NATUKE AND PROPEKTIES. 259 



a great amount of potash did not always indicate a great 

 amount of carbonate of potash. Although tobaccos 

 yielding a great amount of carbonate of potash in their 

 ash generally burn well, there may be conditions which 

 neutralize the good effect of this combination, as a large 

 proportion of albuminoids. It may therefore be said 

 that the combustibility of a tobacco is improved in pro- 

 portion as its ash yields more carbonate of potash, other 

 conditions being equal. 



Among the minor salts, the chlorides deserve most at- 

 tention. It has been found that they generally retard the 

 burning of tobacco, and that as they increase, carbonate of 

 potash decreases. Lime is invariably found more or less 

 in the ash, but it has not been ascertained to what extent 

 its presence affects the quality of the tobacco; good 

 tobacco may contain much or little, so that its presence is 

 probably not of great importance. The same may be said 

 of soda, magnesia, and phosphoric acid. According to 

 Nessler, their proportions may vary thus : — Potash, 

 1-95-5 per cent.; lime, 6 •5-9- 2; soda, 0-1-63; 

 magnesia, 0-12-0*99 ; phosphoric acid, 0*57-1 -39. 



In connection with the chemistry of tobacco, and the 

 rational manuring of the crop, the name of Prof. S. W. 

 Johnson, Chemist to the Connecticut State Board of 

 Agriculture, must be placed in the foremost rank. In- 

 debtedness is acknowledged to Prof. Johnson for a copy 

 of his valuable report, quoted in the Bibliography at the 

 end of this work. 



In November, 1884, a paper was read by Dr. John 

 Clark, on the composition of tobacco, before the Society 



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