Nov. 6, 1916 
Grain of the Tobacco Leaf 
275 
The ash of the grain, however, contained a large amount of carbonate and 
therefore indicated the presence of some organic acids other than oxalic. 
Aside from the solubility of the grain material in water and the detec¬ 
tion of only a small amount of oxalic acid by ordinary qualitative means, 
Borodin’s method (2), which consists of treating the substance to be 
tested with a saturated solution of the suspected substance, showed the 
grain to be composed of a salt or salts other than calcium oxalate. 
Further, through the interest and kind assistance of Dr. F. E. Wright, 
of the Geophysical Laboratory of the Carnegie Institution of Washington, 1 
the application of the petrographic microscope and methods to a study of 
the crystalline substances of the grain revealed the presence of normal 
calcium malate in these bodies. These methods also showed the presence 
of other crystalline substances, the identity of which has not yet been 
established. As is evident from the detailed quantitative analyses 
hereinafter recorded, the grain is a mixture of salts some of which may 
be double or even triple combinations, and the difficulties of procuring 
these various possible compounds in crystalline form for a comparison 
of their optical properties with those of the salts entering into the com¬ 
position of the grain have not been surmounted at this stage of the 
investigation. 
QUANTITATIVE ANALYSES 
The data given in Table I represent quantitative determinations made 
on portions of the same material as that from which samples were taken 
for a study of the hygroscopic properties. The mineral components were 
determined by the official methods 2 and the organic acids by the method 
of Kissling. 3 
Table I. —Composition of the leaf web , vein, and grain of Pennsylvania tobacco , on 
basis of sand-free,air-dry material 
Constituents determined. 
Leaf web pass¬ 
ing through 
200-mesh sieve. 
Large vein 
(excluding 
midrib) not 
passing through 
20-mesh sieve. 
Small,vein 
passing through 
30-mesh but 
not 80-mesh 
sieve. 
Grain of 
various sizes. 
Moisture.. 
Pure ash. 
Potassium oxid. 
Calcium oxid. 
Magnesium oxid. 
Oxalic acid. 
Citric acid... 
Malic acid.. 
Total determined a . 
Per cent. 
7. 80 
16. 48 
4 - n 
6. 70 
i- 33 
3. 16 
3. 26 
3 - 46 
Per cent. 
7. II 
17. 80 
5 - 72 
6. 65 
1. 46 
2. 75 
15 
4*09 
- Per cent. 
6. 25 
16. 91 
5 - 29 
6.6 
*■ 59 
3 -o 
2. 91 
5 - 24 
Per cent. 
8.06 
40. 26 
3 * 42 
26. 34 
3 - 13 
.82 
22. 38 
13. 58 
29. 82 
28.93 
30. 88 
77 - 73 
1 The writer wishes to express his deep appreciation of Dr. Wright's assistance. 
2 Wiley, H. W., ed. Official and provisional methods of analysis, Association of Official Agricultural 
Chemists. As compiled by the committee on revision of methods. U. S. Dept. Agr. Bur. Chem. Bui. 
107 (rev.), 272 p., 13 fig. 1908. Reprinted, 1912. 
3 Kissling, Richard. Beitrage zur Chemie des Tabaks. Zur Tabakanalyse. In Chem. Ztg., Jahrg. 28, 
No. 66 , p. 77S-776, 1 fig. 1904* 
« Pure ash not included. 
