431 



catalyse!' ; in order to investigate this the Cu-spiral was switched 

 off without substituting a pjrogallol-soiution, the reduction was once 

 more very regular and even took place with greater velocity than 

 when the pyrogallol-solution was used. (N". 19). 



The Cu-spiral was switciied on again, but this time it had 

 evidently not completely freed the hydrogen from oxygen, as the 

 course of the reaction was fairly rapid and regular. (N°. 19). 



Therefore some quantitative experiments were started with the 

 Cu-spiral as above; the reaction took place; but no paralysis set 

 in, it appeared finally that 6 ccm. too much had been absorbed. 

 As the contents of the hydration-vessel are ± 600 ccm., and 300 ccm. 

 have been received from the burette, the total amount of gas that 

 has been in contact with the catalyser amounts to ± 900 ccm. The 

 surplus 6 ccm. corresponds to 2 ccm. 0,, hence its amount is 

 ± 0.2 "/„. So this quantity proves to be amply sufficient, to keep up 

 the reaction. (N«. 20). 



With a subsequent experiment (N°. 21) we had reduced the 

 Oj-quantity (calculated from the surplus gas that had been used) 

 to 0,1 **/„ ; otherwise everything being similar; the velocity of reduc- 

 tion was appreciably less and a stronger retardation set in. 



This was still more obvious, when we had decreased the Oj-quantity 

 to 0,003°/,; towards the end the velocity had decreased to zero, 

 so that a small amount of catalyser had to be added to bring the 

 reduction to an end. 



To demonstrate the activating effect of the oxygen still more 

 clearl3% the hydrogen was mixed with a still far greater quantity, 

 viz. with 4,8 "/u ^'i<^ compared with hydrogen that had been care- 

 fully purified (but evidently still containing oxygen). 



2,0336 Or. cinnamic acid-methylester hydrated with 4 ccm. sol, 

 absorbed 391 ccm., calculated 306 ccm. 



The blank experiment also with 4 ccm. Pd sol showed volume- 

 contraction of 65 ccm. It is remarkable that this reaction i. e. the 

 water- formation, proceeded rather slowly, the sol being completely 

 paralysed, even after the addition of another cmm. Pd-sol. 



The control-experiment with purified H^ with a very slight oxygen- 

 quantity was performed with 1,9958 substance, 4 ccm. Pd-sol and 

 like the two preceding ones at 25° C. and with 2250 rotations of 

 the spray -stirrer. 



Absorbed 291 ccm., calculated 294. (This deficiency is probably 

 to be attributed to a not inconsiderable change of temperature in 

 ihe neighbourhood of the gas-burette, during the experiment, on 

 account of which the volume-calculation has been less accurate). 



