1453 
When nitrobenzene is present in great concentration no hydrogen 
generation is observed; the solution of the metal and the generation 
of hydrogen is, however, accelerated by a smaller concentration of 
the nitrobenzene. 
Two strips of zinc-leaf, weighing 10.18 gr., surface 38.6 cm’, 
etched with 2 norm. HCI, were placed in 190 cc. of 80°/, acetic 
acid, while to one besides 2 cc. of nitrobenzene was added. After 
having been kept at 73° for 40 min., the zine was weighed and the 
generated hydrogen measured. The zine in the nitrobenzene experi- 
ment weighed 7,45 gr, the quantity of hydrogen was 17 ce. (11° 
and 772 mm.). The zine in the blank experiment weighed 10.15 gr. 
and the quantity of hydrogen was 6 cc. 
In this experiment there is, however, an unfairness towards the 
zine in the blank experiment, because though the two experiments 
start with the same surface, the nitrobenzene very soon considerably 
enlarges the surfaces through its strongly corrosive action, which 
gives il a permanent advantage. Therefore an experiment was made 
in which the zine was etched first with diluted hydrochloric acid, 
then one of the strips of zinc besides with nitrobenzene in 80°/, 
acetic acid, and after purification this latter was used for the blank 
experiment. The result was now as follows: 
Weight of the zinc 16.32 gr. Surface 59.2 cm’. The cone. of the 
nitrobenzene was taken still smaller, viz. 2,4 gr. to 170 ce. of 80°/, 
acetic acid. A third experiment was made with benzophenone, viz. 
3.6 gr. to 170 ee. of 80°/, acetic acid. In connection with the benzo- 
phenone experiment the temperature was chosen 20° higher, i.e. 93°. 
After 30 min. the condition was as follows: Weight zine in blank 
experiment 16,04 gr., generated hydrogen 50 cc. (temp. 11°, baro- 
meter 767 mm.). Weight zinc nitrobenzene experiment: 12.50 gr, 
generated hydrogen 115 cc. Weight zinc benzophenone experiment: 
16,09 gr., generated hydrogen 10 cc. 
It appears from this, just as from the table that a reducible 
compound can exert both an accelerating and a retarding influence as 
well on the dissolving of the metal and on the hydrogen generation. 
Finally a similar experiment was made with zine that had been 
etched in boiling 30°/, acetic acid, to which nitrobenzene was added, 
so that the nature of the zine surface was the same as in the 
presence of nitrobenzene for all experiments. The quantity of benzo- 
phenone was doubled, so that the quantity of reducible oxygen was 
equal to that of nitrobenzene. 
Weight zinc: 14,32 gr., surface 60 cm’. Blank experiment con- 
tained 170 cc. of 80°/, acetic acid; the two others resp. 2,4 gr. 
