313 



QUESTIONS. 



418. "What two methods of classifying organic bodies may be pursued? 

 Give the scientific classification in seven groups. 419. What is said of the 

 compounds of hydrogen and carbon as to number and variety ? How do 

 these isomeric bodies differ in constitution ? Name some of the hydro- 

 carbons of the Ethylene Series. 420. Explain the terms homologous and 

 isologous. 121. Show how bodies are formed by substitution. What is 

 CHC1 3 ? What is hydroxyl? 422. Show the relation between alcohols 

 and hydrocarbons. Explain, taking common alcohol as an illustration. 

 423. What are ethers ? 424. What are the relations of acids to alcohols ? 

 Illustrate with acetic acid. 425. Whence are amines derived ? How ? 

 How is ethylamine practically prepared? How theoretically derived? 

 What important constituents of plants belong to this class of bodies ? 

 426. What is said of zinc-ethyl? 427. What are the divisions of organic 

 analysis ? Illustrate. Explain briefly the method of ultimate analysis. 



CHAPTER XXV. 



CONSTITUENTS OP PLANTS, ETC. 



428. Variety of Vegetable Substances. There is a great 

 variety in the substances which are produced in plants. 

 They are wood, starch, gums, gluten, fatty substances, vola- 

 tile oils, coloring matters, alkaloids, etc. Then from many 

 of these are developed other compounds. A very wide 

 field is thus opened ; and, numerous as are the valuable 

 combinations already discovered, we know probably but 

 little as yet of the extent of the discoveries which are to 

 be made in this field. Stockhardt says on this point: 

 " Thousands of such new combinations have been discovered 

 within the last twenty years ; our posterity will probably 

 count them by millions." 



Of the products of vegetation, there are some which are 



O 



