— 58 — 



results, the residue of evaporation being increased by 1,7° and its saponi- 

 fication number by 94,7. 



Now, applying the result of these observations to the two samples 

 under consideration, and assuming the average sap. no. of the residue of 

 evaporation of a pure oil at 160, No. I will be found to show an excess 

 of 261,9— 160= 101,9. We have seen that the addition of 1% triethyl 

 citrate increases the sap. no. of the residue of evaporation by 47,7, and 

 from this we may infer that the proportion of adulterant added to the two 

 oils in question was about 2°/ . If we consider that 1 g. triethyl citrate 

 requires for its saponification the same quantity of potash as does 2,13 g. 

 linalyl acetate, it follows that the 2% of citric acid ester raise the linalyl 

 acetate content of bergamot oil apparently by 4,3%, which is sufficient, 

 in certain circumstances, to render an oil which is really poor in ester 

 to all appearance one of fair merchantable quality. 



The remarkable behaviour of the two oils when saponified also 

 deserves notice. Pure bergamot oils give quite clear solutions with alco- 

 holic potash liquor, but in the case of the oils adulterated with citric acid 

 ester turbidity was clearly perceptible, especially at the commencement 

 of the process of saponification. This was due to the separation of citrate 

 of potash, which is sparingly soluble in alcohol. 



Apart from the fact that we had isolated the citric acid direct from 

 the oils, we also traced the adulteration by the calcium chloride test, as well 

 as by Deniges' 1 ) method, by converting it into acetone dicarboxylic acid 

 and isolating the mercury double-compound of this acid. For this purpose 

 we used the oils themselves as well as their residues of evaporation. We 

 made the test by saponifying about 2 g. of the oil, or the residue of 

 evaporation of 5 g. of oil, with alcoholic potash, diluting the solutions with 

 water, neutralising with hydrochloric acid, removing the alcohol on the 

 water-bath and then extracting the solutions with ether and filtering. For 

 the calcium test the solutions are rendered faintly alkaline with a trace 

 of soda liquor, after which a few drops of concentrated chloride of calcium 

 solution is added and the whole boiled. Any citric acid which is present 

 then reveals itself by a precipitate, which is often formed only after some 

 lapse of time. 



Deniges' test consists in vigorously shaking 10 cc. of the solution 

 with 1 to 1,5 g peroxide of lead, adding 2 cc. solution of mercuric 

 sulphate-) and filtering. Of the filtrate, 5 cc. is heated to boiling point, 

 after which a 2°/o solution of permanganate of potassium is added by 

 drops, under stirring, until the latter ceases to discolor immediately. If 

 citric acid is present a flocculent, white or pale yellow precipitate shows 

 itself after the first drop. 



x ) Bull. Soc. ph. de Bordeaux 1898, 33; quoted from Chem. Zentralbl. 1898, II. 135. 

 '-) To be prepared from 5 g. oxide of mercury, 20 cc. concentrated sulphuric acid, and 

 100 cc. water. 



