8k 
AND 
Shmarfifftts. 
YOL. II.—No. I. —JULY 1, 1871. 
THE APPLICATION OF THE MOLECULAR 
ROTATION TO THE DETERMINATION 
OF THE VALUE OF CINCHONA BARES. 
BY DR. E. J. DE YRIJ. 
The strong deviation of the plane of polarization 
in different direction or different intensity by all the 
known cinchona alkaloids, induced me to try to 
apply this action to test the value of the cinchona 
barks; and, although I readily confess that my ex¬ 
periments in this direction are far from being com¬ 
plete, yet the results already obtained seem to me 
interesting enough to fix attention on this new me¬ 
thod of investigation, so that then* publication may, 
perhaps, afford some interest. 
Before proceeding to the description of my method, 
it may, perhaps, not be superiluous to state the 
principles upon which it is based. 
The molecular rotations of the cinchona alkaloids 
which are known with certainty arc the following:— 
a 
Quinine : 
in alcoholic solution 
in acid solution . . 
Quinidine: 
in alcoholic solution 
in acid solution . . 
Cinchonine: 
in alcoholic solution [a 
in acid solution . . [a 
Cinclionidine : 
in alcoholic solution 
in acid solution . . 
a JJ 
a 
= 184°'35^ ) De Vrij and 
=287°TG ,, [ Alluard. 
=250°*75'? Pasteur. 
, not yet determined. 
, not yet determined. 
= 190°*40' : C Bouchardat. 
= 144°'C1 , X/ Pasteur, 
a] j, not yet determined. 
Besides these four alkaloids, about whose existence 
all chemists agree, and whose properties are well 
known, there exists in the cinchona barks still a 
fifth alkaloid, which is amorphous, soluble in ether, 
and whose compounds with acids are equally amor¬ 
phous. I have long been uncertain if this alkaloid 
lias an action on the plane of polarization, and it is 
only very recently that I became persuaded that it 
deviates from that plane slightly to the right. I 
have, however, not yet succeeded in determining the 
exact amount of this deviation, because this alkaloid 
is always jffilow-coloured, and veiy difficult to ob¬ 
tain perfectly pure. 
It is clear from the preceding that the different 
cinchona alkaloids possess a different rotation, and 
that some of them deviate the plan of polarization 
in an opposite direction. Therefore, in examining 
optically the combined alkaloids of any bark, three 
cases can occur:— 
Third Series, No. 53. 
I. The alkaloids may prove inactive, viz. to exer¬ 
cise no deviation at all. This case, although not 
yet observed by me, may present itself, if the rela¬ 
tive quantities of the alkaloids are such that their 
opposite deviations neutralize each other. 
II. They are turned to the right (dextrogyre = L) 
if the quantity of quinidine, cinchonine or amor¬ 
phous alkaloid exceeds that of quinine or cinclio- 
nidine. 
III. They are turned to the left (lievogyre = *x ) if 
the quantity of quinine or cinchonidine exceeds 
that of the other alkaloids. 
From the facts mentioned, it appears that the 
; deviation produced by quinine is different, depending 
; on its being observed in solution in alcohol or in a 
. diluted acid. It is very probable that this differ¬ 
ence exists in the same direction with the other 
alkaloids, and its determination will be very desir¬ 
able. 
Taking now in consideration that, of the five 
mentioned alkaloids, two of them, viz. the quinine 
and the amorphous alkaloid, are very soluble in 
ether, whilst the three remaining alkaloids are spa¬ 
ringly soluble in this liquid; it follows that, if the 
alkaloids are treated with ether, the deviation exer¬ 
cised by the part insoluble hi ether will prove to be 
very different from that observed before. This dif¬ 
ferent deviation may be the following:— 
(1.) No deviation, if the part insoluble in ether 
contains enough of cinchonidine to neutralize the 
opposite deviation of the cinchonine.* 
(2.) Deviation to the right (dextrogyre) if the part 
insoluble in ether consists of cinchonine or quinidine, 
or both of them, or if their quantity is superior to 
that of the eventually present cinchonidine. The 
intensity of the deviation may throw some light upon 
this alternative. 
(3.) Deviation to the left (Itevogyre), if the part in¬ 
soluble in ether consists either totally or chiefly of 
cinchonidine. In this case the intensity of the de¬ 
viation will equally throw light upon the alternative. 
The great difficulty with these observations con¬ 
sists in the difficulty to obtain solutions of the alka¬ 
loids which are not too much coloured. The first 
* As quinidine deviates to the right like cinchonine, it cay 
! equally neutralize the deviation to the left of the cinchoni¬ 
dine. It is, however, very rare that cinchonidine and qui¬ 
nidine occur in the same bark. Till now I have only found 
one example of this combined occurrence, viz. in the bark of 
the hybrid from C. Calisaya and C. Palmdiana (the so-called 
C. Hasskcirliana, Miq.), in which bark I tound the tour 
alkaloids, together with the amorphous alkaloid soluble in. 
i ether. 
