TKRNARY PRINCIPLES STARCH. 88 



to the jatropha containing poisonous juice. The two yucas are, 

 however, but one and the same species ; at least a skilful botanist, 

 M. Goudot, who resided for several years in America, could not 

 perceive any specific differences between them. The poisonous 

 principle of the yuca brava must be very volatile, or readily destroy- 

 ed by heat, for the root may be eaten with impunity after it has 

 Deen roasted, while the animals who eat it in the raw state soon ex- 

 perience the most distressing effects. 



The Indians seldom prepare starch from the jatropha ; but the 

 root frequently constitutes the staple of their food. It is from the 

 yvca brava that they obtain the cassava,, which supplies the place of 

 bread with them. Among the Indians in the country near the river 

 Malta, one of the principal tributaries of the Oronoko, I have seen 

 the cassava prepared in the following manner : the roots of the 

 manioc were scraped on a sort of rasp formed of small fragments of 

 flint stuck into a plank ; the pulp was then put to drain in a long 

 strainer made of the entire bark of a species of fig ; the juice having 

 drained away, water was added to finish the washing ; the liquid 

 came out nearly clear and without bringing away any perceptible 

 quantity of starch. To form the pulp into cakes of cassava, it was 

 spread out on an earthen dish placed over the fire ; the process was 

 complete when the cassava was dry, and slightly toasted on the out- 

 side. Cassava bread is not very palatable, but it possesses the pro- 

 perty of keeping for a long time in spite of heat and moisture, and is 

 frequently an indispensable article of provision with the South Amer- 

 ican traveller. The Indians say that they cannot obtain cassava 

 from the yuca dulce. 



Starch from pabns. In the Moluccas and Philippine Islands, 

 and in the plains of Apure, there are certain palms which yield a 

 species of fecula. This fecula is found in a soft substance, general- 

 ly situated in the centre of these trees. The marrow of these palms 

 is dried, and when sifted presents itself in the form of grains, which 

 in commerce bear the name of sago. 



None of the amylaceous principles or feculas obtained by the 

 processes which I have mentioned are absolutely pure ; even sup- 

 posing all the soluble substances to have been removed by washing, 

 they still retain fatty matters, azotized principles, and coloring 

 substances. Starch is purified by following up the water washings 

 by the action of alcohol, of acetic acid, and of ammonia. Starch in 

 its state of greatest purity, and dried at 100° cent. (212" Fahr.) 

 contains, according to the analysis of M. Jacquelain : 



Carbon 44.9 



Hydrogen 6'3 



Oxygen • 48.8 



100.0* 



By slight roasting, amylaceous feculas undergo considerable 

 changes ; they become soluble in water, and then present the pro- 

 perties of gura.f Starch thus roasted, supplies the place of gtra ia 



• Jacquelain, Annales de Chimie et de Physique, t. Ixiiii. p. 181, 2e »6rie. 

 f Vaoquelin and Booillun Lagrange, Bulletin de Phnrmacio, t. ill. p. 54. 



