70 REPORTS ON THE STATE OF SCIENCE.—1917. 
patent (Eng. Pat. 24,455, 1895) it is proposed to treat first with K.MnO,, 
then by HCl, and finally to remove excess of Cl, by means of SQ,, or 
a dilute solution of a bisulphite. The soluble starch is stated to form 
a clear filterable solution with dilute potash solution. 
¥. Fritsche (Eng. Pat. 1,351, 1908) claims the application of perborates 
for the preparation of soluble starch ; perborate of soda is also used for 
rendering starch, gums, algz, lichens, &c., soluble by heating (Stolbe 
and Kopke, Fr. Pat. 384,704, 1907, and addition Jan. 23, 1905); F. G. 
Perkins (U.S. Pat.—1,020, 656—1912) uses sodium peroxide for rendering 
starch soluble. 
5. Alkalies—J. Kantorowitz (Eng. Pat. 5,844, 1896) claims the pre- 
paration of soluble starch by treating ordinary starch with NaHO, neutra- 
lising with HCl, and precipitating the product with MgSO, or by keeping 
at a temperature of 20° C. for several hours. In a later patent (Eng. 
Pat. 10,216, 1910) Kantorowitz claims the application of caustic soda, 
but to prevent the former swelling the reaction is carried on in presence 
of concentrated solutions of salts, e.g., Na sSO,. 
6. Treatment with neutral salts—Soluble starch can be formed by 
heating starch with a strong solution of KCNS and alcohol, the latter 
probably added to prevent swelling, as in the last example. (The Arabol 
Man. Co., Fr. Pat. 394,167, 1908.) 
C. F. Cross and J. 8. Remington (Eng. Pat. 1,035, 1899) propose to 
use the fruit of the horse-chestnut as a source of starch or soluble starch. 
Soluble starch does not differ in appearance from ordinary starch, 
except that in some cases the hilum of the granules appears to be fractured. 
On heating with water, however, it behaves quite differently; thus 
1 part of ordinary starch heated with 9 parts of water yields a stiff white 
paste, which on cooling becomes a white opaque gel from which after 
a time water separates. On the other hand, soluble starch in the same 
proportion forms a thin opalescent but nearly clear sol which remains 
fluid on cooling, for which reason it is known as thin-boiling starch. The 
change which has taken place is probably largely one of de-polymerisation. 
M. Sauree and 8. Jencic (‘ Koll. chem. Beihefte,’ 1915, 7, 137-171) 
state that the formation of soluble starch is accompanied by a reduction 
in the size of the molecule, but this is not always the case. Dextrin is 
almost always present, although it is claimed that in certain products 
it is absent. The soluble starches usually, although not invariably, con- 
tain a higher mineral content than ordinary starch, amounting to about 
1-5 per cent., and this being alkaline will have a decided effect upon their 
properties ; the amount of water is also higher, 7.e., 17 to 21 per cent. 
Soluble starch on heating with caustic alkali yields a higher percentage 
of acetic acid, 7.e., about 13 per cent. of KHO is neutralised, pointing to 
a molecular change. It is precipitated by tannic acid, but to a lesser extent 
than ordinary starch. Soluble starch reverts to the insoluble form when 
a solution is allowed to stand (E. Fouard, ‘Compt. Rend.’ 1908, 147, 
931-933). Soluble starch is used in sizing and finishing, but more parti- 
cularly for the latter purpose; it yields a continuous film and imparts 
a ‘fuller’ feel to fabrics than does ordinary starch. 
Dextrin. 
The products sold under the name of dextrin or ‘ British gum’ vary 
very widely in their properties, being complexes of true dextrin, soluble 
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