Chemistry and Physics. 471 



— |— 0*1 9 calories per gram. As to the cause of multi-rotation, the 

 authors conclude that it is probably " an effect of chemical change 

 brought about by the interaction of sugar and its solvent." — J. 

 Chem. Soc, lxxi, 756-783, July, 1897. g. f. b. 



2. On the Chemical Action of Electrical Oscillations. — The 

 chemical action of an oscillating electric field upon various sub- 

 stances has been studied by De Hemptinne. His apparatus, 

 which was a modification of that of Lecher, consisted of a pair 

 of plate condensers, one side of each being connected with a 

 Wimshurst machine, driven at a constant speed by a gas motor, 

 an adjustable spark gap being placed between the two plates. 

 The other coatings were connected to two wires of considerable 

 length, terminating in two plates facing each other. Substances 

 placed in the space between these plates are subjected to the 

 influence of the oscillating discharge of the condensers, whose 

 frequency and pressure may be varied at will. If a wire be 

 placed across the two conductors at certain points, an illuminated 

 vacuum tube between the plates becomes dark ; while on shifting 

 this wire along, points are reached at intervals where the tube 

 again glows. The distances between these points, as Wiedemann 

 and Ebert have shown, represent the wave length of the oscilla- 

 tion. When very high pressure was needed the author used a 

 Tesla apparatus, the current of an alternating machine being 

 transformed up one hundred fold. The secondary of this trans- 

 former was connected to a condenser, and, through a spark gap, 

 with the primary of an induction coil ; thus giving in the secon- 

 dary of this coil, whose terminals ended in two plates opposite 

 to one another, an oscillating discharge of high frequency and 

 pressure. The gas to be examined was contained in a glass 

 cylinder 4 cm broad and 12-1 3 cm long, having taps at its ends, the 

 lower one terminating in a smaller and graduated tube dipping 

 under mercury; so that the pressure in the cylinder was less than 

 that of the atmosphere. It was observed that no" action took 

 place within the tube unless it became luminous. Moreover two 

 tubes may screen each other ; and if the pressure of the gas in 

 the tubes be slightly different, then when they are placed between 

 the plates and the discharge is so adjusted that only one glows, a 

 slight increase of pressure in this tube causes it to become dark 

 while the other one glows and is decomposed. The substances 

 exposed to the action of the discharge were ammonia, carbon disul- 

 phide, glycerin, oxalic acid and calcium carbonate. It 

 appeared that the speed of decomposition increased with increasing 

 pressure, these pressures being 5, 15 and 50 mm ; a maximum being 

 reached soon after the decomposition began and then decreased. 

 Moreover this speed is decidedly influenced by the energy of the 

 discharge. The amount of the ammonia eventually decomposed 

 varies with the pressure, being about 50 per cent at 49 mm 

 and 95 per cent at 20 mm , though the values obtained do not agree 

 with the expression p x p\lp | =k, which theory gives for dissocia- 

 tion by heat. Addition of nitrogen or hydrogen lowers the 



