CHARACTER OF THE ASH. 21 



holding capacity. To obtain some indication as to 'whether lime and 

 magnesia can partly replace the organic potash, the alkalinity of the 

 ash due to these bases was also determined, but the evidence on this 

 point was all of a negative character, for the alkalinity due to lime 

 and magnesia collectively did not show any apparent relation to the 

 glowing capacity. In the case of the alkalinity due to potash — that 

 is, the quantity of the potassium carbonate — however, there is unmis- 

 takable evidence of a close relation between these values and the 

 capacity for holding fire, and if the method were really a true meas- 

 ure of the organic potash it is believed that there would be very few, 

 if any, exceptions to this rule. 



The samples used for this test were selected with special reference 

 to the tobacco-breeding experiments which are being carried on by the 

 Bureau of Plant Industry, and were taken from crops produced from 

 the seed of individual selections of four different types of tobacco 

 originally found growing in the same field. Both the light and the 

 dark wrappers were examined in each case, and in every instance the 

 former as compared with the latter showed a much greater fire- 

 holding capacity and a much higher percentage of potassium car- 

 bonate in the ash. Also as regards the same grade of leaf of the 

 different strains of each type, as well as of the different types taken 

 collectively, the potash alkalinity was found to be directly propor- 

 tional in nearly every case to the capacity for holding fire. This was 

 especially true of the different strains of any one type. These 

 tobaccos were all grown under as uniform conditions as could be ob- 

 tained with reference to soil and fertilizers, and the results make it 

 very probable that certain types or strains of tobacco possess the 

 power of appropriating potash in forms favorable to the burning 

 qualities to a greater degree than others growing under the same con- 

 ditions, though further data are required to fully prove this point. 

 The question is certainly a very important one from the standpoint 

 of practical tobacco breeding and is worthy of very careful study. 



THE CHARACTER OF THE ASH. 



A tobacco with satisfactory burning qualities besides having the 

 necessary capacity for holding fire must also yield a good ash. 

 Although the organic potassium salts greatly favor the fire-holding 

 capacity, they tend to produce a mottled, dark-colored ash. This is 

 no doubt due to the easy fusibility of the alkali carbonate, which in 

 melting incloses very small particles of unburned carbon and thus 

 prevents complete combustion. Moreover, these salts when present 

 in considerable quantity show a tendency to cause the tobacco to 

 " coal " or carbonize in advance of the glowing portion, because they 

 decompose so readily when heated. 



105 



