Patent Publication Number: US-2023157359-A1

Title: Aerosol generating assembly

Description:
PRIORITY CLAIM 
     The present application is a National Phase entry of PCT Application No. PCT/GB2021/050634, filed Mar. 12, 2021, which claims priority from GB Application No. 2003675.2, filed Mar. 13, 2020, each of which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates, without limitation, to an assembly for generating an inhalable medium, a cartridge for use in an assembly for generating an inhalable medium, a method of generating an inhalable medium, a kit, a liquid pod, and a nicotine-containing pod. 
     BACKGROUND 
     Smoking articles such as cigarettes, cigars and the like burn tobacco during use to create tobacco smoke. Alternatives to these types of articles, release compounds without burning to form an inhalable medium. 
     Examples of such products are heating devices, including e-cigarette/heat-not-burn hybrid devices, also known as electronic tobacco hybrid devices. These hybrid devices contain a liquid that is vaporized by heating to produce an inhalable vapor and/or aerosol. The liquid may contain flavorings and/or aerosol-generating substances, such as glycerol and in some instances, nicotine. The vapor and/or aerosol passes through a substrate in the device and entrains one or more constituents of the substrate to produce the inhaled medium. The substrate material may be, for example, tobacco, other non-tobacco products or a combination, such as a blended mix, that may or may not contain nicotine. 
     SUMMARY 
     According to a first aspect of the present invention, there is provided an aerosol generating assembly comprising: 
     a solid, nicotine-containing material having a pH of at least 7; 
     an aerosolizable liquid comprising an acid, and having a pH of at least 2 and less than 7; and 
     wherein the assembly is configured to heat the aerosolizable liquid to form a vapor and/or an aerosol, wherein the vapor/aerosol is contacted with the solid, nicotine-containing material to entrain one or more components thereof, and thus forming an inhalable medium. 
     The assembly may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is tobacco material. In some cases, the assembly is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     In some cases, the pH of the solid, nicotine-containing material is of from 8 to 9.5 of from 8.5 to 9. In some cases, the aerosolizable liquid has a pH of from 4 to 5 or from 4.3 to 4.8. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapor pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. In some cases, the acid has a pKa greater than 0.5, greater than 1, greater than 1.5, greater than 2, greater than 2.5 or greater than 3, suitably, of from 3.7 to 4.3. 
     According to a second aspect of the present invention, there is provided an aerosol generating assembly comprising: 
     a solid, nicotine-containing material having a pH of at least 7; 
     an aerosolizable liquid comprising an acid, the acid with a pKa greater than 0.5; and 
     wherein the assembly is configured to heat the aerosolizable liquid to form a vapor and/or an aerosol, wherein the vapor/aerosol is contacted with the solid, nicotine-containing material to entrain one or more components thereof, and thus forming an inhalable medium. 
     The assembly may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is tobacco material. In some cases, the assembly is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     In some cases, the pKa of the acid is greater than 3 or from 3.7 to 4.3. In some cases, the pH of the solid, nicotine-containing material is of from 8 to 9.5 or from 8.5 to 9. In some cases, the aerosolizable liquid has a pH of at least 2 and less than 7, or from 4 to 5, suitably from 4.3 to 4.8. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapour pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. 
     According to a further aspect of the present invention, there is provided a cartridge for use in an assembly for generating an inhalable medium, the cartridge comprising an aerosolizable liquid comprising an acid in a first chamber, the aerosolizable liquid having a pH of at least 2 and less than 7, and a solid, nicotine-containing material having a pH of at least 7 in a second chamber. In some cases, the aerosolizable liquid has a pH of from 4 to 5 or from 4.3 to 4.8. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a pKa greater than 0.5 or greater than 3, suitably, of from 3.7 to 4.3. In some cases, the solid, nicotine-containing material has a pH of from 8 to 9.5 or from 8.5 to 9. In some cases, the acid has a vapour pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. 
     The cartridge may be for use in an assembly that may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is tobacco material. In some cases, the cartridge is for use in an assembly that is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     According to a further aspect of the present invention, there is provided a cartridge for use in an assembly for generating an inhalable medium, the cartridge comprising an aerosolizable liquid comprising an acid in a first chamber, the acid having a pKa greater than 0.5, and a solid, nicotine-containing material having a pH of at least 7 in a second chamber. In some cases, the acid has a pKa of greater than 3 or from 3.7 to 4.3. In some cases, the aerosolizable liquid has a pH of less than 7, or of from 4 to 5, suitably from 4.3 to 4.8. In some cases, the solid, nicotine-containing material has a pH of from 8 to 9.5 or from 8.5 to 9. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapour pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. 
     The cartridge may be for use in an assembly that may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is tobacco material. In some cases, the cartridge is for use in an assembly that is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     According to a further aspect of the present invention, there is provided a method of generating an inhalable medium using an assembly comprising an aerosolizable liquid comprising an acid, the aerosolizable liquid having a pH of at least 2 and less than 7, and a solid, nicotine-containing material having a pH of at least 7, the method comprising:
         heating the aerosolizable liquid to form a vapor and/or an aerosol;   forming an inhalable medium, by contacting the aerosolizable liquid in the form of a vapor and/or an aerosol with the solid, nicotine-containing material to entrain one or more components thereof. In some cases, the aerosolizable liquid has a pH of from 4 to 5 or from 4.3 to 4.8. In some cases, the acid has a pKa greater than 0.5 or greater than 3, suitably, of from 3.7 to 4.3. In some cases, the solid, nicotine-containing material has a pH of from 8 to 9.5 or from 8.5 to 9. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapor pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight.       

     In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is a tobacco material. In some cases, the assembly is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     According to a further aspect of the present invention, there is provided a method of generating an inhalable medium using an assembly comprising an aerosolizable liquid comprising an acid, the acid with a pKa greater than 0.5, and a solid, nicotine-containing material having a pH of at least 7, the method comprising:
         heating the aerosolizable liquid to form a vapor and/or an aerosol;   forming an inhalable medium, by contacting the aerosolizable liquid in the form of a vapor and/or an aerosol with the solid, nicotine-containing material to entrain one or more components thereof. In some cases, the acid has a pKa of greater than 3 or from 3.7 to 4.3. In some cases, the aerosolizable liquid has a pH of at least 2 and less than 7, or from 4 to 5, suitably from 4.3 to 4.8. In some cases, the solid, nicotine-containing material has a pH of from 8 to 9.5 or from 8.5 to 9. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapor pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight.       

     The assembly may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is a tobacco material. In some cases, the assembly is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     According to a fifth aspect of the present invention, a use is provided for an acidic vapor and/or aerosol to extract nicotine from a solid, nicotine-containing material having a pH of at least 7, wherein the rate of nicotine extraction exceeds the rate of nicotine-salt formation in the solid, thereby providing an increased nicotine content in the vapor and/or aerosol as compared to using a neutral vapor and/or aerosol. 
     According to a further aspect of the present invention, there is provided a kit comprising: 
     (i) a liquid pod containing an aerosolizable liquid comprising an acid, the aerosolizable liquid having a pH of at least 2 and less than 7; and 
     (ii) a nicotine-containing pod, containing a solid, nicotine-containing material having a pH of at least 7; 
     wherein the liquid and nicotine-containing pod are configured for use in an assembly for use in generating an inhalable medium, the assembly being such that in use, an inhalable medium is generated by contacting the aerosolizable liquid in the form of a vapor vapour and/or an aerosol with the solid, nicotine-containing material to entrain one or more components thereof. 
     The liquid and nicotine-containing pod may be for use in an assembly that may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is a tobacco material. In some cases, the liquid and nicotine-containing pod are configured for use in an assembly that is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     In some cases, the aerosolizable liquid has a pH of from 4 to 5 or from 4.3 to 4.8. In some cases, the pKa of the acid is greater than 0.5 or greater than 3, suitably of from 3.7 to 4.3. In some cases, the vapor pressure of the acid at 25° C. is of from 0.1 Pa to 2.5 kPa. In some cases, the pH of the solid, nicotine-containing material is of from 8 to 9.5 or from 8.5 to 9. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. 
     According to a further aspect of the present invention, there is provided a kit comprising: 
     (i) a liquid pod containing an aerosolizable liquid comprising an acid, the acid with a pKa greater than 0.5; and 
     (ii) a nicotine-containing pod, containing a solid, nicotine-containing material having a pH of at least 7; 
     wherein the liquid and nicotine-containing pod are configured for use in an assembly for use in generating an inhalable medium, the assembly being such that in use, an inhalable medium is generated by contacting the aerosolizable liquid in the form of a vapor and/or an aerosol with the solid, nicotine-containing material to entrain one or more components thereof. 
     The liquid and nicotine-containing pod may be for use in an assembly that may be referred to as an electronic tobacco hybrid device. In some cases, the solid, nicotine-containing material comprises a tobacco material. In some cases, the solid, nicotine-containing material is a tobacco material. In some cases, the liquid and nicotine-containing pod are configured for use in an assembly that is configured such that the solid, nicotine-containing material is heated only by the vapor/aerosol. 
     In some cases, the pKa of the acid is greater than 3 or from 3.7 to 4.3. In some cases, the pH of the solid, nicotine-containing material is of from 8 to 9.5 or from 8.5 to 9. In some cases, the aerosolizable liquid has a pH of at least 2 and less than 7, or from 4 to 5, suitably from 4.3 to 4.8. In some cases, the difference between the pH of the solid nicotine-containing material and the pH of the aerosolizable liquid is of from 3.0 and 5.5. In some cases, the acid has a vapor pressure at 25° C. of from 0.1 Pa to 2.5 kPa. In some cases, the aerosolizable liquid has an amount of acid of from 0.001 to 5% by weight. 
     To the extent that they are compatible, features described in relation to one aspect of the invention are explicitly disclosed in combination with each and every other aspect. For instance, features described in relation to the assembly, cartridge, nicotine-containing pod, liquid pod or kit are explicitly disclosed in combination with the each of the others of the assembly, cartridge, nicotine-containing pod, liquid pod and kit. Specifically, features of the solid, nicotine-containing material and aerosolizable liquid comprising an acid as described herein are explicitly disclosed in combination with the assembly, cartridge, nicotine-containing pod, liquid pod, and kit embodiments of the invention. Similarly, features described in relation to apparatus are explicitly disclosed in combination with method and use aspects of the invention, and vice versa. 
     Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of assemblies and cartridges for generating an inhalable medium according to the invention are described below with reference to the accompanying drawings, in which: 
         FIG.  1    shows a schematic longitudinal cross-sectional view of an example of an assembly for generating an inhalable medium; 
         FIG.  2    shows a schematic longitudinal cross-sectional view of another example of an assembly for generating an inhalable medium; 
         FIG.  3    shows a schematic longitudinal cross-sectional view of another example of an assembly for generating an inhalable medium; 
         FIG.  4    shows a schematic longitudinal cross-sectional view of an example of a cartridge having a liquid chamber and an integral chamber for solid material; 
         FIG.  5    shows a schematic longitudinal cross-sectional view of an example of a cartridge having a liquid chamber and a detachable chamber for solid material; 
         FIG.  6    shows nicotine delivery from assemblies according to embodiments of the invention, and a comparative assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The present invention relates to improving the taste of an inhalable aerosol, and increasing the amount of nicotine delivery in an assembly for use in a hybrid device, where the nicotine has been pH-treated to raise its pH. 
     At its most general, the assembly described herein volatilizes an aerosolizable liquid to form a vapor and/or an aerosol that passes through a solid nicotine-containing material so as to produce an inhalable medium that contains one or more constituents, such as nicotine, derived from the solid. 
     In some assemblies, base-treated nicotine may be included in the solid, nicotine-containing material. The nicotine reacts with the base; this reaction deprotonates nicotine, increasing its volatility and releasing it from its bound state to provide nicotine in its deprotonated basic form (herein referred to as “deprotonated nicotine” or simply “free nicotine”). As a result, base-treated nicotine will be more readily volatilized upon heating. The present inventors have found, however, that inhalable aerosols (sometimes referred to herein as “inhalable medium”) containing free nicotine have a less desirable taste, in comparison to those containing nicotine salts. 
     In some embodiments, the inhalable aerosol of the assembly may have improved sensory qualities, such as taste. In some embodiments, the inhalable aerosol may have a higher amount of nicotine delivery, and may promote the extraction of nicotine from a nicotine source, where the nicotine source has been treated with base to raise its pH, in comparison to other inhalable aerosols. 
     The inventors have determined that by including an acid in the aerosolizable liquid, better tasting inhalable aerosols are produced. The acid in the vapor/aerosol—produced by heating the aerosolizable liquid—reacts with the free nicotine from the solid, nicotine-containing material to provide nicotine in its better tasting, salt form. That is, the acid and free nicotine undergo an acid-base salt formation to produce nicotine salts in the vapor/aerosol. 
     It was thought that whilst the use of an acidic aerosol/vapor would improve the taste, it was expected that some reduction in the overall nicotine delivery would be observed as less volatile nicotine salts would form in the solid, nicotine-containing material, upon contact with the acidic vapor/aerosol. 
     Surprisingly, the inventors found that including an acid in the aerosolizable liquid of an assembly actually increases the overall nicotine delivery during use, in comparison to a neutral aerosolizable liquid. Without being limited by theory, it is thought that the affinity between the free nicotine and the acid in the vapor/aerosol may draw or extract the nicotine out of the solid, nicotine-containing material. It is thought that this extraction occurs at a rate that is faster than the rate of formation of nicotine salt in the solid. Hence, an inhalable aerosol with improved taste and higher nicotine content may be provided. Using an acidic vapor/aerosol may also allow for a higher overall amount of nicotine to be extracted from the solid. 
     Solid, Nicotine-Containing Material 
     In some cases, the invention provides an assembly for generating an inhalable medium or a cartridge for use in an assembly for generating an inhalable medium, wherein the assembly or cartridge includes a solid, nicotine-containing material (herein referred to as “nicotine source” or simply “solid”). 
     The nicotine source has a pH of at least 7. In some cases, the nicotine source has a pH of from 8 to 9.5, of 8.2 to 9.3, of 8.3 to 9.2, of 8.4 to 9.1. Suitably, the pH may be of from 8.5 to 9, or may be 8.5. This allows for the nicotine in the solid, nicotine-containing material to be provided in its deprotonated basic form (as free nicotine), thereby increasing the volatility of the nicotine so that it is more readily volatilized on heating. 
     In some cases, the pH of the nicotine source is selected such that there is a difference between the pH of the nicotine source and the pH of the aerosolizable liquid of from 3 to 5.5, of 3.5 to 5, of 3.7 to 4.8, suitably from 4.1 to 4.2, suitably from 3.6 to 3.8. Without being limited by theory, it is thought that a larger pH difference will result in higher affinity between the acidic vapor/aerosol and the free nicotine, thereby increasing the rate of extraction, to provide a higher amount of nicotine delivery in the inhalable medium. 
     The nicotine source may have been treated to raise its pH—the pH measured according to the CORESTA protocol for measuring the pH of tobacco, CORESTA Recommended Method No. 69 (CRM-69). An example method of pH-treatment may comprise the addition of a solution of base to the nicotine source. The solution of base may, in some cases, comprise an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, sodium carbonate, potassium carbonate, calcium carbonate or mixtures thereof, or other GRAS water-soluble bases, for example. 
     In some cases, the nicotine source comprises tobacco material. In some cases, the nicotine source is tobacco material. This may provide the inhalable medium with tobacco flavors. 
     As used herein, the term “tobacco material” refers to any material comprising tobacco or derivatives thereof. The term “tobacco material” may include one or more of tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes. The tobacco material may comprise one or more of ground tobacco, tobacco fiber, cut tobacco, extruded tobacco, tobacco stem, reconstituted tobacco, agglomerated tobacco, spheronized tobacco and/or tobacco extract. 
     The tobacco used to produce tobacco material may be any suitable tobacco, such as single grades or blends, cut rag or whole leaf, including Virginia and/or Burley and/or Oriental. It may also be tobacco particle ‘fines’ or dust, expanded tobacco, stems, expanded stems, and other processed stem materials, such as cut rolled stems. The tobacco material may be a ground tobacco or a reconstituted tobacco material. The reconstituted tobacco material may comprise tobacco fibers, and may be formed by casting, a Fourdrinier-based paper making-type approach with back addition of tobacco extract, or by extrusion. 
     In some cases, the nicotine source may be porous, such that an aerosol and/or vapor can pass through the solid nicotine source. This provides a high contact area for the nicotine source to contact the aerosol and/or vapor. Thus, components of the nicotine source are efficiently entrained in the aerosol/vapor. 
     The nicotine source may additionally comprise flavorings and/or aerosol generating agents. As used herein, the terms “flavor” and “flavorant” refer to materials that, where local regulations permit, may be used to create a desired taste or aroma in a product for adult consumers. 
     In some cases, the nicotine source may be provided in one of two chambers of a cartridge as described herein. 
     In some cases, the nicotine source may be provided in a nicotine-containing pod, configured for use in an assembly for use in generating an inhalable medium, as part of a kit as described herein. 
     Aerosolisable Liquid 
     In some cases, the invention provides an assembly for generating an inhalable medium or a cartridge for use in an assembly for generating an inhalable medium, wherein the assembly or cartridge includes an aerosolizable liquid (sometimes herein referred to as simply “liquid”). 
     The aerosolizable liquid may, in some cases, comprise a gel and/or liquid. Suitably, the aerosolizable liquid comprises, substantially consists of, or consists of a liquid. 
     The aerosolizable liquid may comprise liquids that are conventionally used in e cigarette or Hybrid assemblies. In some cases, the aerosolizable liquid may comprise flavorings and/or aerosol-generating agents, including but not limited to propylene glycol and/or glycerol. The aerosolizable liquid is typically volatilized at around 100-300° C., suitably at around 150-250° C. In some cases, the aerosolizable liquid does not contain nicotine. 
     The aerosolizable liquid comprises an acid, such that the aerosolizable liquid may have a pH of from at least 2 to 7, or from about 2.5 to about 5. In some embodiments, the pH of the aerosolizable liquid is from 4 to 5. In some cases, the liquid has a pH of from 4.1 to 4.9, of 4.2 to 4.8, suitably of from 4.3 to 4.8, suitably 4.37, suitably 4.8. 
     In some cases, the liquid has a pH of from 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or from 4 and of up to 6.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6, 5.9, 5.8, 5.7, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5, 4.9, 4.8, 4.7, 4.6, 4.5, 4.4, 4.3, 4.2, 4.1 or up to 4. Without being limited by theory, it is thought that this results in an affinity between the free nicotine from the nicotine source and the acid in the vapor/aerosol; the affinity is such that the vapor/aerosol may draw or extract the nicotine out of the nicotine source. It is thought that a lower pH of the aerosolizable liquid will result in a higher affinity between the free nicotine and the aerosolizable liquid, and thus may increase the extraction rate. 
     The pH of the aerosolizable liquid is dependent upon various properties, such as pKa or concentration of the acid, and the acidity or basicity of any other components in the aerosolizable liquid. 
     In some cases, the pH of the aerosolizable liquid is selected such that there is a difference between the pH of the nicotine source and the pH of the aerosolizable liquid of from 3 to 5.5, of 3.5 to 5, of 3.7 to 4.8, suitably from 4.1 to 4.2, suitably from 3.6 to 3.8. Without being limited by theory, it is thought that a larger pH difference will result in higher affinity between the acidic vapor/aerosol and the free nicotine, thereby increasing the extraction rate to provide a higher amount of nicotine delivery in the inhalable medium. 
     In some cases, any characteristic of the aerosolizable liquid may be altered or selected in order to increase affinity of the liquid with the free “deprotonated” nicotine in the nicotine source, including but not limited to dipole moment, polarity, and vapor pressure. For example, a higher dipole moment, polarity or vapor pressure may increase affinity of the liquid with the free “deprotonated” nicotine in the nicotine source. The addition of an acid may alter the polarity and vapor pressure characteristics of the aerosolizable liquid, which are important for the desired effect in this invention. Further, a non-acid substance that can alter polarity (increasing more positive dipole in the liquid); this may lead to similar effect like addition of acid. 
     ACID 
     Any acid that is suitable for the protonation of nicotine may be used in the aerosolizable liquid. Examples of acids include, but are not limited to, inorganic acids such as hydrochloric, hydrobromic, or sulfuric acid, and organic acids including saturated and unsaturated aliphatic acids, saturated and unsaturated alicyclic acids, aromatic acids (including heterocyclic aromatic), polycarboxylic acids, hydroxy, alkoxy, keto, and oxo acids, thioacids, amino acids, and each of the preceding optionally substituted with one or more heteroatoms, including but not limited to halogens. In some cases, the acid is a carboxylic acid, suitably benzoic acid. In some cases, the carboxylic acid is a hydroxyl acid, suitably lactic acid. In some cases, the acid is selected from the group consisting of benzoic acid, lactic acid, and combinations thereof. The selected acid may protonate the free nicotine, and promote acid-base salt formation upon contact of the aerosol/vapor with the nicotine source, thereby providing nicotine salts. This promotes extraction of the nicotine from the nicotine source to increase nicotine delivery of the assembly, and improves the taste of nicotine in the inhalable medium. 
     In some cases, the acid selected has a pKa greater than 0.5, 1, 1.5, 2, 2.5, 3, or greater than 3.5, or suitably of from 3.7 to 4.3. Without being limited by theory, it is thought that this promotes the acid-base salt formation of free nicotine to improve the flavor and the amount of nicotine delivery by the inhalable medium; a lower pKa, or a stronger acid, for the same pH of a nicotine source, will increase the affinity between the aerosolizable liquid and the free nicotine, and may promote extraction of nicotine from the nicotine source to provide a higher nicotine delivery in the inhalable medium during use. 
     In some cases, the acid has a pKa of greater than 3, or of from 3.7 to 4.3, and provides an aerosolizable liquid with a pH of from 4 to 5, of 4.1 to 4.9, of 4.2 to 4.8, suitably from 4.3 to 4.8, suitably 4.37, suitably 4.8. Thus, in some embodiments, this promotes the acid-base salt formation of free nicotine to provide improved flavor and increase the amount of nicotine delivery by the inhalable medium during use. 
     In some cases, the aerosolizable liquid comprises an acid with a vapor pressure at 25° C. of from 0.05 Pa to 3 kPa, from 0.1 Pa to 2.5 kPa, from 0.1 Pa to 2 kPa, from 0.1 Pa to 1.5 kPa, from 0.1 Pa to 1 kPa, from 0.1 Pa to 750 Pa, from 0.1 to 500 Pa, from 0.1 to 250 Pa, from 0.1 to 100 Pa, from 0.1 to 90 Pa, from 0.1 to 80 Pa, from 0.1 to 70 Pa, from 0.1 to 60 Pa, from 0.1 to 50 Pa, from 0.1 to 40 Pa, from 0.1 to 30 Pa, from 0.1 to 20 Pa, from 0.1 to 11 Pa, suitably from 0.1 to 0.2, suitably from 9 to 11 Pa. An acid with a higher vapor pressure at 25° C. will be more volatile. Thus, more acid may be present in the aerosol/vapor and this may further increase the rate of extraction of free nicotine from the nicotine source during use. 
     In some cases, the aerosolizable liquid comprises an acid in an amount of from 0.001 to 5% by weight. In some embodiments, the aerosolizable liquid comprises an acid in an amount of at least 0.01%, 0.1%. 0.5%, 0.6%, 0.7%, 0.8% 0.9% or at least 1% acid. In some embodiments, the aerosolizable liquid comprises as acid in an amount of up to 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, 0.1% or up to 0.01% by weight. Including the acid in the aerosolizable liquid at higher concentrations will increase the acidity and lower the pH of the aerosolizable liquid. Without being limited by theory, it is thought that a higher acidity of the aerosolizable liquid may result in it having a higher affinity to the free nicotine in the nicotine source, thereby facilitating the extraction of nicotine to increase the amount of nicotine delivery by the inhalable medium during use. 
     In some cases, the aerosolizable liquid comprising an acid may be provided in one of two chambers of a cartridge as described herein. 
     In some cases, the aerosolizable liquid comprising an acid may be provided in a liquid pod, configured for use in an assembly for use in generating an inhalable medium, as part of a kit as described herein. 
     In some cases, the acid may be selected such that the conjugate acid-base salt formed upon reaction with the free nicotine in the aerosol/vapor has a high volatility (i.e. has a high vapor pressure). This may further increase the amount of nicotine delivery in the inhalable medium. 
     In some embodiments, the conjugate acid-base will have a vapor pressure similar to or slightly less than that of the acid used. Conjugate acid-base formation is one mechanism of elevating vapor pressure. 
     Assembly 
     The assembly according to some examples of the invention may be configured such that in use, liquid volatilized by the heater passes, in the form of at least one of a vapor and an aerosol, through the solid nicotine source to thereby entrain one or more components from the nicotine source to produce the inhalable medium. In some cases, the inhalable medium passes out of an outlet. 
     The assembly may comprise components such as a first chamber (referred to herein as the “liquid chamber”) for housing the aerosolizable liquid, and a second chamber (referred to herein as the “solid chamber”) for housing the solid, nicotine-containing material. The assembly may further comprise an outlet, and a flow path between the chambers and the outlet. 
     When the vapor/aerosol passes through the nicotine source, it is contacted with the nicotine source to entrain one or more components thereof. Once entrained in the vapor/aerosol, the one or more components from the nicotine source may undergo reactions with components in the vapor/aerosol. For example, acid-base salt formation reactions may occur. Without being bound by theory, it is thought that the acid-base salt formation reaction in the vapor/aerosol occurs at a higher rate than the acid-base salt formation reaction in the solid. The use of an acidic vapor/aerosol may result in a higher amount of nicotine to be extracted or drawn out of the tobacco, when compared to a vapor/aerosol with a neutral pH. 
     In some embodiments, the assembly heats the nicotine source in use, encouraging release of components thereof into the inhaled medium. In other embodiments, the assembly heats both the nicotine source and the aerosolizable liquid. Suitably, the assembly may be configured such that the heater only heats the aerosolizable liquid directly and the nicotine source is heated by warmth carried in the vapor/aerosol formed from the aerosolizable liquid (thereby volatilizing components of the nicotine source that are then entrained in the vapor/aerosol flow). That is, the assembly is configured such that it directly heats the aerosolizable liquid, but does not directly heat the solid, nicotine-containing material. 
     In some cases, the invention provides a cartridge for use in an assembly for generating an inhalable medium, the cartridge comprising an aerosolizable liquid comprising an acid in a first chamber, the liquid corresponding to the liquid as described hereinabove, and a solid, nicotine-containing material in a second chamber, the solid, nicotine-containing material corresponding to the nicotine source described hereinabove. The cartridge is configured such that in use, a vapor and/or an aerosol generated from the aerosolizable liquid passes through the second chamber containing the nicotine source and entrains one or more constituents of the nicotine source. Suitably, the cartridge may be adapted for use in the assembly for generating an inhalable medium described herein. 
     In some embodiments, the assembly comprises a cooler or cooling zone downstream of the heater and upstream of the second chamber containing a nicotine source, the cooler or cooling zone being arranged to cool vaporized material to form an aerosol of liquid droplets that, in use, pass through the nicotine source in the second chamber. In some embodiments, the cooler may be arranged in effect to act as a heat exchanger, allowing for recovery of heat from the vapor and/or aerosol. The recovered heat may be used, for example, to pre-heat the nicotine source and/or to assist in heating the aerosolizable liquid. 
     In an embodiment, the assembly is battery-operated. 
     In an embodiment, the or each heater is an electrically resistive heater. 
     In an embodiment, the heater is puff actuated. That is, the assembly includes a puff-detector and only heats the aerosolizable liquid on detection of a puff. This means that vapor/aerosol forms in the assembly only during puffs. 
     In an embodiment, the first and/or second chamber is removable. The first and/or second chamber may be in the form of a pot or the like (that in some embodiments may be annular for example), and/or an absorbent wadding or the like. The first and/or second chamber may in effect be a disposable item that is replaced as a whole after use. As an alternative, the arrangement may be such that the user removes the first and/or second chamber from the assembly, replaces used material or tops up the material in the first and/or second chamber, and then places it back in the assembly. 
     In some cases, the first and/or second chamber may be non-removable from the assembly. In such an embodiment, the user may just replace used material or top up material in a chamber after use as necessary. 
     In some cases, the first and second chamber are an integral unit. In some cases, the integral unit is a cartridge that can be removed from the assembly. 
     In some cases, the first and/or second chamber is removable from the assembly. The first and/or second chamber may be, for example, in the form of a cartridge or the like which contains the nicotine source before use. The second chamber containing the nicotine source may in effect be a disposable item, which is replaced as a whole after use. As an alternative, the arrangement may be such that the user removes the second chamber from the assembly, replaces used material in the second chamber, and then places the second chamber back in the assembly. 
     The invention also provides a kit comprising an aerosol-generating assembly according to embodiments of the invention. The kit comprises (i) a liquid pod containing an aerosolizable liquid according to the embodiments described herein, (ii) a nicotine-containing pod containing a solid, nicotine-containing material according to the embodiments described herein. Features described hereinabove in relation to the assembly are explicitly disclosed in combination with the kit aspect of the invention. Thus, for example, the assembly may include one or more puff actuators, a cooling element or cooling zone, actuation means such as a button, further heaters, a pump for the wetting agent, and so on. 
     The invention also provides the use of an acidic vapor and/or aerosol to extract nicotine from a solid, nicotine-containing material having a pH of more than 7, wherein the rate of nicotine extraction exceeds the rate of nicotine-salt formation in the solid, nicotine-containing material, thereby providing an increased nicotine content in the vapor and/or aerosol as compared to using a neutral vapor and/or aerosol. 
     Examples of cartridges, liquid pods, nicotine-containing pods and assemblies for generating an inhalable medium according to some embodiments of the invention will now be described, with reference to the accompanying drawings. 
     Referring to  FIG.  1   , there is shown an example of an assembly  1  for generating an inhalable medium. In broad outline, the assembly  1  volatilizes an aerosolizable liquid to form a vapor and/or an aerosol which passes through a nicotine source so as to produce an inhalable medium that contains one or more components derived from the nicotine source. 
     In this respect, first it may be noted that, in general, a vapor is a substance in the gas phase at a temperature lower than its critical temperature, which means that for example the vapor can be condensed to a liquid by increasing its pressure without reducing the temperature. On the other hand, in general, an aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. A “colloid” is a substance in which microscopically dispersed insoluble particles are suspended throughout another substance. 
     Returning to  FIG.  1   , the assembly  1  of this example has a generally hollow cylindrical outer housing  2 . The housing  2  has an open end  3 . In this example, a tubular mouthpiece  4  is provided in the open end  3 . The mouthpiece  4  in this example is removable by a user from the housing  2 . An O¬ring or other seal  5  assists in sealing the mouthpiece  4  in the housing  2 . At or towards the other end  6  of the housing  2  is a battery  7  for powering various components of the assembly  1 , as will be discussed further below. The battery  7  may be a rechargeable battery or a disposable battery. A controller  8  is also provided in the housing  2  for controlling the operation of various components of the assembly  1 , as will be discussed further below. 
     The housing  2  has a chamber  9  (sometimes referred to herein as “liquid chamber”) for holding or containing an aerosolizable liquid (sometimes referred to herein as simply “liquid”)  10 . The liquid  10  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. Various different forms for the liquid chamber  9  may be used. In the example of  FIG.  1   , the liquid chamber  9  is in the form of an annular chamber  9  provided in the housing  2  between the open end  3  and the other end  6 . In this particular example, the housing  2  is in two parts, a first part  2   a  being towards the open end  3  and a second part  2   b  towards the other end  6 . The first and second parts  2   a ,  2   b  of the housing  2  may connect to each other via a screw thread, a bayonet fitting or the like. In use, a user can separate the first and second parts  2   a ,  2   b  of the housing  2  to allow the aerosolizable liquid  10  to be replenished or replaced as necessary. Alternatively, the mouthpiece  4  can be removed to provide access to the liquid chamber  9 . It will be understood however that other arrangements are possible. For example, the liquid  10  may be provided in a discrete annular pot-like liquid chamber, which can be removed as a whole from the housing  2 . Such a discrete liquid chamber may be disposable so that the user replaces the liquid  10  by fitting a new liquid chamber with liquid  10  in the housing  2 . Alternatively, such a chamber may be reusable. In such a case, the user may replenish or replace liquid  10  in the liquid chamber whilst it has been removed from the housing  2  and then replace the refilled liquid chamber in the housing  2 . It will be understood that the housing  2  need not be in two parts and that other arrangements enabling access for the user may be provided, for example, to enable refilling in situ. 
     A heater  11  is provided generally centrally of the housing  2 , that is, centrally along the length and width of the housing  2  in this example. In this example, the heater  11  is powered by the battery  7  and is therefore electrically connected to the battery  7 . The heater  11  may be an electrically resistive heater, including for example a nichrome resistive heater, a ceramic heater, etc. The heater  11  may be for example a wire, which may for example be in the form of a coil, a plate (which may be a multi-layer plate of two or more different materials, one or more of which may be electrically conductive and one or more of which may be electrically non-conductive), a mesh (which may be woven or non-woven for example, and which again may be similarly multi-layer), a film heater, etc. Other heating arrangements may be used, including non-electrical heating arrangements. 
     This heater  11  is provided for volatilizing the liquid  10 . In the example shown, an annular wick  12  surrounds the heater  11  and is in (thermal) contact with the heater  11 . The outermost surface of the annular wick  12  is in contact with liquid  10  contained in the liquid chamber  9 . The wick  12  is generally absorbent and acts to draw in liquid  10  from the liquid chamber  9  by capillary action. The wick  12  is preferably non-woven and may be for example a cotton or wool material or the like, or a synthetic material, including for example polyester, nylon, viscose, polypropylene or the like. Whilst this will be described more fully below, it may be noted here that in use, liquid  10  drawn into the wick  12  is heated by the heater  11 . The liquid  10  may be volatilized so as to produce an aerosol of liquid droplets or sufficiently heated to produce a vapor. The aerosol and/or vapor so produced exits the wick  12  and passes towards the mouthpiece  4  as shown by the arrows A under the action of the user drawing on the mouthpiece  4 . The heater  11  and wick  12  may be provided as a single, effectively integral item, sometimes referred to as an “atomizer”, such that the heating and wicking is effectively carried out by a single unit. 
     The housing  2  further contains a chamber (sometimes referred to herein as “solid chamber”)  13  which holds or contains a solid, nicotine-containing material (referred to herein as “nicotine source”)  14  in the assembly  1 . The nicotine source  14  corresponds to the nicotine source described hereinabove, is base-treated, and may have a pH of from 8 to 9.5, for example. In use, a user can access the solid chamber  13  to replace or replenish the nicotine source  14  through the open end  3  of the housing  2  by removing the mouthpiece  4  and/or by separating the two parts  2   a ,  2   b  of the housing  2 . Various different forms for the solid chamber  13  may be used. For example, the solid chamber  13  may be a tube which is completely open at both ends and which contains the nicotine source  14 . As another example, the solid chamber  13  may be a tube, which has one or more end walls, which have through holes through which a vapor and/or aerosol can pass. The solid chamber  13  may remain in situ within the housing  2  whilst the user removes and replaces the nicotine source  14 . Alternatively, the solid chamber  13  containing the nicotine source  14  may be a discrete item, which in use is inserted into and removed from the housing  2  as a whole. A removable solid chamber  13  of this type may be disposable so that the user replaces the nicotine source  14  by fitting a new solid chamber  13  containing a fresh nicotine source  14  into the housing  2 . As an alternative, the solid chamber  13  may be reusable. In such a case, the user may replace the nicotine source  14  in the solid chamber  13  whilst the solid chamber  13  has been removed from the housing  2  and then replace the refilled solid chamber  13  in the housing  2 . In yet another example, the solid chamber  13  may comprise clips or the like provided internally of the housing  2  and which retain the nicotine source  14  in position. In some examples, the nicotine source  14  could simply fit snugly within the solid chamber  13 . As another alternative, the chamber  9  for containing the liquid  10  may itself be arranged to support or carry the nicotine source  14 . For example, the liquid chamber  9  may have one or more clips, a tube, or the like for receiving and holding the nicotine source  14  in position. Such a dual function liquid chamber  9 /solid chamber  13  for both containing the liquid  10  and receiving the nicotine source  14  may be in the form of a cartridge or the like and may be a disposable item or may be re-useable, with the liquid  10  and nicotine source  14  being replaced or topped up by the user as required. In some cases, it may be that the user only needs to top up or replace the nicotine source  14  from time to time, with sufficient liquid  10  being provided for several uses. Once the liquid  10  has been consumed, the user disposes of the dual function liquid chamber  9 /solid chamber  13  and uses a new one. Likewise, it may be that the user only needs to top up or replace the liquid  10  from time to time, with sufficient nicotine source  14  being provided for several uses. Once the nicotine source  14  has been consumed, the user disposes of the dual function liquid chamber  9 /solid chamber  13  and uses a new one. Specific examples of dual function liquid chambers/solid chambers are discussed further below. 
     The nicotine source  14  is located in the housing  2  downstream of the location where the aerosol and/or vapor is produced from the liquid  10  and upstream of the open end  3  of the housing  2  and the mouthpiece  4 . In this particular example, the nicotine source  14  is effectively provided in the same portion or chamber of the housing  2  as the wick  12 . The aerosol and/or vapor produced from the liquid  10  exits the wick  12  and passes as shown by the arrows A towards the nicotine source  14  under the action of the user drawing on the mouthpiece  4 . In particular embodiments, the nicotine source  14  is porous so that the aerosol and/or vapor passes through the nicotine source  14  and then through the open end  3  of the housing  2  and the mouthpiece  4 . 
     In some embodiments, the nicotine source  14  and/or its chamber  13  are arranged so that there is no air gap between the nicotine source  14 /solid chamber  13  and the interior of the housing  2  so that the aerosol and/or vapor flows entirely through the nicotine source  14 . 
     The liquid  10  is suitably a liquid that is volatilizable at reasonable temperatures, preferably of from 100-300° C. or more particularly around 150-250° C., as that helps to keen down the power consumption of the assembly  1 . Suitable materials include those conventionally used in e cigarette assemblies, including for example propylene glycol and glycerol (also known as glycerine). The liquid  10  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. 
     The nicotine source  14  imparts a flavor to the aerosol and/or vapor produced from the liquid  10  as the aerosol and/or vapor passes through the nicotine source  14 . As the acidic aerosol and/or vapor passes through and over the nicotine source  14 , the hot aerosol and/or vapor entrains organic and other compounds or constituents from the nicotine source  14  that lend the nicotine source its organoleptic properties, thus imparting the flavor to the aerosol and/or vapor as it passes to the mouthpiece  4 . In particular, the free “deprotonated” nicotine in the nicotine source  14  undergoes acid-base salt formation with the acidic vapor and/or aerosol from the liquid  10 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  14  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  14 , nicotine is provided in its better tasting, salt form. 
     The assembly  1  provides nicotine for the user. The nicotine is obtained from the nicotine source  14 , or it may be provided as a coating or the like on the nicotine source  14 , or a combination of these. Likewise, flavorings may be added to the nicotine source  14  and/or to the liquid  10 . 
     In the example shown in  FIG.  1   , the only heat source for heating the nicotine source  14  in the assembly  1 , which is required so as to generate the organic and other compounds or constituents from the nicotine source  14 , is the hot aerosol and/or vapor produced from heating the liquid  10 . 
     Referring now to  FIG.  2   , there is shown another example of an assembly for generating an inhalable medium. In the following description and in  FIG.  2   , components and features that are the same as or similar to the corresponding components and features of the example described with reference to  FIG.  1    have the same reference numeral but increased by  200 . For the sake of brevity, the description of those components and features will not be repeated in its entirety here. It will be understood that the arrangements and alternatives, etc. described above in relation to the example of  FIG.  1    are also applicable to the example of  FIG.  2   . Again, in broad outline, the assembly  201  of  FIG.  2    heats a liquid to form a vapor and/or an aerosol which passes through a nicotine source  214  so as to produce an inhalable medium that contains one or more components derived from the nicotine source  214 . 
     The assembly  201  of this example has a generally hollow cylindrical outer housing  202  with an open end  203  and a tubular mouthpiece  204 . The mouthpiece  204  in this example is removable by a user from the housing  202  and an O¬ring or other seal  205  assists in sealing the mouthpiece  204  in the housing  202 . A battery  207  for powering various components of the assembly  201  and a controller  208  are provided at or towards the other end  206  of the housing  202 . The housing  202  of this example is in two parts, a first part  202   a  being towards the open end  203  and a second part  202   b  towards the other end  206 . 
     The housing  202  has a chamber (sometimes referred to herein as “liquid chamber”)  209  for holding or containing an aerosolizable liquid (sometimes referred to herein as simply “liquid”)  210 . The liquid  210  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. The liquid chamber  209  may be of any of the types described above in relation to the example of  FIG.  1   . A heater  211  is provided generally centrally (lengthwise and widthwise) of the housing  202  for volatilizing the liquid  210 . In this example, the heater  211  is powered by the battery  207  and is therefore electrically connected to the battery  207 . The heater  211  may be an electrically resistive heater, a ceramic heater, etc. The heater  211  may be for example a wire, which may for example be in the form of a coil, a plate (which may be a multi-layer plate of two or more different materials, one or more of which may be electrically conductive and one or more of which may be electrically non-conductive), a mesh (which may be woven or non-woven for example, and which again may be similarly multi-layer), a film heater, etc. Other heating arrangements may be used, including inductive heating arrangements or non-electrical heating arrangements. An annular wick  212  surrounds the heater  211  and is in (thermal) contact with the heater  211 . The outermost surface of the annular wick  212  is in contact with liquid  210  contained in the liquid chamber  209 . The liquid  210  may be heated so as to produce an aerosol of liquid droplets or sufficiently heated to produce a vapor. The aerosol and/or vapor so produced exits the wick  212  and passes towards the mouthpiece  204  as shown by the arrows A under the action of the user drawing on the mouthpiece  204 . The heater  211  and wick  212  may be provided as a single, effectively integral item such that the heating and wicking is effectively carried out by a single unit. 
     The housing  202  further contains a chamber (sometimes referred to herein as “solid chamber)  213  which holds or contains a nicotine source  214  in the assembly  201 . The nicotine source  214  corresponds to the nicotine source described hereinabove, is base-treated, and may have a pH of from 8 to 9.5, for example. The solid chamber  213  may be of any of the types described above in relation to the example of  FIG.  1   . The nicotine source  214  is located in the housing  202  downstream of the location where the aerosol and/or vapor is produced from the liquid  210  and upstream of the open end  203  of the housing  202  and the mouthpiece  204 . In this particular example, the nicotine source  214  is effectively provided in the same portion or chamber of the housing  202  as the wick  212 . The aerosol and/or vapor produced from the liquid  210  exits the wick  212  and passes as shown by the arrows A towards the nicotine source  214  under the action of the user drawing on the mouthpiece  204 . In particular embodiments, the nicotine source  214  is porous so that the aerosol and/or vapor passes through the nicotine source  214  and then through the open end  203  of the housing  202  and the mouthpiece  204 . 
     In some embodiments, the nicotine source  214  and/or its chamber  213  are arranged so that there is no air gap between the nicotine source  214 /chamber  213  and the interior of the housing  202  so that the aerosol and/or vapor flows entirely through the nicotine source  214 . As the aerosol and/or vapor passes through and over the nicotine source  214 , the hot aerosol and/or vapor entrains organic and other compounds or constituents from the nicotine source  214  that lend the nicotine source its organoleptic properties, thus imparting the flavor to the aerosol and/or vapor as is passes to the mouthpiece  204 . In particular, the free “deprotonated” nicotine in the nicotine source  214  undergoes acid-base salt formation with the acidic vapor and/or aerosol from the liquid  210 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  214  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  214 , nicotine is provided in its better tasting, salt form. 
     The liquid chamber  209  for containing the liquid  210  may itself be arranged to support or carry the nicotine source  214 . For example, the liquid chamber  209  may have one or more clips, a tube, or the like for receiving and holding the nicotine source  214  in position. Such a dual function liquid chamber  209 /solid chamber or receptacle  213  for both containing the liquid  210  and receiving the nicotine source  214  may be in the form of a cartridge or the like and may be a disposable item or may be re-useable, with the liquid  210  and nicotine source  214  being replaced or topped up by the user as required. In some cases, it may be that the user only needs to top up or replace the nicotine source  214  from time to time, with sufficient liquid  210  being provided for several uses. Once the liquid  210  has been consumed, the user disposes of the dual function liquid chamber  209 /solid chamber  213  and uses a new one. Likewise, it may be that the user only needs to top up or replace the liquid  210  from time to time, with sufficient nicotine source  214  being provided for several uses. Once the nicotine source  214  has been consumed, the user disposes of the dual function liquid chamber  209 /solid chamber  213  and uses a new one. 
     In the example assembly  201  of  FIG.  2   , a second heater  215 , such as an oven heater, is provided in thermal contact with the nicotine source  214  to pre-heat the nicotine source  214  and/or provide additional heat to the nicotine source  214  throughout use of the assembly  201 . This encourages release of constituents from the nicotine source  214  as the vapor and/or aerosol passes through the nicotine source  214  in use. The amount of heated liquid  210  to achieve desirable heating of the nicotine source  214  may be reduced. The second heater  215  may be an electrically resistive heater, a ceramic heater, etc., powered by for example the battery  207 . The second heater  215  may be for example a wire, which may for example be in the form of a coil, a plate (which may be a multi-layer plate of two or more different materials, one or more of which may be electrically conductive and one or more of which may be electrically non-conductive), a mesh (which may be woven or non-woven for example, and which again may be similarly multi-layer), a film heater, etc. The second heater  215  may be an inductive heater powered by for example the battery  207 . Nicotine source  214  may include materials susceptible to inductive heating. Other heating arrangements may be used for the second heater  215 , including non-electrical heating arrangements. 
     In the example assembly  201  of  FIG.  2   , the heater  215  for heating the nicotine source  214  is provided externally of the nicotine source  214  and heats the nicotine source  214  by heat conduction from the exterior of the nicotine source  214 . The heater  215  in this example is generally cylindrical. The heater  215  may in effect be an integral part of the assembly  201  and be provided as part of the housing  202 . As an alternative, the heater  215  may be provided integrally with the solid chamber  213  which holds or contains the nicotine source  214 . In this alternative, in the case that the solid chamber  213  is disposable, the heater  215  will be replaced when a new solid chamber  213  with fresh nicotine source is loaded into the assembly  201  by the user. 
     Referring now to  FIG.  3   , there is shown another example of an assembly for generating an inhalable medium. In the following description and in  FIG.  3   , components and features that are the same as or similar to the corresponding components and features of the example described with reference to  FIG.  1    have the same reference numeral but increased by  300 . For the sake of brevity, the description of those components and features will not be repeated in its entirety here. It will be understood that the arrangements and alternatives, etc. described above in relation to the examples of  FIG.  1    and  FIG.  2    are also applicable to the example of  FIG.  3   . Again, in broad outline, the assembly  301  of  FIG.  3    heats a liquid to form a vapor and/or an aerosol which passes through a nicotine source  314  so as to produce an inhalable medium that contains one or more constituents derived from the nicotine source  314 . 
     The assembly  301  of this example again has a generally hollow cylindrical outer housing  302  with an open end  303  and a tubular mouthpiece  304 , which is removable by a user from the housing  302 . O¬ring or other seal  305  assists in sealing the mouthpiece  304  in the housing  302 . A battery  307  for powering various components of the assembly  301  and a controller  308  are provided at or towards the other end  306  of the housing  302 . The housing  302  of this example is again in two parts, a first part  302   a  being towards the open end  303  and a second part  302   b  towards the other end  306 . 
     The housing  302  has a chamber (sometimes referred to herein as “liquid chamber”)  309  for holding or containing an aerosolizable liquid (sometimes referred to herein as simply “liquid”)  310 . The liquid  310  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. The liquid chamber  309  may be of any of the types described above in relation to the examples of  FIGS.  1  and  2   . A heater  311  is provided generally centrally of the housing  302  for heating the liquid  310 . The heater  311  may be any of the types described above. In this example, the heater  311  is powered by the battery  307  and is therefore electrically connected to the battery  307 . An annular wick  312  surrounds the heater  311  and is in (thermal) contact with the heater  311 . The outermost surface of the annular wick  312  is in contact with liquid  310  contained in the liquid chamber  309 . The liquid  310  may be heated so as to produce an aerosol of liquid droplets or sufficiently heated to produce a vapor. The aerosol and/or vapor so produced exits the wick  312  and passes towards the mouthpiece  304  as shown by the arrows A under the action of the user drawing on the mouthpiece  304 . The heater  311  and wick  312  may be provided as a single, effectively integral item such that the heating and wicking is effectively carried out by a single unit. 
     The housing  302  further contains a chamber (sometimes referred to herein as “solid chamber”)  313  which holds or contains a nicotine source  314  in the assembly  301 . The nicotine source  314  corresponds to the nicotine source described hereinabove, is base-treated, and may have a pH of from 8 to 9.5, for example. The solid chamber  313  may be of any of the types described above in relation to the examples of  FIGS.  1  and  2   . (In the example shown in  FIG.  3   , the solid chamber  313  is in the form of a tube which has end walls  316  which have through holes  317  through which a vapor and/or aerosol can pass, which was mentioned as an option above.) The nicotine source  314  is located in the housing  302  downstream of the location where the aerosol and/or vapor is produced from the liquid  310  and upstream of the open end  303  of the housing  302  and the mouthpiece  304 . In this particular example, again, the nicotine source  314  is effectively provided in the same portion or chamber of the housing  302  as the wick  312 . The aerosol and/or vapor produced from the liquid  310  exits the wick  312  and passes as shown by the arrows A towards the nicotine source  314  under the action of the user drawing on the mouthpiece  304 . In particular embodiments, the nicotine source  314  is porous so that the aerosol and/or vapor passes through the nicotine source  314  and then through the open end  303  of the housing  302  and the mouthpiece  304 . 
     In some embodiments, the nicotine source  314  and/or its chamber  313  are arranged so that there is no air gap between the nicotine source  314 /chamber  313  and the interior of the housing  302  so that the aerosol and/or vapor flows entirely through the nicotine source  314 . As the aerosol and/or vapor passes through and over the nicotine source  314 , the hot aerosol and/or vapor entrains organic and other compounds or constituents from the nicotine source  314 , thus imparting flavor to the aerosol and/or vapor as is passes to the mouthpiece  304 . In particular, the free “deprotonated” nicotine in the nicotine source  314  may undergo acid-base salt formation with the acidic vapor and/or aerosol from the liquid  310 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  314  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  314 , nicotine may be provided in its better tasting, salt form. 
     The chamber  309  for containing the liquid  310  may itself be arranged to support or carry the nicotine source  314 . For example, the liquid chamber  309  may have one or more clips, a tube, or the like for receiving and holding the nicotine source  314  in position. Such a dual function liquid chamber  309 /solid chamber or receptacle  313  for both containing the liquid  310  and receiving the nicotine source  314  may be in the form of a cartridge or the like and may be a disposable item or may be re-useable, with the liquid  310  and nicotine source  314  being replaced or topped up by the user as required. In some cases, it may be that the user only needs to top up or replace the nicotine source  314  from time to time, with sufficient liquid  310  being provided for several uses. Once the liquid  310  has been consumed, the user disposes of the dual function liquid chamber  309 /solid chamber  313  and uses a new one. Likewise, it may be that the user only needs to top up or replace the liquid  310  from time to time, with sufficient nicotine source  314  being provided for several uses. Once the nicotine source  314  has been consumed, the user disposes of the dual function liquid chamber  309 /solid chamber  313  and uses a new one. 
     In the example assembly  301  of  FIG.  3   , a second heater  318  is again provided in thermal contact with the nicotine source  314  to heat the nicotine source  314  to encourage release of constituents from the nicotine source  314  as the vapor and/or aerosol passes through the nicotine source  314  in use. The second heater  318  may be an electrically resistive heater, a ceramic heater, etc., powered by for example the battery  307 . Other heating arrangements may be used for the second heater  318 , including non-electrical heating arrangements. 
     In the example assembly  301  of  FIG.  3   , the heater  318  for heating the nicotine source  314  is provided internally of the nicotine source  314  and heats the nicotine source  314  by heat conduction from the interior of the nicotine source  314 . The heater  318  in this example is generally in the form of a cylindrical rod located along the central longitudinal axis of the nicotine source  314 . In other arrangements, the heater  318  may be a wire, which may for example be in the form of a coil, a plate (which may be a multi-layer plate of two or more different materials, one or more of which may be electrically conductive and one or more of which may be electrically non-conductive), a mesh (which may be woven or non-woven for example, and which again may be similarly multi-layer), a film heater, etc. The nicotine source  314  in this case is generally tubular or otherwise has an internal aperture for receiving the heater  318 . The heater  318  may in effect be an integral part of the assembly  301  and be provided as part of the housing  302 . In this case, as the nicotine source  314  is loaded into the assembly  301  (for example, as the solid chamber  313  containing the nicotine source  314  is loaded into the assembly  301 ), the nicotine source  314  surrounds the second heater  318 . As an alternative, the heater  318  may be provided integrally with the solid chamber  313  which holds or contains the nicotine source  314 . In this alternative, in the case that the solid chamber  313  is disposable, the heater  318  will be replaced when a new solid chamber  313  with a fresh nicotine source is loaded into the assembly  301  by the user. 
     In another example, plural internal heaters  318  may be provided, so as to provide for more efficient heating of the nicotine source  314 . In another example, the nicotine source  314  may be heated by both one or more external heaters (like the second heater  215  of the example of  FIG.  2   ) and by one or more internal heaters (like the second heater  318  of the example of  FIG.  3   ). 
     Referring now to  FIG.  4   , there is shown a schematic longitudinal cross-sectional view of an example of a cartridge  600  having a liquid chamber  601  for containing aerosolizable liquid  602 , and a receptacle or chamber (sometimes referred to herein as “solid chamber”)  603  for a nicotine source  604 . The liquid  602  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. The nicotine source  604  corresponds to the nicotine source described hereinabove, is base-treated, and may have a pH of from 8 to 9.5, for example. In this example, the liquid chamber  601  and the nicotine source chamber  603  are provided as one integral component, either by being formed integrally initially or being formed initially of two parts, which are then assembled in a substantially permanent fashion. The cartridge  600  is arranged so that as the liquid  602  is volatilized so as to produce an aerosol of liquid droplets or sufficiently heated to produce a vapor, at least some and preferably all or substantially all of the aerosol and/or vapor passes through the nicotine source  604  to pick up flavor from the nicotine source  604 . In particular, the free “deprotonated” nicotine in the nicotine source  604  may undergo acid-base salt formation with the acidic vapor and/or aerosol from the liquid  602 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  604  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  604 , nicotine may be provided in its better tasting, salt form. 
     In the example of  FIG.  4   , the liquid chamber  601  is provided generally centrally of the cartridge  600 . The liquid chamber  601  in the example shown is frustoconical in shape, but may have a different shape, such as conical, cylindrical, etc. The liquid chamber  601  is surrounded by an outer shell  605  which defines an annular channel  606  around the outside of the length of the liquid chamber  601  and which extends from one end of the liquid chamber  601  to the other. The outer shell  605  extends beyond a first end wall  607  of the liquid chamber  601  to define a chamber  608  beyond the first end wall  607  of the liquid chamber  601 . In the example shown, both the chamber  608  and the annular channel  606  contain the nicotine source  604  and so can be regarded as together providing the solid chamber  603  for the nicotine source  604 . In other examples, the nicotine source  604  may be provided only in the chamber  608 , which therefore defines the solid chamber  603  for the nicotine source  604 , and the annular channel  606  is empty. The chamber  608  is closed off by an end wall  609  which is spaced from the end wall  607  of the liquid chamber  601 . The end wall  609  may be part of the outer shell  605  or may be a separate plastics, rubber cap, or the like. In yet other examples, the annular channel  606  contains the nicotine source  604  and there is no material in the chamber  608 , and indeed the chamber  608  may be omitted and the channel  606  effectively terminates at the end wall  609 . The channel  606  and/or chamber  608  may be entirely filled with nicotine source  604  or may only contain a portion or plug of nicotine source  604 . The end wall  609  is porous and/or has one or more through holes  610  to enable the aerosol and/or vapor to exit the cartridge  600  to be inhaled by a user. The liquid chamber  601  and the solid chamber  603  may each be formed of rigid, watertight and airtight materials, such as metal, suitable plastics, etc. 
     The example cartridge  600  shown in  FIG.  4    is provided with a heater  611  and a wick  612  in (thermal) contact with the heater  611 . In this example, the heater  611  and the wick  612  are provided as a single unit, often referred to as an “atomizer”. In this case, where the cartridge  600  includes an atomizer, such a cartridge is often referred to as a “cartomizer”. The orientation of the heater  611  is shown schematically and for example, the heater  611  may be a coil having its longitudinal axis perpendicular to the longitudinal axis of the cartridge  600  rather than parallel as shown in  FIG.  4   . 
     The wick  612  is in contact with the liquid  602 . This may be achieved by for example the wick  612  being inserted through a through hole (not shown) in the second end wall  613  of the liquid chamber  601 . Alternatively or additionally, the second end wall  613  may be a porous member (shown schematically in  FIG.  4    by dashed lines) which allows liquid to pass through from the liquid chamber  601 , and the wick  612  may be in contact with the porous second end wall  613 . The second end wall  613  may be for example in the form of a porous ceramic disk. A porous second end wall  613  of this type helps to regulate the flow of liquid onto the wick  612 . The wick  612  is generally absorbent and acts to draw in liquid  602  from the liquid chamber  601  by capillary action. The wick  612  is preferably non-woven and may be for example a cotton or wool material or the like, or a synthetic material, including for example polyester, nylon, viscose, polypropylene or the like. 
     In use, the cartridge  600  is connected by the user to a battery section of an assembly (not shown) to enable the heater  611  to be powered. When the heater  611  of the atomizer is powered (which may be instigated for example by the user operating a button of the overall assembly or by a puff detector of the overall assembly, as is known per se), liquid  602  drawn in from the liquid chamber  601  by the wick  612  is heated by the heater  611  to volatilize or vaporize the liquid. As the user draws on a mouthpiece of the overall assembly, the vapor and/or aerosol passes into the annular channel  606  around the outside of the length of the liquid chamber  601  and into the chamber  608  as shown by the arrows A. The vapor and/or aerosol picks up flavor from the nicotine source  604  and entrains one or more components thereof. When the vapor/aerosol contacts the nicotine source  604 , the free “deprotonated” nicotine in the nicotine source  604  may undergo acid-base salt formation with the acidic vapor and/or aerosol from the liquid  602 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  604  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  604 , nicotine may be provided in its better tasting, salt form. The vapor and/or aerosol can then exit the cartridge  600  through the end wall  609  as shown by the arrow B. Optionally, a one way valve  614  may be provided inside the end wall  609  so that the vapor and/or aerosol can only exit the cartridge  600  and cannot back-flow to the heater  611  or the electronics of the assembly as a whole. 
     Referring now to  FIG.  5   , there is shown a schematic longitudinal cross-sectional view of another example of a cartridge  700  having a chamber (sometimes referred to herein as “liquid chamber”)  701  for containing aerosolizable liquid (sometimes referred to herein as simply “liquid”)  702  and a chamber (sometimes referred to herein as “solid chamber”)  703  which defines a chamber  708  for containing a nicotine source  704 . The liquid  702  corresponds to the liquid described hereinabove and may have a pH of from 4 to 5, and/or may comprise an acid with a pKa greater than 3, for example. The nicotine source  704  corresponds to the nicotine source described hereinabove, is base-treated, and may have a pH of from 8 to 9.5, for example. In the following description and in  FIG.  5   , components and features that are the same as or similar to the corresponding components and features of the example described with reference to  FIG.  4    have the same reference numeral but increased by 100. For the sake of brevity, the description of those components and features will not be repeated in its entirety here. 
     In this example, the liquid chamber  701  and the solid chamber  703  of the cartridge  700  are provided as separate components, which are detachably connected to each other in use. The liquid chamber  701  and the solid chamber  703  may for example be clipped or otherwise detachably fixed to each other, or for example, the solid chamber  703  may simply rest on or be a tight friction fit on the liquid chamber  701 . The cartridge  700  is arranged so that as the liquid  702  is volatilized so as to produce an aerosol of liquid droplets or sufficiently heated to produce a vapor, at least some and preferably all or substantially all of the aerosol and/or vapor passes through the nicotine source  704  to pick up flavor from the nicotine source  704  and entrains one or more components thereof. When the vapor/aerosol contacts the nicotine source  704 , the free “deprotonated” nicotine in the nicotine source  704  may undergo acid-base salt formation with the acidic vapor and/or aerosol from the liquid  702 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  704  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  704 , nicotine may be provided in its better tasting, salt form. 
     In this example, the liquid chamber  701  is surrounded by an outer shell  705  which defines an annular channel  706  around the outside of the length of the liquid chamber  701  and which extends from one end of the liquid chamber  701  to the other. The outer shell  705  extends beyond a first end wall  707  of the liquid chamber  701  and terminates in an end wall  709 . The end wall  709  may be a separate plastics, rubber cap, or the like. The end wall  709  is porous and/or has one or more through holes  710  to enable the aerosol and/or vapor to exit the annular channel  706 . A one way valve  714  may be provided inside the end wall  709  so that the vapor and/or aerosol can only exit the annular channel  706  at the end remote from the heater  711  and wick  712  and cannot back-flow to the heater  711  or the electronics of the assembly as a whole. The nicotine source chamber  703  is located in use over the end wall  709  so that vapor and/or aerosol exiting through the end wall  709  passed into the solid chamber  703 . The solid chamber  703  has an exit aperture and/or or a porous end wall  715  to enable the aerosol and/or vapor to exit the cartridge  700  to be inhaled by a user. 
     In use, the cartridge  700  is connected by the user to a battery section of an assembly (not shown) to enable the heater  711  to be powered. When the heater  711  of the atomizer is powered (which may be instigated for example by the user operating a button of the overall assembly or by a puff detector of the overall assembly as is known per se), liquid  702  drawn in from the liquid chamber  701  through the end wall  713  by the wick  712  is heated by the heater  711  to volatilize or vaporize the liquid. As the user draws on a mouthpiece of the overall assembly, the vapor and/or aerosol passes into the annular channel  706  around the outside of the length of the liquid chamber  701  towards the end wall  709  of the outer shell  705  as shown by the arrows A. The vapor and/or aerosol then passes through the end wall  709  (via the one-way valve  714  if present) and into the solid chamber  703  where it picks up flavor from the nicotine source  704  contained in the solid chamber  703 , and entrains one or more components of the nicotine source  704 . When the vapor/aerosol contacts the nicotine source  704 , the free “deprotonated” nicotine in the nicotine source  704  may undergo acid-base salt formation with the acidic vapor and/or aerosol from the liquid  702 . In this way, nicotine may be drawn out or extracted by the acidic vapor and/or aerosol from the nicotine source  704  to increase the amount of nicotine delivery in the inhalable medium. Furthermore, by passing the acidic vapor/aerosol through and over the nicotine source  704 , nicotine may be provided in its better tasting, salt form. The vapor and/or aerosol can then exit the cartridge  700  through the end wall  715  of the solid chamber  703  as shown by the arrow B. 
     The examples shown in  FIGS.  4  and  5    are particularly suitable for use with so-called modular or “e go” products, in which the cartomizer is fitted to a battery section (not shown), typically by a screw thread, a bayonet fitting or the like. The cartomizer as a whole is typically discarded after use and a new, replacement cartomizer used. As an alternative, it may be possible for the user to re-use the cartridge by refilling the liquid and/or replacing the solid material from time to time as necessary. 
     The examples shown in  FIGS.  4  and  5    may easily be adapted for use with other types of an electronic tobacco hybrid device, which are known per se. There are for example so-called “look alike e cigarette” or “cig-alike” assemblies which are generally small and have a form and appearance similar to a conventional cigarette. In such assemblies, the liquid chamber typically includes some wadding material, of for example cotton or the like, for holding the liquid. The cartridge or cartomizer in such known assemblies is typically disposable as a whole, but it may be possible to refill the liquid and/or replace the sold material in examples that use an embodiment of the present invention. As another example, there are so-called tank assemblies or personal vaporizers, which generally have large liquid chambers for holding relatively large volumes of liquid and also provide for advanced functions that allow users to control a number of aspects of the assembly. 
     As an alternative to any of the cartomizer arrangements discussed above, the atomizer (i.e. the heater and the wick) for the liquid may be provided separately of the liquid and solid chambers. The atomizer may for example be provided as part of the battery section of the overall assembly to which the cartridge is detachably fitted by the user in use. 
     In any of the examples described above in relation to  FIGS.  4  and  5   , there may also be provided a heater for the nicotine source so as to “pre-heat” it. This heater may be provided as part of the cartridge or as part of the battery section of the assembly to which the cartridge is fitted in use. 
     EXAMPLES 
     Several experiments were tested to evaluate the effects of using an acidic vapor and/or aerosol on nicotine extraction from a nicotine source to provide an enhanced amount of nicotine delivery in an inhalable medium. 
     In this example, the objective was to test whether using an acidic aerosolizable liquid would extract nicotine from pH-treated tobacco to increase the amount of nicotine delivery in the inhalable medium. Three aerosolizable liquids were prepared for the experiments:
         1-C, a control sample an e-liquid composition of glycerol (17% w/w), propylene glycol (71% w/w) and water (12% w/w);   1-BA, a sample containing 0.04% by weight benzoic acid and the e-liquid; and   1-LA, a sample containing 0.04% by weight lactic acid and the e-liquid.       

     The solid, nicotine-containing material used was a tobacco blend, treated with base to have a pH of 8.5. The materials were loaded onto a standard test system as pods and the liquid was heated; the heater element had a power of 7.5 W. The vapor/aerosol formed from the liquid was then passed through or over the pH-treated tobacco composition, entraining one or more components thereof to provide an inhalable medium, which passes to a detector through an outlet. 
     During one experiment, the system performed 60 puffs in total per pod, formed of three 20-puff blocks, measuring the nicotine delivery at each 20-puff interval. The puffing was done using a 55/3/30 regime (55 ml puff of 3-second duration every 30 seconds). The measurements were repeated four times for each sample. A summary of the results is shown in the tables below. 
     Puff block=20 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 Nicotine 
                 StDev 
               
               
                   
                 SampleMean 
                 (ug/Puff) 
                 (ug/Puff) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 1-C 
                 67.19 
                 11.97 
               
               
                   
                 1-BA 
                 78.58 
                 5.80 
               
               
                   
                 1-LA 
                 99.50 
                 8.13 
               
               
                   
                   
               
            
           
         
       
     
     Puff block=40 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 Nicotine 
                 StDev 
               
               
                   
                 SampleMean 
                 (μg/Puff) 
                 (μg/Puff) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 1-C 
                 50.91 
                 8.13 
               
               
                   
                 1-BA 
                 49.37 
                 8.01 
               
               
                   
                 1-LA 
                 60.38 
                 8.83 
               
               
                   
                   
               
            
           
         
       
     
     Puff block=60 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 Nicotine 
                 StDev 
               
               
                   
                 SampleMean 
                 (μg/Puff) 
                 (μg/Puff) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 1-C 
                 24.92 
                 3.20 
               
               
                   
                 1-BA 
                 30.40 
                 4.25 
               
               
                   
                 1-LA 
                 28.50 
                 8.88 
               
               
                   
                   
               
            
           
         
       
     
     Referring to  FIG.  6   , a graph of the results from the experiments described above are shown, and demonstrates examples of nicotine delivery from assemblies according to embodiments of the invention, as well as a comparative assembly. 
     For the 1-20 puff block measurement on each sample, the nicotine delivery has increased for the acidified liquids. For benzoic acid containing liquids, the nicotine delivery has increased from 67.2 μg/puff (control, 1-C) to 79 μg/puff (1-BA). For lactic acid containing liquids, the nicotine delivery has increased from 67.2 μg/puff (control, 1-C) to 100 μg/puff (1-LA). 
     Accordingly, the results of the experiments show that the use of an acidic vapor/aerosol (such as one formed from a liquid containing benzoic acid or lactic acid in 1-BA or 1-LA, respectively) increases the amount of nicotine delivered to the user, compared to a neutral vapor/aerosol (such as the liquid used in 1-C). 
     Furthermore, the above results show that the total nicotine content removed from the solid tobacco is higher when an acidic vapor/aerosol is used. That is, a higher amount of nicotine is extracted from the tobacco when using an acidic vapor/aerosol (1-BA, 1-LA) compared to a neutral vapor/aerosol (1-C). Thus, in some embodiments the assembly allows for the rate of nicotine extraction to be increased, as well as the total amount of nicotine that is available to be extracted from the nicotine source to be increased. 
     As used herein, “aerosol generating agent” refers to a compound or mixture that promotes the generation of an aerosol. An aerosol-generating agent may promote the generation of an aerosol by promoting an initial vaporization and/or the condensation of a gas to an inhalable solid and/or liquid aerosol. 
     In general, any suitable aerosol-generating agent or agents may be included in the aerosolizable liquid or nicotine source. Suitable aerosol generating agents include, but are not limited to: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate. 
     As used herein, the terms “flavor” and “flavoring” refer to materials which, where local regulations permit, may be used to create a desired taste or aroma in a product for adult consumers. They may include extracts (e.g., liquorice, hydrangea, Japanese white bark magnolia leaf, chamomile, fenugreek, clove, menthol, Japanese mint, aniseed, cinnamon, herb, wintergreen, cherry, berry, peach, apple, Drambuie, bourbon, scotch, whiskey, spearmint, peppermint, lavender, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, honey essence, rose oil, vanilla, lemon oil, orange oil, cassia, caraway, cognac, jasmine, ylang-ylang, sage, fennel, piment, ginger, anise, coriander, coffee, or a mint oil from any species of the genus Mentha), flavor enhancers, bitterness receptor site blockers, sensorial receptor site activators or stimulators, sugars and/or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharine, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanicals, or breath freshening agents. They may be imitation, synthetic or natural ingredients or blends thereof. They may be in any suitable form, for example, oil, liquid, or powder. 
     For the avoidance of doubt, where in this specification the term “comprises” is used in defining the invention or features of the invention, embodiments are also disclosed in which the invention or feature can be defined using the terms “consists essentially of” or “consists of” in place of “comprises”. 
     As used herein, the term pH is used as a reference to the pH measured at room temperature, i.e. at 20-22° C. In some embodiments, room temperature is 20° C. 
     The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims. 
     The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.