ils off first is collected separately from the acetic
acid which afterwards comes over. The acid is used for the preparation
of alumina and iron mordants (see next lecture), or is neutralised with
lime, forming grey acetate of lime, from which, subsequently, pure
acetic acid or acetone is prepared. The crude wood spirit is mixed with
milk of lime, and after standing for several hours is distilled in a
rectifying still. The distillate is diluted with water, run off from any
oily impurities which are separated, and re-distilled once or twice
after treatment with quicklime.

_Stiffening and Proofing Process._--Before proceeding to discuss the
stiffening and proofing of hat forms or "bodies," it will be well to
point out that it was in thoroughly grasping the importance of a
rational and scientific method of carrying out this process that
Continental hat manufacturers had been able to steal a march upon their
English rivals in competition as to a special kind of hat which sold
well on the Continent. There are, or ought to be, three aims in the
process of proofing and stiffening, all the three being of equal
importance. These are: first, to waterproof the hat-forms; second, to
stiffen them at the same time and by the same process; and the third,
the one the importance of which I think English hat manufacturers have
frequently overlooked, at least in the past, is to so proof and stiffen
the hat-forms as to leave them in a suitable condition for the
subsequent dyeing process. In proofing the felt, the fibres become
varnished over with a kind of glaze which is insoluble in water, and
this varnish or proof is but imperfectly removed from the ends of the
fibres on the upper surface of the felt. The consequence is a too slight
penetration of the dyestuff into the inner pores of the fibres; indeed,
in the logwood black dyeing of such proofed felt a great deal of the
colour becomes precipitated on the outside of the fibres--a kind of
process of "smudging-on" of a black pigment taking place. The subsequent
"greening" of the black hats after a short period of wear is simply due
to the ease with which such badly fixed dye rubs off, washes off, or
wears off, the brownish or yellowish substratum which gradually comes to
light, causing a greenish shade to at length appear. If we examine under
the microscope a pure unproofed fur fibre, its characteristic structure
is quite visible. Examination of an unproofed fibre dyed with logwood
black