138 Journal of the Mitchell Society [^December 



obtain the same results in sizing and finishing without changing 

 tlie formula for each lot of starch. 



In practice the starch solution is boiled from tbirty minutes 

 to one bour before being used. It is therefore very important 

 to know the effect produced by boiling on the viscosity of the 

 starch solution. This is shown in the following table. 



Table II. — Showing the Effect of Boiling on the Viscosities of 



Commercial Starches. 



(i2 grams starch in 300 cc. water.) 



Starch Minutes Boiled Viscosity 



Corn at boil 2.15 



" 10 2.73 



" 20 4.26 



" 30 7-00 



Potato at boil 16.37 



" 5 19.51 



" 10 14.31 



" 30 6.33 



Cassava at boil 9.93 



" 5 4.53 



" 10 3.88 



" 20 3.91 



" 30 417 



Sago at boil 1.88 



" 5 1.62 



" 10 I.S7 



" 30 1.66 



Wheat at boil 1.20 



" 5 1.22 



" 10 1.26 



" 20 1.24 



" 30 1.33 



Rice at boil i.oo 



" 10 i.oo 



" 30 1.08 



From tbe above table it will be seen that the viscosity of 

 corn starch increases uniformly with the length of time of 

 boiling. This increase is about what would be expected with 

 the concentration of the solution when there is no change in 

 the starch. This is a very valuable property of corn starch as 

 compared with other starches and gives corn starch a much 

 wider application in the textile industry than any other starch. 

 The value of this property will be seen more clearly by com- 

 parison with potato starch. 



Potato starch reaches its maximum viscosity after being 

 boiled five minutes. From this point the viscosity decreases 



