Oe —— 
ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 55 
perhaps not in a regular formation. As already suggested, there is no 
necessity to discuss the molecular weight of the cellulose colloid 
since it only exists in the solid state. The fibre itself may be con- 
sidered to be a molecule in so far as the atoms composing it are 
bound together in the same way as in any other molecule. 
Mechanical disintegration produces changes corresponding to 
depolymerisation, B 7° 7° 31 343° in the same way that mastication is 
considered to produce depolymerisation of rubber. (Compare 
Journ. Soc. Chem. Ind., 37, 3134 (1918).) 
The substance of the cotton fibre is known in many colloidal 
states; in the fibre itself it exists as a porous, adherent mass, showing 
turbidity in the ultramicroscope, which indicates amicroscopic 
structure. Treatment with sulphuric acid of 1:70 Sp G causes the 
fibre to swell and eventually pass into solution. In the swollen 
state the fibre shows a distinct granular structure, which the author 
succeeded in photographing.”** Since the acid acts in the direction 
of solution and not coagulation, the author is of the opinion that the 
structure of the swollen fibre is an extension of that of the original 
fibre, this extension allowing the structure to be resolved. 
The double refraction of cotton fibres has been shown to be due to 
the presence of internal stresses, which become active when the fibre 
is softened.”2-23. There is no doubt that the celiulose is in different 
colloidal states in different parts of the cotton fibre, the outer portions 
being more solid than the inner. There are markings on the fibre 
(Refs. °-!°) which have physiological importance which it is not 
proposed to discuss in this review. The colloid chemical investiga- 
tion of cotton indicates that itis first formed in somewhat gelatinous 
filaments which harden from the outside by drying or by some 
chemical change. 
The following extract from W. L. Ball’s observations on the 
development of cotton appear to be in agreement with the view just 
expressed :— 
“The full diameter of the seed hair is attained almost at once, 
when its length is only ;4 m.m. while its length continues to in- 
- crease until the 25th day of development after which its wall begins 
to thicken, giving strength to the lint. This thickening is not 
uniform but leaves simple pits in the wall set obliquely, and the 
closure of these pits when the wall dries after the boll opens, gives 
twist to the fibre. The uninucleate cell contents remain alive until 
the boll begins to open, when they die from desiccation.” 
“The cell wall is extremely thin for the first three weeks and the 
cuticle which covers it can scarcely be differentiated unless the 
wall has been swollen with Schweitzer’s reagent when (being 
unaffected by the ammoniacal copper oxide) it causes the familiar 
beaded appearance, the cellulose of the wall swelling through the 
torn places in the cuticle.” 
The difference between the outer cell wall or cuticle and the 
inner portions of the fibre is most probably one of colloidal state 
and not of chemical nature. A similar difference exists between the 
outer layers of starch granules and the inner portions and it kas been 
shown that this difference is one of colloidal state. 
