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KN'OW'LKDGR 



December, 1912. 



ti{,'Iinat<' (11., 

 gcraiiimu. 



(11 : C 



CU, 



coo-c. 



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(.5) Of frequent orcurrcncc in volatile oils are the 

 following phenols: — eugenol C,„ H,2 ().j. thymol and 

 rarvacrol. 



The relations of the latter two to each other and 

 to cymene (i)-methylisopropyl benzene) are expressed 

 hv the followintr formulae:— 



CH» 



.CVi, 



CHa 



XH' 



CH' 



CH. 

 Cymene. 



CH:, 



Thvinol. 



CH:, 



CH' 



CH. 

 Carvacrol. 



(4) Of this class 

 the following alde- 

 hydes constitute a 

 large percentage 

 of many volatile 

 oils : — cin n a ni ic 

 aldehvde, Ci.H-, 

 (CH :"("H ■(■ HOi. 

 be n z a 1 (I (■ li \ d c . 

 CfiHr, -CHO,' and 

 anise aldeliydr. 

 (aubepine) C',, H , 

 (OCH.,) (CHO), 

 while the ketones 

 arc represented by 

 pulegonc (C,„H,bO) 

 in the oil of pennv- 

 royal. Table 50 

 (see page 457) will 

 show how the con- 

 st it uentsof the essen- 

 tial oils remain fairh- 

 constant throughout 

 each natural order, and will indicate the occurrence 

 of the \arious chemical substances above mentioned, 

 in their respective oils. The letters in brackets 

 after the names of the constituents refer to the 

 particular groujis of chemical compounds to whicli 

 the latter belong. 



cY &■ Co. 

 4S4. 

 A huge still of tifty tliousand' gallons 

 capacity. 



I -Tcrpenes. 



S — Susqiiilerpenes. 



.'\ — Alcohol derivatives of terpenes. 



Al— Aldehydes. 



K — Ketone derivatives of the terpenes. 



ICn — Produced by enzyme action. 



D — Aldehyde derivatives of the terpenes. 



K — Esters. 



G — Alcohols of the Geraniol series. 



When we consider the high 

 prices reached by some of the 

 essential oils, Otto de Rose at 

 the present time almost attaining 

 seventj- shillings per ounce, it is 

 evident that they offer great 

 temptation to the manufacturers 

 and dealers to impoverish them 

 bv adulteration or partial removal 

 of \aluahle odoriferous con- 

 stituents. The usual adulterants 

 are alcohol, terpenes, fixed oils 

 and resins. The presence or 

 absence of all of these sub- 

 stances may usually be ascer- 

 tained by the odour of the oils 

 and by the determination of 

 their ph\'sical and chemical con- 

 stants, the figures so obtained 

 being compared with those 

 generalK- accepted for a genuine 

 oil. 



The methods of examination 

 mav be divided into the following 

 classes ; 



A roc 



Figure i 

 tho Distillery of Messrs. Schimmel & Co., the largest in 



the world. 



(1) Physical. 



(2) Chemical. 



Concerning the 

 former, the routine 

 operations consist of 

 the determination of 

 tlie si)ecific gravitv 

 and other constants, 

 such as the optical 

 rotation, refractive 

 iiuicx. anil solubilit\' 

 in a given solvent. 

 The congealing (or 

 melting) point, 

 residue on evapora- 

 tion, and the be- 

 liaviour of the oil on 

 fractional distilla- 

 tion also ofTer 

 \aluable clues as to 

 any sophistication. 



The specific 

 gravit\' is usually 

 mall aiijiaratus known 



determined at 15-5" C in 

 as the Sprengel tube. 



This tared tube (see Figure 490) is filled up to the 

 mark on the larger limb at the specified temperatme. 

 weighed, and the specific gravity calculated by 

 deducting the weight of the tube and dividing the 



