1912'] The Value of Commebcial Starches 139 



rapidly with the increase in time of boiling, the concentra- 

 tion of the solution apparently having no effect on the viscosity. 

 After boiling ten minutes potato starch has a viscosity slightly 

 more than five times as great as corn starch, while after boiling 

 thirty minutes the viscosity of potato starch is less than that 

 of corn starch which has been boiled the same length of time. 

 This property of potato starch of liquefying on boiling is a 

 very important point to be considered in using this starch. In 

 sizing the starch is boiled from thirty minutes to one hour be- 

 fore being used, hence, as will be seen from the table, a size 

 mixture made of potato starch will have a viscosity less than that 

 of a similar size made of corn starch at the time it is ready to 

 be applied to the yarn. In other words, the potato starch size 

 will not be as valuable for sizing as the corn starch size, but 

 it will cost approximately twice as much as the size made from 

 corn starch. 



Cassava starch attains its maximum viscosity at the boiling 

 point. The solution apparently has a higher viscosity shortly 

 after complete gelatinization takes place, but no measurements 

 were made of this as the starch is not used until it has been 

 boiled. After reaching the boiling point the viscosity decreases! 

 uniformly with the length of time of boiling. After boiling 

 thirty minutes there is an increase in the viscosity over that of 

 the solution boiled twenty minutes. This increase is probably 

 due to increase in concentration. As will be seen from the 

 table, cassava starch behaves in a manner very similar to potato 

 starch as regards liquefaction of the solution, but not to the 

 same extent. Cassava starch therefore has a much broader 

 application in sizing and finishing than potato starch. 



Sago starch has a much lower viscosity than any of the 

 starches so far considered. Like cassava starch it apparently 

 has a higher viscosity at the time of complete gelatinization, 

 but no measurements were made of this. The viscosity is high- 

 est at the boiling point and decreases uniformly on boiling, 

 though not to the same extent as the other starches. After boil- 

 ing thirty minutes there is a slight increase in viscosity due 

 to the concentration of the solution. While having a consider- 



