14 
BULLETIN 54, HAWAII EXPEBIMENT STATION 
Apparently, therefore, certain arbitrary conditions must be con- 
formed to when the viscosity of a starch is measured. The viscosity 
thus observed holds true only for these conditions. The method of 
procedure adopted for this study was as follows: Varying amounts 
of starch were Weighed into 100 cubic centimeter flasks graduated 
at 80° C, and shaken with 10 .cubic centimeters of cold water. 
Boiling water was then added with vigorous shaking and the flask 
made up to the mark at 80° C. with hot water. After thorough 
mixing they were placed in boiling water for one hour without 
agitation. They were then quickly cooled to 80° C. with as little 
agitation as possible and the viscosity determined at this tempera- 
ture by means of a Saybolt standard viscosimeter. Results can be 
duplicated with fair accuracy at 80° C. but will vary widely, prob- 
ably due to the tendency of the colloid to form a plastic gel, if the 
solution is cooled to room temperature. 
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-Comparison of the viscosities of various solutions of edible canna starch, potato starch, corn 
starch, and cassava starch. 
The Saybolt universal viscosimeter is essentially a cylindrical tube 
having a diameter of 3 centimeters, a height of 10 centimeters, and a 
capacity of 70 cubic centimeters. The bottom of the tube is con- 
stricted to an opening 1.77 millimeters in diameter. The tube is sur- 
rounded by a water or oil bath so that any desired temperature can 
be maintained. The viscosity is determined by filling the tube with 
the solution to be tested, and noting the time necessary to fill a flask 
of exactly 60 cubic centimeters capacity through the opening in the 
bottom of the tube. This type of viscosimeter is probably not so 
well adapted for the measurement of the viscosity of starches as is 
the torsion viscosimeter, which would have less destructive effect on 
the easily affected structure of the starch solution. 
A comparison of the viscosities of various solutions of edible canna 
starch, potato starch, corn starch, and cassava starch are given in 
the following table, and also graphically in Figure 4. 
