90 A MODIFICATION OF THE ADAMS METHOD 



to the top of the condenser is attached a tube leading under 

 a slush of ice and water, this methyl iodide can be recovered. 

 Of course the tube must have in it a trap — preferably a Bunsen 

 valve — to prevent water from being drawn back into the 

 apparatus. 



THE PREPARATION OF METHYL IODIDE 



Methyl iodide is the only one of the series prepared with 

 this apparatus by the writer. The details of the method used 

 are given here for the sake of completeness, though they are 

 largely adapted from the directions given by Adams and 

 Voorhees. 



In the reaction flask put 1600 g. of absolute methyl alcohol, 

 200 g. of yellow phosphorus and 240 g. of red phosphorus. The 

 absolute methyl alcohol can be conveniently prepared by add- 

 ing magnesium turnings and a few crystals of mercuric chloride 

 to the technical alcohol. After refluxing, distill using a good 

 fractionating column. Any acetone present is reduced during 

 the formation of magnesium alcoholate, and the alcoholate 

 reacts with the water present. Fill the separatory funnel A 

 with 2 kg. of iodine, being careful not to let crystals fall below 

 the perforated platinum foil. Set up the rest of the apparatus 

 and open both stopcocks C and G. Heat the oil bath to 100° 

 C. At first alcohol distills, is condensed and flows back into 

 the reaction flask through the iodine container. When the 

 iodine solution begins to enter the flask, partly close stopcock 

 G so that the reaction proceeds not too violently. After some 

 methyl iodide is formed, it, being more volatile than the alco- 

 hol, acts as the solvent for the iodine. The temperature of the 

 bath is then lowered to about 70-75° C. The flow through 

 stopcock G at this point has to be further cut down because 

 iodine is more soluble in methyl iodide than in methyl alcohol. 



When all the iodine has been dissolved, close both stop- 

 cocks, with a rotary motion lower the separatory funnel and 

 fill with a second charge of 2 kg. of iodine. Raise the separatory 

 funnel to its former position. Open stopcock C wide, then 

 stopcock G part way as before. 



