12 BURNING QUALITIES OF TOBACCO. 



filter paper, but when applied to tobacco in sufficient quantities to 

 influence the burn the effect is very injurious. Conclusive results 

 can not therefore be obtained b}^ the use of filter paper alone; 

 nevertheless they are of value as supplementing the test applied 

 directly to the tobacco. 



Dr. E. H. Jenkins ° determined the amounts of potassium carbonate 

 in the ash of a number of different types of tobacco, which is a rough 

 measure of the quantities of organic potash salts originally present 

 in the unburned tobaccos. No constant relation was found to exist 

 between the amount of carbonate and the fire-holding capacity, and 

 Jenkins concludes that the burning qualities are largely influenced 

 by the organic constituents of the tobacco. 



Van Bemmelen ^ maintains that the glowing capacity is governed 

 by the relative quantities of alkali and of hydrochloric and sulphuric 

 acids — expressed in chemical equivalents — in the tobacco. In good- 

 burning samples the potash is largely in excess of the acids, while 

 in the bad-burning samples the acids are equal to or in excess of the 

 alkali. Apparent exceptions to this rule are explained by the as- 

 sumption that the potash may be partly replaced by lime and mag- 

 nesia. This theory appears to be the nearest approach to the true 

 explanation of the cause of the good and bad burning qualities of 

 tobacco of any yet offered, but the assumption that the favorable 

 influence of the potash on the burn may be also exerted to any con- 

 siderable extent by lime and magnesia under certain conditions is 

 contrary to the evidence bearing on this point. 



Fesca ^ from his studies of Japanese tobacco, concludes that chlorin 

 and sulphur have a very unfavorable influence on the burn, but 

 phosphorus is indifferent. 



Earths <* agrees in general with the conclusions reached by Nessler 

 and Mayer, and believes that the beneficial effect of potash salts are 

 produced by the reduction of the potash compounds to potassium 

 oxid and free potassium, which serve as energetic oxygen carriers, 

 as was suggested by Xessler. The injurious effects of certain inor- 

 ganic salts are due either to their nonreducibility or to their easy 

 fusibility. The alkali phosphates are regarded as particularly inju- 

 rious because of their easy fusibility. 



Summarizing the results obtained by the investigators mentioned, 

 it is evident that the only two facts which have not been disputed 

 are (1) that chlorin injures the fire-holding capacity and (2) that 

 potash favors this property. 



The effects of sulphates and phosphates and the relative value of 

 the different salts of potash in promoting the fire-holding capacity 



aAnn. Rpt. Conn. Agr. Expt. Sta., 1884, p. 96. <" Landw. Jahrb., 1888. 329. 

 6 Landw. Vers. Stat.. 37, 409. <* Landw. Vers. Stat., 39. 81. 



105 



