STUDIES ON THE CURING OF LEAF TOBACCO. 27 



There is undoubtedly a considerable loss in nicotine content in 

 curing due to simple volatilization, but all this loss is not shown in 

 our experiments, for the reason that the green or uncured, as well 

 as the cured, leaves were dried at about 80° C. and this temperature is 

 sufficient to expel the more readily volatile portion of the nicotine. 1 

 In the leaf as a whole there appears to be no marked change in the 

 content of nitric acid in either method of curing. The indicated loss 

 of nitrate in the stem is probably only apparent, at least in part, since 

 about the same losses are indicated for curing the primed leaves as 

 for curing on the stalk. The determinations of nitrate were based on 

 the well-known method of reduction with ferrous chlorid in acid solu- 

 tion and measurement of the oxid of nitrogen liberated. In all cases, 

 however, it was found that with the green stems a sharp end reaction 

 could not be obtained, for, after the principal reaction was com- 

 pleted, a slow evolution of gas continued almost indefinitely, appar- 

 ently due to some reaction other than the reduction of the nitrate. 

 The values for nitric acid in the green stems are therefore somewhat 

 too high, which would, of course, have the effect of indicating a loss 

 of nitric acid in curing. That the results for the green stems are too 

 high is further indicated by the fact that the sum of the protein, 

 nicotine, and nitrate nitrogen as obtained somewhat exceeds the total 

 nitrogen in the green stems. 



In the primed leaves there is a very marked increase in the amid and 

 amido compounds, corresponding to the large decrease in protein. A 

 considerable portion of these cleavage products of protein pass from the 

 leaf web into the stem, which in the green condition contains practically 

 none of these products. In the case of stalk-cured leaves there is no 

 increase in amid and amido products, but, on the contrary, a con- 

 siderable decrease, although the decrease in protein in this method 

 of curing is even greater than in curing the primed leaves. Evi- 

 dently the phenomenon of translocation is here an important factor. 

 In the leaves cured by priming there is always a considerable loss of 

 total nitrogen, which can not be due to translocation, and since there is 

 no equivalent loss of nicotine the nitrogen doubtless escapes in the form 

 of ammonia. The odor of ammonia is readily recognized in the cur- 

 ing barns, and there can be no doubt that it is liberated during the 

 curing process. In other words, the cleavage products of protein are 

 further changed, with ammonia as one of the decomposition products. 

 The observed increase in content of ammonia, therefore, represents 

 only a portion of the total quantity formed during the curing, the 

 amount which becomes fixed in the leaf doubtless depending on the 

 quantity of free acid present. 



1 Garner, W. W. Relation of nicotine to the quality of tobacco. U. S. Department of Agriculture, 

 Bureau of Plant Industry, Bulletin 141, p. 5-16, 1909. 



