392 BIOT ON THE EMPLOYMENT OF POLARIZED LIGHT 
energetic rotatory power, proportional to its mass, and directed 
towards the right of the observer; a fact which led M. Persoz 
and myself to give it the denomination of dextrine when we had 
isolated it, and ascertained this character*. But the propor- 
tionality of the optical action to the active mass dissolved, as 
long as it exists, attests a constant molecular state. Now the 
following experiment is sufficient to establish this permanence 
of molecular action in all the degrees of attenuation which the 
substance composing the globules may admit. If, by degrees, a 
sufficient quantity of very concentrated nitric acid be poured 
over some starch in a glass mortar, disaggregating the lumps by 
continued trituration in order to render the action of the acid uni- 
form and general, we obtain, after some instants, a diaphanous 
liquid, which, on mixture with water, deposits a white powder, 
which M. Braconnot, who first obtained it, has named awyloidine, 
and which M. Pelouze has found to contain the elements of nitric 
acid, joined or combined with those of the starch +t. But, the 
* Researches on the modifications which starch and gum experience under 
the influence of acids. (Mémoires de !’ Académie des Sciences, vol. xiii.) In 
this memoir, which was drawn up by M. Persoz and myself, we have studied 
the progress of disaggregation of starch under the influence of water and acids 
aided by heat, from the moment when the system becomes completely fluid, to 
that at which the starchy substance is converted into fermentable sugar, which 
takes place by a sudden transformation accompanied by a considerable diminu- 
tion of the rotatory power. I have since added to this investigation some ex- 
periments made with a view to prove directly the exact identity of the active 
substance thus obtained by disaggregation, under the influence of various acids. 
They consist first in forming with each of them aqueous solutions the strengths 
of which have been accurately ascertained. Then having taken known weights 
of each, in counterpoised phials, ascertained weights of the same starch taken in 
an hygrometric state common to all its parts are introduced, and the temperature 
of these systems is slowly raised to the precise point of their liquefaction, and 
the small quantity of water removed by evaporation is restored on the balance, 
or the diminution of weight is estimated and taken into account in the calcula- 
tion, which comes to the same thing. The optical effect of these solutions is now 
observed in tubes of a known length, and their densities likewise measured at 
the same temperature; and from these elements we conclude the proper rota- 
tory power of the starchy substance they contain. We find it the same for all, 
whatever acid be employed, provided that we stop carefully at the precise limit 
of liquefaction, so that no portion of the matter employed has passed into the 
state of sugar; or thatif such an alteration has taken place in some of the par- 
ticles, which it is very difficult to avoid, their weight at least may be insensible 
in comparison to the total mass employed. I have published these experiments 
in the journal L’ Jnstitut, vol. iii. page 13 ; but it is desirable that they should 
be repeated, as they might be now, with more precision and generality. 
+ De la transformation de plusieurs substances végétales en un principe 
nouveau, by M. Braconnot (Annales de Chimie et de Physique, 2nd Series, 
vol. lii. page 290). This memoir is anterior to the researches mentioned in the 
