52 BOTANICAL GAZETTE [JULY 
marked effect in promoting the combustion of tobacco. SLIGH 
and KRrayBILL (16) have determined the temperatures of burning 
cigars and have found some evidence which suggests that the 
moisture content as well as the composition of the cigar has an 
effect upon the burning temperature. It is planned to study this 
problem further with the object of determining the extent to which 
this hypothesis may be applied. 
BartTH (1) considers the harmful effect of chlorides to be due 
to the fact that they fuse and coat over the material, thereby 
preventing complete combustion. SLicH and KRavyBItt (16) found 
the temperature in the cigar varying from 813° C. to 925° C. during 
a puff, and from 584° C. to 803° C. at stationary temperatures 
between the puffs. It is doubtful whether the temperature of 
the burning strip of a leaf of tobacco would be as high as these 
stationary temperatures of the cigar. The temperature of the 
leaf then would not be high enough to fuse pure sodium chloride 
or pure potassium chloride. It would seem then as though the 
theory of BARTH would not account for the harmful effect of the 
chlorides. An objection might be raised from the standpoint , 
that we have in the leaf mixtures of salts, and that their fusing 
‘points would be lower than that of the pure salts. The fusing 
point of sodium chloride is about 820° C., and that of rubidium 
: carbonate is 837° C. (9). Tt would he Gilet te anileeatnad why © 
= one salt should harm the burn by fusing and the other should - 
ee the ‘same tem- 
perature. 
An attempt was ‘ead: to tabulate and compare the chemical 
and physical properti ee eee celia eh Ue hope of merci 
a ae the melting points, specific heats, weed ok ‘vaporization, ot 
dissociation | rbon A very careful com- 
