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United States Patent: 4,257,430 Page 8 of 16 composition of the extraction medium is maintained constant, reliable results permitting accurate control of the process are obtained. The following examples are illustrative of the present invention, including the preparation of casings containing insoluble palladium, the formation of tobacco compositions containing non-extractable palladium, and the testing of such tobacco compositions. In the examples, the tobacco samples and the casing samples were analyzed for non-extractable and insoluble palladium, respectively, by the following procedures: I. Analysis for Non-Extractable Palladium in Tobacco The "non-extractable" palladium is the palladium in tobacco which is not extracted with ammoniacal ethylenediamine tetra-acetic acid, and is determined by subtracting the extractable palladium from total palladium. The total palladium and extractable palladium are determined by the following procedure: Determination of "Total Palladium" In Tobacco An accurately weighed sample of about 1 gram of tobacco is placed in a 100-ml beaker, 5 to 10 ml of 1:1 reagent grade nitric acid and reagent grade perchloric acid is added, the beaker is covered with a cover glass and heated on an electrical hot plate at a moderate rate for at least 2 hours. The cover is then removed, and heating is continued to evaporate the sample to dryness. The beaker is then cooled to ambient temperature, 1 ml of reagent grade concentrated hydrochloric acid is added, and the cover is replaced. The mixture is heated to boiling momentarily, 10 ml of 0.1 N nitric acid is added, and the solution is digested by heating near boiling (80.degree.- 100.degree. C.) for 10 minutes. The solution is cooled to ambient temperature, and diluted with 0.1 N nitric acid to 25 ml to form an analytical sample. Determination of "Extractable Palladium" From Tobacco An accurately weighted sample of tobacco weighing from about 1 to about 2 grams is mixed with 50 ml of an ammoniacal solution of ethylenediamine tetra-acetic acid (EDTA) (0.1 M in EDTA and 1 M in NH.sub.4 OH) having a pH of about 10. The resulting mixture is continuously agitated for 30 minutes, and is immediately filtered through a membrane filter having pore size of not greater than 0.45 microns. A 10.0 ml portion of the filtrate is evaporated to dryness in a 100-ml beaker and 5 to 10 ml of 1:1 reagent grade nitric acid and reagent grade perchloric acid is added to the residue. The beaker is covered with a cover glass and heated on an electrical hot plate at a moderate rate for at least 2 hours after the appearance of HC1O.sub.4 fumes, the cover is then removed and heating is continued to evaporate the sample to dryness. The beaker is cooled to ambient temperature, 1 ml of concentrated reagent grade http://164.195.100.11/netacgi/nph-Parser?Sect1=PTO1&Sect2=HIT.../425743 2/13/01

United States Patent: 4,257,430 about 70.degree. C. to about 80.degree. C. being preferred. Page 7 of 16 The heating is carried out for a period of time sufficient to effect the desired degree of conversion of soluble palladium to insoluble palladium. It is preferred that there be substantially total conversion of soluble palladium to insoluble palladium, thereby achieving the maximum catalytic activity possible. Complete conversion is not essential, however, and useful results are achieved when the proportion of soluble palladium is reduced to less than about 50 percent of the total palladium in the solution. It is preferred, however, that the soluble palladium in the solution be reduced to not more than 5 percent of total palladium. In general, this will require heating for at least about 4 hours at 75.degree.-80.de ree. C., and a correspondingly longer time at lower temperatures. Heating for still longer times can be employed if desired, but ordinarily is unnecessary. Extended heating periods, i.e., for 24 hours or more, especially at temperatures of about 80.degree. C., or above, are not desired because of the increased risk of agglomeration or the formation of undesirable degradation products. After formation of insoluble palladium, the resulting aqueous mixture is then applied to the tobacco by any suitable technique, such as those commonly employed to apply casing solutions to tobacco. For example, the mixture may be sprayed onto the tobacco. The thus-treated tobacco is then formed into smoking articles such as cigars or cigarettes, or packaged as pipe tobacco. The resulting tobacco product will contain non-extractable palladium in an amount proportional to the amount of insoluble palladium in the solution used to treat the tobacco. However, the relative proportion of non-extractable to total palladium in the tobacco will be somewhat less than the proportion of insoluble to total palladium in the treating solution. When the preferred levels of soluble palladium (5 percent or less of the total palladium) are achieved in the aqueous medium, the extractable palladium ordinarily comprises no more than about 10 percent of the total palladium in the tobacco. This difference may be due to the use of alkaline EDTA as the extracting medium. It also has been observed that the specific base employed in preparing the alkaline EDTA extraction medium will affect the absolute value of extractable palladium found. Consequently, in analyzing for extractable palladium it is important that the same extraction medium be employed. The alkali metal hydroxides, e.g., sodium hydroxide and potassium hydroxide, and ammonium hydroxide are the preferred alkaline materials used to form the extraction medium. Ammonium hydroxide is especially preferred. The pH of the extraction medium is not narrowly critical, nor is the concentration of EDTA. It is preferred, however, that the pH be approximately 10 (i.e., from about 9.5 to about 10.5), and that the concentration of EDTA be approximately 0.1 molar (i.e., from about 0.09 to about 0.11 molar). So long as the http://164.195.100.11/netacgi/nph-Parser?Sect1=PTO1&Sect2=HIT.../425743 2/13/01

United States Patent: 4,257,430 Page 4 of 16 wherein the palladium is in a form which minimizes the biological activity of the smoke therefrom. Still another object of this invention is to provide a method for depositing palladium on tobacco in a more active form. More specifically, an object of this invention is the provision of a method for depositing palladium on smoking tobacco which maximizes the proportion of non- extractable palladium on the tobacco. A still further object of this invention is the provision of an analytical method for determining the proportion of palladium which is in a form capable of reducing the biological activity of tobacco smoke. According to U.S. Pat. No. 4,055,191, palladium is incorporated into a tobacco composition either in finely-divided metallic form and/or in the form of a palladium salt which is decomposable, in situ, preferably by heat, into metallic palladium. A preferred procedure which is disclosed is the deposition of palladium, initially in the form of an ammonium chloropalladate salt, in combination with a nitrate com ound, from a solution of these additives in a conventional casing so ution comprising glycerine, propylene glycol and sugars. It has been discovered in accordance with this invention that the catalytic activity of the palladium is highly dependent upont the proportion of palladium which is in the form of "non-extractable palladium", which in turn is highly dependent upon the conditions under which the palladium is applied to the tobacco. As employed herein, the term "extractable palladium" is that palladium deposited on the tobacco which can be extracted from treated tobacco by aqueous, alkaline ethylenediamine tetraacetic acid (EDTA). The chemical form of this "extractable palladium" is not known; it may be a form of metallic palladium in view of available evidence that the extracting medium can dissolve small particles of palladium metal, or it may be ioNc palladium or a mixture of metallic anc ionic palladium. The term "non-extractable palladium" as employed herein is that palladium deposited on the tobacco which is not extracted from treated tobacco by aqueous, alkaline EDTA. The form of this "non-extractable" palladium is thought to be metallic palladium on the basis of available evidence. The specific value of extractable palladium which is obtained will be dependent, inter alia, on the composition of the EDTA reagent, and the conditions of the treatment of the casing or tobacco. However, for each set of conditions, consistent results are obtained, and it is estimated that a single determination of extractable palladium has a standard deviation of 0.001 percent palladium, which corresponds to about 1 to about 10 percent of the total palladium preferably employed in accordance with U.S. Pat. No. 4,055,191. http://164.195.100.11/netacgi/nph-Parser?Sect1=PTO1&Sect2=HIT.../425743 2/13/01

United States Patent: 4,257,430 Page 12 of 16 that the casing solution contained 1.5 percent (NH.sub.4).sub.2 PdCl.sub.4 rather than 1.2 percent (NH.sub.4).sub.2 PdCl.sub.6, and the amounts of Mg (NO.sub.3).sub.2.6H.sub.2 0, glycerine and water were each reduced by 0.1 percent, there was prepared a casing solution having a pH of 2.5, in contrast to a pH of 0.8 for the solutions of Example 2. The solution was heated at 70.degree. C. and periodically , analyzed for soluble palladium. The insoluble palladium formed in the first hour was 59 percent of the total palladium, and the first order rate constant, k was 0.25 hr..sup.- 1. EXAMPLE 4 The experiments described in Example 3 suggested that pH affected the rate of formation of insoluble palladium; however, the level of total palladium in that experiment was greater than in the experiments described in Example 2. Consequently, two new experiments were performed at constant total palladium content to evaluate the effect of pH alone. The compositions of the casing solution and the analytical results after heating at 70.degree. are as follows: Solution Component, weight % A B Invert Sugar 10.2 10.1 Flavor 2.9 2.8 Propylene glycol 1.4 1.4 Glycerine 4.3 4.3 Corn Syrup 3.2 3.2 Lactic acid 0.3 0.3 (NH.sub.4).sub.2 PdCl.sub 6 0.80 (NH.sub.4).sub.2 PdCl.sub.4 0 6 . (Total Pd) (0.22) (0.22) Mg(NO.sub.3).sub.2 .sub.2 ~18_7 18.6 Water 58.2 58-'T Total 100.00 100.00 pH 0.8 2.5 Insoluble Pd as % Total Palladium, 1 of hr. 56 3 C ` 00 Reaction Constant, k, hr..sup.-1 0.25 0.61 i -.. to , http://164.195.100.11/netacg'i/nph-Parser?Sect1=PTO1&Sect2=HIT.../425743 2/13/01

United States Patent: 4,257,430 Page 5 of 16 In the practice of this invention, there is formed an aqueous solution containing a dissolved palladium compound and a compound which acts as a reducing agent for ionic palladium. The solution is heated at a temperature of up to about 80.degree. C. for a period of time sufficient to form "insoluble palladium", and the resulting mixture is blended with tobacco to deposit the palladium on the tobacco. As employed herein, "soluble palladium" is that palladium in an aqueous mixture, which when the mixture is diluted with water and filtered through a membrane filter with 0.45.mu. pores, appears in the filtrate. The palladium which is retained on the filter is defined as "insoluble palladium". The chemical form of this "insoluble palladium" has been found to be predominantly, if not completely, metallic palladium. The chemical form of the "soluble palladium" is considered to be essentially all ionic, based on available evidence. Though the precise forms of soluble and insoluble palladium have not been conclusively established, the present invention is intended to extend to "insoluble palladium" formed in the manner described, regardless of the precise chemical and physical form of the palladium. The palladium compound which is employed can be any water-soluble compound containing palladium which is capable of yielding ionic palladium, such as the salts disclosed in U.S. Pat. No. 4,055,191. Such compounds include simple salts such as palladium nitrate, palladium halides such as palladium chloride, diammine complexes such as palladous dichlorodiammine (Pd(NH.sub.3).sub.2 Cl.sub.2), and palladate salts, especially ammonium salts such as anunonium tetrachloropalladate and ammonium hexachloropalladate. The amount of palladium compound in solution is not critical, provided the concentration is adequate to deposit sufficient palladium on the tobacco to provide the desired catalytic effect. As is taught by U.S. Pat. No. 4,055,191, the palladium can be present in the tobacco in amounts of from about 0.001 to about 1 wei ht ercent and preferably from a out 0.01 to about 0.1 wei~h~ercent. It has been found that the rate ~~~n ~~~ o t"I 1i "~e re uc on o~~~f b~e pallac~iumto insoluble palladium increases with decreasing palladium concentration. On the other hand, if the solution is too dilute, excessive amounts of solution may be required to deposit a catalytically effective amount of palladium. In general, palladium concentrations of from about 0.1 to about 2 weight percent palladium are useful, with concentrations of from about 0.2 to about 0.5 weight percent palladium being preferred. A second required component of the solution (other than water) is a reducing agent capable of reducing dissolved palladium ionic to metallic palladium. Since palladium salts are well known as oxidizing agents any mild reducing agent may be used. Although any compound capable of reducing ionic palladium can be employed, as a practical matter the reducing agent should be non-toxic and should not form toxic by- http://164.195.100.11/netacgi/nph-Parser?Sect1=PTO1&Sect2=HIT.../425743 2/13/01

United States Patent: 4,257,430 Page 6 of 16 products when pyrolyzed during smoking. In addition, the reducing agent should be water soluble. Preferred reducing a ents are organic aldeh des, m~Cl~in4 hydroxyl containing aldehydes such as the ugars e.g. ucose t~tnannos (galactos~,~xylose~ tribos abinose. Other sugars containing hemiacetal or~kefo groupings may be employed, e.g. maltose, sucrose, lactose, fructose and sorbose. Pure sugars may be employed, but crude sugars and syrups such as honey, corn syrup, invert syrup and the like may also be employed. Other, albeit less effective reducing agents include alcohols, preferably polyhydric alcohols, such as Ig ycer~l, sorb~itol, the ls especially ethylene glyco and propylene glycol, and polyglycols such as ol eth~lene a dn polyprop~ ylerie gTycols Meit '~MT"1VMdfft?'gtMe re uc~" ng agnts may be used suc as car on monox~. e, hydrogen, ethylene, and titanous salts. The solution may contain still other additives which do not interfere with the interaction of the palladium compound and the reducing agent. Thus, the solution may contain a nitrate salt of the type disclosed in U.S. Pat. No. 4,055,191. It will be appreciated by those skilled in the art that the reducing agents referred to above are commonly employed components of casing solutions heretofore employed in the manufacture of smoking tobacco, and indeed the addition of a water-soluble palladium salt to a conventional casing solution is a convenient, and preferred, method of practicing the present invention. Although the use of such casing solutions has been described in U.S. Pat. No. 4,055,191, there is no recognition in that patent that a heating step, as hereinafter described, is required as a practical matter to form insoluble palladium. The insolubilization of~alladium will occur very slowly at ambient temperature, and . .~.,.a;a~n .e...s.° .w,av:cx~.ua.m,vwww.u.....c .< ~nt~s,zcaa,a. :.,..nw~s..~ r^a exce vel lon ~enods of time are re~uirec to ac~iieve practica conversions of the ua3ru ap. e TFCa.A`Yd~e~ ~vf isul^'..3.a.1.mLrcw.:-.(:tir. 2cRa+ ~~ .T~kNl1nY'~' VS".4Yu4-4Y.Csolu e p adium to msolubpe palla~ium. Conse uen~C ~o achieve practica~ rates o~ ~ ~ ~ ~ ~.~ ~ : . ~ .~ ~ ' ~ conversi _on_the so~uhon is heaiec~at eEl'evated temperatures, with the rate of ormarion ~ •,~.~~ ~~.~..d.~.,- of insoluble palladium increasmg wil7i increasmg temperature. However, as the temperature increases, the insoluble palladium tends to form agglomerates of insoluble palladium which presents difficulties in obtaining uniform distribution of the metal. The formation of such agglomerates can be inhibited through the inclusion of pro elatin ums such as gum tragacanth, and the like, in 1 weight percent, and pre era y rom a out . o a ou 6Z" " amounts of up to 7 weight percent ac ~. "~ica ion, er~o Ou Re~Cas 2e 89),~ fi on d .. .:..n ...w= ec. -...+ . ""' 44-^%m+.*»r++4 '^' ' N o °° - ve.. W . . Mai%+haYa:u:xlYr .J sc oF3: T' even date herewitclosure of wluc~ is mcorporated ~ierem by reference 7h ~ . ~~ However, at tempn excess of about~g ilegree. C the formation of the palladium agglomerates becomes excessive. Fu~ftYreitYio~ xtended heating at fk- ;: elevated temperatures can cause breakdown of sugars or other compounds present in the aqueous solution, forming decomposition products which have an adverse effect on the taste of tobacco smoke. In general, then, temperatures in the range of from about 50.degree. C. to about 90.degree. C. are employed, with temperatures of from 0 http://164.195.100.11/netacgi/nph-Parser?Sectl=PTO1&Sect2=HIT.../425743 2/13/01