124 THE SIMPLER NATURAL BASES 



B. SPECIAL METHODS. PROPERTIES OF INDIVIDUAL BASES AND 



OF THEIR SALTS. 



4 



Bases Volatile with Steam. 



Methyl-, dimethyl-, and trimethylamine, isobutyl- and the amyl- 

 amines can all be readily distilled by passing steam into their alkaline 

 solutions. The last two can be separated from the others by extract- 

 ing an alkaline solution with chloroform or ether and distilling ; 

 isobutylamine boils at 68, isoamylamine at 95. 



The separation of the first three bases from one another can be 

 accomplished in various ways. Delepine [1896, Ch. I] dissolves the 

 mixture of their salts in cold concentrated formaldehyde solution. 

 An equal volume of potassium hydroxide is added and the solution 

 is distilled. Trimethylamine passes over as such, dimethylamine 

 forms CH 2 [N(CH 3 )J 2 and CH 2 (OH)N(CH 3 ) 2 , b.p. 80-85, and 

 monomethylamine yields (CH 2 : NCH 3 ) 2 , b.p. 166. 



For the quantitative determination of trimethylamine and ammonia, 

 Budai (Bauer) [1913] has worked out a titration method with for- 

 maldehyde. The neutral aqueous solution of the mixed hydrochlorides 

 is treated with an excess of formalin (10 c.c.), previously neutralised 

 to phenolphthalein. The solution is then titrated with standard 

 potassium hydroxide until pink with phenolphthalein ; this gives the 

 amount of ammonia present. The solution, together with the hexa- 

 methylene tetramine formed from the ammonia, is strongly acidified 

 with concentrated hydrochloric acid and boiled down to one-third of 

 its original volume. It is then distilled with excess of potassium 

 hydroxide. This gives ammonia + trimethylamine ; the latter is 

 estimated by difference. 



The quantitative separation of ammonia, mono-, di-, and 

 trimethylamine is carried out by processes due to Bresler [1900], 

 Bertheaume [1910, i, 2], and Francois [1907, I, 2] and is chiefly based 

 on the fact that trimethyl- and dimethylamine hydrochloride alone are 

 soluble in boiling chloroform. 1-2 grm. of the mixed hydrochlorides 

 are dried at 1 10, weighed out, dissolved in a little very dilute hydro- 

 chloric acid, mixed with at least 20 grm. of pure silver sand, dried in 

 vacuo over sulphuric acid, and extracted with hot chloroform in a 

 small funnel tube over glass wool. 



The chloroform is evaporated, the residue is weighed and dis- 

 solved in 2000 parts of water ; 200-300 c.c. of the solution are 

 measured, cooled to o and for every 100 c.c. of solution taken, at least 

 30 c.c. of an ice cold solution of 127 grm. of iodine and 15 grm. of 

 potassium iodide in 100 c.c. of water are added. After one hour the 



