M. Caventou's Chemical Researches on Starch. 363 



Thus I received some sago which had only a very slight 

 degree of solubility in cold water, and some which had none 

 at all. M. Boutron gave me also at the same time three sam- 

 ples of tapioca ; one came from the islands, and he supposed 

 the other two to be factitious ; that is to say, to have been 

 fabricated in France. The tapioca of the islands was acted 

 on by cold water like that which had been the subject of my 

 experiments : as to the factitious specimens, they appeared to 

 be composed of two distinct substances ; the one was in round, 

 transparent, and pretty regular grains ; the other, in very irre- 

 gular, larger, opaque grains, presented all the counterfeit ap- 

 pearance of the tapioca of the isles. 



These two substances have been isolated and put in con- 

 tact with cold water, for comparison with the tapioca of the 

 isles. The three liquors acted in. the following manner : with 

 iodine the maceratum of the transparent grains took a slight 

 blueish green tint, that of the opaque grains did not change, 

 whilst the maceratum of the natural tapioca took a beautiful 

 blue colour. We must not, indeed, attribute more importance 

 to these results than they merit; for there is no actual proof 

 that it was factitious tapioca with which I had to do : besides, 

 it would not be surprising to find a tapioca very pure, quite 

 American, and which would be completely insoluble in cold 

 water. 



If, as every thing leads us to believe, spurious tapioca is 

 manufactured in France with the fecula of potatoes, nothing 

 appears more difficult to me than to distinguish it chemically 

 from the genuine which comes to us from the West Indies, 

 especially if the sort of baking which the moist fecula is made 

 to undergo for granulation is well managed. Yet the very 

 decided swelling which genuine tapioca undergoes in cold 

 water, and which in my opinion the fecula of our own country 

 cannot so well exhibit, might perhaps afford some indications 

 of spuriousness. Be that as it may, I see no harm in such a 

 substitution, when it is publicly excited by the love of our 

 country, and not by a vile and interested cupidity. 



I diluted in cold water some recent empois of starch : after 

 the starch not decomposed or modified had become precipitated 

 by rest, the liquid was decanted and filtered, and was perfectly 

 transparent : tried by the following reagents, it was rendered 

 slightly turbid by the sub-acetate of lead, gave an abundant 

 precipitate with gall-nuts, and took a beautiful blue colour with 

 iodine. The aqueous maceratum of tapioca from the islands, 

 and the cooled and filtered decoction of the same substance, 

 are acted on in like manner by the same reagents ; the turbidity 

 produced by the sub-acetate of lead is only less sensible in the 



Vol. 68. No. 343. Nov. 1826. 2 Z maceratum 



