EFFECTS OF CONSTITUENTS OF ASH. 19 



carbonate. It was found, in fact, that the carbonate itself is just as 

 efficient in imparting the property of glowing to tobacco as the 

 organic salts, and the same is true of the bicarbonate. This fact 

 points strongly to the conclusion that the favorable action of the 

 potash salts is dependent on the ease with which they yield the car- 

 bonate. It seems possible that the carbonate or bicarbonate by alter- 

 nately giving off and taking up carbon dioxid may serve as a means 

 of removing this gas at the most favorable moment, the effect being 

 somewhat the same as when nitrates render organic substances com- 

 bustible by supplying oxygen in a highly concentrated state. It may 

 be. however, that the potassium oxid formed from the carbonate is 

 further reduced to the metallic state by the highly heated carbon, thus 

 serving as an energetic oxygen carrier, as was suggested by Xessler. 

 Whatever may be the peculiar properties of these potash salts which 

 give them the power of imparting the property of glowing to tobacco, 

 it is certain that these properties are not shared by the salts of 

 calcium and magnesium except to a very limited degree. 



While the inorganic salts of calcium are injurious to the fire- 

 holding capacity, the compounds of this base considered collectively 

 may be said to be inert with reference to this quality. The com- 

 pounds of magnesium are all injurious, but the harmful effects are 

 greatly reduced when the magnesium occurs in combination with the 

 organic acids. 



The question has often been raised whether lime and magnesia may 

 not, in part at least, replace potash without injuring the burning 

 qualities. Many ash analyses which have been made seem to indi- 

 cate that this is the case, while others point to the opposite view. 

 This assumption is made by Van Bemmelen a to explain the fact that 

 in some samples of tobacco which show a good fire-holding capacity 

 the total quantity of potash is only very slightly in excess of that 

 necessarv to neutralize the sulphuric and hydrochloric acids. But 

 Van Bemmelen 's calculations are all based on the ash analyses, and it 

 has been pointed out that the estimation of the sulphuric acid in the 

 ash gives no indication of the quantity of sulphur actually present in 

 the tobacco in the form of sulphates and therefore that the amount of 

 potash in organic form may be considerably greater than calculations 

 based on these data would indicate. 



In so far as lime alone is concerned the conclusion to be drawn 

 from our experiments is that this can only replace part of the potash 

 when the latter is present in combination with organic acids in 

 quantities larger than are necessary to produce a good burn ; for while 

 organic salts of lime do not appear to injure the fire-holding capacity, 

 they do not specially favor it. The amount of potash in organic form 



a Landw. Vers. Stat. 37, 409. 



105 



