BULLETIN No. 90a. 
15 
OCCURRENCE OF NITRATES IN TOBACCO. 
In nearly all varieties of tobacco a part of the nitrogen is found 
to exist in the form of nitrate. Just how this form of nitrogen finds 
its way into the plant has been a disputed question. Some authorities 
claim that it is a product of decomposition, and the amount maybe 
regulated, to a certain extent, in the process of curing, while others 
claim that it is taken directly into the plant from the soil through 
the roots in the process of nutrition, where part or all of it is decom¬ 
posed to form the other nitrogenous compounds of the plant. From 
the results of analyses given in the accompanying table it will be 
seen that the latter theory is more plausible. 
The tobacco used in the analyses was the ordinary “bright tobacco” 
peculiar to certain portions of North Carolina. The seed were sown 
in the seed-bed, and the plants were transplanted in the field when 
of proper size. Samples were taken from time to time, commencing 
at the time the plants were transplanted, and analyses made of the 
different samples, giving the percentage of nitrogen as nitrate, 
together with the other forms of nitrogen existing in the different 
parts of the plant at the different stages of growth. From an 
inspection of the table it will be noticed that the nitrates are con¬ 
fined almost entirely to the stalk and stems in the younger growth 
of the plant, while the other nitrogenous substances are more abun¬ 
dant in the leaves. This would indicate that the nitrates had been 
taken into the plant in the process of nutrition, and used to form 
the nitrogenous compounds of the rapidly-growing plant, while 
later the larger plant seems to have consumed the nitrates as fast as 
they were supplied. These facts lead to one of two conclusions: 
either the nitrates have, in some mysterious way, passed out of the 
plant, or the more rational conclusion that the nitrates have been 
decomposed to form other nitrogenous compounds. In this experi¬ 
ment we have no indication of nitrates being found in the mature 
tobacco from decomposition in the process of curing. Unfortu¬ 
nately, however, this variety of tobacco is exceedingly free from 
nitrates as compared with other varieties, as will be seen from the 
analysis of stems of other varieties. 
The methods of analysis used in Table I are those in ordinary 
use. The total nitrogen was determined by the Kjeldahl method as 
modified by Scovell to include nitrates. The nitrogen existing as 
nitrate was determined by the Tiemann Schultze method. The 
nitrogen existing as nitrate, subtracted from the total nitrogen, 
gives the organic or nitrogen not in the form of nitrate. All 
analyses are calculated to the air-dry sample. 
