C. If turpentine be added to such an oil the rotatory 

 power will naturally decline and the sp. gr. increase. Thus, an 

 examination being made of a suspected sample, the specific rotatory 

 power was found to be + 65^20', and the sp. gr. at lo*^ C. 0-856, 

 data which indicated gross adulteration with turpentine ; in 

 confirmation of this, the turpentine was separated out and 

 identified. During the distillation 50 per cent, of the oil came 

 over below 170''', that is to say, much below the boiling point of 

 Limonene, the chief ingredient of genuine oils. By repeated 

 fractional distillation a considerable quantity of almost pure Pinene 

 was recovered from the oil. It possessed the following 

 properties : — 



Boiling point 158^-162^ C. 



Specific gravity 0861 at 15^ C. 



rotatory power + 6'^40 ' (100 m. m.) 



* Journ. de Pharm., xxvii. (1893), p. 49. 



