Title:
Tobacco and method of treating tobacco
United States Patent 2131160


Abstract:
This invention relates to improvements in method of treating tobacco and to improvements in smoking tobacco as an article of manufacture. This invention relates especially to improvements in the color and burning properties of smoking tobacco and to novel methods whereby improvements of this...



Inventors:
Avedikian, Souren Z.
Application Number:
US1383735A
Publication Date:
09/27/1938
Filing Date:
03/30/1935
Assignee:
Avedikian, Souren Z.
Primary Class:
Other Classes:
8/111
International Classes:
A24B15/28
View Patent Images:



Description:

This invention relates to improvements in method of treating tobacco and to improvements in smoking tobacco as an article of manufacture.

This invention relates especially to improvements in the color and burning properties of smoking tobacco and to novel methods whereby improvements of this character may be achieved.

It is a purpose of this invention to bleach tobacco so that its color is made more attractive and in such a manner that the flavor and aroma of the tobacco is not impaired. Many tobaccos of desirable flavor and aroma are of an undesirably dark and dirty color which makes them undesirable for use except in the lower grades of smoking tobacco products. Leaves of a light brown and pleasing color suitable for wrappers in making cigars and the like, are costly at the present time. Heretofore, attempts have been made to bleach tobacco with bleaching agents of various types so that dark colored tobaccos could be used as wrappers for cigars. However, such attempts have not been successful due primarily to the fact that the bleaching treatments employed have resulted in such undesirable effects as impairment in the flavor and aroma of the tobacco, impairment of the texture of the tobacco so that it is excessively brittle and impairment of the burning properties of the tobacco. If attempt is made to apply the methods of bleaching heretofore employed with less severity so as to preserve to greater degree the flavor, aroma, texture and burning qualities of the tobacco; then the bleaching action, is too slight to be beneficial and is likely to be only temporary in character. While bleaching of tobacco has been regarded as desirable for many years, it is not employed commercially for reasons including those above mentioned.

It is a further purpose of this invention to improve the burning properties including the rate of burning of the tobacco and the color of the ash. Further purposes of this invention relate to improving upon the texture and quality of the tobacco.

It is one of the features of this invention that the bleaching agent employed to bleach the tobacco comprises one or more oxides of nitrogen.

Preferably nitrogen trioxide (N203) is used as the bleaching agent.. Other oxides of nitrogen such as N02 and N204 may also be employed, however. Pure NO is not regarded as a desirable bleaching agent, but when oxygen as from the air is mixed therewith as in converting the substance to N203, NO2 or. N204, then it becomes a desirable bleaching agent. It is to be understood that the term "oxide of nitrogen" as used herein includes NO mixed with some oxygen or any other oxide of nitrogen or mixtures thereof. Oxide of nitrogen may be used alone, but'is preferably employed in combination with other gases such as oxygen, nitrogen, air, carbon dioxide, carbon monoxide, argon, neon, helium, and other similar inert gases, inert in the sense that their function is merely to act as diluents, and not, in any other way, influence the bleaching process nor interfere with the action of oxides of nitrogen on cured tobacco, or mixtures thereof. I have found that oxide of nitrogen brings about the desired bleaching of the tobacco so as to produce from tobacco which is dark and dirty a tobacco which has a very pleasing and uniform light color.

Any degree of bleaching from a slight lightening in color to extremely pale effects can be effected according to the process of this invention. Preferably, the bleaching is conducted until the tobacco leaves are of a medium to light brown color.

Leaf tobacco bleached according to this invention is particularly desirable in making cigar wrappers.

The tobacco may be bleached in the practice of this invention after the tobacco has first been cured. In curing tobacco, green tobacco is subjected to controlled conditions of temperature and moisture to develop flavor and aroma by fermentation and bacterial actions which proceed during the curing process. Certain chemical treatments to effect or aid in curing have also in certain instances been resorted to. During the curing of tobacco, the green chlorophyll in the leaves becomes brown and the tobacco frequently becomes of a dark, dirty and unpleasant color as referred to above. As distinguished from the curing of tobacco, this invention is directed to the problem of improving the color and burning characteristics of tobacco. It is preferable to cure tobacco before it is treated and improved according to this invention. After the tobacco has been brought to desired flavor and aroma by curing according to a variety of known methods, I have found that its color and burning characteristics can be improved according to this invention without impairment of its flavor and aroma.

While the exposure of tobacco to an oxide of nitrogen to effect substantial bleaching of tobacco is an important feature of this invention, further features of this invention relate to the treatment of the tobacco prior to such bleaching step, the control of conditions during the bleaching step, and the treatment of the tobacco following the bleaching step. Thus, in bleaching tobacco using an oxide of nitrogen according to this invention, the tobacco should be in a moistened condition. If attempt is made to bleach tobacco with an oxide of nitrogen while the tobacco is dry and in an atmosphere which is so dry tobacco cannot absorb a substantial amount of moisture therefrom, extremely poor or no bleaching effects result. If the tobacco contains a substantial amount of moisture the bleaching action of the oxide of nitrogen in the bleaching operation is rendered much more effective. Moreover, the atmosphere in which the bleaching is conducted should also contain a relatively high proportion of moisture in order to obtain the most desirable results.

In conditioning tobacco prior to the bleaching step, not only is it desirable to include in the tobacco a substantial amount of moisture but also further advantages are obtained by seeing to it that the moisture is distributed as uniformly as possible in the tobacco. Ordinarily tobacco contains some moisture, but the moisture is not sufficient in amount or distributed evenly enough to obtain the most desirable bleaching effects. The most desirable bleaching effects are produced when the tobacco carries a relatively large amount of moisture which is substantially uniformly distributed in all parts of the tobacco. Thus, in the normal practice of this invention, the conditioning of tobacco prior to bleaching preferably includes a moistening step as by immersion in water or contact with a humid atmosphere and in addition a further step, by which the moisture is evenly distributed in the tobacco. In certain instances, these steps may be combined, but preferably they follow each other. Especially when the tobacco is in leaf form, the conditioning treatment may include a drying operation in which any excess moisture, occurring, for example, as droplets of free moisture, is removed by such methods as contacting the tobacco with absorbent rollers and/or exposing the tobacco to an atmosphere, having such humidity as to leave a desired amount of moisture Sin the tobacco without excess on the surface.

In the bleaching step the tobacco, preferably after it has been placed in a receptive condition for bleaching as above described, is exposed to oxide of nitrogen and this is preferably accomplished by. disposing the tobacco in such a way that the surfaces thereof will be in contact with an atmosphere containing oxide of nitrogen.

Preferably, the tobacco is exposed for a relatively short time to an atmosphere containing a relatively high concentration of oxide of nitrogen at moderate temperatures and for best results both the tobacco and the atmosphere in which the tobacco is placed contain a relatively high amount of moisture. Further details of bleaching treatment and the conditions under which the bleaching is effected will be described below.

After the bleaching step, the tobacco is subjected to further treatment to place it in better form for marketing. After the bleaching step, it is usually desirable to subject the tobacco to washing with water or air or both water and air to remove from the tobacco oxide of nitrogen and/or acid carried thereby. The washing step is then preferably followed by a neutralization step which neutralizes any acidic matter remaining in the tobacco after the washing operation.

While it is preferable to first wash the bleached tobacco and then neutralize the tobacco, it is possible to combine those steps by washing the tobacco with a mildly alkaline solution.

After the tobacco has been treated as above described, it can be dried so that it will have the moisture content that is desired in the finished product. The product not only is improved in color, namely, is bleached to a pleasing light brown color, but also retains its flavor and aroma substantially unimpaired. In certain cases, the treatment above described has been found to result in definite improvement in the texture of tobacco which originally was of a coarse character and in improvement in the flavor. In preferred practice of this invention, the tobacco is treated further to incorporate salts therewith which improve the burning properties of the'tobacco. Thus not only will the tobacco be improved in color, but also will have its burning properties improved.

In the practice of this invention, the steps thereof, materials used and items of apparatus included therein may be employed conjointly and when so used one obtains the special advantages of such conjoint use but it is to be understood that such features of this invention may likewise be employed separately in achieving some of the advantages of this invention. Oxide of nitrogen for use as a bleaching agent in the practice of this invention may be prepared in several known ways. Preferably, the means used for generating oxide of nitrogen is such as to result in the production of a major proportion of nitrogen tri-oxide. For purposes of illustration, certain desirable methods for supplying oxide of nitrogen will be described. (a) Oxide of nitrogen may be generated by catalytic oxidation of ammonia. This may be accomplished by passing oxygen or an oxygen containing gas in admixture with ammonia over a catalyst such as heated platinum gauze. A suitable mixture of NO and NO2 which results in the formation of N203, can be obtained by 90 judicious choice of temperature and oxygen feed as is well known. The gas can be taken directly from the generator to the chamber in which tobacco is being treated or it can be liquefied and stored for subsequent use in any concentration which is desired.

(b) Oxide of nitrogen can also be generated by decomposing nitrates such as copper nitrate, lead nitrate, barium nitrate, etc. The decomposition of such nitrates with the generation of ni- g0 trogen oxides may be accomplished by means of heat.

(c) Oxide of nitrogen can also be prepared by the reaction between metals such as copper, tin, silver, etc., and nitric acid to produce oxides of nitrogen, including nitrogen tri-oxide.

Further purposes, features and advantages of this invention will be apparent in connection with the following description of specific illustrations of the practice of this invention in connection with the accompanying drawings, wherein: Figure 1 is a flow sheet wherein the steps comprising one method of bleaching and treating tobacco according to this invention are indicated; Figure 2 shows diagrammatically a side sectional view of one form of apparatus for treating tobacco according to this invention; Figure 2-A shows a continuation of the apparatus shown in Figure 2; Figure 3 shows diagrammatically a side sectional view of an alternate form of apparatus which may be used in treating tobacco according to this invention; Figure 4 shows diagrammatically a side sectional view of apparatus for use in neutralizing or chemicalizing the tobacco and Figure 5 is a plan view of a portion of the screen conveyor employed in connection with the appaS ratus shown in Figures 2 and 2-A.

An illustration of the practice of this invention will be given first in connection with the apparatus shown in Figs. 1, 2, 2-A and 5. The tobacco to be treated is normally cured tobacco in the form of partially dried leaves. Such tobacco, for example, is preferably first introduced into wetting or moistening chamber 10. In the chamber 10, the tobacco is subjected to water either in liquid or vapor state to preliminarily wet the tobacco so that the tobacco will be more receptive to the subsequent bleaching operation and so that the leaves will be rendered pliable and free from each other. The chamber 10 is provided with suitable inlets for water and/or steam. Thus the chamber may be provided with one or more water inlets, such as inlet I controlled by valve 13 and leading to spray nozzle 14 which is adapted to spray water upon the tobacco leaves 15 hanging on racks 16.

Steam may also be introduced into the chamber by means of steam lines 17 controlled by valves 18. To maintain the conditions in chamber 10 as uniform as possible, one or more agitators 19 driven by any suitable means, not shown, may be employed. The chamber 10 may have a suitable drain 20 to take off excess water or steam condensate.

After the tobacco has been moistened in chamber 10, it is preferable to further condition the tobacco before it is subjected to the bleaching treatment which is to follow. For this purpose, the tobacco leaves are loaded in flatwise arrangement on one or more continuous conveyors preferably in the form of a coarse screen which is made of a suitable non-corrosive material, such as stainless steel and which offers as small an area of contact as possible with the tobacco, leaves. In Figs. 2 and 2-A two conveyor screens 21 of this type are shown. Detail of such screens is shown in Fig. 5, reticulated wires 64 being employed. The loading of the tobacco on the screens is accomplished in the loading room 22. In order to insure against displacement of the tobacco . leaves, screens 23 which may be similar to screens 21 are employed and are adapted to become superimposed upon the tobacco resting upon screens 21 during the travel of the tobacco through the apparatus. To afford. continuous movement of the screens 21 and 23, rollers 24 and 25 are employed. Any one or more of such rollers may be driven by suitable means not shown.

The movement of the screens in carrying the tobacco through the apparatus may be continuous or intermittent as desired.

After the tobacco ias been loaded upon the 00 conveyor screens, it is introduced into conditioning chamber 26 in which the tobacco attains the desired amount of moisture, substantially uniformly distributed in the tobacco.

The atmosphere in chamber 26 can be main05 tained at desired humidity by any suitable means.

In the drawings, an air inlet 21 is shown through which air previously conditioned to the proper degree of humidity is introduced. The air thus introduced escapes through the various openings 28 through which the conveyor screens 2 and 23 pass. To keep the atmosphere in the chamber 26 as uniform as possible, agitators 29 driven by any suitable means (not shown) are preferably employed. The air that is introduced through inlet 7i 27 is preferably and by way of illustration approximately saturated with moisture. Care should be taken, however, hot to introduce such an excessive amount of moisture that free moisture will condense on the tobacco. The tobacco is maintained in the chamber 26 until the moisture content of the tobacco is substantially uniform throughout. To afford a specific illustration, the tobacco is maintained in chamber 26 until it is about 85% to 95% saturated with moisture throughout. The presence of free drops of water on the surface of the tobacco is preferably avoided.

Alternatively in the chamber 26, the atmosphere may be kept in a humidified state by other suitable means such as inlets 61 for steam or water which can be distributed in the chamber to maintain the desired humidity therein.

When the leaves emerge from the chamber 26, they are treated to remove free moisture, thereon, if any, as by passing the leaves between rollers 30. The rollers are preferably made of some water-absorbent material, such as cloth. If the conditioning in chamber 26 is carefully conducted, the rollers 30 may be dispensed with as exposure to atmosphere in chamber 26 can be controlled so as to prevent the existence of free water on the tobacco. However, especially when there is an excess of moisture in chamber 26, the employment of special means such as rollers 30 to remove free water is desirable. The tobacco leaves by the foregoing arrangement are placed in a condition to be bleached in bleaching chamber 31, which, together with the other apparatus associated with this chamber'are preferably made of some non-corrosive material, such as stainless steel. Alternatively wood or concrete lined with asphalt or other resistant material may be used. In this chamber, the tobacco is exposed to an atmosphere comprising oxide of ntirogen which is introduced into chamber 31 by line 32 controlled by valve 33.

Adjacent openings 34 through which the conveyor screens 21 and 23 pass are flap valve arrangements 35 which may be made of flexible material such as rubber so as to .prevent at least in part the escape of oxide of nitrogen from the chamber 31. If there is excess of oxide of nitrogen in chamber 31, such excess can be withdrawn through take-off line 36 controlled by valve 37.

In order to keep the atmosphere in the chamber31 o0 homogeneous, agitators 38 are employed which may be driven by any suitable means (not shown). Likewise, distributing nozzle 39 is preferablyemployed. Thechamber31 may be provided with a drain 40 and to control the temperature in the chamber a coil 63 or other similar device is preferably employed, through which heating or cooling fluid may be circulated.

By way of illustration, the previously conditioned tobacco is exposed in chamber 31 to an atmosphere containing about 15 to 35% of oxide of nitrogen of which the major portion is nitrogen tri-oxide. The balance of the atmosphere in the chamber may be air. The atmosphere in the chamber is preferably'of high humidity, i. e. just 05 below 100% saturation. For this purpose, steam may be mixed with the oxide of nitrogen that is introduced into the chamber as by steam inlets 66 controlled by valves 67. The chamber is preferably maintained at a temperature of about 20° C. Under those conditions the' tobacco is bleached to a pleasing light brown color in about 15 to 30 minutes.

In order that the concentration of oxide of nitrogen may be kept constant in the chamber 31, 76 some means for rapid analysis is required. For this purpose, I utilize the optical characteristics of the gaseous mixture in the chamber and have associated with the chamber 31 a device indicated generally by the reference character 62.

The device may comprise known means responsive to the optical characteristics of the atmosphere such as the index of refraction of the atmosphere or the light absorption characteristics of the atmosphere. By having the device properly calibrated the concentration of the oxide of nitrogen in the chamber 31 may be readily determined at any time.

At the completion of the bleaching treatment, the tobacco is passed into a washing chamber 41, where the tobacco is either immersed or sprayed with water. Preferably sprays such as sprays 42 are employed, which spray water over the leaves on the conveyor screens passing through chamber 41. The washing may include subjecting the leaves to blasts of air which aids in degassing the tobacco. By incorporating an alkaline material such as ammonia with the air, the atmosphere thus can be employed to neutralize any acid carried by the tobacco. As the leaves pass into and/or out of the chamber, they may be subjected to direct rinsing action either with water or moisture conditioned air directed against the tobacco by nozzles 43. The chamber 41 is provided with an outlet 68.

The tobacco may likewise be subjected to another type of neutralization treatment. For this purpose, the conveyor screens are passed through a neutralization tank 44 containing an alkaline liquid 45, such as a solution of sodium or potassium carbonate or bicarbonate or other alkaline reagent. The conveyor screens are guided through the alkaline solution by means of a plurality of guide rollers 46 and 41. A mildly alkaline solution having a pH value -f about 8 is preferred.

In the neutralization step, any remaining nitric acid is converted into neutral nitrates which are useful in improving the burning properties of the tobacco. To place the tobacco in condition for marketing,itis carried by the conveyor screens between rollers 48 in the event that a neutralizing solution has been employed which remove some of the excess moisture and then into drying chamber 49. In the drying chamber, the leaves are subjected to an atmosphere of desired humidity.

Conditioned air is introduced by means of inlet 50 and withdrawn by outlet 51. The atmosphere in chamber 49 is preferably agitated by means of agitators 52 which are driven by any suitable means (not shown). In the chamber 49, the leaves attain the moisture content which is desired, depending upon the purpose for which the tobacco is intended. As the tobacco emerges from the chamber 49, it is unloaded from the conveyor screens and is in condition for any commercial use that is desired.

As shown in the flow sheet of Fig. 1, the water from chamber 41 which is somewhat acidic in character-may be neutralized for the recovery of salts. This may be done by evaporating the salt solution by any suitable means. At the same time that this solution is evaporated for the recovery of salt, waste solution from the neutralizing tank may likewise be evaporated in the evaporator for the recovery of the salt content thereof.

To further illustrate the practice of this invention and possible embodiments thereof, it will be described in connection with the apparatus shown in Figs. 3 and 4. Instead of employing a continuous conveyor screen of the type shown in Figs. 2 and 2-A, the tobacco may be treated while disposed on other types of carriers. Thus, carriers 53 of any suitable type may be employed. In the embodiment shown in the drawings, the carriers 53 comprise a plurality of racks or frames 54 from which the tobacco is suspended in "hands" or as free leaves with the leaves as free from each other as possible. The tobacco can be placed on the carriers 53 after having been moistened in a chamber such as the chamber 10 shown in Fig. 2. The carriers 53 are mounted on wheels 55 adapted to travel on floor 56.

In Fig. 3, a treating chamber 57 is shown through which the carriers 53 can pass. Preferably, the treating chamber 57 is provided with outer doors 58 and inner doors 59 which doors are spaced from each other in the direction of travel of the conveyors 53 therethrough. With this arrangement, one of the doors 58 may be opened, for example, while the door 59 adjacent thereto is closed, so that a carrier 53 may be placed in the space between these doors. Thereafter, the door 58 is closed and the door 59 opened so that the carriage 53 may be moved into the inner part of the treating chamber. The carriage 53, after the tobacco has been treated in the treating chamber may be removed from the chamber by first opening a door 59 to bring the carriage between door 59 and door 58, then closing the door 59 and lastly opening door 58. Any number of carriages such as carriages 53 may be included in the chamber 57 between doors 59 and in normal operation as one carriage 53 is moved into chamber 57 another carriage bearing bleached tobacco is moved out of the chamber in the manner above described.

The treating chamber 57 may be substituted for any of the treating chambers 10, 26, 31, 41 or 49 shown in Figs. 2 and 2-A. The treating chamber 57 of the type shown in Fig. 3 is especially adapted, however, for subjecting tobacco to the bleaching action of oxides of nitrogen.

When used for this purpose, the chamber may be supplied with suitable inlets, outlets and agitators of the type shown in Figs. 2 and 2-A. By such construction, the interior of the chamber can be maintained with a desired concentration of oxides of nitrogen therein and the carriers 53 may be moved therethrough so as to subject tobacco thereon for the desired length of time to the action of oxides of nitrogen.

A chamber such as the chamber 57 may also be employed to preliminarily condition the tobacco in the same way that chamber 26 is employed. For example, conditioned air may be passed into and out of the chamber by means of any suitable arrangement of inlets and outlets. A chamber such as chamber 57 may also be employed to wash the tobacco after it has been bleached and for this purpose one or more sprays, such as the sprays 42 shown in Fig. 2-A may be employed.

When it is desired to subject the tobacco on carriers 53 to a neutralizing bath, this can be done in several ways. According to one method, the entire carrier 53 can be bodily removed from the floor 56 and immersed in an alkaline solution 60 in tank 65. After the neutralization treatment, the carrier may be removed from the tank 65 and taken to any suitable drying chamber in which the air is preferably conditioned so that the desired amount of moisture will be retained in the tobacco.

While movement of tobacco between successive chambers has been described above in practicing the process of this invention, it is apparent that any number of steps and even the entire process may be carried out in a single chamber. Thus the tobacco could be placed in a single chamber such as chamber 57 and moistened by sprays.

The tobacco could then be exposed to conditioned air, bleached, washed, neutralized and dried while remaining in the chamber by varying the conditions in the chamber. It could also be treated to improve its burning qualities. After completion of the treatment of one batch, a second batch could be similarly processed.

The foregoing description has been confined principally to method and apparatus for the bleaching of tobacco to improve its color. It is of great significance and importance that the bleaching to desired light color is accomplished without substantial impairment of the flavor and aroma of the tobacco. In addition to the foregoing, the tobacco can be further improved in the practice of this invention so that it will have better burning properties. For this purpose, the tobacco is treated with one or more salts of nitric acid or of mono- or poly-basic organic acids having 1 to 5 carbon atoms, the salts being salts of metals selected from the group consisting of alkaline earth metals, alkali metals and magnesium. Preferably, alkali metal salts of such acids are Used in conjunction with alkaline earth salts and/or magnesium salts of such acids. For example, the tobacco may be treated with potassium nitrate in admixture with magnesium or calcium nitrate as a combination of prepared salts. Other alkali metal salts of such acids may be used such as the sodium salts. Of the alkaline earth salts, the salts of calcium and strontium are preferred. Illustrations of mono- and polybasic organic acids having 1 to 5 carbon atoms are citric acid, acetic acid and oxalic acid.

The treatment -of tobacco with the salts above mentioned may be accomplished in any suitable way so that the salts will be incorporated therewith. The term incorporated therewith includes impregnation of the tobacco or surface application of the tobacco with the salts. The salts may be incorporated with the tobacco, for example, by placing a solution of such salts in the tank 44 in lieu of a neutralizing solution. Preferably, however, the tobacco is first subjected to neutralization In tank 44-and is-thereafter treated with the salt solution. For this purpose, a second tank similar to tank44may be employed in which the tobacco is immersed in the salt solution. Alternatively, the tobacco while on a carrier of the type of carrier 53 may be immersed in a solution of such salts. The concentration of the salt solution is preferably from about 3% to 31/2% although solutions containing approximately 1% to 5% may also be advantageously employed. It is understood, however, that the concentration may be varied without departing from the scope of this feature of my Invention.

Immersion of the tobacco leaves for about 2 to 30 minutes in the usual case is sufficient to permit absorption of salts and about 5 to 10 minutes is ordinarily enough. After the chemicalization of the tobacco has been completed the tobacco can be dried as above described.

While certain examples of the practice of this invention have been given above, it is apparent that the procedure above described can be varied considerably without departing from the scope of this invention. For purpose of affording a fuller understanding of this invention, some of the principles underlying this invention will be discussed from a more general point of view. Thus, the preliminary wetting and/or conditioning can be varied considerably and can even be eliminated especially when the tobacco is received in a relatively moist condition. However, if the preliminary wetting and conditioning are eliminated, tests have shown that inferior bleaching is normally effected In the case of tobacco in the condition in which it is ordinarily received. About 10% to 30% of moisture is desirable in the tobacco prior to bleaching. When the tobacco contains about 30% of moisture, it approaches saturation. If about 15% to 25% moisture is contained in the tobacco, the best results are achieved. However, nearly complete saturation gives excellent results. If the tobacco contains less than 10% of moisture, more time is required for bleaching and it is difficult to obtain uniform bleaching. If the tobacco is too dry during the entire exposure to oxide of nitrogen, very inferior bleaching or no bleaching is obtained.

In preliminary conditioning the tobacco, the wetting and moisture conditioning steps may be combined, but if wetting alone is employed, care should be taken to remove free water from the surface of the tobacco by exposure to air of uniform humidity or by mechanical means. Prolonged soaking is not ordinarily desirable, however, as this is likely to result in some loss of aroma. Conditioning in a humid atmosphere has been found to best preserve the flavor and aroma of the tobacco.

In the bleaching operation the concentration of oxide of nitrogen in the bleaching chamber may vary from about 5% to 50%. Concentrations even as high as 100% may be employed, but to operate with such high concentration requires excessive generation of the oxide of nitrogen and attendant increased expense. Also, it has been found that the lower concentrations above mentioned afford a more desirable product. Likewise concentrations of oxide of nitrogen as low as 1% may afford some bleaching under favorable conditions of temperature and moisture but the time for achieving substantial bleaching at such low concentrations is impractical commercially.

Preferably about 10% to 40% of oxide of nitrogen is employed. As the concentration of oxide of nitrogen is increased, the bleaching action is more rapid. When a concentration of the oxide of nitrogen is about 15% to 25% bleaching can be accomplished in about 15 to 30 minutes to produce a pleasing color. If the concentration oftheoxide of nitrogen is about 5%, the bleaching is somewhat slower and can be accomplished in about 30 minutes to 1 hour depending upon the amount of bleaching-desired. Preferably, an atmosphere containing about 10% to 40% of oxide of nitrogen is employed for periods of from about five minutes to one hour.

The temperature at which the bleaching is conducted may vary from about 10° C. to about 50' C. although temperatures of from about 18' C. to 35 -C. are normally to be preferred. As the temperature is lowered, the bleaching action is slower and there is likelihood of condensation of water and/or oxide of nitrogen.

At higher temperature than about 50° C. the resulting bleached tobacco does not have as desirable a texture. If excessively high temperatures are used together with high concentrations of oxide of nitrogen and long periods of time the tobacco may be rendered somewhat brittle and there may be some impairment of the flavor of the tobacco. But such extreme conditions are not necessary as even extremely pale effects can be secured according to this invention without substantial weakening of the texture of the tog bacco or impairment of flavor.

The atmosphere in the bleaching chamber preferably carries a high degree of humidity. If tobacco, which is nearly saturated with moisture is carried into the bleaching chamber, the atmosphere tends to become moist. However, it is normally preferable to introduce moisture along with the oxide of nitrogen into the bleaching chamber so that the atmosphere is more than about 75% saturated with moisture. Preferably, the atmosphere in the bleaching chamber is about 85% to 95% saturated. It is preferable to avoid complete saturation as this tends to cause formation of droplets of free moisture on the tobacco with resultant non-uniformity of bleaching.

The washing step, after the tobacco has been bleached, may be modified so that the tobacco is either de-gassed with conditioned air or by means of water. These steps may even be eliminated so that the washing is conducted in an alkaline solution, the washing and neutralization thereby being performed in a single operation. The neutralization may be performed by immersing the tobacco in a liquid or alternatively by means of sprays. Or the use of liquid neutralizing agents and washing may be entirely omitted and only gaseous neutralization employed. As described above, an atmosphere containing gaseous ammonia, or ammonia itself in the pure state, may be used to accomplish the neutralization. LikeU wise, the neutralization chemicals may be combined with the salts above described which are utilized to improve the burning properties of the tobacco.

It has previously been mentioned that it is preferable to treat tobacco according to this invention after it has previously been cured.

By previous curing it is meant that the curing has progressed until the tobacco has become darkened to such an extent that the bleaching process of this invention may be utilized in improving the color of the tobacco. In ordinary practice, the tobacco is first cured and thereafter the dark tobacco is treated according to this invention to improve its color and/or burning properties and this is the preferred practice. Subjecting any tobacco to treatment of the nature above described to accomplish substantial bleaching in a tobacco product is, however, to be regarded as coming within the scope of this invention. While the bleaching has been described in connection with exposing tobacco to an atmosphere containing oxide of nitrogen in gaseous form, it is not without the scope of this invention to expose tobacco to oxide of nitrogen in other ways. For example, oxide of nitrogen may be dispersed in water or other vehicle which is contacted with the tobacco so that the tobacco is subjected to the bleaching action of the oxide of nitrogen.

S While specific forms of apparatus have been Sdescribed it is to be understood that this has been done for purposes of illustration and that the specific forms shown are subject to considerable variation.

The foregoing description has been directed chiefly to the treatment of leaf tobacco. However, finely divided tobacco can also be treated according to the invention and appropriate carriers therefor used. Likewise, finished articles such as cigars can be treated to bleach the wrappers thereof and make them of more pleasing appearance.

The tobacco that is produced in the practice of this invention has increased value due to its greatly improved color. Likewise, it frequently F, has Improved texture. As a result of the treatment, small quantities of reaction products resulting from the reaction between ingredients in tobacco and oxide of nitrogen are retained in the tobacco. When the tobacco is neutralized with an alkali metal compound, the small amount of acidity that is neutralized is chiefly due to nitric acid that is formed as a result of the action of oxide of nitrogen and moisture in the tobacco and in the bleaching chamber, and the neutralization process leaves a small amount of alkali metal nitrate in the tobacco such as sodium nitrate or potassium nitrate. When alkaline compound of alkali metals are used for neutralization, the presence of such nitrates, together with compounds that are reaction products between constituents of the tobacco and nitrogen oxides further identifies one type of tobacco treated according to this invention and likewise serves to improve the burning properties of the tobacco.

The incorporation with tobacco of salts of alkali metals, alkaline earths, and magnesium, which salts are formed from nitric acid and/or organic mono- and poly-basic acids having 1 to 5 carbon ,0 atoms has been discussed above and the presence of such added salts further distinguishes preferred embodiments of this invention.

While this invention has been described above in connection with a number of specific examples s3 of embodiments thereof, it is to be understood that this has been done merely for the purpose of illustration.

I claim: 1. A method of treating cured tobacco which comprises effecting substantial bleaching of tobacco by exposure of cured tobacco in the presence of a substantial quantity of moisture to oxide of nitrogen, said oxide of nitrogen being the primary bleaching agent. 2. A method of treating cured tobacco which comprises effecting substantial bleaching of cured tobacco by exposure of said cured tobacco to moistened oxide of nitrogen, said oxide of nitrogen being the primary bleaching agent. 3. A method of treating cured tobacco of dark color which comprises exposing the cured tobacco in a moistened condition to an atmosphere containing oxide of nitrogen to afford substantial bleaching of the tobacco. 4. A method of bleaching tobacco which has previously been cured which comprises exposing the cured tobacco containing over about 10% of moisture to an atmosphere containing over 5% of oxide of nitrogen, initially in gaseous form to afford substantial bleaching of the tobacco.

5. A method of treating cured tobacco which comprises wetting the tobacco, moisture conditioning the tobacco by exposure to atmosphere to effect substantially even distribution of moisture 3 in the tobacco, and bleaching the tobacco in a uniformly moistened condition by exposure to oxide of nitrogen, initially in gaseous form.

6. A method of treating cured tobacco which comprises moistening the cured tobacco, subject- o7 ing the moistened tobacco to an atmosphere of oxide of nitrogen initially in gaseous form, removing the tobacco from said atmosphere containing oxide of nitrogen, and washing the tobacco. 7. A method of treating cured tobacco which comprises moistening the cured tobacco by conditioning by exposure to humidified air, subjecting the moistened tobacco to an atmosphere of oxide of nitrogen Initially in gaseous form, removing the tobacco from said atmosphere containing oxide of nitrogen, and washing the tobacco with moisture conditioned air.

8. A method of treating cured tobacco which comprises moistening the cured tobacco, subjecting the moistened tobacco primarily to an atmosphere of oxide of nitrogen applied initially in gaseous form, removing the tobacco from said atmosphere containing oxide of nitrogen, and neutralizing acid carried by the tobacco after the bleaching step.

9. A method of treating cured tobacco which comprises moistening the cured tobacco, subjecting the moistened tobacco to an atmosphere of oxide of nitrogen applied initially in gaseous form, removing the tobacco from said atmosphere containing oxide of nitrogen, and neutralizing the tobacco after bleaching with an alkaline solution.

10. A method of treating cured tobacco which comprises moistening the cured tobacco, subjecting the moistened tobacco to an atmosphere of oxide of nitrogen applied initially in gaesous form, removing the tobacco from said atmosphere containing oxide of nitrogen, and neutralizing the tobacco after the bleaching step by contacting the tobacco with an atmosphere containing ammonia.

11. A method of treating cured leaf tobacco which comprises moistening the tobacco leaves, distributing the moisture substantially uniformly in the tobacco leaves without free moisture on the surface thereof, subjecting the tobacco to an atmosphere containing more than 5% of oxide of nitrogen initially in gaseous form at a temperature between about 10" C. and about 50" C. to bleach the tobacco, removing the tobacco from said atmosphere, neutralizing the tobacco by contacting it with an atmosphere containing ammonia and air-conditioning said tobacco.

12. A method of treating tobacco which comprises subjecting the tobacco to an atmosphere containing a concentration of 5% to 50% of N203.

13. A method of treating cured tobacco which comprises moistening tobacco substantially uniformly throughout, exposing the tobacco to an atmosphere containing about 5% to 50% of oxide of nitrogen at a temperature of from about 10° C. to about 50" C., removing the tobacco from said atmosphere, and then neutralizing any acid carried by the tobacco.

14. A method of treating cured leaf tobacco which comprises washing the leaves to moisten them, moisture conditioning the leaves by exposure to atmosphere so that the leaves will contain about 15% to 25% of moisture, removing any free drops of water on the surface of the leaves, exposing the tobacco leaves to an atmosphere containing about 10% to 40% of oxide of nitrogen a major proportion of which is in the form of N203 which atmosphere is about 85% to 95% saturated with moisture at a temperature of from about 18* C. to 35" C. to bleach the tobacco, and washing and neutralizing the bleached tobacco.

15. A tobacco leaf wrapper having cured and bleached characteristics, the bleached characteristics being obtained by exposure of previously cured tobacco primarily to oxide of nitrogen, in a moistened condition..

16. A tobacco article consisting of cured tobacco having a bleached characteristic, said characteristic being obtained by treating the tobacco primarily with oxide of nitrogen in the presence of a substantial amount of moisture after the tobacco has been cured, and having added to it an alkali metal nitrate. 17. A tobacco leaf wrapper having cured and bleached characteristics, the bleached characteristics being obtained by exposure in a moistened condition primarily to oxide of nitrogen and having incorporated therewith an added salt of a metal selected from the group consisting of alkali metals, alkaline earth metals, and magnesium formed with an acid selected from the group consisting of nitric acid and organic mono- and polybasic acids having 1 to 5 carbon atoms. 18. A tobacco article consisting of cured tobacco having a bleached characteristic, said characteristic being obtained by treating the tobacco primarily with oxide of nitrogen after the tobacco has been cured, and having incorporated therewith added salts comprising a first salt selected from the group consisting of alkali metal salts of nitric acid and of organic mono- and poly-basic acids having 1 to 5 carbon atoms, and a second salt selected from the group consisting of alkaline 4 earth metal salts and magnesium salts of nitric acid and of organic mono- and poly-basic acids having 1 to 5 carbon atoms.

19. A method of treating cured tobacco which comprises effecting substantial bleaching of tobacco by exposure of cured tobacco in an atmosphere containing a substantial proportion of moisture to oxide of nitrogen, said oxide of nitrogen being applied originally in gaseous form.

SOUREN Z. AVEDIKIAN. 5