— n8 — 



be thoroughly removed (distilled and kept over barium oxide). According 

 to Oddo 1 ), pyridine forms with magnesium organic compounds peculiar 

 complexes; yet the compound (C 5 H 5 N) 2 • IMgCH 3 • 0.(Ofc H n ) a which 

 separates out when a solution of CH 3 Mgl in amyl ether is mixed 

 with pyridine, reacts with bodies containing hydroxyl in the same 

 manner as free CH 3 MgI. When using pyridine the determination 

 must be carried out at ordinary temperature, and the volume of gas 

 must be read off as quickly as possible, as soon as the temperature in 

 the apparatus is again brought to the initial temperature, as otherwise 

 the pyridine also enters into reaction, with evolution of gas. 



The determination is carried out in an apparatus which consists 

 chiefly of a cylindrical reaction - vessel provided with a lateral bulb, 

 and a gas-measuring apparatus resembling Lunge's nitrometer. The 

 apparatus and reagents must be absolutely dry. 0,03 to 0,2 g. 

 of the substance (according to the molecular weight and hydroxyl 

 number) are dissolved in about 15 cc. solvent in the reaction- vessel ; 

 now by means of a special funnel 5 cc. of the magnesium organic 

 compound (in solution) are placed in the bulb in which not a drop 

 of the first-named solution may have entered, and the vessel is tightly 

 closed by connecting it with the measuring apparatus. In order to 

 obtain the proper temperature, the apparatus is immerged in water. 

 After atmospheric pressure has again been restored in the apparatus, 

 and the gas- collecting tube has been filled with mercury, the methyl 

 magnesium iodide is mixed with the solution of the substance to be 

 examined, by allowing the contents of the bulb to flow into the cylin- 

 drical portion of the apparatus; at the same time the connection 

 is made with the collecting tube by turning the cock in a suitable 

 position. When the reaction-vessel is strongly shaken, a brisk evolution 

 of gas takes place. As soon as the volume of gas no longer increases, 

 the vessel is again put in the water-bath so as to obtain the original 

 temperature, when a contraction of volume takes place. If pyridine 

 is used as solvent, the volume must be read off immediately the 

 contraction ceases, as otherwise a continuous, though slow, increase 

 of the volume of gas takes place. For calculation, the minimum 

 should always be taken. If amyl ether is used, the volume of gas 

 does not alter once the temperature is constant. 



Simultaneously with the determination of the volume, the tempera- 

 ture of the gas and the barometric pressure are noted. If pyridine 

 is used, 16 mm. must be deducted from the atmospheric pressure ob- 

 served, as this represents the vapour-tension of pyridine at 18 . If 

 amyl ether is employed, its vapour-tension at ordinary temperature 

 may be neglected. 



x ) Chem. Zentralbl. 1904, II. 836. 



