445 



closed space by a cover of incombustible material. This space is 

 divided in two by a vertical partition. On the left there are found 

 two gas-burners connected with a thermo-regulator, and on the right 

 there is adjusted a Heraeus quartz lamp. To work this the wall in 

 the lefthand side of the framework is made. like a door (drawn 

 halfopen in the figure); in the front partition at the place of Ihe 

 incandescent body there is a ventilator which works by suction 

 and serves to cool the lamp. The water in the thermostat can further 

 be cooled by means of a cooling spiral, through which water tlows 

 under constant pressure, a screw stirrer ensuring thorongh mixing 

 in the trough; besides the windows, the vertical walls are insulated 

 with felt. Ventilator and stirring apjiaratus are worked by separate 

 regiilatable motors. The lemperatme of the thermostat can be kept 

 constant at 35 -|- '/i„,°, which temperature has been chosen, because 

 at this temperature the thermostat can be regulated most accurately. 



As reaction vessel I, at first, used the before described stirring- 

 apparatus ') (fig. 2) ; it possesses the drawback, however, that the 

 surface of illiimiuation is small, the accuracy of the measurement 

 being seriously impaired by the rapid contamination of the mercury 

 in the mercury feal. Therefore I tried to modify the reaction 

 vessel in such a way that also without intensive mixing of gassnd 

 liquid, an alcoholic liquid could be obtained, which remains saturated 

 with oxygen, or contains at least siu'h an excess of oxygen that 

 there can be no question of measuring a velocity of diffusion instead 

 of a velocity of reaction. 



This is possible when the thickness of the liquid layer is taken very 

 small (about 1 mm.). According to fig. 3 a reaction vessel is then obtained, 

 which chiefly consists of a flask with a perfectly flat bottom; the 

 diiuensions being such that 5 cc. of liquid give a thickness of 

 layer of 5 mm. The neck is narrow and possesses a ground piece 

 to which a bent capillary tube with tap can be attached. Near the 

 bottom there is further a side tube with tap, through which the 

 whole ai)paratus can be filled with oxygen. Besides there is a filling 

 body in the flask, to make the gas-volnrae as small as possible 

 in proportion to the surface of illumination; this considerably 

 enhauces the accuracy of the measurement. For definite purposes 

 this filling body has been made to a second reaction vessel within 

 Ihe former; then an apparatus is obtained as is shown in fig. 4. 



By the aid of a uarrow tube the reaction vessel is connected 

 with the micromanometer. The lefthand leg of this has a capacity 



1) These Proc. XVltl, p. 1642. 



29* 



