1905] BRIEFER ARTICLES 307 
3. The content of the grain consists of at least two different substances, 
as first pointed out by NAGELI (2), and later confirmed by Meyer (6), 
SCHIMPER (5), and others, who showed in addition that the structure might 
be compared to that of sphero-crystalloids. 
THE ACTION OF IODIN UPON STARCH. 
The effect of iodin upon starch has been the subject of considerable 
investigation and speculation by both botanists and chemists. MyLius (7) 
eld to the view that the blue coloration formed on the addition of 
iodin to starch is due to the formation of a compound of hydriodic 
acid and starch. MrrNEKE (8) also contended that hydriodic acid is 
essential to the formation of the blue color of an iodin-starch solution. 
Stocks (9), SEYFERT (10), and Rouvier (11) are of the opinion, however, 
that this colored compound does not contain hydriodic acid, the last named 
investigator having shown that it may be formed in the presence of alcohol 
as well as water, and all of them agreeing that a true chemical compound 
(iodid of starch) is formed. 
On the other hand, Kiister (12) and Meyer (6) believe that the 
so-called iodid of starch is not a true chemical compound, but that the 
todin and starch are combined in much the same way as the ingredients 
man emulsion. This latter view has been more or less sanctioned on 
‘ccount of the statements in the textbooks that the iodin is removed from 
the combination on treatment with carbon disulfid. My observations, 
however, show that if the starch is in excess of the iodin (using 12” of 
potato starch and roc¢ of a solution containing 0.1 per cent. of iodin and 
°5 Per cent. of potassium iodid), or if the iodin and starch be in such 
Proportion that all of the free iodin is taken up, and the mixture is dried 
before adding the carbon disulfid, even on allowing it to act for six months» 
wd carbon disulfid is not colored; that is, does not take up the iodin, the 
same being true of alcohol and chloroform. This result, taken together with 
- Previous experiments in the treatment of starch with sand and then 
with lodin, would seem to confirm the view that a true chemical com- 
ie ily Produced by iodin and soluble starch, whether in the grain or in 
ori oat the amount of soluble starch varies in the starch grains of different 
hae ss be demonstrated by the treatment of definite amounts of 
of the se with definite quantities of iodin solution. On treating 0.5 
of iodin veral commercial starches with 2°¢ of iodin solution (0.1 per eae 
is a a er per cent. of potassium iodid), it will be found that t 
Potat difference in the intensity of the color in the grains, those 0 
© and maranta being colored deep blue, while those of corn and wheat 
