1918] 
BONNS—ETHERIZATION AND ENZYME ACTIVITY 265 
EXPERIMENTAL 
A preliminary experiment was made with tulip bulbs for 
the purpose of obtaining data on optimum conditions of tem- 
perature and exposure with respect to etherization. The bulbs 
were freed of their papery integuments without injury to the 
scales and etherized after disinfection, as already outlined. 
In one series a temperature of 25°C. was maintained and in 
the other 35?C. At each temperature exposures to ether of 
12, 24, and 36 hours were made, with corresponding controls. 
The method of obtaining the plant extracts for the analyses 
has already been stated. After extraction the solutions were 
heated as rapidly as possible to 90°C. in the hope of inhibit- 
ing further action of enzymes present and, upon cooling, made 
up to liter volume. Analyses of aliquot parts were then made 
for eontent of glucose, sucrose, and maltose, using the modi- 
fied Bertrand method of Shaffer (714). For the maltose de- 
terminations hydrolysis was effected with 5 ce. concentrated 
hydrochloric acid plus 50 cc. distilled water per 20 се. extract. 
All portions were simultaneously heated for 14 hours at 100° 
C. in an Arnold sterilizer, after which they were neutralized 
to phenolphthalein with 20 per cent sodium hydroxide and 
made up to 100 ce. volume. Ten-cc. portions were then taken 
for sugar determinations. 
In making determinations of sucrose content based upon in- 
vert sugar values, a modification of the order of procedure 
in the Shaffer method was necessary. It was found that if 
inversion were attempted with 10 per cent citric acid, as sug- 
gested by Davis and Daish (713), and the Shaffer method then 
used, that it was impossible to centrifuge out the colloids pre- 
cipitated by addition of the dialyzed iron. It is possible that 
this is due to a solution of the iron in some citrate combina- 
tion analogous to solution of copper in Fehling's solution. To 
avoid this diffieulty, the proteins were first precipitated from 
equal portions of each solution by the same method and then 
inverted with citric acid by exposure to boiling temperature 
in the Arnold sterilizer for 15 minutes. The usual neutral- 
ization with alkali and inerease to standard volume followed, 
after which the balanee of the Shaffer method was continued, 
