Dkcembhr, 1912. 



KNOWLEDGE. 



459 



remainder by tlio weight of an equal 

 \olume of water at the same 

 tem[)erature. 



The o[)tical rotation is usually 

 determined by means of the modern 

 half-shadow polariscope in a tube 

 one hundred millimetres long, while 

 the refractive index is found 

 preferably b}' means of an Abbe 

 refractometer, fitted with a constant 

 temperature arrangement. 



Fractional distillation is conducted 

 in a Ladenburg flask, illustrated by 

 F"igure 488, and the solubility determination in a 

 stoppered and graduatetl glass cylinder, having a 

 cajjacitv of ten cubic centimetres. 



The chemical quantitative methods of testing 

 applied to the anahsis of essential oils are exceedingly 

 numerous, so that only a few of the most typical and 

 generally employed will be referred to. 



These consist of the estimation of esters, free 

 alcohols, and other well-defined constituents, such 

 as phenols and aldehydes. 



The principle of the determination of esters 

 depends upon their being liydrolysed by boiling with 

 alcoholic potash, according to the equation : — 



RA + KOH = R5)H + KA 

 Where R is the alkyl and A the acid radicle. 



The quantitative analysis of oils containing free 

 alcohols consists of converting the latter into their 

 acetyl derivatives by boiling with acetic anhydride, 

 and saponifying the separated product by boiling 

 with a standard solution of alcoholic alkali as repre- 

 sented bv the above equation. Many constituents of 

 the volatile oils, which are practically quite insoluble 

 in water, readil\- form soluble compounds with solu- 

 tions of inorganic bodies. Aldehydes, for example, 

 are dissolved by sodium hydrogen sulphite, and 

 phenols by potassium hydroxide solution. The 

 residual oil, non-aldehyde or non-phenol, as the case 

 may be, is left floating upon the aqueous solution, 

 and may be estimated by bringing it into the gradu- 

 ated neck of the special flash used for this purpose, 

 by adding more of the aqueous solution, or of water, 

 and reading the volume of the oil there indicated. 

 One of these so-called " Cassia " flasks, usually 

 made of two hundred cubic centimetres capacity, 

 with the neck graduated from • 1 

 to ten cubic centimetres, is seen 

 in Figure 489. 



As the perfume industry is 

 dependent upon products of the 

 animal as well as the plant world, 

 we will now, therefore, consider 

 the sources and properties of a 

 few animal and artificial substances 

 used in the art. 



Of the former articles, musk 

 ranks first in importance, but 

 mention will also be made of 

 ci\et and ambergris. These 



JOooDOQaqonmqq, 



ionooonQ3onoap.nr) 



Figure 486. 

 Oleo-resin duct of Piniis. 



Figure 487. 

 Lysigenous cavity in the pericarp of the 

 orange, containing a drop of ethereal oil. 



materials are. properly S|)eaking, 

 not perfumes, but, by their special 

 characteristics, c.^'., their persistent 

 but not sweet odour, serve to " fix," 

 as it is technicall}- termed, other 

 odours which are too delicate and 

 tlccting. Indeed, in many cases 

 these products possess a very 

 disagreeable smell, as thev are 

 frequentl)- in a state of [lartial 

 decomposition. 



Musk is a ver\- valuable sub- 

 stance obtained from the preputial 

 follicles of the musk deer (Moscliits mosclii/cnr), 

 a graceful animal inhabiting Central Asia. The 

 males bear a small sac, containing the soft, 

 unctuous and granular secretion which possesses 

 a penetrating ammoniacal odour. Civet, another of 

 the above-mentioned animal products, is obtained 

 from the perineal glands of the civet cat (Viverra 

 civetta) and other species of Viverra (Natural Order 

 Carnivora). It is imported from Africa and the 

 West Indies. The animal is a domestic one ami 

 the natives extract, usuall\- twice a week, the secretion 

 from the glands, and place it in the horns of 

 buffaloes, in which form it is usually seen in com- 

 merce. Its strong characteristic odour somewhat 

 resembles that of musk, and in a state of great 

 dilution the article is advantageously employed to 

 modify other essences and perfumes. The remaining 

 substance of animal origin. Ambergris, concerning 

 which many theories are afloat, is a product of the 

 sperm \\\ia\e.{Physeter mac rocepli al ii s) ,a.nd is believed 

 to be the indurated faeces, probably somewhat 

 altered by disease. It is an opaque, greyish, 

 striated solid of irregular shape and friable 

 nature, found floating in large masses at various 

 times on the surface of the sea near Madagascar 

 and Japan. With increased knowledge and 

 insight into the constituents of odorous plants 

 it has become possible to isolate numerous 

 important active ingredients : and the science of 

 organic chemistry in one of its important branches 

 has been and is directed to producing naturally 

 occurring plant and animal principles by synthetical 

 methods. The more important isolated odorous 

 constituents of plants include vanillin, from 

 the vanilla pod, and coumarin, from the tonquin 

 bean. Both these principles 

 are now produced by synthetical 

 methods : vanillin (Q H, (C O H) 

 (O C H3) (O H)), from the glu- 

 coside coniferin (CiGH„.,Ort+2H20), 

 and coumarin (CgHgOj), the 

 f?-lactone of coumarinic acid, 

 from salicvlic aldehyde CgHj (OH) 

 (CHO). 



Chemical compounds without 

 nimiber are now prepared for use 

 in the manufacture of perfumes ; 

 but only those of definite con- 

 stitution will be mentioned. 



