EFFECTS OF CONSTITUENTS OF ASH. 15 



ou^niy .saturate them, thus avoiding any leaching out of the soluble 

 constituents of the leaf, or by spraying the strips and allowing them 

 to stand in a moist atmosphere until the solution had diffused through 

 the leaf. In every case a strip of the leaf adjoining the portion 

 t- ited with the solution was reserved for comparison. The tests on 

 ^r$nt samples of tobacco did not always agree, as was to be 

 jccecl, since the quantities of the various salts already present in 



*j leaf are subject to wide variation, and these differences in some 

 c£ses may overshadow the effects of the salt added. For the same 



^K>n the concentration of the solution added must be taken into 



pount. To overcome these factors it is necessary to apply each 

 tests .to a number of different samples of tobacco. The tests on 

 obacco were always further supplemented with similar experiments 

 on strips of filter paper. 



There are three base-forming elements which occur in tobacco in 

 sufficient quantities to require consideration — potassium, calcium, and 

 magnesium — while the important mineral acids are sulphuric, phos- 

 horic, hydrochloric, and nitric, and the chief organic acids are citric, 

 malic, and oxalic. Little is known of the actual distribution of the 

 three bases among the acids and so it is necessary to test all of the pos- 

 sible combinations. It is probable, however, that the sulphuric, 

 nitric, and hydrochloric acids are for the most part combined with 

 potash so far as the quantit}^ of this base present will suffice to neu- 

 tralize these acids and that any excess of potash would be in combina- 

 tion with the organic acids. All of the oxalic acid appears to be 

 combined with lime. If the acids and bases were allowed to interact 

 in the presence of water, the distribution of the latter among the 

 former would be controlled simply by the relative solubilities of the 

 resulting salts and the strengths of the acids and bases ; but during the 

 life processes of the plant, which do not cease until some time after 

 the tobacco has been placed in the curing shed, other forces come into 

 play, and it hardly seems probable that there is sufficient water left 

 in the leaf after the life activities have ceased to permit of a readjust- 

 ment between the acids and bases according to purely chemical forces. 



POTASSIUM. 



All the salts of potassium are soluble, so that there is no difficulty 

 in testing the salts at any desired concentration. Those most used 

 for applying the tests to tobacco contained 1 per cent and 2 per cent, 

 respectively, of potassium, while for tests with filter paper much 

 weaker solutions gave the best results. In the case of the chlorid it 

 was found that the addition of comparatively large quantities prac- 

 tically destroyed the burning qualities of tobacco, while moderate 

 amounts caused very incomplete combustion, leaving a heavy black 



105 



