1818.] the Commencement of the Year 1817. Part I. 35 



they yield a notable quantity of acid containing much oxygen 

 united to hydrogen and carbon. They usually contain gum. 

 Examples ; extract of liquorice, onion, squill, calaguala, polypo 

 dium, saffron, rhubarb, cachou, cassia, tamarinds ; rob of elder, 

 currants, &c. 



(5.) Oxygenized extracts, veiy bitter. — Their taste is bitter, 

 owing to the presence of a bitter principle associated with gum. 

 They are not acted on by nutgalls. When distilled, they yield 

 much acid, and no ammonia. Examples ; extract of gentian, 

 little centaury, quassia, &c. — (Jour, de Phys.lxxxiv. 267.) 



3. Oils contained in different Species of Corn. — It is well 

 known in this country that ardent spirits from unfermented 

 barley have a peculiar odour, distinguished on the Continent by 

 the name of J ousel. — It has been the general opinion, since the 

 time of Scheele, that this odour is owing to the presence of a 

 peculiar oil. In the year 1804, I obtained from barley, by 

 digesting it in alcohol, a yellow, solid oil, possessed of exactly 

 the flavour that distinguishes spirits from unmalted barley, and 

 communicating that flavour to any spirit in which it was 

 dissolved, I concluded that the odour was owing to this oil, 

 which exists ready formed in barley. Some years after, Four- 

 croy and Vauquelin extracted the same oil from barley, and 

 drew the same conclusion (Ann. du Museum d'Hist. Nat. vii. 7). 

 Gehlen described the properties of this oil at still greater length 

 (Journal, i. 277 ; New Series). Schrader has lately extracted a 

 yellow oil from rye by the same process. This oil was of the 

 consistence of butter; but was distinguished by no peculiar 

 taste or smell, and had nothing similar to the flavour of j ousel 

 (Bibl. Univers. iv. 266). It is probable that eveiy species of 

 corn contains an oil in greater or smaller quantity ; but no doubt 

 the flavour which it communicates to spirits will differ with the 

 oil. I think it extremely probable that if the distillation be 

 conducted at too high a temperature, the nature of the oil may 

 be altered, and its flavour greatly heightened, and rendered more 

 disagreeable. I found it easy to distil the alcohol from this oil 

 in a retort. Hence it is not very volatile. In all probability, 

 then, manufacturers might succeed in obtaining their spirits free 

 from all admixture of oil, and consequently without any peculiar 

 odour, if they were to conduct their distillation at a lower tem- 

 perature by means of a vacuum. Some such method would 

 probably improve the flavour of spirits prodigiously, and render 

 the importation of foreign spirits unnecessary. 



4. Vegetable Milk. — It is sufficiently known that the milky 

 juices of European vegetables have all an acrid or narcotic 

 quality. But in South America M. de Humboldt observed a 

 tree which yielded a milky juice destitute of these qualities, 

 and employed by the natives as a nourishing article of food. 

 This tree was called in the country cow-lrec, and the milk of it 

 on standing formed a film on the surface resembling in its pro- 



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