THE VOLATILE PART OF PLANTS. 63 
dilute solution of caustic soda is used to dissolve the al- 
buminoids, see p. 95. The starch and bran remaining, are 
separated by diffusing both in water, when the bran rap- 
idly settles, and the water being run off at the proper 
time, deposits the pure starch, corn-starch of commerce, 
also known as mazzena. 
Starch is prepared by similar methods from rice, horse- 
chestnuts, and various other plants. 
Arrow-root is starch obtained by grating and washing 
the root-sprouts of Maranta Indica, and M. arundinacea, 
plants native to the West Indies. , 
Exp. 25.—Reduce a clean potato to pulp by means of a tin grater. 
Tie up the pulp in a piece of not too fine muslin, and squeeze it repeat- 
edly in a quart or more of water. The starch grains thus pass the 
meshes of the cloth, while the cellulose is retained. Let the liquid stand 
until the starch settles, pour off the water, and dry the residuc. i 
Starch, as usually seen, is a white powder which con- 
sists of minute, rounded grains, and hence has a slightly 
harsh feel. When observed under a powerful magnifier, 
these grains often present characteristic forms and dimen- 
sions. 
In potato-starch they are egg or kidney-shaped, and are 
Fig. 12. 
distinctly marked with curved lines or ridges, which sur- 
round a point or eye; a, fig. 12. Wheat-starch consists of 
grains shaped like a thick burning-glass, or spectacle-lens, 
having a cavity in the centre, 6. Oat-starch is made up 
of compound grains, which are easily crushed into smaller 
