lO ORGANIC AGRICULTURAL CHEMISTRY 



tubes. Heat the tube slowly and thoroughly until all the gas is 

 evolved. Collect three or four bottles or tubes of gas. (b) While 

 the gas is generating freely insert a glass jet at the end and ignite 

 the gas, and repeat Experiment I, i, ^. c. d. 



(2) (a) Bring a flame to the mouth of one of the bottles of gas. 



(b) Mix one bottle with an equal volume of air and ignite the mixture. 



(c) Mix one volume of gas with ten volumes of air and ignite. 



(d) Mix one volume of dry gas with two volumes of dry chlorine gas 

 and ignite. Note character of flame and residue of carbon in the 

 bottle after ignition. After ignition add a little water to the bottle 

 and shake. Test water in bottle for hydrochloric acid, (e) Mix oite 

 volume of dry gas with two and one half volumes of dry chlorine gas. 

 Allow the mixture to stand in the light for several days. Test for 

 hydrochloric acid and examine for carbon residue. {Note. — These 

 last two experiments are better performed in the lecture room. If 

 they have been done there omit, but write up the results in the note- 

 book.) 



SUBSTITUTION 



For the most part the hydrocarbons are characterized as 

 inactive compounds. This is indicated by the name given to 

 those similar to methane, viz. paraffins, from " parum af- 

 finitas,'* little affinity. This property of inactivity shows itself 

 toward almost all ordinary reagents, such as acids, alkalies, 

 oxidizing and reducing agents, etc. Toward only one group 

 of elements does methane show any reactivity. The halogen 

 elements, chlorine and bromine, do react with methane when 

 brought in contact with it. 



When chlorine reacts with methane suddenly at high tem- 

 peratures, as when a mixture of the two gases is ignited, the 

 methane is decomposed and all of the hydrogen unites with the 

 chlorine, forming hydrogen chloride, and the carbon is left free. 

 (See Exp. II, 2, d.) This is represented by the following re- 

 action : 



CH4 + 2 Cl2->C + 4HCI 



Methane 



If, however, the action takes place slowly, as in case a mixture 

 of the two gases is allowed to stand in diffused light, then 



