109 
the structure of wood, depends on the use of nitric acid and 
chlorate of potash (Schulze’s macerating mixture). This reagent 
. can be used for fibres, but its action is slow unless heat is applied, 
and in the latter case the acid fumes given off are a drawback to 
the method. 
Among other reagents which have been recommended for 
macerating fibres are solutions of caustic potash and chromic acid, 
the material being either boiled in the potash solution or soaked 
in cold chromic acid solution. Different details of treatment 
are given by different writers as regards the strength of the solu- 
tions to be used and the time requisite for maceration.* 
As a strong solution is normally more energetic in action than 
a weak one, maceration is more rapid in the former. Though 
convenient in causing quick maceration, a strong solution has the 
disadvantage that its action may readily become too general. 
us, if concentrated chromic acid be used, the removal of the 
middle lamellas (which causes maceration of the specimen) may 
not be completed before the other parts of the cell-walls np ba 
to be attacked.t In such cases portions of the walls may be dis- 
solved away, or the fibres may all become very fragile. Wit 
potash solution too severe treatment may cause considerable swell- 
ing of the cell-walls. 
fibre may by that time be sufficiently macerated. If so, it is 
found to be limp, and may be gently transferred to a vessel of 
ee 
* See Herzog, Microphot. Atlas d. technisch wichtigen Faserstoffe 
(1908), p. 16, and other works on fibres referred to by Herzog on p. 41. 
aterial to be treated, if not already in the form of hair-like strands, 
should be sliced into rather thin strips ; 
n Some experiments one part of saturated chromic solution to three 
of water was used, and worked satisfactorily. It is perhaps better however 
to employ the weaker solution an strengthen it if necessary. _ 
._§ Certain kinds of fibres are satisfactorily macerated by this treatment 
with potash alone, and do not require the chromic acid. 
