FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENT RULES, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION "IMPROVED PROCESS FOR PREPARING HYDRATES of 2-{2-[4- (BIS(4-FLOUROPHENYL)METHYL)-N-PIPERAZINYL]ETHOXY) ACETIC ACID OR SALTS AND INTERMEDIATES THEREOF" We, CADILA HEALTHCARE LIMITED, a company incorporated under the Companies Act, 1956, of Zydus Tower, Satellite Cross Road, Ahmedabad - 380015, Gujarat, India. The following specification particularly describes the nature of the invention: 1 FIELD OF INVENTION The present invention relates to a new process for preparing Efletrizine or its pharmaceutical ly acceptable salts thereof. The present invention also relates to the process of preparation of novel intermediate thereof in crystalline form. The present invention further provides the process for preparation of substantially pure 2-{-2-[4-(bis(4-flourophenyl-)methyl)-1-piperazinyl]ethoxy} acetic acid dihydrochloride. 2-{-2-[4-(bis(4-flourophenyl-)methyl)-l-piperazinyl]ethoxy} acetic acid commonly known as efletrizine and represented by Formula I. Efletrizine is useful as therapeutic agents for the treatment of allergic diseases and other disorders. BACKGROUND OF THE INVENTION Efletrizine is chemically known as 2-{-2-[4-(bis(4-fiourophenyl-)methyl)-l-piperazinyl]ethoxy} acetic acid of Formula I, have been proven useful as therapeutic agents for the treatment of allergic diseases and other disorders. Efletrizine is a substituted benzhydrylpiperazine derivative encompassed within general formula (I) of European Patent No. 0058146. It has been demonstrated to have antiallergic and antihistaminic properties and has been suggested for the treatment of seasonal and perennial allergic rhinitis. Efletrizine has been found to possess excellent antihistaminin properties. It belongs to the pharamcological class of second generation histamine Hi -receptor antagonists and shows in vitro high affinity and selectivity for H]-receptors. Efletrizine is useful as an antiallergic, 2 antihistaminic, bronochodilator and antispasmodic agent. Recent clinical studies have shown the utility of efletrizine when administered in the form of a nasal spray for the treatment of allergic rhinitis and rhino-conjunctivities (J.F Dessanges et.al. Allergy and Clin. Immunol .News (1994), Suppl. No. 2, abstract 1864; C. De Vos et al., Allergy and Clin. Immunol. News (1994), Suppl. No. 2, abstract 428). Another recent clinical pharmacological study has shown that efletrizine gives unexpectedly good results in the treatment of urticaria, atopic dermatitis ad pruritis. DESCRIPTION OF PRIOR ART Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. Efletrizine is encompassed within the general formula of European patent No. 0 058 146 and may be prepared according to the general process described in this patent. Said process for the synthesis of 2-{-2-[4-(bis(4-flourophenyl-)methyl)-l-piperazinyl]ethoxy} acetic acid derivatives comprises reacting a l-(diphenylmethyl)-piperazine derivative with methyl(2-chloroethoxy)acetate or 2-(2-chloroethoxy)acetamide to form a methyl 2-{-2-[4-(diphenylmethyl)-l-piperazinyl]ethoxy} acetate or a 2-{-2-[4-(diphenylmethyl)-l-piperazinyl]ethoxy} acetamide, respectively. Thus formed methyl ester or acetamide is then subjected to basic hydrolysis followed by acidification and isolation of the free carboxylic acid. This material is then transformed into its dihydrochloride salt. Processes for preparing efletrizine or a pharmaceutically acceptable salt thereof have been described in International patent applications WO 99/28310, WO 97/37982 and WO 03/09849. International patent application WO 99/28310 and European patent application number EP 0919550 Al describe pseudopolymorphic forms of efletrizine dihydrochloride. WO 2006/050909 Al discloses an amorphous form of efletrizine dihydrochloride obtained by freeze-drying. The patent also discloses various solvate form of efletrizine dihydrochloride characterized by x-ray powder diffraction. U.S. Patent 6,335,331 B2 discloses the pseudopolymorphic forms of efletrizine dihydrochloride characterized by x-ray powder diffraction pattern and their process of preparation. Thus, US '331 B2 provides two pseudopolymorphic forms, namely anhydrous efletrizine dihydrochloride and efletrizine dihydrochloride monohydrate. The anhydrous efletrizine dihydrochloride is designated as "Form A" and efletrizine dihydrochloride monohydrate is designated as "Form B". 3 US 2004/0254375 Al discloses a new process for the synthesis of 2-{-2-[4-(bis(4-flourophenyl-)methyl)-l-piperazinyl]ethoxy} acetic acid and their corresponding salt forms is provided. In particular, it discloses the process for the manufacture of 2-{-2-[4-(bis(4-flourophenyl-)methyl)-l-piperazinyl]ethoxy} acetic acid, amides and related derivatives of the general formula (A) below. as well as non-toxic; pharmaceutically acceptable salts and mixtures thereof, characterized by (a) reacting compound of formula (B) wherein L' represents a leaving group, with a compound of formula (C) (b) reacting corresponding compound of formula (D) with a compound of formula (E) (E) wherein L2 represents a leaving group and Y in the presence of an inert solvent and a proton acceptor. US 6,255,487 Bl discloses the process for preparing [2-(l-piperazinyl)ethoxy]methyl compounds of general formula A' which comprises reacting a substituted [2-(l-piperazinyl)ethoxy]methyl compound of formula B' with a diphenyl halide of formula C. (A') (B') The above known processes in the prior art make use of hazardeous reagents and non-ecofriendly. There is a desire for an alternative economical and high yielding process for the synthesis of efletrizine dihydrochloride with novel intermediates. OBJECTS OF INVENTION It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. It is the object of the present invention to provide simple, cost effective, non-hazardeous, ecofriendly and high yielding process for preparation of efletrizine dihydrochloride. Thus, it is the object of the present invention to provide a new and improved process for preparation of efletrizine dihydrochloride or its pharmaceutical ly acceptable salts thereof. It is also the object of the present invention to provide crystalline intermediates for preparation of crystalline efletrizine dihydrochloride. 5 It is yet another object of the present invention to provide crystalline efletrizine dihydrochloride having particle size D50 less than or equal to 250 /.im. It is yet another object of the present invention to provide crystalline efletrizine dihydrochloride having purity greater than about 99% by area percentage of HPLC and having dimer impurity less than about 0.1% by area percentage of HPLC. The total impurities are less than about 0.4% by area percentage of HPLC. SUMMARY OF THE INVENTION According to the present invention, there is provided a process for the preparation of Eflitrizine of the formula (I) or its non-toxic pharmaceutically acceptable salts thereof which comprises steps of a) reacting 4,4'-diflourobenzophenone of formula (II), with ammonium formate in a suitable organic solvent to give N-(bis(4-fluorophenyl)methyl)formamide of formula (III); b) hydrolyzing N-(bis(4-fluorophenyl)methyl)formamide of formula (III) to obtain bis(4- fluorophenyl)methanamine of formula (IV) or its salts in presence of suitable reagent; 6 c) reacting bis(4-fluorophenyl)methanamine of formula (IV) with compound of formula (V) in suitable organic solvent to give compound of formula (VI); d) reacting compound of formula (VI) with suitable reagent in presence of acid to give l-(bis(4-fluorophenyl)methyl)piperazine formula (VII); . e) reacting l-(bis(4-fluorophenyl)methyl)piperazine formula (VII) with amide of formula (VIII) where X represents leaving group such as OTs, OMs, CI, F or Br etc., preferably CI, to prpvide compound of formula (IX) 7 treating compound of formula (IX) with mineral acid provide Eflitrizine of formula (I) g) optionally converting the compound of formula (1) to its non-toxic pharmaceutically acceptable salts thereof. According to the present invention, Efletrizine hydrochloride can be in the form of Anhydrous Form A or monohydrate form. The present invention, further provides the process for the preparation of N,N-bis(2-chloroethyl)-4-rnethylbenzenesulfonamide of formula (V), which is a key intermediate for the preparation of Eflitrizine CIH2CH2C^ /=N-S02-<\ />—CH3 CIH2CH2C V (/ (V) which comprises reacting bis(2-chloroethyl amine) HC1 with a base to obtain bis(2-chloroethyl amine), which is subsequently treated with p-toluenesulphonyl chloride in presence of base to obtain N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V). N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V) is isolated by the conventional method. According to the still further aspect of the present invention, there is provided crystalline form of intermediates of formula (III) and formula (VI). Preferably, the compound of formula (I) or its pharmaceutically acceptable salts i.e. efletrizine dihydrochloride monohydrate in crystalline form is having particle size D50 less than or equal to 250 ^m. Preferably, the compound of formula (I) or its pharmaceutically acceptable salts i.e. efletrizine dihydrochloride monohydrate in crystalline form is substantially pure having purity greater about 99% by area percentage of HPLC and having dimer impurity less than about 0.1% by area percentage of HPLC. The total impurities is less than about 0.4% by area percentage of HPLC is also within the scope of the present invention. 8 According to further aspect of the present invention, the compound of formula (I) or its pharmaceutically acceptable salts i.e. efletrizine dihydrochloride anhydrous in crystalline form is substantially pure having purity greater about 99% by area percentage of HPLC and having dimer impurity less than about 0.1% by area percentage of HPLC. The total impurities is less than about 0.4% by area percentage of HPLC is also within the scope of the present invention. BRIEF DISCRETIONS OF DRAWINGS A preferred embodiment of the invention will now be described, by way of examples only, with reference to the accompanying drawings in which: FIG.l is a differential scanning calorimetry (DSC) thermogram of compound of formula (III) FIG.2 is powder X-ray diffraction pattern of compound of formula (III) FIG.3 is an FTIR spectrum of compound of formula (III). FIG.4 is a differential scanning calorimetry (DSC) thermogram of compound of formula (IV) FIG.5 is powder X-ray diffraction pattern of compound of formula (IV) FIG.6 is an FTIR spectrum of compound of formula (IV) FIG.7 is a differential scanning calorimetry (DSC) thermogram of compound of formula (VI). FIG.8 is powder X-ray diffraction pattern of compound of formula (VI) FIG.9 is an FTIR spectrum of compound of formula (VI). FIG. 10 is a differential scanning calorimetry (DSC) thermogram of efletrizine dihydrochloride monohydrate FIG.l 1 is powder X-ray diffraction pattern of efletrizine dihydrochloride monohydrate FIG. 12 is an FTIR spectrum of efletrizine dihydrochloride monohydrate FIG. 13 is a differential scanning calorimetry (DSC) thermogram of efletrizine dihydrochloride anhydrous FIG. 14 is powder X-ray diffraction pattern of efletrizine dihydrochloride anhydrous FIG.15 is an FTIR spectrum of efletrizine dihydrochloride anhydrous DETAILED DESCRIPTION OF THE INVENTION 9 The present invention provides a process for the preparation of Eflitrizine of the formula (I) or its non-toxic pharmaceutically acceptable salts thereof (I) which comprises steps of a) reacting 4,4'-diflourobenzophenone of formula (II), c=o F (II) with ammonium formate in a suitable organic solvent to give N-(bis(4-fluorophenyl)methyl)formamide of formula (III); C—NH—CHO F (III) b) hydrolyzing N-(bis(4-fluorophenyl)methyl)formamide of formula (III) to obtain bis(4-fluorophenyl)methanamine of formula (IV) or its salts in presence of suitable reagent; C/-NH2 )) F (IV) c) reacting bis(4-fluorophenyl)methanamine of formula (IV) with compound of formula (V) >-S02- Reservoir A and 65% Reservoir B, and at time 50.0 min 35% Reservoir A and 65% 18 Reservoir B, and at time 55.0 min 65% Reservoir A and 35% Reservoir B, and at time 70.0 min 65% Reservoir A and 35% Reservoir B. The system equilibrated further for 10 min and a flow rate of 1.3 mL/min. The detector was set for 220 nm. The sample volume was 20 mL and the diluent was acetonitrile: water 50:50. As commonly known by the skilled artisan, the mobile phase composition and flow rate may be varied in order to achieve the required system suitability. The sample was prepared by weighing accurately about 10 mg of Efletrizine dihydrochloride sample in a 20 ml amber volumetric flask. Dissolving the sample with 10 ml of acetonitrile and diluting to the desired volume with water. Thereafter, the freshly prepared sample was injected. The sample solutions were injected into the chromatograph and the chromatogram of sample was continued up to the end of the gradient. Thereafter, the areas for each peak in each solution was determined using a suitable integrator. The calculations were obtained using the following formula: Impurity Profile Determination % impurity = area impurity in sample X 100 Total area Although the invention has been described with reference to a specific examples, it will be appreciated by those skilled in the art that the invention can be embodied in many other forms. The process of the present invention will be explained in more detail with reference to the following examples, which are provided by way of illustration only and should not be constructed as limit to the scope of the claims in any manner Example-1: Preparation of N-(bis(4-fluorophenyl)methyl)formamide of formula (III) 4,4'-difluorobenzophenone (100 gm, 0.458 mole) (II), Ammonium Formate (232 gm, 3.67 mole) were taken in 56 mL of foramide in RBF. The reaction mixture was heated slowly to 175°C to 180°C within 3 hours and maintained for 6-7 hours. The reaction mass was quenched in 400 mL of water within 1 hour and stir for 30 min. The product was filtered and suck dried. The product was washed with water and suck dried. The product was dried in oven at 50°C to 55°C to N-(bis(4-fluorophenyl)rnethyl)formamide of formula (III). ExampIe-2: preparation of bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) 19 N-(bis(4-fluorophenyl)methyl)formamide (III). (100 gm, 0.405 mole) and Cone. HCl (700 mL) were taken in RBF and heated at 95°C to 100°C. The reaction mass was cooled upto room temperature and further chilled to 0°C to 5°C and stirred for 1 hour. The product was filtered and washed with toluene. The wet-cake was taken in 400 mL of toluene and stirred for 1 hour at room temperature. The product was filtered and washed with toluene and suck dried. The wet-cake was further dried at 75°C to 80°C to give bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa). Example-3: Preparation of bis(4-fluorophenyl)methanamine of formula (IV) bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) (100 gm, 0.391 mole) was taken in 800 mL of water and stirred for 10 min. 25% NaOH solution was added till alkaline pH 12. Methylene dichloride (500 mL) was added and the reaction mass was stirred for 15 min. The layers were separated. The aqueous layer was extracted with 300 mL of methylene dichloride. The organic layer was washed with 300 mL of water and layers were separated. The organic layer was treated with sodium bisulfate and filtered. The methylene dichloride was distilled atmospherically and finally under vacuum to remove the traces of methylene dichloride to give bis(4-fluorophenyl)methanamine of formula (IV). Example-4: Preparation of N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V) N, N'-Bis (2-chloroethyl)amine hydrochloride (112.5 gm, 0.63 mole), methylene dichloride (800 mL) and triethylamine (182 mL) were taken in RRF. Freshly prepared solution of p-toluene sulfonyl chloride (100 gm, 0.524 mole) in methylene dichloride (400 mL) was added slowly within 1 hour at room temperature. After addition is completed the reaction mixture was heated to reflux at 40°C to 43°C for 6 hours. The reaction mass was cooled to room temperature. The organic solution was washed with water and stirred for 15 minutes. The layers were separated. The organic layer was washed with mixture of 1:9 HCl and water. Further organic layer of methylene dichloride was treated with sodium bisulfate and filtered. The methylene dichloride was distilled atmospherically and finally under vacuum to remove the traces of methylene dichloride. The residue was treated with 600 mL of hexane and stirred at room temperature. The isolated precipitates were stirred for 1 hour, filtered, suck dried and washed with hexane. The product thus obtained was air dried to give N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V). ExampIe-5: Preparation of l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) 20 4,4'-diflourobenzyhydrarylamine (100 gin, 0.456 mole) were taken in 100 mL of diisopropyl ethyl amine. N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V) (135 gm, 0.456 mole) in 100 mL of diisopropyl ethyl amine was added to it and the reaction mass was stirred for 10 min. The reaction mixture was heated to reflux temp at 125°C to 127°C for 17 to 18 hours and cooled to 75°C. 400 mL of methanol was added and refluxed at 65°C to 70°C for 1 hour. The reaction mixture was cooled to room temperature and chilled to 0°C to 5°C with stirring for 3 hours. The product was filtered, suck dried and washed with 100 mL of chilled methanol. The product was dried at 50°C to 55°C to give 1 -(bis(4-fluorophenyl)methyl)- 4-tosylpiperazine (VI) ExampIe-6: Preparation of l-(bis(4-fluorophenyl)methyl)piperazine formula (VII) The solution of hydrobromic acid acetic acid (550 mL) was prepared and chilled to 0°C to 5°C. 4-hydroxy benzoic acid (152.8 gm, 1.107 mole) was added to the above solution. 1- (bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) (100 gm, 0.226 mole) was added slowly at same temperature. The reaction mass was treated with 50 mL HBr in acetic acid and stirred for 30 min. The reaction mixture was gradually heated at 45°C to 47°C within 1 hour to 1.5 hour and stirred for 4 hours at same temperature. The reaction mass was cooled to room temperature and treated with 1000 mL of water with stirring for 1 hour. The product was filtered and washed with water. The product was suck dried. The aqueous filtrate was extracted with toluene. Further 1000 mL of toluene was added to aqueous filtrate. 50% NaOH solution was added to it till the alkaline pH 9 to 10. The layers were separated. The aqueous layer was again extracted with toluene 500 mL. The organic layer of toluene, acetic acid (100 mL) solution in (642.5 mL) of water was added. The separated aqueous layer was washed with tuluene. The organic layer was treated with Na2S04. The toluene was distilled under vacuum at 50°C to 55°C. Excess of toluene was further co-distilled with hexane (100 mL). The product was washed with water and suck dried followed by drying at 50°C to 55°C to give l-(bis(4-fluorophenyl)methyl)piperazine formula (VII). ExampIe-7: Preparation of 2-(2-(4-(bis(4-fluorophenyl)methyl)piperazin-l- yI)ethoxy)acetamide of formula (VIII) 4,4'-diflourobenzyl piperazine (100 mg, 0.346 mole), 2-(2-chloroethoxy) acetamide (95.15 gm, 0.692 mole) and sodium carbonate (73.35 gm) were taken in RBF. Xylene 400 mL was added to the reaction mass and stirred for 10 min. The reaction mass was heated at 120°C to 125°C for about 11-13 hours. The product was filtered and washed with toluene. The filtrate was cooled to 20°C to 25°C. Dilute HC1 (66.09 mL make upto 725 mL) was added and stirred for 30 minutes at room temperature. The layers were separated. The aqueous layer was washed with 21 toluene 600 mL. The separated aqueous layer was treated with IN 725 mL of NaOH and stirred for 10 minutes. 600 mL of methylene dichloride was added. The layers were separated and aqueous layer was extracted with 400 mL of methylene dichloride. The combined methylene dichloride was washed with 400 mL of water. The methylene dichloride was distilled out atmospherically at 50°C to 55°C further under vacuum to remove the traces. Diisopropyl ether (200 mL) was added and distilled out under vacuum at 50°C. Further diisopropyl ether (500 mL) was added , stirred at 50°C to 55°C and cool to room temperature. The product was filtered and suck dried followed washing with diisopropyl ether. The product was finally dried at 50°C to 55°C for 12 hours to get 2-(2-(4-(bis(4-fluorophenyl)methyl)piperazin-l-yl)ethoxy)acetamide (VIII) ExampIe-8: Preparation of EFLETRIZINE DIHYDROCHLORIDE MONOHYDRATE 2-(2-(4-(bis(4-fluorophenyl)methyl)piperazin-l-yl)ethoxy)acetamide (VIII) (100 gm) and 230 mL of water were taken at room temperature. 30% HCI (290 gm) was added within 10 minutes. The reaction mass was heated upto 65°C and stirred for 1 hour. Cooled to 0°C and stirred for 3 hours and 30 minutes. The product thus obtained was filtered and washed with dil HCI solution. The product was suck dried to obtain wet-cake. The wet-cake was treated with 489.1 mL of water at room temperature and heated to 60°C to get clear solution. The solution was treated with toluene and layers were separated. Aqueous layer was treated with charcoal and stirred for 30 min. The aqueous layer was cooled upto room temperature and acidified with 714.95 gm of Cone. HCI and chilled to 0°C with stirring for 4 hours. The product was filtered and washed with 86.95 mL chilled HCI and suck dried. The compound was further dried at 50°C to 55°C temperature to give Efletrizine dihydrochloride monohydrate. The samples were analyzed by HPLC. The fractions with a purity of > 99.0% were pooled. In the pooled fractions the HPLC purity was about > 99.7%. ExampIe-9: Preparation of EFLETRIZINE DIHYDROCHLORIDE ANHYDROUS Efletrizine dihydrochloride monohydrate (100 gm) was taken in 300 mL of methylethyl ketone. The reaction mixture was refluxed to the reflux temperature of the solvent to get clear solution. The product was cooled to room temperature. The product thus obtained was filtered, washed with methyl ethyl ketone and dried at 50°C to 55°C to obtain Efletrizine dihydrochloride anhydrous. The samples were analyzed by HPLC. The fractions with a purity of > 99.0% were pooled. In the pooled fractions the HPLC purity was about > 99.7%. 22 Claims: 1. A process for the preparation of Efletrizine of the formula (I) or its non-toxic pharmaceutically acceptable salts thereof H-C-N' NN^^O^COOH F (I) which comprises steps of a) reacting 4,4'-diflourobenzophenone of formula (II), c=o 0 F (II) with ammonium formate in a suitable organic solvent to give N-(bis(4-fluorophenyl)methyl)formamide of formula (III); W //H F. C—NH—CHO F (III) b) hydrolyzing N-(bis(4-fluorophenyl)methyl)formamide of formula (III) to obtain bis(4-fluorophenyl)methanamine of formula (IV) or its salts in presence of suitable reagent; C-NH2 )/> F (IV) c) reacting bis(4-fluorophenyl)methanamine of formula (IV) with compound of formula (V) 23 ^N-S02-(\ />—CH3 (V) CIH2CH2C V V in suitable organic solvent to give compound of formula (VI); A ^A /=H—C —N N—SO, <\ /)—CH, F d) reacting compound of formula (VI) with suitable reagent in presence of acid to give (bis(4-fluorophenyl)methyl)piperazine formula (VII); H-C—N NH R F (VII) e) reacting l-(bis(4-fluorophenyl)methyl)piperazine formula (VII) with amide of formula (VIII) o NH2 (VIII) where X represents leaving group such as OTs, OMs, CI, F or Br etc., preferably CI, to provide compound of formula (IX) F, H-C-N ;-^VCON^ F (IX) f) treating compound of formula (IX) with mineral acid provide Efletrizine of formula (I) g) optionally converting the compound of formula (I) to its non-toxic pharmaceutically acceptable salts thereof. 24 2. The process as claimed in claim 1, wherein suitable organic solvents used in step (a) comprises a polar solvent selected from amides like formamide, dimethyl formamide, and sulfoxides like dimethyl sulfoxides. 3. A process as claimed in claim 1 or 2 wherein step (a) is carried out at temperature in the range of about 100°C to 250°C, preferably 150°C to 200°C, most preferably 175°C to 180°C. 4. A process as claimed in any preceding claim wherein acid used in step (b) is selected from inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid. 5. A process as claimed in any preceding claim wherein base used in step (c) is selected from sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, sodium methoxide, potassium methoxide, amines such as ammonia, methyl amine, ethyl amine, tri ethyl amine, diethyl amine, isopropyl amine, diisopropyl amine or mixtures thereof. 6. The process as claimed in any preceding claim wherein suitable organic solvent in step (c) is selected from the group consisting of ketonic solvents such as acetone, ethylmethyl ketone, methyl isobutyl ketone and the like; ether solvents such as diethyl ether, dimethyl ether, di-isoopropyl ether, methyltertiarybutyl ether, tetrahydrofuran, 1,4-dioxane and the like; hydrocarbon solvents such as toluene, xylene and the like; nitrile solvents such as acetonitrile, propionitrile and the like; halogenated solvents such as dichloromethane, 1,2-dichloromethane, chloroform, carbon tetrachloride and the like; aprotic polar solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide and the like; or mixtures of any two or more thereof in various proportions. 7. A process as claimed in claim 6, wherein the suitable organic solvent is methylene dichloride. 8. A process as claimed in any preceding claim wherein the hydroxy acid in step (d) is p-hydroxy benzoic acid. 9. A process as claimed in claim 1, wherein said suitable reagent in step (d) is HBr in acetic acid. 10. The process as claimed in any preceding claim wherein said base in step (e) is selected from inorganic base or organic base such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, potassium tert-butoxide, tri ethyl amine, diisopropyl amine and the like. 11. A process as claimed in any preceding claim wherein said mineral acid in step (f) is Hydrochloric acid, sulfuric acid, hydrobromic acid, nitric acid, phosphoric acid. The preferred acid is hydrochloric acid. 25 12. A process as clamed in any preceding claim wherein said Efletrizine is converted to efletrizine dihydrochloride monohydrate. 13. A process as clamed in claim 1, wherein said Efletrizine is converted to efletrizine dihydrochloride anhydrous. 14. Efletrizine dihydrochloride monohydrate prepared by the process as claimed in any preceding claims is substantially pure having purity greater than or equal to about 99% by area percentage of HPLC. 15. Efletrizine dihydrochloride monohydrate as claimed in claim 14, wherein the purity is greater than or equal to about 99.6% by area percentage of HPLC. 16. Efletrizine dihydrochloride monohydrate in a solid state having less than or of about 0.4% total impurities as measured by area percentage of HPLC. 17. Efletrizine dihydrochloride in a solid state, wherein the monohydrate does not have detectable level of dimer impurities when measured by HPLC at RRT 3.80. 18. Efletrizine dihydrochloride anhydrous prepared by the process as claimed in any preceding claims is substantially pure having purity greater than 99% by area percentage of HPLC. 19. Efletrizine dihydrochloride anhydrous as claimed in claim 18, wherein the purity is greater than or equal to about 99.6% by area percentage of HPLC. 20. Efletrizine dihydrochloride anhydrous in a solid state having less than or of about 0.4% total impurities as measured by area percentage of HPLC. 21. Efletrizine dihydrochloride in a solid state, wherein the anhydrate does not have detectable level of dimer impurities when measured by HPLC at RRT 3.80. 22. A compound N-(bis(4-fluorophenyl)methyl)formamide of formula (III) C—NH—CHO 0 F 23/A compound N-(bis(4-fluorophenyl)methyl)formamide of formula (III) as claimed in claim 22, is crystalline in nature being characterized by x-ray powder diffraction as depicted in FIG 2. 24. A crystalline compound N-(bis(4-fluorophenyl)methyl)formamide of formula (III) as claimed in claim 22, being further characterized by differential scanning calorimety profile as depicted in FIG.l and having endothermic peak at about 117.2°C. 26 25. A crystalline compound N-Formyl-N-(4,4?-diflourobenzhydraryl) of For N-(bis(4- fluorophenyl)methyl)formamide of formula (III) as claimed in claim 22, being characterized by x-ray powder diffraction pattern having characteristic peaks at 29 (±0.2) values 7.7°, 11.1°, 15.5°, 21.1° and 25.2°. 26. A crystalline compound N-(bis(4-fluorophenyl)methyl)formamide of formula (III) as claimed in claim 22, characterized by FTIR spectrum as depicted in FIG 3 with characteristic peaks at about 3278, 1658, 1602, 1390, 833 and 732 cm"1. 27. A crystalline bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) characterized by x-ray powder diffraction as depicted in FIG-5. 28. A crystalline bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) as claimed in claim 27, being characterized by differential scanning calorimety profile as depicted in FIG-4 and having endothermic peak at about 227.1°C. 29. A crystalline bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) as claimed in claim 31, being characterized by x-ray powder diffraction pattern having characteristic peaks at 29(±0.2) values 7.4°, 15.1°, 19.8° and 25.0°. 30. A crystalline bis(4-fluorophenyl)methanamine hydrochloride of formula (IVa) as claimed in claim 31, being characterized by FTIR spectrum as depicted in FIG-6 with peaks at about 2962,2908, 1602, 1514, 1244 and 553 cm-1. 31. A compound l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) N-S02—A />— CH; R (VI) 32. A compound l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) as claimed in claim 31, is crystalline in nature being characterized by x-ray powder diffraction as depicted in FIG 8. 33. A crystalline l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI)as claimed in claim 31, being further characterized by differential scanning calorimety profile as depicted in FIG.7 and having endothermic peak at 196.93°C. 34. A crystalline l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) as claimed in claim 31, being characterized by x-ray powder diffraction pattern having characteristic peaks at 20 (±0.2) values 6.2°, 12.5, 15.3, 16.0° and 22.3°. 27 35. A crystalline l-(bis(4-fluorophenyl)methyl)-4-tosylpiperazine (VI) as claimed in claim 31, characterized by FTIR spectrum as depicted in FIG-9 with characteristic peaks at about 3278, 1658, 1602, 1390, 833 and 732 cm"1. 36. A crystalline Efletrizine dihydrochloride monohydrate having particle size D50 is less than or equal to 400 ^m, as measured by Malvern light scattering instrument. 37. A crystalline efletrizine dihydrochloride monohydrate as claimed in claim 36, wherein particle size D50 is less than or equal to 250 mm as measured by Malvern light scattering instrument. 38. A crystalline efletrizine dihydrochloride monohydrate as claimed in claim 36, wherein particle size D50 is less than or equal to 175 mm as measured by Malvern light scattering instrument. 39. A crystalline Efletrizine dihydrochloride anhydrous having particle size D50 is less than or equal to 400 //m, as measured by Malvern light scattering instrument. 40. A crystalline efletrizine dihydrochloride anhydrous as claimed in claim 39, wherein particle size D50 is less than or equal to 250 mm as measured by Malvern light scattering instrument. 41. A crystalline efletrizine dihydrochloride anhydrous as claimed in claim 40, wherein particle size D50 is less than or equal to 175 mm as measured by Malvern light scattering instrument. 42. Efletrizine dihydrochloride monohydrate in crystalline form being characterized by at least one of: a) Differential scanning calorimetry having endotherm at 160.22°C as depicted in FIG-10; b) X-ray powder diffraction pattern having characteristic peaks from atleast one of 7.3°, 10.3°, 17.7° and 24.5° as depicted in FIG-11; and c) FTIR Spectrum having characteristic peaks at 3398, 2922, 1712, 1512, 1120, 869 and 574 cm-1 as depicted in FIG-12. 43. Efletrizine dihydrochloride anhydrous ins crystalline form being characterized by at least one of: a) Differential scanning calorimetry having endotherm at 226.22°C as depicted in FIG-13; b) X-ray powder diffraction pattern having characteristic peaks from atleast one of 13.6°, 14.8°, 18.4° and 25.0° as depicted in FIG-14; and c) FTIR Spectrum having characteristic peaks at 2949, 1749, 1514, and 829 cm-1 as depicted in FIG-15. 44. A process for the preparation of N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V), 28 CIHoCHoC. ^N-S02 CIH2CH2C (V) which comprises reacting bis(2-chloroethyl amine) HC1 with a base to obtain bis(2-chloroethyl amine), which is subsequently treated with p-toluenesulphonyl chloride in presence of base to obtain N,N-bis(2-chloroethyl)-4-methylbenzenesulfonamide of formula (V). 45. A process as claimed claim 44, wherein said base is selected from the group of inorganic bases like sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate; or organic bases like isopropyl amine, diisopropyl amine, triethylamine, ammonia, pyridine etc. 46. The process as claimed in claim 45, wherein the base is triethyl amine. 47. The process as claimed in claim 44, wherein suitable organic solvent can be selected from members from the classes: ketonic solvents such as acetone, ethylmethyl ketone, methyl isobutyl ketone and the like; ether solvents such as diethyl ether, dimethyl ether, di-isoopropyl ether, methyltertiarybutyl ether, tetrahydrofuran, 1,4-dioxane and the like; hydrocarbon solvents such as toluene, xylene and the like; nitrile solvents such as acetonitrile, propionitrile and the like; halogenated solvents such as dichloromethane, 1,2-dichloromethane, chloroform, carbon tetrachloride and the like; aprotic polar solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide and the like; or mixtures of anwo or more thereof in various proportions. 48. The process as claimed in claim 47, wherein said organic solvent is methylene dichloride. 49. A process for preparation of crystalline efletrizine dihydrochloride of Formula (I) and its non-toxic pharmaceutically acceptable salts and hydrates thereof substantially as herein described with reference to the accompaying drawings and examples. Dated this the 16th day of June 2007 29 ABSTRACT A process for the preparation of Efletrizine of the formula (I) or its non-toxic pharmaceutical Iy acceptable salts thereof ,CL XOOH H-C-N N' F (I) is disclosed. The process comprises a) reacting 4,4'-diflourobenzophenone of formula (II), F (II) with ammonium formate in a suitable organic solvent to give N-(bis(4-fluorophenyl)methyl)formamide of formula (III); , C—NH—CHO F (HI) b) hydrolyzing N-(bis(4-fluorophenyl)methyl)formamide of formula (III) to obtain bis(4- fluorophenyl)methanamine of formula (IV) or its salts in presence of suitable reagent; C-NH2 F (IV) 30 c) reacting bis(4-fluorophenyl)methanamine of formula (IV) with compound of formula (V) CIH2CH2C ^N-S02-(v />-CH3 (V) CIH2CH2C ^_y in suitable organic solvent to give compound of formula (VI); H-C-N N-S02—<\ h—CH3 W F (VI) d) reacting compound of formula (VI) with suitable reagent in presence of acid to give 1- (bis(4-fluorophenyl)methyl)piperazine formula (VII); H-C-N NH 0- F (VII) e) reacting l-(bis(4-fluorophenyl)methyl)piperazine formula (VII) with amide of formula (VIII) o X ^-^ ^"^ NH2 (VIII) where X represents leaving group such as OTs, OMs, CI, F or Br etc., preferably CI, to provide compound of formula (IX) 0W F (IX) f) treating compound of formula (IX) with mineral acid provide Efletrizine of formula (I) g) optionally converting the compound of formula (I) to its non-toxic pharmaceutically acceptable salts thereof. 31