Nature of Cigaret S m o k e Volatile B a s e s and Acids’ J. A. BRADFORD, E. S. HARLOW, W. R. HARLAN, A N D H.R. HANMER American Tobacco Company, Richmond, Va.
acteristics by virtue of the methods of curing. Bright tobacco is flue-cured-that is, dried quickly by artificial heat which fixes quantities of reducing sugars in the leaf. Burley and Maryland types are slowly air-cured or dried, with the resultant degradation and loss of practically all of their reducing sugars. Turkish tobaccos are sun-cured, which results in a partial degradation of carbohydrate material. The subtypes vary from almost a Burley t o a BrightAike-type, Within these geographical groups the expert defines his grades, relying principally on certain recognizable physical characteristics such as color, texture, thickness, elasticity, and “grain.” Much of the chemical investigation of tobacco has been hampered by the lack of any primary reference standard of quality. But by extensive chemical analyses of various types carefully graded by leaf experts, a n accurate evaluation of the various grades has been made. Large variations are found, not only between different types, but within each type, depending upon geographical origin, position on the stalk, and climatic and soil conditions. Skillful blending is required to combine the good features of each type to produce a palatable cigaret. The analysis of smoke produced from these various types has made it possible t o define the characteristics of smoke in terms of its chemical composition and to relate these characteristics to the composition of the tobacco from which it is produced. Fundamentally, the character of smoke depends upon the aromatic substances produced on pyrolysis of the resinous material peculiar to each of the tobacco types, and the base content, as tempered by the proportional quantity of acids present. Chemical Drorserties
Aside from the nature of the aromatic substances present, cigaret smoke is characterized by its volatile base content and the proportion of acids to bases. The basic and acidic constituents of smoke are related to the composition of the tobacco from which it is derived. These relations are altered by changes in physical properties and smoking environment, as they influence the combustion of the finished cigaret. Methods for the analysis of tobacco and smoke are outlined, and precise methods for the determination of volatile bases, volatile acids, nicotine, and formic acid are described.in detail. Data on several types of cigarets are given, and the significance of some chemical and physical properties is indicated.
R
EPORTED chemical analyses of tobacco smoke have
been concerned chiefly with two objectives: the correlation of tobacco quality with the constituents of smoke and the determination of its physiologically active constituents. The present research undertakes to point out certain characteristics which influence the palatability of smoke and to associate these with the chemical and physical properties of the cigaret from which the smoke is derived.
Cigaret Tobacco I n the blending of cigaret tobacco for the American market, four major types predominate: Turkish, which is imported .-
from Turkey and neighboring countries, and the three domestic types, Bright, Burley, and some Maryland to enhance combustion. Subtypes are designated according to their geographical origin and each bears the stamp of its own locality in certain distinguishing charact e r i s t i c s . Subordinate to the main geographical types are the “markets” in the case of domestic tobacco and the “villages” in the case of Turkish. In these the differences are distinguishable but not so great as between main subtypes. Aside from differences in variety of seed, soil, c l i m a t i c conditions, and culture, the major types possess quite different char-
1 T h e first article in this series appeared in July, 1936 (6).
GUILLOTINE CUTTINGMACHINES WHERETHE LEAF BLENDIs CUT INTO SHREDS FOR CIGARET MANUFACTURE 45
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weight, size, moisture content, etc., play in modifying the conditions of combustion is recognized, a general relation is found between the constituents of tobacco and its smoke. It has been found possible, in most instances, to. relate changes in taste, irritation, and apparent strength to alteration in smoke composition.
Smoke Bases The presence in tobacco of nicotine and related alkaloids, with other nitrogenous compounds which are not found to any great extent in other leafy material, has focused the greatest attention on the bases of smoke. Schmuck (19) enumerates the probable nitrogen compounds in cigaret smoke as nicotine, ammonia, simplest amines, pyridine bases, and pyrrole derivatives. Gavrilov and Koperina (9) found in the types they studied a high base content in tobaccos they described as harsh and strong, together with a decrease in the ratio of nicotine to total FIQURE1 nitrogen as quality diminished. Hall and Earl (13)concur on this point, and note that a high base content in smoke may be compensated for by sufficient cigaret smoke are: the nitrogen content and its distribuneutralizing acids. tion among the various forms, principally nicotine and the The transfer of a portion of the nicotine in tobacco to its easily liberated ammonia; the carbohydrate content, insmoke is now generally accepted. At one time reports were cluding both the naturally occurring and added sugars; conflicting, but the preponderance of concordant chemical and the ash content, which to some extent serves as an index and biological evidence has definitely established the presence to combustibility in domestic tobaccos. of considerable amounts of the unchanged alkaloid (7, 11, Table I shows chemical analyses of a representative grade 18, 80). Jensen and Haley (14) studied the silicotungstic of each of the three major cigaret types. acid method for the determination of nicotine, and demonstrated that pyridine did not interfere. The identity of the insoluble silicotungstate of TABLEI. ANALYSESOF REIPRESENTATIVE TYPESOF CIQARET TOBACCOS (IN PERCENTMOISTURE-FREE TOBACCO) smoke distillate with nicotine silicotungstate Ratio has been established in this laboratory by mixed T. V. B. Nicotide melting points of the picrates and picrolonates of Total Protein minus as NHa to Reducing Tobaoco N a8 Nas T.V. B.” Niootine T. V. B. Sugars as the regenerated base. This has been confirmed as NHs Dextrose Ash as NHa Nicotine as NHa NHa Type NHa by determining the loss in weight on ignition of 0.120 0.69 20.4 14.3 2.68 0.69 0.391 Bright 2.22 Bui?y 3.87 1.67 0.650 2.90 0.345 0.47
