348 Wisconsin Academy of Sciences , Arts, and Letters. 
It is a fact that at the present writing no worker in the Johns 
Hopkins University chemical laboratory has brought dry ben¬ 
zene into contact with dry hydrogen chlorides and dry zinc. 
Consequently any statement from that laboratory can be only 
speculation. 
There is then no difference in our results save the length of 
time during which the zinc is acted upon. I took back to Mad¬ 
ison with me samples of the zinc used at Johns Hopkins by Mr. 
Falk, and using them with my zinc and with a bright bar of 
magnesium from Schuchardt repeated my experiment using an 
entirely new set of apparatus, in which extraordinary pre¬ 
cautions were taken to dry all the parts. The only possible 
points open to criticism were the use of rubber connections 
where glass tubes join, of rubber stoppers, and of phosphorus 
pentoxide from E. de Haen which had not been resublimed. 
Dr. Uernsen thought the use of pumice (which had been 
thoroughly heated) in the drying towers might account for 
the action I got upon zinc in my first experimlent. So 
in this last one I used glass wool in all my phosphorus 
pentoxide drying tubes, first heating it nearly to the melt¬ 
ing point of glass before loading the tubes and towers. 
All the glass with which the benzene and metals came into con¬ 
tact was steamed, treated with sulphuric acid and chromic acid, 
washed with distilled water repeatedly and dried by heating 
the outside and blowing dust-free air through it. The dried 
containers were allowed to cool in contact with phosphorus 
pentoxide tubes after the metals had been introduced hot. A 
stream of air dried by the phosphorus pentoxide train was 
drawn through while the containers were cooling. 
A photograph of the apparatus is given in figure 2. Hum¬ 
ber 1 is the evolution flask containing c. p. concentrated sul¬ 
phuric acid into which concentrated c. p. aqueous hydrochloric 
acid is allowed to drop. Z is a two-way stopcock for relieving 
pressure; 2, 3 and 4 are wash bottles containing c. p. concen¬ 
trated sulphuric acid. Q is a stopcock protect the towers 5, 
6, and 7 from moisture if it be desired to break the train. 
These towers 5, 6 and 7 are of the same dimensions: 40 c. m. 
high and 4 c. m. in diameter and were filled with alternate 
