EFFECTS OF CONSTITUENTS OF ASH. 15 



ouglily saturate them, thus avoidiu*^ any h'acliin<2: out of the sohil)le 

 constituents of the leaf, or hy s|)rayinj>: the strips and allowinp; them 

 to stand in a moist atnu)sphere until the solution had ditl'used throui^h 

 the leaf. In every case a strip of the leaf adjoinin<r the portion 

 ti'eated with the solution was reserveil for comparison. The tests on 

 <litierent samples of tobacco did not always a<j:ree, as was to be 

 expected, since the ([uantities of the \arious salts already present in 

 the leaf are subject to wide variation, and these ditferences in some 

 cases nuiy overshadow the idl'ects of the salt added. Foi* the same 

 reason the concentration of the solution added iiiust be taken into 

 account. To overcome these factors it is necessary to ajjply each 

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

 tobacco were always further supplemented with similar exj)eriments 

 on strips of filter paper. 



There are three l)ase-fonnin<>: elements which occur in tobacco in 

 sufficient quantities to require consideration — potassium, calcium, and 

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

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

 malic, and oxalic. TJttle is known of the actual distrii)ution 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 quantity of this base present will suffice to neu- 

 tralize these acids and that any excess of potash Avould 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, wdiile moderate 

 amounts caused very incomplete combustion, leaving a heavy black 



105 



