148 CHEMISTRY FOR AGRICULTURAL STUDENTS 



conifers, and in most of the volatile oils of plants, are hydrocarbons having 

 the formula QoHig. Benzene, Cgllg, is the first member of an important 

 series, having the general formula CnHan-s ; while naphthalene and 

 anthracene are the starting-points of a series of hydrocarbons containing a 

 still larger proportion of carbon. 



XXXI. THE ALCOHOLS: FERMENTATION 



Dissolve 150 grams of sugar in a liter of water, place the solu- 

 tion in a flask fitted with a cork and delivery tube as figured, 



Fig. 49. 



and add a few grams of yeast. Note that fermentation soon 

 commences, and a gas is given off which, if collected in a test- 

 tube or cylinder, will be found to extinguish a taper, and to 

 render lime water milky. Keep the apparatus in a warm place 

 for a few days, — a temperature of 25° to 30° C. will be found 

 most favourable, — then, if evolution of gas has ceased, replace 

 the delivery tube by a Liebig's condenser, and distil the mix- 

 ture from a water bath, keeping the whole flask covered with a 

 cloth to aid the process. Note that the alcohol thus obtained 



