Nov., 1922] SPONSLER — STRUCTURE OF STARCH GRAIN 
485 
the relation between the wave-length, the distance between planes of atoms, 
and the glancing angle 6. The tables also give, for comparison, the calcu- 
lated distances between planes based on the assumption that line I was 
produced by the 100 planes of the crystals. 
Table 2. Lines Produced by Sodium-chloride Powder; Khodium Anticathoie; X = .533 A. 
No. of 
Line 
|8 Lines 
Distance 
between 
Lines 
(mm.)* 
Glancing 
Angle 
d 
Sin e 
Distance 
between 
Atomic 
Planes 
d 
Calculated 
Ratio 
Indices 
of 
Planes 
I 
2 
3 
53 
76 
95 
5° 26' 
7° 47' 
9° 35' 
.09469 
•13543 
.16648 
2.81 A. 
1.96 
1.60 
... A. 
1.99 
1.62 
1. 00 
.707 
•577 
100 
I 10 
III 
* These lines are so faint that close measare.Ti3nt is n3t passible. 
Since the actual and calculated values are so close, two inferences may 
be drawn: first, that any lines produced by another powder, in place of the 
salt, must be reflected by the same sort of planes, i.e., planes of atoms; 
and secondly, that the principal lines will be a lines. 
It is possible to cut out the /3 lines completely or practically so by using 
a filter made from the metal, or a simple salt of the element, which occurs 
in the periodic table one or two places below the metal used in the anti- 
cathode. In the case of a rhodium anticathode the filter would be made of 
ruthenium. But the filter reduces the intensity of the lines perhaps 50 
percent, and this would mean a considerable increase in the time of exposure. 
Since, however, the salt photograph shows that the principal lines are the 
a lines, the preHminary work can be carried on without using a filter. 
There is supposed to be a relation between the intensity of the secondary 
waves produced by an atom and its atomic weight. On this account, it 
was thought necessary to try a carbohydrate known to be crystalline, such 
as cane sugar, in order to determine the best conditions for getting reflec- 
tions from carbon and oxygen atoms. The upper half of figure 5 shows 
Fig. 5. Above, cane sugar; below, dextrine. 
