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plane and is acted upon by streams of water. These sieves are 

 subjected to interrupted lateral motion, so that the wet pulp is 

 shifted about and constantly subjected to the jets of water thrown 

 upon it. On this account the batteries of sieves are known as 

 "shakers." The starch milk which passes through the sieves 

 flows into vats or tanks, where the starch is repeatedly washed 

 to separate out the impurities. It is either allowed to settle in 

 tanks or, in some factories, is concentrated by means of vacuum 

 pans without heat. It then goes through further washings and 

 is treated with dilute alkalies — processes the object of which is 

 to purify and bleach the product and create uniformity of grade. 

 The purified starch is finally kiln-dried with dry air and is ready 

 to pack in barrels for export or home consumption. The pulp 

 which flows from the lov/er end of the sieves is either treated as 

 a waste product or is dried, pressed into bales and used for cattle 

 feed. 



In Florida this dried pulp is said to have a value of $io to $12 

 per ton, but far more has been produced than could be utilized. 

 This waste pulp contains at least 20%' and often 25% to 30% of 

 all the starch that was in the root. 



In the "shaker method" of starch manufacture the extraction 

 depends upon (a) the fineness to which the pulp is ground or 

 grated and (b) the thoroughness with which the pulp can be 

 washed. It has been unfortunate that the machinery used in 

 cassava factories has been in most cases adapted from forms first 

 invented for other lines of manufacture. Cassava starch grains 

 are very minute, approximating those of corn rather than potato. 

 The pulp graters used for cassava were modified either from 

 potato graters or from sugar beet pulpers. Potato starch grains 

 are very much larger than cassava, and it is needless to mention 

 that the extraction of soluble sugar from beet pulp is quite unlike 

 removing solid starch grains from their station in the plant cell. 

 It is difficult to brine about a sufticiently fine subdivision of the 

 root tissues so that each cell shall be ruptured permitting its 

 starch grains to escape. A certain amount of starch is bound to 

 remain. This starch residue in the pulp may represent the profit 

 of manufacture, so that unless a market can be created for the 

 waste there may be too narrow a margin of safety between profit- 

 able and unprofitable manufacture. 



The manufacturers of corn starch, on the contrary, starting as 

 they did with a hard and flinty seed as the source of their product, 

 rather than a fleshy watery root, used the ordinary flour milling 

 machinery as the basis of evolution for their special machinery' 

 Manufacturers of corn starch use a burr-stone modified for treat- 

 ing v/et grain. Obviously, the corn pulp is thus at the start in 

 a much more finely-divided condition than the cassava or potato 

 pulp produced by saw-tooth graters. The corn starch manufac- 

 turers save practically all of the starch in the corn kernel. 



The new method of manufacturing starch from cassava roots 



