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CLASS 203,	DISTILLATION: PROCESSES, SEPARATORY
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SECTION I - CLASS DEFINITION

GENERAL STATEMENT OF CLASS SUBJECT MATTER

This is the residual class for processes for separating a liquid mixture (distilland) by vaporizing and condensing at least a portion thereof to isolate in the condensed liquid (distillate) or in the unvaporized portion (residue) a comparatively pure compound which was present as such in the original mixture. The original mixture may be a solid under normal atmospheric conditions if it liquifies below the vaporization temperature.

To come within the purview of this class (203) the distilland must have a boiling point above 0°C. under normal atmospheric pressure. Because the C4 hydrocarbons have boiling points above and below 0°C., all C4 hydrocarbons are arbitrarily classified as having boiling points above 0°C.

Sublimination (see Glossary) is excluded from this class (203). See References to Other Classes, below.

When claims are presented which recite a specific chemical compound or mixture to be recovered, the enumerated classifications set forth in Lines With Other Classes must be consulted to see if such subject matter is provided for in other than Class 203.

SECTION II - LINES WITH OTHER CLASSES AND WITHIN THIS CLASS

LINES WITH CHEMICAL COMPOSITION CLASSES

(1) Products whether claimed in terms of their composition or claimed in terms of the process of making are classified in the appropriate composition class even if the process merely recites a separatory distillation operation.

(2) Processes including a chemical reaction and a separatory distillation operation are classified here only when the chemical reaction merely facilitates the isolation by the separatory distillation operation of a preexisting substance in the distilland. See Class 260, Chemistry of Carbon Compounds, Class 423, Chemistry of Inorganic Compounds, or Class 585, Chemistry of Hydrocarbon Compounds for a process of preparing a compound and isolating it by a separatory distillation process.

(3) Processes including a separatory distillation step and a disparate physical separation step, such as extraction, are classified in this class (203) if the disparate separating step follows the distillation step and the process is not otherwise provided for. When the disparate separation step precedes the distillation step, the process is generally provided for elsewhere.

See Class 260, Chemistry of Carbon Compounds (including Class 585, Chemistry of Hydrocarbon Compounds) or Class 423, Chemistry of Inorganic Componds, for a process of extraction of a compound, either as a sole step or followed by isolating the compound by a separatory distillation process.

(4) Processes directed solely to a separatory distillation operation are classified in this class (203) unless otherwise provided for:

(a) Processes for the distillation of metals, such as mercury or zinc are classified in Class 75, Specialized Metallurgical Processes, Compositions for Use Therein, Consolidated Metal Powder Compositions, and Loose Metal Particulate Mixtures.

(b) Processes for distilling a mineral oil in which the product isolated is a pure compound are classified in this class (203). However, when the distillation process produces as the product a mineral oil, it is classified in Class 208, Mineral Oils: Processes and Products.

(c) Processes which include fermentation are classified in 435, Chemistry: Molecular Biology and Microbiology, even if such processes also include distillation.

(d) Processes for distilling fermented beverage to produce a distilled beverage are classified in Class 426, Food or Edible Material: Processes, Compositions, and Products, but processes for distilling a fermented beverage to isolate alcohol are classified here (203).

(e) When a patent contains a Class 423, Chemistry of Inorganic Compounds, process claim and a Class 203, Distillation: Processes, Separatory, process claim, the patent is classified in Class 423 and cross-referenced to Class 203.

PROCESSES INCLUDING EVAPORATION

Processes for evaporating without a condensing step are generally excluded from this class. For specific lines between the processes of this class and other processes including an evaporating step, see below.

This class (203) is distinguished from Class 34, Drying and Gas or Vapor Contact With Solids, in that the material treated herein (203) is a liquid or a liquefiable solid from which volatile material is to be separated and condensed or absorbed. The product recovered must be a relatively pure substance which existed as such in the original material. The material of Class 34 is a solid or semi-solid from which it is desired to remove a liquid, leaving the residue chemically unchanged.

Class 134, Cleaning and Liquid Contact With Solids, takes claimed combinations of work handling or supporting means or steps with means or steps to apply a liquid to the work, as by spraying or immersion, where said liquid is distilled or evaporated, whether or not the resulting vapor is (1) directly contacted with the work or (2) condensed for reuse to contact the work. When only the liquid distillation subcombination or the vapor-phase work contact subcombination has been claimed, see above for the line between Class 203 and Class 34.

Class 62, Refrigeration, includes processes for separating a mixture of substances having boiling points below 0°C. (32°F) at atmospheric pressure by the steps of vaporizing a component and condensing the vapor. When a patent includes species claims classifiable in Class 62 and Class 203, it is classified in Class 62 and cross-referenced to Class 203.

Class 95, Gas Separation: Processes, takes processes in which gas is removed from a liquid wherein the gas is normally gaseous at a temperature of 0°C and a pressure of 760 mm Hg (e.g., hydrogen sulfide (H₂S), carbon monoxide (CO), carbon dioxide (CO₂), etc.). The volatile need not be condensed. The line between Class 95 and Class 203 is that a Class 203 operation requires vaporizing and condensing a material which is normally a liquid, while Class 95 does not.

Class 159, Concentrating Evaporators, takes processes for concentrating solids in solution or suspension by volatilizing the liquid. It is distinguished from this class (203) by the fact that the volatile material is not condensed.

Some additional classes which provide for processes that include an evaporating step or a concentrating step are: Class 23, Chemistry: Physical Processes; Class 127, Sugar, Starch, and Carbohydrates; Class 260, Chemistry, Carbon Compounds; Class 426, Food or Edible Material: Processes, Compositions, and Products; Class 520, Synthetic Resins or Natural Rubbers; Class 585, Chemistry of Hydrocarbon Compounds; Class 588, Hazardous or Toxic Waste Destruction or Containment.

CLASS 201, DISTILLATION: PROCESSES, THERMOLYTIC, IS SUPERIOR TO CLASS 203.

SECTION III - REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:

SECTION IV - GLOSSARY

AZEOTROPIC DISTILLATION

A separatory distillation of a liquid in which a substance is added to the distilland mixture in order to assist separation of its components by forming with one or more of the components a mixture having a minimum boiling point. (The art has also used the term for a distillation process in which two substances in the starting material are removed by their forming a minimum boiling mixture).

CONDENSATE

See "distillate" in the class definition.

CONVECTIVE DISTILLATION

A separatory distillation operation in which an inert vapor is passed through a heated liquid to reduce the partial vapor pressure of the component in the liquid desired to be recovered. It permits the separation of heat sensitive high boiling substances at temperatures below their decomposition temperature. Steam distillation is the most commonly used type of convective distillation.

DISTILLAND

For purposes of this class the liquid or liquefied material which is undergoing a distillation operation.

DISTILLATE

The liquid product condensed from vapor during the distillation operation.

EVAPORATION

The process of changing a solid or liquid into a vapor. This is the generic term for both sublumination and vaporization. It differs from "distillation" in that distillation includes the additional step of condensing vapor produced to a liquid.

EXTRACTIVE DISTILLATION

A separatory distillation in which a generally less volatile substance, often referred to as a solvent, is added to the distillation column to preferentially remove some component of the vapor by dissolving it. The added substance and the dissolved component are removed below the point at which the less volatile substance is added to the distillation column.

FLASH VAPORIZATION

The process in which the distilland is heated under pressure high enough to prevent ebullition (usually above atmospheric pressure) and the heated distilland is then introduced into a zone of lesser pressure resulting in the volatilization of at least a position of the distilland.

FRACTIONAL DISTILLATION

A separatory distillation operation in which distillate is collected over specific temperature intervals.

MOLECULAR DISTILLATION

A high vacuum separatory distillation process for distilling high boiling, heat sensitive substances in which the distance from the liquid surface to the condensing surface is less than the mean free path.

SEPARATORY DISTILLATION

A process of vaporizing at least a portion of a liquid mixture (distilland) and condensing at least a portion of the vapor to separate the liquid mixture into distinct parts. The substances recovered as products must have preexisted in the original mixture.

STEAM DISTILLATION

A form of convective distillation in which the inert vapor passed through the heated liquid is steam. The adding of water or steam to a distillation column or the adding of water to a distilland is not within the meaning of this term.

SUBLIMATION

A process in which a solid passes into the vapor state without liquefaction and the vapor returns to the solid state without passing through the liquid phase.

THERMOLYTIC DISTILLATION

A distillation in which material found in the distilland undergoes chemical decomposition (thermolysis) to form different substances at least some of which are volatile at the temperature employed. The volatile substances are recovered by condensation or sorption.

VAPORIZATION

The process of changing a liquid into a vapor. See "Evaporation".

SUBCLASSES

1	WITH MEASURING, TESTING OR INSPECTING:
	This subclass is indented under the class definition.  Processes combined with the positive step of visually, chemically or physically determining some chemical or physical characteristic or property of the feed, vapor, residue or condensate. (1) Note. The chemical or physical characteristic must be positively stated in the claim for the purpose of this and indented subclasses, e.g., measuring the temperature. Heating to a specified temperature is not determining a characteristic within the purview of this and indented subclasses. SEE OR SEARCH CLASS: 73,  Measuring and Testing,   appropriate subclasses for measuring and testing apparatus. 137,  Fluid Handling,   subclasses 2+ for a process in which a condition or characteristic of a fluent material is determined and used to control the system. 162,  Paper Making and Fiber Liberation,   subclass 238 for a digester with automatic control means. 196,  Mineral Oils: Apparatus,   subclass 132 for mineral oil vaporizing apparatus provided with automatic control. 201,  Distillation: Processes, Thermolytic,   subclass 1 for a process directed to thermolytic distillation combined with measuring, testing or inspecting. 202,  Distillation: Apparatus,   subclasses 151 , 160, 193, 196, 206 for distillation apparatus having control devices and see "SEARCH CLASS" under each subclass. 361,  Electricity: Electrical Systems and Devices,   appropriate subclasses for electrical systems not otherwise classified and see "SEARCH CLASS" under the class definitions for various types of electrical systems. 436,  Chemistry: Analytical and Immunological Testing,   subclasses 230+ for a process of chemically testing not combined with a distillation process.

2	Of temperature or pressure:
	This subclass is indented under subclass 1.  Processes directed to specifically determining the temperature and/or pressure of the feed, vapor, residue or condensate. SEE OR SEARCH CLASS: 73,  Measuring and Testing,   appropriate subclasses for device for quantitatively measuring temperature and 700+ for a device for the direct measurement of pressure. 137,  Fluid Handling,   subclasses 2+ for a process of fluid handling in which one or more characteristics or conditions of a fluent material are determined, particularly subclass 14 for a process involving pressure control. 202,  Distillation: Apparatus,   subclass 160 for a separatory distillation system including a column provided with automatic temperature and/or pressure control, and see "SEARCH THIS CLASS, SUBCLASS" and "SEARCH CLASS" thereunder for related fields of search. 374,  Thermal Measuring and Testing,   subclasses 100+ for a device for quantitatively determining temperature. 532,  Organic Compounds,   appropriate subclasses for a process directed to temperature control. 585,  Chemistry of Hydrocarbon Compounds,   subclass 956 for a collection of patents concerned with condition-responsive control procedures in hydrocarbon purification processes.

3	Of concentration:
	This subclass is indented under subclass 1.  Processes including the steps of determining the concentration of the feed, vapor, residue or condensate. SEE OR SEARCH CLASS: 73,  Measuring and Testing,   subclasses 32+ for apparatus for determining density and/or specific gravity of a liquid. 137,  Fluid Handling,   subclasses 2+ for a process of fluid handling in which one or more characteristics or conditions of a fluent material are determined. 356,  Optics: Measuring and Testing,   subclass 450 for interferometers and subclasses 128+ for refractometers.

4	INCLUDING PURGING OF THE SYSTEM:
	This subclass is indented under the class definition.  Processes combined with a step of removing a contaminant from the separatory apparatus. (1) Note. Usually a material, such as a gas, is passed through the apparatus to remove the contaminant. SEE OR SEARCH CLASS: 95,  Gas Separation: Processes,   subclasses 241+ for degasification of liquid. 134,  Cleaning and Liquid Contact With Solids,   subclasses 1+ for a process of separating or removing adherent undesired matter from solid material and subclasses 43+ for apparatus for cleaning by liquid contact. 137,  Fluid Handling,   subclasses 15.01 through 15.26for a process of cleaning, repairing or assembling. 201,  Distillation: Processes, Thermolytic,   subclass 2 for a process of cleaning the apparatus or removing adhering char product.

5	SEPARATING ISOTOPES OR TAUTOMERS:
	This subclass is indented under the class definition.  Processes directed to separating (1) the atoms of a given element or a compound containing said atoms according to the atomic weights of said atoms according to the atomic weights of said atoms or (2) a mixture containing at least two tautomeric forms of a substance initially in a state of equilibrium. (1) Note. A mixture of H2O and D2O is an example of a feed mixture containing hydrogen atoms of different atomic weights. (2) Note. Separating by distillation the ketoenol forms of a compound is within the purview of this subclass. SEE OR SEARCH CLASS: 95,  Gas Separation: Processes,   subclasses 31+ for processes in which a plurality of gases is separated by making use of physical difference in weight. 423,  Chemistry of Inorganic Compounds,   subclass 580.1 for processes of producing water and subclass 580.2 for processes of producing heavy water including a chemical reaction.

6	ADDITION OF MATERIAL TO DISTILLAND TO INHIBIT OR PREVENT REACTION OR TO STABILIZE:
	This subclass is indented under the class definition.  Processes including adding an element or a chemical compound or mixture (of substances) to the distilland or the vapor to inhibit or prevent formation of scale on the apparatus and/or to inhibit or prevent corrosion of the apparatus and/or to inhibit or prevent an unwanted reaction of the feed, vapor, residue or condensate. (1) Note. The addition of a scale inhibiting material to water being distilled or the addition of a corrosion inhibiting material to an acidic material being distilled or the addition of a material which inhibits the polymerization of an olefin at the temperature of the distillation are nonlimiting examples of the scope of this and indented subclasses. SEE OR SEARCH THIS CLASS, SUBCLASS: 86, for a separatory distillation process including the use of a surface of a specific composition which thereby inhibits or prevents an unwanted reaction. SEE OR SEARCH CLASS: 252,  Compositions,   subclasses 397+ for compositions for preventing, inhibiting or reducing oxidation, chemical decomposition, or other chemical change. 260,  Chemistry of Carbon Compounds,   and its daughter Classes 530-570 for a nonhydrocarbon organic compound containing a stabilizer. 422,  Chemical Apparatus and Process Disinfecting, Deodorizing, Preserving, or Sterilizing,   subclasses 7+ for process of maintaining an environment nondestructive to metal. 585,  Chemistry of Hydrocarbon Compounds,   subclasses 1+ for a hydrocarbon compound containing a stabilizer.

7	For scale inhibiting or corrosion preventing:
	This subclass is indented under subclass 6.  Processes directed to adding a substance to inhibit or prevent corrosion of the apparatus and/or to inhibit or prevent scale formation. SEE OR SEARCH CLASS: 196,  Mineral Oils: Apparatus,   subclass 133 for a mineral oil vaporizer having some special feature of construction. 202,  Distillation: Apparatus,   subclass 267.1 for apparatus in terms of the materials of construction. 208,  Mineral Oils: Processes and Products,   subclass 47 for a process of treating mineral oil including a step to prevent or reduce corrosion or erosion of the apparatus employed in the process and see "SEARCH THIS CLASS, SUBCLASS" and "SEARCH CLASS" thereunder for related fields of search. 252,  Compositions,   subclasses 175+ for water-softening or purifying or scale-inhibiting agents, and subclasses 387+ for anti-corrosion agents.

8	For inhibiting or preventing a polymerization reaction:
	This subclass is indented under subclass 6.  Processes directed to adding a substance to inhibit or prevent unwanted polymerization. SEE OR SEARCH THIS CLASS, SUBCLASS: 30, for a separatory distillation process in which a substance is added to cause a desired polymerization of at least one component.

9	Of unsaturated hydrocarbon:
	This subclass is indented under subclass 8.  Processes directed to inhibiting or preventing the polymerization of an unsaturated hydrocarbon.

10	WATER PURIFICATION ONLY:
	This subclass is indented under the class definition.  Processes of purifying water in which the only material recovered as a product is water. SEE OR SEARCH CLASS: 159,  Concentrating Evaporators,   subclasses 5+ for concentrating apparatus of the film type, subclasses 13.1+ for evaporating apparatus designed to maintain the liquid being evaporated in a film, and subclass 49 for an evaporating process in which the liquid to be concentrated is spread in a thin film. 165,  Heat Exchange,   appropriate subclassesfor a process of adding water vapor to air or removing water vapor from air. 202,  Distillation: Apparatus,   subclass 167 for a separatory distillation apparatus which includes a still and a feed water heater. 210,  Liquid Purification or Separation,   subclasses 600+ for a process of purifying a liquid not otherwise provided for. 423,  Chemistry of Inorganic Compounds,   subclass 580.1 for processes of producing water and 580.2 for processes of producing heavy water including a chemical reaction.

11	Under pressure or vacuum:
	This subclass is indented under subclass 10.  Processes in which distillation is carried out under a pressure greater than atmospheric or under a vacuum. SEE OR SEARCH THIS CLASS, SUBCLASS: 73+, for a plural distillation process in which at least one distillation is under pressure or vacuum. 91+, for a single distillation process carried out under pressure or vacuum.

12	DISTILLING TO SEPARATE OR REMOVE ONLY WATER:
	This subclass is indented under the class definition.  Processes in which only water is removed from the feed mixture. (1) Note. For purposes of this and indented subclasses water is the impurity of the distilland which is to be removed. A process of removing other impurities as well as water is excluded. (2) Note. A plural distillation process of separating only water by adding an extraneous liquid to the distilland to alter the relative volatility of water and the liquid be dried in the initial distillation step and then distilling a product of the initial distilling operation to separate the extraneous liquid is classified here. SEE OR SEARCH THIS CLASS, SUBCLASS: 10+, for a process in which the only material recovered as a product is water. 50+, for a process directed to adding a specific extraneous material to alter the relative volatility of a component of a mixture. SEE OR SEARCH CLASS: 23,  Chemistry: Physical Processes,   subclass 306 for a process of concentrating a solution of a liquid in a liquid not otherwise provided for. 34,  Drying and Gas or Vapor Contact With Solids,   appropriate subclasses, under "Processes" for a process for separating a liquid from a solid. 62,  Refrigeration,   subclasses 93+ for a process of removing moisture from air. 95,  Gas Separation: Processes,   appropriate subclasses for processes of removing water from a gaseous fluid mixture. See particularly subclasses 117+ for solid sorption processes to remove water from a gaseous fluid mixture and subclass 231 for processes of liquid contacting to remove water from a gaseous fluid mixture.

13	From nitric acid:
	This subclass is indented under subclass 12.  Processes in which the liquid substance is aqueous nitric acid. SEE OR SEARCH CLASS: 423,  Chemistry of Inorganic Compounds,   subclasses 390.1+ for producing nitric acid by a chemical reaction.

14	From organic compound:
	This subclass is indented under subclass 12.  Processes for separating water from an organic compound. (1) Note. Mixtures of organic substances from which only water is separated by a distillation step are included in this and indented subclasses unless otherwise provided for. SEE OR SEARCH CLASS: 208,  Mineral Oils: Processes and Products,   subclasses 187+ for a process for removing water from mineral oils and see "Note", "SEARCH THIS CLASS, SUBCLASS" and "SEARCH CLASS" in subclass 187 for related processes for removing water from organic mixtures. 260,  Chemistry of Carbon Compounds,   appropriate subclasses for a process including removing water by distillation combined with a step for forming a compound or extracting the compound from a natural source.

15	Organic acid:
	This subclass is indented under subclass 14.  Processes in which the organic substance is an organic acid. (1) Note. The term "organic acid" includes organic compounds which contain an acid function, e.g., boro, phosphor, sulfa or carboxylic group and see Class 260, Chemistry of Carbon Compounds, subclass 500 "(1) Note". SEE OR SEARCH THIS CLASS, SUBCLASS: 14, for a separatory distillation process for removing only water from salts or esters of organic acids.

16	Acetic:
	This subclass is indented under subclass 15.  Processes in which the organic acid is acetic acid.

17	Aldehyde or ketone:
	This subclass is indented under subclass 14.  Processes in which the organic substance is an aldehyde or a ketone. (1) Note. The terms "aldehyde" and "ketone" include those compounds having the structure R1COR2 wherein R1 is hydrocarbon and R2 is either hydrogen or hydrocarbon. See Class 568, Organic Compounds, subclasses 303 and 420 and the notes thereunder.

18	Alcohol:
	This subclass is indented under subclass 14.  Processes in which the organic substance is an alcohol. (1) Note. For purposes of this and indented subclasses the term "alcohol" is limited to a hydroxy group bonded to carbon.

19	Ethanol:
	This subclass is indented under subclass 18.  Processes in which the alcohol is ethanol.

20	INCLUDING DEFOAMING OR INHIBITING FOAM:
	This subclass is indented under the class definition.  Processes directed to defoaming or inhibiting the formation of foam. SEE OR SEARCH CLASS: 95,  Gas Separation: Processes,   subclass 155 for processes of gas separation involving liquid contacting and the use of a defoaming or antifoaming agent; subclass 157 for processes of gas separation involving liquid contacting and defoaming the liquid; and subclass 242 for defoaming a liquid, per se. 137,  Fluid Handling,   appropriate subclassesfor apparatus for controlling the degree of foaming in a gas charged liquid. 201,  Distillation: Processes, Thermolytic,   subclass 9 for a process of surface treating the solid particles of the charge to inhibit, reduce or prevent foaming during distillation. 202,  Distillation: Apparatus,   subclass 264 for distillation apparatus intended to break foam or inhibit foaming. 435,  Chemistry: Molecular Biology and Microbiology,   subclass 266 for a fermentation process including the step of treating the foam produced. 516,  Colloid Systems and Wetting Agents; Subcombinations Thereof; Processes of Making, Stabilizing, Breaking, or Inhibiting,   subclasses 115+ for processes of or compositions for or subcombination compositions for the breaking of or inhibiting of foam colloid systems, when generically claimed or when there is no hierarchically superior provision in the USPC for the specifically claimed art.

21	AND RECOVERING HEAT BY INDIRECT HEAT EXCHANGE:
	This subclass is indented under the class definition.  Processes directed to recovering waste heat by indirect heat exchange with (1) a disparate source or (2) a product of a distillation step. (1) Note. Heat generated by an engine which runs a compressor used in the process is a disparate source of "waste heat" within the scope of this and indented subclasses. SEE OR SEARCH THIS CLASS, SUBCLASS: 100, for a digest of distillation processes directed to specific type of heating. SEE OR SEARCH CLASS: 34,  Drying and Gas or Vapor Contact With Solids,   subclasses 427 and 513 for a process including conserving heat by indirect heat exchange. 62,  Refrigeration,   subclass 96 for a process in which heat from a gas being cooled is transferred to a heat absorber by indirect heat exchange, and subclass 113 for a process of refrigeration in which one function is in heat exchange relation with a second function. 165,  Heat Exchange,   appropriate subclasses for heat exchange apparatus and note Search Class under Class definition for related fields of search. 196,  Mineral Oils: Apparatus,   subclass 134 for apparatus for vaporizing mineral oils including means for heat recovery from the vapor or residuum. 202,  Distillation: Apparatus,   subclass 146 for a horizontal retort with flues wherein the air and/or gas for combustion is heated by the waste products of combustion by means of a single-surface heater and subclass 150 for a similar apparatus using a double-surface heater. 208,  Mineral Oils: Processes and Products,   subclass 365 for a process wherein the mineral oil distilland is heated by indirect contact with a heated product of the distillation. 237,  Heating Systems,   appropriate subclass for a heating system which may use the heat rejecting portion of a refrigeration system with additional heating means. 261,  Gas and Liquid Contact Apparatus,   subclasses 158+ for apparatus for indirect interchange of heat between contact fluids.

22	Utilizing recovered heat for heating feed:
	This subclass is indented under subclass 21.  Processes in which the feed is heated by the recovered waste heat. SEE OR SEARCH CLASS: 34,  Drying and Gas or Vapor Contact With Solids,   subclass 513 for a process of including the step of exchanging heat between the incoming and outgoing gases. 196,  Mineral Oils: Apparatus,   subclass 134 for mineral oil vaporizing apparatus having means for preheating the oil by the heat of the vapor or residue. 201,  Distillation: Processes, Thermolytic,   subclasses 14+ for a thermolytic distillation process directed to using a conversion product as an indirect source of heat for heating the feed. 202,  Distillation: Apparatus,   subclass 159 for a distillation system including a device for heating the feed with a product of the distillation step and subclasses 177+ for a still system including a device for preheating the feed with a product of the distillation step.

23	Distillation residue as heat source:
	This subclass is indented under subclass 22.  Processes in which distillation residue is the source of recovered heat. SEE OR SEARCH CLASS: 208,  Mineral Oils: Processes and Products,   subclass 353 for a process wherein one component being distilled is heated by indirect heat exchange of a component of the process, usually by the residue.

24	Compressed vapor as heat source:
	This subclass is indented under subclass 22.  Processes in which compressed vapor is the source of waste heat.

25	Utilizing recovered heat for heating the distillation zone:
	This subclass is indented under subclass 21.  Processes in which the distillation zone is heated by the recovered waste heat. SEE OR SEARCH CLASS: 202,  Distillation: Apparatus,   subclass 174 for multiple effect still series apparatus, 187 for apparatus in which the still and condenser are concentric and 192 for apparatus to which the cooling liquid in the condenser passes to the still to be distilled.

26	Compressed vapor as heat source:
	This subclass is indented under subclass 25.  Processes in which the source of waste heat is compressed vapor.

27	Utilizing recovered heat in subsequent step in process:
	This subclass is indented under subclass 21.  Processes in which the recovered waste heat is utilized in a step subsequent to the step in which the heat was produced.

28	WITH CHEMICAL REACTION:
	This subclass is indented under the class definition.  Processes including the step of producing a chemical reaction of a component of the mixture being separated to facilitate separation of the desired substance in the original mixture. (1) Note. To come within the purview of this and indented subclasses a chemical change must occur which facilitates the recovery without chemical change of the desired substance which was present in the original mixture. SEE OR SEARCH CLASS: 208,  Mineral Oils: Processes and Products,   subclasses 46+ for a process of treating mineral oil which results in a chemical alteration of at least some of the hydrocarbon molecules thereof. 546,  Organic Compounds,   subclasses 134+ for a general process of chemically treating a carbon compound not otherwise provided for. 588,  Hazardous or Toxic Waste Destruction or Containment,   subclasses 300 through 320for the use of a chemical reaction with distillation as part of a process of the destruction of hazardous or toxic waste.

29	Including step of adding catalyst or reacting material :
	This subclass is indented under subclass 28.  Processes directed to adding a catalyst or a material which reacts with a component of the mixture to assist the separation of the desired component in the original mixture. (1) Note. A chemical reaction for purposes of this and indented subclasses includes such reactions as (1) forming hydrates, (2) adjusting of hydrogen ion concentration, (3) polymerizing a component, (4) oxidizing or reducing a component or the addition to the mixture being acted upon of an oxidizing or reducing agent, and (5) the forming of different substances. SEE OR SEARCH THIS CLASS, SUBCLASS: 50+, for adding a substance to alter the relative volatility of components of the incoming feed without specifically producing a new chemical compound.

30

For polymerizing unwanted component:

This subclass is indented under subclass 29.  Processes in which the added material causes unwanted material in the feed to enter a reaction forming polymeric material. SEE OR SEARCH CLASS: 520,  Synthetic Resins or Natural Rubbers,   subclasses 1+ for a process of polymerizing, per se, and products resulting therefrom. 530,  Chemistry: Natural Resins or Derivatives; Peptides or Proteins; Lignins or Reaction Products Thereof,   subclasses 211+ for a process polymerizing, per se, and products resulting therefrom. 554,  Organic Compounds,   subclasses 25 through 29for a process polymerizing, per se, and products resulting therefrom. 585,  Chemistry of Hydrocarbon Compounds,   subclasses