Schorger—Chemistry of American Conifers. 
765 
the end of which is attached for a receiver a 500 c.c. distilling 
flask cooled with a stream of water and connected with a mano¬ 
meter and suction pump. 
Place a few pieces of pumice in the boiling flask and then add 
200 c.c. of the filtrate obtained above (in the case of hardwoods 
use 100 c.c.). The flask is heated in an oil bath maintained 
at 85° C. while the pressure is reduced to 40-50 mm. When 
the contents of the flask are reduced to about 20 c.c., add dis¬ 
tilled water through the dropping funnel, drop by drop, at the 
same rate that distillation takes place. When 100 c.c. of wash 
water have been distilled over, titrate the distillate with N/10 
NaOH using phenolpthalein as the indicator. If (a) 200 c.c. 
or (b) 100 c.c. of solution were taken for distilla¬ 
tion, multiply the number of c.c. of NoOH used by (a) 5/4 
or (b) 5/2 respectively, and calculate as acetic acid. 
This method gives accurate results. - Duplicate determinations 
should agree within 0.10 of 1 per cent. It is necessary to use 
low temperatures and pressures to prevent decomposition of the 
carbohydrates, etc., by the sulphuric acid before all the acetic 
acid is removed. 
All the distilled water used in this determination should have 
been recently boiled to expel carbon dioxide. 
Determination of Methoxy Group (CH s O)-—The principle of 
the methoxy determination depends upon heating the sub¬ 
stance to be examined with hydriodic acid, whereby methyl iodide 
is formed. The methyl iodide is swept from the reaction flask 
into vessels containing a known volume of an alcoholc solution 
of N/IQ silver nitrate, the methyl iodide being decomposed with 
the formation of silver iodine. The undecomposed silver ni¬ 
trate is estimated volumetrically or the silver iodide formed is 
precipitated by diluting the solution, filtering, and weighing. 
Since 1 part of silver iodide is equivalent to 0.132 part of CH 3 0 
or 1 part of Ag N0 3 is equivalent to 0.1823 part of CH 3 0 the 
percentage of methoxy groups in the sample can be easily cal¬ 
culated. The details of the Zeisel method may be found in most 
works on organic chemistry or organic analysis. 
