the additives of the present invention are applied under mild conditions in solution , usually an aqueous solution , to contact substantially with the tobacco , which is usually in a form shredded to filler dimensions . this is merely followed by a drying stage to remove the solvent . for reasons of efficiency and economy , the process may be carried out during the casing process , rather than at some point prior to casing , by methods known in the art for the incorporation of specified amounts of additives , although there is no requirement that the application be so limited . the additives are dissolved or dispersed in an appropriate solvent and may be applied , therefore , as a spray before , during or after casing . amounts of the multivalent metal or acid salt applied to the tobacco products may range from 0 . 2 % to 7 . 5 % of dry tobacco weight to produce significant increases in filling power . a preferred range is from 1 . 0 % to 4 . 0 % of dry tobacco weight . a 3 % by weight chemical addition appears to provide the best result . levels greater than 7 . 5 % by weight appear to have a tendency to affect the subjective smoking value or flavor of the tobacco products . levels less than 0 . 2 % do not appear to provide worthwhile filling power increases . it is believed that upon addition of the solution of the multivalent metal or acid salt , expansion of the tobacco product takes place by means of the solvent and , upon drying , the various salts and ions thereof have bound to the pectinaceous materials , to stiffen the pectins , and prevent the return of the tobacco to its original unexpanded form . the pliability of individual shreds is reduced , therefore , fewer treated and stiffened tobacco shreds are needed to fill the space with equal firmness as compared to untreated shreds . it is , therefore , an object to obtain a filler having increased bulk volume . by utilizing a lesser absolute amount of tobacco , it is an object to produce , for example , a firm tobacco rod , which favorably compares with the firmness and subjective smoking qualities of identical tobacco rods which have not been treated in accordance with the teaching of the present invention . it is desired to achieve an overall tobacco savings in the range of 5 - 15 % due to an increase of filling power of 5 - 25 %. in comprehending the following examples , it is to be understood that the filling power is measured as the minimum weight of the material which will produce a tobacco rod of specified dimensions and firmness . the filling power is the ability of the material to provide a firm rod . the filling power may be measured as the volume occupied by a specified weight of filler in an upright cylinder while a specified piston weight is applied to its top surface , as set forth in &# 34 ; filling volume of cut tobacco and cigarette hardness ,&# 34 ; h . wakeham , et al ., tobacco science xx : 164 - 167 , 1976 . standard equilibrium conditions for measurement of filling power is usually 60 % relative humidity ( rh ) at 75 ° f . ( 23 . 9 ° c .). further it is to be understood throughout the following examples that the oven volatiles ( ov ) measurement is the standard weight loss in circulating air oven in three hours at 100 ° c . the cylinder volume ( cv ) measurement of filling power , is determined by placing 10 . 0 grams of filler in a standard metal cylinder , 3 . 358 cm . in diameter , and then by compressing the same , by vibration , under a piston weighing 1875 grams having a diameter of 3 . 335 cm . this vibrating compression continues for one - half ( 0 . 5 ) minute ( s ) and then is followed by still compression for five ( 5 . 0 ) minutes . the volume reading is then taken . the standard deviation of the cylinder volume measurement is about 1 . 5 %. in the following examples , unless otherwise noted , the sample has been previously conditioned to equilibrium at 24 ° c . and 60 % rh . two samples of a cigarette filler blend were sprayed after casing with 2 % and 5 % respectively , by weight , of al 2 ( so 4 ) 3 . 18h 2 o which had been dissolved in water to give an approximately 50 % aqueous solution . the filler was dried at room temperature for 4 days and conditioned at 24 ° c . and 60 % rh . comparative measurements , illustrated in table 1 , indicated a filling power increase of about 20 % for the tobacco treated with the 5 % salt and about a 10 % increase for the tobacco treated with the 2 % salt . table 1______________________________________ cv cc / 10 g ov % ______________________________________control 33 . 7 12 . 7experimental , 5 % 40 . 7 11 . 6experimental , 2 % 37 . 2 12 . 7______________________________________ three samples of cut , uncased tobacco filler shreds were sprayed with varying levels of aluminum sulfate , by means of an aqueous solution of aluminum sulfate . after drying , the samples were analyzed for aluminum sulfate concentration and ov and cv values were measured . table 2______________________________________ cv cc / ov cv % % al . sub . 2 ( so . sub . 4 ). sub . 3 . 18h . sub . 2 o 10 g % increase______________________________________control -- 37 . 6 14 . 8 -- experimental 4 . 32 43 . 8 14 . 0 20experimental 6 . 05 44 . 3 14 . 5 21experimental 6 . 69 46 . 1 14 . 4 26______________________________________ cigarettes were prepared at three weight levels , using a commercial tobacco blend treated with al 2 ( so 4 ) 3 . 16h 2 o being 2 . 8 % of dry tobacco weight , in the casing . comparisons were made with cigarettes of similar weight levels prepared with the same commercial tobacco blend which was untreated . one - half of the treated and untreated cigarettes were selected for equal weight in each category for the determination of rod firmness by means of a compacimetric test . due to the volume increase in the treated filler , a 7 . 3 % weight reduction was possible at equal firmness . due to the 2 . 8 % salt in the filler , the true tobacco saving was 9 . 9 % compared with the non - treated cigarette at equal rod firmness . the other half of the cigarettes underwent accelerated aging for three weeks by alternated placement of the cigarettes in a cabinet under conditions of 110 ° f . and 15 % rh and in another cabinet under conditions of 100 ° f . and 90 % rh . after aging , the firmness of the cigarettes was determined in the same manner as above . the volume increase , as well as the firmness of the treated cigarettes , proved to be stable . comparisons were made at equal firmness and at equilibrium moisture of the treated and untreated cigarettes . a 6 . 8 % weight reduction , comparable to that of the of the non - aged , treated cigarettes , was achieved in the aged , treated cigarettes , consideration being made for the exchange of salt for tobacco . the true tobacco saving in cigarettes that underwent accelerated aging was 9 . 4 % compared with the non - treated cigarette at equal rod firmness . cigarettes were prepared by machine with a control tobacco , one portion being untreated and another portion of the same tobacco being treated with 3 % by weight of aluminum sulfate . conventional filters were attached . these were presented to an experienced panel of smokers in paired comparison . though there was no significant preference , the panel found the untreated cigarette harsher at a 99 . 9 level of significance . the panel further found the untreated cigarettes more spicy , more bitter and hotter at a 99 level of significance . the cigarette tobacco filler blend used in example 1 was treated with a 3 . 0 %, by dry weight , salt combination composed of 0 . 75 % potassium aluminum sulfate , 0 . 75 % ammonium aluminum sulfate , and 1 . 5 % aluminum sulfate . after equilibration , the following results were obtained : ______________________________________ control treated______________________________________cv cc / 10 g 35 . 7 38 . 0ov % 12 . 9 12 . 9______________________________________ these results show an increase in filling power of about 6 . 5 %. the same tobacco filler used in example 1 was treated with 3 % calcium acetate , the results being as follows : these results show an increase in filling power of about 12 . 4 %. as in example 1 , a cigarette tobacco blend was treated with magnesium sulfate comprising 3 % of the blend weight . when compared with the control , these results were observed . roughly about 8 % more cigarettes could be prepared from the tobacco treated with magnesium sulfate due to an increase of filling power approximating 9 . 0 %. in a similar manner to example 1 , a cigarette tobacco filler treated with 3 % by weight of ferrous sulfate resulted in a comparable increase in filling power . in a similar manner to example 1 , a cigarette blend was treated with calcium sulfamate comprising 3 % of the blend weight which also resulted in a comparable filling power increase . in the following examples 10 - 13 , experiments were conducted with various three percent addition salt solutions to treat a control tobacco , the results of which were compared to the untreated control tobacco . ______________________________________ cv ov______________________________________3 % potassium titanium oxalate oncontrol k . sub . 2 tio ( c . sub . 2 o . sub . 4 ). sub . 2 . 2h . sub . 2 o 39 . 4 12 . 82control 35 . 5 13 . 04______________________________________ these results illustrate an increase in filling power of approximately 10 %. ______________________________________ cv ov______________________________________3 % tannic acid on control 42 . 8 12 . 09control 37 . 2 12 . 97______________________________________ these results illustrate an increase in filling power of approximately 15 %. ______________________________________ cv ov______________________________________3 % ca - gluconate on control 39 . 0 12 . 62control 37 . 2 12 . 97______________________________________ these results illustrate an increase in filling power of 4 to 5 %. ______________________________________ cv ov______________________________________3 % ( nh . sub . 4 ). sub . 2 mg ( so . sub . 4 ). sub . 2 . 6h . sub . 2 o 40 . 5 12 . 75control 37 . 2 12 . 97______________________________________ these results show an increase in filling power of about 8 %. a combination of aluminum citrate , 1 % by dry weight of the tobacco , and citric acid , 2 % by dry weight of the tobacco were found to cause only an increase in filling power of about 2 % to 4 %. it will be apparent to those skilled in the art that various modifications and variations of the invention of the preceeding disclosure may be made without departing from the spirit and scope thereof . it will be understood , therefore , that the claims hereinafter set forth should be limited only by such limitations as expressly set forth .
through interaction with the pectinaceous materials of tobacco smoking products , increased filling power of tobacco constituents is accomplished , in accordance with the present invention , by means of maintaining the tobacco , usually in shredded form , in an expanded form by applying , in solution thereto , multivalent metal and organic acid salts , especially those salts found in the hydrated form . the multivalent salt additives cause the pectinaceous materials of the tobacco to retain the expanded bulk volume of the tobacco .