m — 6i — 



of its specific gravity being too low, its optical rotation too high and its 

 evaporation residue insufficient. 



In contradistinction to this sample the evaporation residue of No. 8 

 (15,8 p. c.) was decidedly too high. Its liquid consistency, its insolubility 

 in hot alcohol and its quite abnormally low saponification value (37,5) 

 pointed to the presence of mineral oil. The insolubility of the oil in 

 90 p. c. alcohol is likewise traceable to the same addition. 



In the oil referred to in the 9 th column of the table no adulteration 

 could be detected and it is therefore not impossible that its inferiority 

 was due to the use in its manufacture, of inferior (waste) fruit. 



Lemon Oil. Lemon oil consists principally of terpenes and sesqui- 

 terpenes, bodies which are of slight importance so far as the odour of 

 the oil is concerned. These compounds are practically insoluble in 80 p. c. 

 alcohol, whereas the constituents of the oil which are valuable from the 

 odoriferous standpoint are readily soluble in the same alcohol. For this 

 reason, G. Patane 1 ) is of opinion that the determination of solubility 

 affords a valuable criterion for the estimation of the value of lemon oil, 

 and has based method of examination upon this property. He employs 

 two different manipulations. The first consists in shaking up at exactly 

 20° in a test-tube of 10 cc. capacity, graduated to 0,1 cc, equal quantities 

 of oil and of alcohol of a given strength. When the mixture has settled 

 completely, the degree of increase of the alcohol-layer is read off. The 

 second method consists in mixing equal quantities of oil and of alcohol 

 of a given strength in the test-tube and in warming them until they are 

 completely dissolved. The mixture is then allowed to cool under constant 

 stirring with a thermometer graded to one-tenth degrees, until clouding 

 ensues. When that moment arrives, the temperature is read off. Differ- 

 ences of temperature of 1 jio\h degree are sufficient to cause clouding. 

 All oils which have the same clouding-temperature show the same con- 

 ditions of solubility in the first test, so that it becomes possible to draw 

 up a comparative scale of clouding-temperature and solubility. If necessary, 

 it is sufficient to apply the second test only, which can be executed quickly 

 and at the same time is said to be very reliable. 



The addition of 10 p. c. of terpenes increases the clouding-temperature 

 Joy more than one degree, of 20 p. c. by about two degrees, and so on, 

 But with this difference that as the terpene-percentage rises the intervals 

 of temperature become smaller and smaller. Moreover, the relation between 

 citral content and solubility is said to admit of further deductions con- 

 cerning the condition of the oil. 



Great care must be taken with the alcohol to be used for the test, 

 because so slight a difference as one-tenth of a degree suffices to alter 

 the clouding-temperature of the alcohol. According to Patane it would 



1 ) Per un piu rationale apprezzamento delle essenze di limone. Acireale 1912. 



