6N COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 69 
the case with soluble starch and dextrin, but in lessening degree. This 
fact should be borne in mind in testing a colloid for gelatine by means of 
tannic acid. 
Ordinary wheat-flour is used very largely for sizing purposes, both in its 
fresh state and after long-continued fermentation. It differs from the 
starches in containing the nitrogenous colloid gluten, a coagulable albumen, 
sugar, dextrin, &c. It is doubtful if in the fresh state the gluten exerts any 
marked influence, but during fermentation the gluten, which suffers 
little in the process, becomes dispersed and forms a colloidal solution in the 
acids, which are generated, thus becoming available as a binding agent ; 
other marked changes also take place (H. B. Stocks, ‘ Jour. Soc. Dyers and 
Colourists,’ 1912, 28, 148-151, also H. B. Stocks and H. G. White, * Jour. 
Soc. Chem. Ind.’ 1903, 22). 
Soluble Starch. 
The so-calied ‘ soluble’ starch may be formed from ordinary starch 
in a variety of ways, the processes which have been proposed falling 
naturally into certain classes. 
1. By heating starch at a regulated temperature but lower than that 
which will convert it into dextrin. 
=e Heating starch with water under pressure (H. Hale, Eng. Pat. 3,311, 
3. Treating starch with acids, J. Sellars (Eng. Pat. 2,810, 1865) pro- 
posed to heat the starch with a mineral or vegetable acid, then neutralise 
withsoda. Rellmas steeps starch in a 1 to 3 per cent. solution of a mineral 
acid at 50° to 55°. Fols carries out the same process at 80° C. A. Schuh- 
mann (Eng. Pat. 5,460, 1887) treats starch with acid in the cold, washes 
out the acid, and heats with SO, under pressure. W. P. Thompson (A. H. J. 
Berge, Eng. Pat. 7,272, 1891) employs SO, under pressure, while W. 
Thompson and J. Morris (Eng. Pat. 21,973, 1906) claim to employ SO, at 
200°-220° F. H. H. Lake (W. Angelo, Eng. Pat. 5,617, 1893) treats starch 
with strong HCl and dries at a low temperature. G. Rivat (Fr. Pat. 433,726, 
1910) claims the application at 100° C. of dilute solutions of H;PO,,HF, 
potassium bitartrate, acid potassium oxalate, or aromatic sulphonic acids. 
Reumer (Eng. Pat. 10,873, 1902) proposed the application of organic acids 
at 115°, while Cross and Traquair (Eng. Pat. 9,868, 1902) claimed the applica- 
tion of carboxylic acids, such as acetic or formic, but specially the former, 
together with dehydrating agents, e.g., alcohol or concentrated solutions 
of salts. The amount of glacial acetic acid employed is from one-third to 
one-half the weight of the starch, and they claim that under these con- 
ditions an acetyl derivative of starch is formed. The product has been 
* ‘feculose* (see also Traquair, ‘Jour. Soc. Chem. Ind.’ 1909, 
4. Oxidising agents —Starch is treated with chlorine or calcium hypo- 
chlorite (C. H. Meyer, Eng. Pat. 1,146, 1893), with hypochlorite or 
chlorate of potassium or sodium (C. Brender, Eng. Pat. 17,650, 1898). 
A. Ashworth (Eng. Pat. 19,720, 1901) treats starch with acid and a chlorate, 
with or without the addition of a catalytic agent, e.g., vanadium chloride, 
CuSO,, or CuCl,. Siemens and Halske (U.S. Pat. 798,509, 1905) propose 
the use of chlorine gas; the use of acids, such as HCl, H,50,, and organic 
acids, is also mentioned in the specification. Chlorine is claimed by H. 
Kindscher (Ger. Pat. 168,980, 1902). In W. von Siemens and C. Witt’s 
