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Transactions of the Society. 
tion, so necessary in commercial work, are best attained with simple 
apparatus of good construction ; the fewer complications the better. 
Manipulation of a universal stand for other than critical and fine work 
is a waste of time and unnecessary deterioration of fine mechanism. 
Note on the Refractive Index and Mounting 
of Cellulose. 
It is rather a remarkable fact that no research work appears to have 
been done on the refractive index of cellulose. In view of the fact 
that recent researches* by the X-ray method appear to indicate that 
cellulose has a definite crystalline structure, this would seem to be a 
promising field towards establishing the molecular constitution of this 
substance, a question still unsettled. 
The cellulose of fibres is doubly refracting, and on this account, as 
well as its minute structure, it is very difficult to determine the R.l. by 
the immersion method. It varies slightly with different fibres according 
to their purity and mineral content. Pure cellulose appears to have a 
R.l. of approximately 1*555 for daylight, so that the index of visibility 
of unstained cellulose is low in Canada balsam. 
For temporary mounts unstained fibres in water, or iodine-stained 
fibres in saline solutions, such as Herzberg’s modification of Schulze’s 
solution, are most convenient, although the latter tends to distort the 
structure. 
For permanent mounts the pure bleached cellulose is best stained 
with a basic aniline dye and mounted in xylol balsam. Magenta on 
account of its high R.l. is a suitable basic dye. 
Herzog and Jancke. 
