458 ANDREWS: PROTOPLASMIC STREAMING IN Mucor 
as the work progressed, some additions to it were found neces- 
sary for the sake of certainty of results and convenience. Fic. 1 
was used especially for obtaining the hydrogen in a pure form. As 
here arranged, the gas generator A is to the left. The generator 
contained the purest zinc made. The sulphuric acid mixture used 
was composed of one part concentrated sulphuric acid diluted with 
nine parts of water,* and on its surface was poured a thick layer of 
liquid paraffin. The generator connects with the four-way stop- 
cock B by means of which the stream of hydrogen may be sent to 
either of the U-tubes Cor C’. Or the stopcock may be so arranged 
that the generator A is cut off from the rest of the apparatus and 
air drawn through B’. Of the U-tubes shown C and C’ contain 
a concentrated solution of potassium hydrate, and in addition the 
arms of the U-tube are in each case nearly filled with pumice stone 
that has been saturated with the same solution. Hydrogen passed 
slowly through a tube arranged in this way will be freed from any 
hydrochloric acid, sulphur dioxid, or hydrogen sulphid that it 
may contain when prepared by the action of sulphuric acid on 
zinc.t| The U-tubes D and D’ contain silver nitrate for removing 
any traces of arsenic which may be present according to the 
equation: 
6AgNO; + AsH; + 3H.O = 6Ag + HAsO; + 6HNOs. 
The U-tubes E and E’ contain potassium permanganate for 
the removal of organic substances and are connected with F and 
containing pyrogallol and concentrated potassium hydroxid for 
freeing the gas from any trace of oxygen.{ It will be seen by the 
* Andrews, F.M. Annals of Botany 19:523. 1905. ‘‘If, as sometimes — 
° ; apid evolution 0 
the sulp d does not attack the zinc readily, so as to cause ar : 
hydrogen, this may be brought about by the addition of a small quantity of plaice 
tetrachloride or copper sulphate to the sulphuric acid.” 
drews, loc. cit. 523, where a similar but briefer metho 
for another set of experiments is discussed. 
t Hempel, W. Methods of gas analysis. Eng. Transl. 149. 
the following formula for making an alkalin solution of pyrogallol 
and rapid absorbent for oxygen. 
“‘s grams pyrogallol dissolved in 15 ccm. of water, 
120 grams potassium hydroxide dissolved in 80 ccm. of water. 
“The absorptions do not take place well,” says Hempel, “under 15° be used "” 
experiments, except those of temperature were above 15° the method 5 uring the 
and ‘A solution prepared as above stated gives off no carbon monoxide 4 
absorption.” 
d of washing hydroge® 
1902. This gives 
which is a good 
