34 



BULLETIN 79, U. S. DEPARTMENT OP AGRICULTURE. 



moved from the second lot of leaves and the half of each leaf thus 

 resulting was plunged into boiling absolute alcohol for a few minutes, 

 while the second set of leaf halves was immediately placed in an air 

 bath heated to 90° C. and dried. The results of the experiment are 

 shown in Table VI. In the case of material killed with alcohol the 

 results were corrected, of course, for the matter extracted by the 

 alcohol. To facilitate comparison, the results are presented on a 

 uniform basis of 14 whole leaves, exclusive of the midribs. 



Table VI. — Effectiveness of hilling fresh tobacco leaves at high temperatures, as compared 

 with killing with hot alcohol in arresting changes in composition. 



1911 material. 



(a) 



Leaf web 



killed with 



alcohol. 



(6) 



Leaf web 

 killed at 

 high tem- 

 perature. 



(c) 



Leaf cured 

 normally. 



Dry weight of 14 leaves grams. . 



Loss of weight in curing per cent.. 



Starch do 



Protein nitrogen do 



Reducing sugars do 



26.64 

 2.04 

 1.21 



124.6 



1.3 



24.57 



2.13 



1.63 



97.5 



22.8 



5.17 



1.22 



3.86 



In the above table the results are calculated on a basis of the 

 original dry weight of the leaves, as represented by a. These results 

 show that, while subjecting the leaf to a temperature of 90° C. does 

 not immediately stop all action upon the carbohydrates, this method, 

 which was employed in all the experiments already described, answers 

 satisfactorily for the purposes in view. Having established this point, 

 the effect on the curing process of chloroforming the leaf was next 

 studied. A lot of five ripe leaves was collected and their midribs 

 removed. The one lot of leaf halves thus obtained was immediately 

 dried at 90° C, as in the preceding experiment, while the second lot 

 was exposed to chloroform vapors in a closed jar for a few minutes 

 and then placed under the proper conditions for normal curing. After 

 four days this material was also dried at 90° C. The results of the 

 experiment are shown in Table VII. 



Table VII. — Effect of exposure to chloroform on the curing of tobacco leaves. 



1912 material. 



Dry weight of 5 half leaves grams. . 



Starch per cent. . 



Protein nitrogen do 



It is obvious that exposure to chloroform effectually prevents 

 those changes in composition which are characteristic of normal 

 curing and, indeed, the appearance and properties of leaves so 



