1921.] Wright.—Chemical Technology of Meat Industry. 157 
In practice sodium sulphide cannot be used alone without causing loss of 
wool, although if it were possible to add to the solution of sodium sulphide 
a material which would be unaffected by the sulphide and which would reduce 
it to the consistency of a cream there would appear to be no objection to it. 
Flour, for instance, has been so used experimentally, but the cost precludes 
its use in this way. 
Milk of lime is also used as a depilatory in some places, but it will not 
remove wool without the aid of bacterial action, and consequently its use 
is but a modification of the 44 sweating ” process in which certain of the 
putrefactive bacteria are held in check. 
The wool, after having been loosened by one or other of the methods 
noted, is then removed from the skin by 44 pulling.” This operation is 
conducted by men termed 44 pullers,” who remove the wool by hand 
after placing the skin flesh-side down upon a round-faced beam. 
The wool thus removed from the skin now requires to be dried in order 
to bring it into a marketable state, for, despite the large amount of water 
from the washing which has been taken out by the hydro-extractors or 
centrifugal machines, a considerable amount of moisture remains. Ordi¬ 
narily the drying of wool is carried out in machine driers by means of hot 
air. Various types of wool-driers are in use, each apparently possessing 
qualities which appeal to the individual users ; in all, however, the 
objective lies in drying the wool quickly and economically to a uniform 
condition—neither too dry nor the reverse. 
A matter of some importance has to be taken into consideration when 
drying wool, this being its property of reabsorbing moisture from the 
atmosphere. The results of a number of investigations have shown that 
various factors enter into this power of moisture-absorption from the 
atmosphere, namely : (1.) The relative humidity of the atmosphere, more 
moisture being absorbed during a period of high relative humidity than when 
the humidity is low ; conversely, some of the moisture absorbed during a 
period of high relative humidity may be lost when the humidity decreases. 
(2.) Pure wool-fibre can absorb up to 20 per cent, of its weight of moisture, 
owing probably in part to the enormous surface area of a given weight of 
wool ; thus 1 lb. of Leicester wool has a surface area of about 400 square 
feet. (3.) The natural wool-grease can absorb up to 17 per cent, of its 
weight of moisture from the atmosphere. (4.) Suint, or wool-perspiration, 
can absorb up to 67 per cent, of its weight of moisture when exposed to the 
atmosphere. Suint, which may be present in greasy wools to an amount 
of nearly 13 per cent., and in slipe wools in amounts of about 2 per cent, 
only, is probably the chief factor which accounts for the different extent to 
which greasy and slipe wools absorb moisture from the atmosphere, it being 
found that a greasy wool absorbed from 24-38 per cent, to 29-27 per cent, 
moisture, while slipe wool under the same conditions absorbed only from 
16-12 per cent, to 20-66 per cent. 
In connection with the drying of wool at or above 212° F. it has been 
found that the wool has, when subsequently exposed to the atmosphere, 
regained a considerable portion of moisture, but not as much as wool dried 
below 212° F. Either a portion of the hygroscopic qualities had been 
destroyed, or more than water of hydration had been driven off, and some 
of the organic compounds which either formed a part of or were present 
within the fibre had commenced to disintegrate. 
