ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS, 91 
hardened with formaldehyde (Soc. anon. frang. de Chim. Ind., Fr. Pat. 
425,204, 1910). 
Casein is also used for waterproofing fabrics and for calico-printing, 
being rendered insoluble by vapours of formaldehyde (J. E. Bousfield 
(F. Cautin, G. Miglioretti, and G. Maffei), Eng. Pat. 1,160, 1901) or alu- 
minium acetate. 
Albuminous substances, particularly casein, are converted into sols 
by alkali sulphocarbonates, the same being coagulated by (NH,),SO, 
and the product drawn into threads, films, &c. (Fr. Pat. 395,402, 1907, 
and addition of July 31, 1909). 
For the preparation, properties, and applications of casein see also 
‘Casein and its Technical Utilisation,’ by Robert Scherer, 1906 (Scott, 
Greenwood & Son). 
Gluten. 
Gluten is one of the proteids of flour, wheat-flour containing a coagu- 
lable albumin, gluten, and gliadin, the total being about 10 per cent. in 
the soft wheats and about 15 per cent. in the hard. When flour is first 
mixed with water it forms a very sticky tenacious mass, but after kneading 
for a little while it becomes quite plastic and may be freely handled. 
The baking properties of flour, 7.e., its capacity for imbibing water 
and retaining the gases generated during the fermentation, are very 
largely dependent upon the quantity and quality of the gluten present. 
Flour which has become deteriorated by storage or damaged by water 
has a weak gluten (7.e., bacterial activity has lowered its viscosity) ; in 
such cases it forms very heavy and dark-coloured bread, 
The baking properties of the flours from different cereals vary con- 
siderably ; this is due not so much to the quantity of gluten present 
as to its quality, and also to the physical characters of the flour. Everyone 
is familiar, for instance, with the differences between wheat and oat bread. 
Gluten is obtained from wheat-flour by washing it in a muslin bag 
in a stream of water, and kneading it till all the starch has passed through 
the cloth ; this is the basis of the manufacture of macaroni and vermicelli 
and also of some of the American chewing gums. The gluten prepared 
in this way is crude, since it contains the cellular tissue of the flour. This 
method i¢ employed in testing flour for sizing purposes. If the flour 
is fresh, the glaten is cream-coloured, stiff, and tenacious, but with deterio- 
rated Hour it is grey, soft, and pulpy, even sometimes passing along with 
the starch through the muslin. Gluten absorbs water to form a plastic 
mass, but after fully drying it does not again swell to the original extent. 
It is readily swollen by alkalies and by dilute acids, eventually passing 
into the state of a colloidal solution. The gluten of wheat-flour is rendered 
soluble by acetic and lactic acids formed during fermentation for sizing 
purposes, but it appears in other respects to be but slightly affected (H. B. 
Stocks and H. G. White, ‘ Jour. Soc. Chem. Ind.’ 1903, 4). This is also 
the reason for the deterioration of baking-flour, and at one time it was 
corrected for by addition of alum, or copper sulphate, which rendered 
the gluten insoluble again and the bread whiter; the addition of these 
substances to flour is now illegal. 
ve Fermented gluten dissolved in ammonia was proposed to be used 
in place of albumin for calico-printing, also for clarifying liquids and for 
photographic purposes (R. A. Brooman (C. Kestner), Eng. Pat. 2,428, 
1864). 
