280 Chemistry. [Lecture 34. 



silver and acetat of lead will precipitate it from 

 the infusions in which it is contained. 



7. The narcotic principle is also contained in 

 many plants ; as Jthe white poppy, which fur- 

 nishes that well-known narcotic drug, opium. 

 It abounds also in the deadly nightshade, and 

 the foxglove; and most of the plants which have 

 a milky juice contain a portion of it, such as the 

 garden lettuce, &c. 



Opium, however, does not consist altogether 

 of the narcotic principle. It contains also resin 

 and extractive matter. By repeated solution in 

 water, and afterwards in alcohol, to take up the 

 resin, the narcotic principle may be obtained 

 pure in the form of white crystals. It is rather 

 more powerful than opium ; but its bad effects, 

 as well as those of opium, may be counteracted 

 by swallowing vinegar. 



8. The acids have been already treated of in 

 the lecture on Salts. 



9. Starch is a well known substance. It is 

 usually obtained from wheat flour, which con- 

 sists entirely of starch and gluten. It is, how- 

 ever, a principal constituent in all kinds of grain, 

 and also in the farinaceous roots, as the potatoe, 

 the orchis, the sago plant, Sec. Barley consists 

 almost entirely of starch. " In the process of 

 malting, which is causing the barley to begin to 

 vegetate, a great part of the starch is converted 

 into sugar. During this process oxygen is ab- 



