Highly dispersible silica for using in rubber The present invention relates to highly disperse precipitated silicas which exhibit an extremely high level of reinforcement of rubber vulcanizates and advantages in vulcanization time, to a process for their preparation, and to their use as filler for rubber mixtures. The use of precipitated silicas in elastomer mixtures, such as tire tread mixtures, has been known for a long time (EP 0 501 227). There are stringent requirements relating to the use of silicas as a reinforcing filler in rubber mixtures, for example those used to produce pneumatic tires and technical rubber products. They have to have low density and have good capability for incorporation and dispersion in the rubber, and undergo "chemical bonding to the rubber in association"with" a coupling reagent, preferably a bifunctional organosilicon compound, this reaction leading to the desired high level of reinforcement of the rubber mixture. The property of reinforcement can in particular be associated with high static stress values and a low abrasion value. The particle size, surface morphology, surface activity, and also the binding power of the coupling reagent, are of particularly decisive importance in relation to the reinforcing property of the silicas. It is known that the properties of a silica are decisively determined by its preparation process. The properties are in particular affected by the conditions of precipitation. The person skilled in the art is aware"' of preparation processes for silicas with a very wide variety of precipitation conditions. For example, EP 0 937 755 describes precipitations at constant pH. DE 101 24 298 disclosed silicas which were precipitated at constant cation excess. DE 101 12 441 Al, EP 0 754 650, EP 0 755 899, and US 4 001 379 described precipitations at constant alkali value (AV). Silicas which were precipitated at constant AV are used as carrier materials, matting agents for paints, as battery separators, in toothpastes, or as flocculation agents. There have hitherto been no known silicas which were precipitated at constant AV and are suitable for applications in elastomers or rubber mixtures. Silicas for rubber applications are generally prepared by a process in which the precipitation takes place at temperatures of from 60 to 95°C and at a pH of from 7 to 10, see for example EP 0 901 986 Al. It is an object of the present invention to provide novel, readily dispersible precipitated silicas which can be incorporated in elastomer mixtures and which improve their properties. Surprisingly, it has now been found that precipitation at a constant AV can give novel silicas which can be incorporated particularly effectively into elastomer mixtures and improve their properties. The present invention therefore provides readily dispersible precipitated silicas characterized by: CTAB surface area 100-160 m2/g, the preferred ranges being 100-150 m2/g, 100-135 m2/g, and 100-120 m2/g, BET surface area 100-190 m2/g, the preferred range being 100-170 m /g, 100-160 m2/g, 100-140 m2/g, and 110-135 m2/g, DBP value 180-300 g/(100 g) , prefer- red range 200-280 g/ (100 g), Sears value V2 15-28 ml/(5 g) , the preferred range being 20-28 ml/(5 g)and 22 to 28 ml/ (5 g) and particularly 25-28 ml/(5 g), Moisture level 4-8%. The precipitated silicas of the invention may moreover preferably have one or more of the following physico-chemical parameters: Ratio of Sears value V2 to BET surface area 0.140-0.280 ml/(5 m2) , the preferred ranges being 0.150-0.280 ml/(5 m2) , 0.170-0.280 ml/(5 m2) , 0.180-0.280 ml/(5 m2) , and particularly preferably 0.190-0.280 ml/(5 m2) and 0.190-0.250 ml/(5 m2) , Ratio of BET to CTAB 0.9-1.2, preferably 1-1.15, Primary particle diameter 10-80 nm. By way of example, the primary particle diameter may be determined by evaluating transmission electron micrographs (TEMs) (R.H. Lange, J. Bloedorn: "Das Elektronenmikroskop, TEM + REM" [The electron microscope, TEM + SEM] Thieme Verlag, Stuttgart, New York (1981)). In a first preferred embodiment, the precipitated silicas of the invention have a DBP value of 200-250 g/ (100 g), and in a second preferred embodiment they have a DBP value of 250-280 g/(100 g). The precipitated silicas of the invention have not only a high absolute number of silanol groups (Sears value V2) , but also, when comparison is made with prior-art precipitated silicas, a markedly increased ratio of the Sears value V2 to the BET surface area. This means that the precipitated silicas of the invention in particular have a very high number of silanol groups based on the total surface area. The precipitated silicas of the invention have not only an increased number of silanol groups but also low microporosity, i.e. a very low ratio of BET to CTAB. The combination of the features mentioned, in particular the high ratio of Sears value V2 to BET, gives the precipitated silicas of the invention excellent suitability as reinforcing fillers for elastomers. These precipitated silicas of the invention have increased rubber activity, and exhibit very good dispersion behavior and a low vulcanization time. The present invention further provides a process which can be used to prepare the precipitated silicas of the invention with CTAB surface area 100-160 m2/g, the preferred ranges being 100-150 m2/g, 100-135 m2/g, and 100-120 m2/g, BET surface area 100-190 m2/g, the preferred range being 100-170 m2/g, 100-160 m2/g, 100-140 m2/g, and 110-135 m2/g, DBP value 180-300 g/(100 g) , prefer- red range 200-280 g/ (100 g), Sears value V2 15-28 ml/(5 g) , the preferred range being 20-28 ml/(5 g) and 22 to 28 ml/(5 g) and particularly 25-28 ml/(5 g) , Moisture level 4-8%, and, where appropriate, with one or more of the following physico-chemical parameters Ratio of Sears value V2 to BET surface area 0.140-0.280 ml/(5 m2) , the preferred ranges being 0.150-0.280 ml/(5 m2) , 0.170-0.280 ml/(5 m2) , 0.180-0.280 ml/(5 m2), and particularly preferably 0.190-0.280 ml/(5 m2) and 0.190-0.250 ml/(5 m2) , Ratio of BET to CTAB 0.9-1.2, preferably 1- 1.15, primary particle diameter 10-80 nm, which comprises first a) taking an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or of an organic and/or inorganic base with an alkali value from 7 to 30 as initial charge, b) metering water glass and an acidifier simultaneously into this initial charge at from 55 to 95°C, with stirring, for from 10 to 120 minutes, preferably from 10 to 60 minutes, particularly preferably from 60 to 100 minutes, in such a way that during the precipitation the AV value remains constant at from 7 to 30, c) using an acidifier to acidify to pH of from about 2.5 to 6, and d) filtering, washing, drying and, where appropriate, pelletizing. The initial charge may amount to about 20, 30, 40, 50, 60, 70, 80, or 90% of the final volume for the precipitation. The basic compounds for the initial charge are in particular selected from the group of the alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkali metal hydrogencarbonates, and alkali metal silicates. Preference is given to the use of water glass and/or sodium hydroxide solution. The constant alkali value in the initial charge and during step b) is in the range from 7 to 30, preferably from 10 to 30, and is particularly preferably from 15 to 25, and it is very particularly preferable for the AV to be held at a value of from 18 to 22. Optionally, the feed during step b) may be interrupted, the steps carried out then comprising b') stopping the feed for from 30 to 90 minutes while maintaining the temperature, and b") then, at the same temperature, for from 10 to 120 minutes, preferably from 10 to 60 minutes, simultaneously adding water glass and an acidifier in such a way that the AV remains constant during the precipitation. Another addition of organic or inorganic salts may moreover optionally be incorporated during one or more of steps a) and/or b) and/or b') and/or b") . This addition may be carried out in solution or in solid form, in each case continuously over the period of addition of the water glass and of the acidifier, or may be batch addition. It is also possible for the salts to be dissolved in one or both of the components and then to be added simultaneously with these. The inorganic salts preferably used are alkali metal salts or alkaline earth metal salts. In particular, use may be made of any of the combinations of the following ions: Li\ Na+, K\ Rb+, Be2+, Mg2+, Ca2+, Sr2+, Ba2\ H+, F", CI", Br", I", S032~, S042", HS04~, P033", P043~, N03", N02", C032", HC03", OH", Ti032", Zr032~, Zr044", A102", Al2042", B043'. Suitable organic salts are the salts of formic, acetic, or propionic acid- Cations which may be mentioned are the abovementioned alkali metal ions or alkaline earth metal ions. The concentration of these salts in the solution added may be from 0.01 to 5 mol/1. The inorganic salt preferably used is Na2S04. Besides water glass (sodium silicate solution), use may also be made of other silicates, such as potassium silicate or calcium silicate. Acidifiers which may be used, besides sulfuric acid, are HC1, HN03, H3PO4, or C02. In step d) , the precipitated silica is first filtered and then washed with water, and dried. The silica here is washed until the content of sodium sulfate is < 4% by weight. The sodium sulfate content may be measured by the method known to the person skilled in the art, e.g. as described in EP 0 754 650 Al. The filtration of the silicas of the invention and their drying for a long or short period are familiar to the person skilled in the art, and details may be found in the abovementioned documents, for example. The filtration of the silicas of the invention and their drying for a long or short period are familiar to the person skilled in the art, and details may be found in the abovementioned documents, for example. The silica precipitated is preferably dried in a pneumatic drier, spray drier, disk drier, belt drier, rotating-tube drier, flash drier, spin flash drier, or spray tower. These drying methods include operation using an atomizer, using a single- or twin-fluid nozzle, or using an integrated fluidized bed. Where appropriate, after the drying process grinding may take place, and/or a roller compactor may be used for pelletizing. After the drying step, the grinding, or the pelletization, the precipitated silica of the invention preferably has a particle shape with an average diameter above 15 µm, in particular above 80 µm, particularly preferably above 200 µm (determined ISO 2591-1, December 1988). The precipitated silicas of the invention particularly preferably take the form of a powder with an average diameter above 15 µm, or take the form of substantively round particles with an average diameter above 80 µm (microbeads) , or take the form of pellets with an average diameter > 1 mm. The present invention also provides the use of a precipitated silica, with a CTAB surface area 100-160 m2/g, the preferred ranges being 100-150 m2/g, 100-135 m2/g, and 100-120 m2/g, BET surface area 100-190 m2/g, the preferred range being 100-170 m2/g, 100-160 m2/g, 100-140 m2/g, and 110-135 m2/g, DBP value 180-300 g/(100 g) , prefer- red range 2 00-280 g/ (100 g), Sears value V2 15-28 ml/(5 g) , the preferred range being 20-28 ml/(5 g)and 22 to 28 ml/(5 g) and particularly 25-28 ml/(5 g), Moisture level 4-8% and also, where appropriate, with one or more of the following physico-chemical parameters Ratio of Sears value V2 to BET surface area 0.140-0.280 ml/(5 m2) , the preferred ranges being 0.150-0.280 ml/(5 m2) , 0.170-0.280 ml/(5 m2) , 0.180-0.280 ml/(5 m2), and particularly preferably 0.190-0.280 ml/(5 m2) and 0.190-0.250 ml/(5 m2) , Ratio of BET to CTAB 0.9-1.2, preferably 1-1.15 primary particle diameter 10-80 nm for preparing elastomer mixtures, vulcanizable rubber mixtures, and/or other vulcanizates. The invention also provides elastomer mixtures, vulcanizable rubber mixtures, and/or other vulcanizates which comprise the silica of the invention, examples being moldings, such as pneumatic tires, tire treads, cable sheathing, hoses, drive belts, conveyor belts, roller coverings, tires, shoe soles, ring seals, and damping elements. The silicas of the invention may also be used in any of the application sectors which usually use silicas, e.g. in battery separators, as antiblocking agent, as matting agent in inks and paints, as carrier for agricultural products and for feeds, in coatings, in printing inks, in fire-extinguisher powders, in plastics, in the non-impact printing sector, in paper pulp, or in the personal care sector, or in specialty applications. Use in the non-impact printing sector, for example in inkjet printing, is use of the silicas of the invention in • printing inks for thickening or for preventing splashing and offset, • paper, as filler or coating pigment, blueprint paper, heat-sensitive paper, thermal sublimation for preventing strike-through of printing inks, for improvement in contrast and image background uniformity, and for improvement in dot definition and color brilliance. Use in the personal care sector is use of the silicas of the invention as filler or thickener, e.g. in the pharmaceutical sector or the body-care sector. The silica of the invention may optionally be modified with silanes or organosilanes of the formulae I to III [SiR1n(OR)r(Alk)m(Ar)p]q[B] (I), SiR1n(OR)3-n(Alkyl) (II) , or SiR1n(OR)3-n(Alkenyl) (III) , where B is -SCN, -SH, -CI, -NH2, -0C(0)CHCH2, -OC(0)C(CH3)CH2 (if q = 1), or -Sw- (if q = 2) , B being chemically bonded to Alk, R and R1 are an aliphatic, olefinic, aromatic, or arylaromatic radical having 2-30 carbon atoms, optionally with substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate, or organosilane radical, where the meaning or substitution of R and R1 may be identical or different, n is 0, 1, or 2, Alk is a bivalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms, m is 0 or 1, Ar is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may have substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thio- cyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, or organosilane radi- 5 cal, p is 0 or 1, with the proviso that p and n are not simultaneously 0, q is 1 or 2, w is a number from 2 to 8, 10 r is 1, 2, or 3, with the proviso that r + n + m + p = 4, Alkyl is a monovalent unbranched or branched saturated hydrocarbon radical having from 1 to 2 0 carbon atoms, preferably from 2 to 8 carbon 15 atoms, Alkenyl is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms. 20 The silica of the invention may also be modified with organosilicon compounds of the composition SiR24_nXn (where n = 1, 2, 3, 4), [SiR2xXyO]2 (where 0 < x < 2; 0 < y < 2; 3 < z < 10, where x + y = 2) , [SiR2xXyN]z (where 0 25 < x < 2; 0 < y < 2; 3 < z < 10, where x + y = 2) , SiR2nXmOSiR2oXp (where 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 < p < 3, where n + m = 3, o + p = 3), SiR2nXrnNSiR2oXp (where 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 "Si"-ONa + HC1 Method 10.00 g of a silica in powder, bead or pellet form, having a moisture level of 5 ± 1%, are comminuted for 60 seconds, using an M 20 IKA universal mill (550 W; 20 000 rpm)- Where appropriate, the moisture content of the starting substance has to be adjusted by drying at 105°C in the drying cabinet or uniform moistening, with repeated comminution. 2.50 g of the silica thus treated are weighed out at room temperature into a 250 ml titration vessel and mixed with 60.0 ml of analytical grade methanol. After complete wetting of the specimen, 40.0 ml of deionized water are added, and the mixture is dispersed, using a T 25 UltraTurrax mixer (KV-18G mixing shaft, 18 mm diameter) for 30 seconds at a rotation rate of 18 000 rpm. The particles of specimen adhering to the edge of the vessel and to the stirrer are flushed into the suspension, using 100 ml of deionized water, and a water bath with thermostat is used to control the temperature of the mixture to 2 5°C. The pH tester (Knick 766 Calimatic pH meter with temperature sensor) and pH electrode (Schott N7680 combination electrode) are calibrated using buffer solutions (pH 7.00 and 9.00) at room temperature. Using the pH meter, the initial pH of the suspension is first measured at 25°C, and then, depending on the result, potassium hydroxide solution (0.1 mol/1) or hydrochloric acid solution (0.1 mol/1) is used to adjust the pH to 6.00. The consumption of KOH solution or HC1 solution in ml required to reach pH 6.00 corresponds to V1' . 20.0 ml of sodium chloride solution (250.00 g of analytical grade NaCl made up to 11 using deionized water) are then metered in. The titration is then continued as far as pH 9.00, using 0.1 mol/1 KOH. The consumption of KOH solution in ml required to reach pH 9.00 corresponds to V2' . The volumes V1' and V2' are first then normalized for a theoretical specimen weight of 1 g, and are then multiplied by 5, thus giving V1 and the Sears value V2 in the units ml/(5 g) . Determination of BET surface area The specific nitrogen surface area (hereinafter termed BET surface area) of the silica in powder, bead, or pellet form is determined to ISO 5794-1/Annex D, using an AREA-meter (Strohlein, JUWE). CTAB surface area determination The method is based on the adsorption of CTAB (N-hexadecyl-N, N,N-trimethylammonium bromide) on the "external" surface of the silica, also termed the "rubber-active surface", and is based on ASTM3765 or NFT 45-007 (Section 5.12.1.3). CTAB is adsorbed in aqueous solution, with stirring and treatment with ultrasound. Excess, unadsorbed CTAB is determined by back-titration with NDSS (solution of the sodium salt of dioctyl sulfosuccinate, "Aerosol OT" solution), using a titroprocessor, the end point being given by maximum clouding of the solution, and determined using a phototrode. The temperature during all of the operations carried out is 23-25°C, in order to prevent CTAB from crystallizing out. The following equation underlies the back-titration reaction: Equipment METTLER Toledo DL 55 titroprocessor and METTLER Toledo DL 7 0 titroprocessor, in each case equipped with: DG 111 pH electrode produced by Mettler, and DP 550 phototrode produced by Mettler 100 ml polypropylene titration beaker 150 ml glass titration vessel with lid Pressure-filtration equipment, capacity 100 ml Membrane filter composed of cellulose nitrate, pore size 0.1 µm, diameter 4 7 mm, e.g. Whatman (order no. 7181-004) Reagents The solutions of CTAB (0.015 mol/1 in deionized water) and NDSS (0.00423 mol/1 in deionized water) are purchased in ready-to-use form (Kraft, Duisburg: order no. 6056.4700 CTAB solution, 0.015 mol/1; order no. 6057.4700 NDSS solution, 0.00423 mol/1), stored at 25°C, and used within one month. Method Blind titration The consumption of NDSS solution for the titration of 5 ml of CTAB solution is to be tested once daily prior to each series of tests. For this, the phototrode is adjusted to 1000 + 20 mV (corresponding to 100% transparency) prior to starting the titration. Exactly 5.00 ml of CTAB solution are pipetted into a titration beaker, and 50.0 ml of deionized water are added. The titration with NDSS solution uses the test method familiar to the person skilled in the art, with stirring, using the DL 55 titroprocessor until max. clouding of the solution has been reached. The consumption V1 of NDSS solution is determined in ml. Three determinations are to be carried out for each titration. Adsorption 10.0 g of the silica in powder, bead or pellet form, with a moisture content of 5 + 2% (the moisture content being adjusted, where appropriate, by drying at 105°C in the drying cabinet or uniform moistening), are comminuted for 30 seconds, using a mill (Krups KM 75, item no. 2030-70). Exactly 500.0 mg of the comminuted specimen are transferred into a 150 ml titration vessel with magnetic stirrer bar, and exactly 100.0 ml of CTAB solution are metered in. The titration vessel is sealed with a lid, and the mixture is stirred for 15 minutes, using a magnetic stirrer. Hydrophobic silicas are stirred, using a T 25 UltraTurrax mixer (KV-18G mixer shaft, 18 mm diameter) , at 18 000 rpm for a maximum of 1 min to give complete wetting. The titration vessel is screw-fastened to the DL 7 0 titroprocessor, and the pH of the suspension is adjusted to a value of 9 + 0.05, using KOH (0.1 mol/1). The suspension is exposed for 4 minutes to ultrasound, in the titration vessel, in an ultrasound bath (Sonorex RK 106 S from Bandelin, 35 KHz) at 25°C. This is followed immediately by filtration under pressure through a membrane filter, the nitrogen pressure being 1.2 bar. The first 5 ml of filtrate are discarded. Titration 5.00 ml of the remaining filtrate are pipetted into a 100 ml titration beaker and made up to 50.00 ml, using deionized water. The titration beaker is screw-fastened to the DL 55 titroprocessor, and the mixture is titrated with NDSS solution, with stirring, until maximum clouding has been reached. The consumption VII of NDSS solution in ml is determined. Each clouding . point is to be determined three times. Calculation The measured values V1 = consumption of NDSS solution in ml when the blind specimen is titrated Vn = consumption of NDSS solution in ml when the filtrate is used give: VI/VII = amount of CTAB in the blind specimen/remaining amount of CTAB present in the filtrate specimen. The amount N of adsorbed CTAB in g is therefore: N = ((VI-VII) * 5.5 g * 5 ml)/VI*l000 ml). Because only 5 ml were titrated from 100 ml of filtrate, and 0.5 kg of silica of a defined moisture level was used, and the area required by 1 g of CTAB is 578435 * 10-3 m2 and: CTAB surface area (not corrected for water) in m2/g = (N*20*578.435 m2/g)/(0.5 g) , and CTAB surface area (not corrected for water) in m2/g = ((VI-VII). 636.2785 m2/g) /V2. The CTAB surface area is based on the anhydrous silica, and the following correction is therefore made: CTAB surface area in m /g = (CTAB surface area (not corrected for water) in m2/g * 100%)/ (100% - moisture level in %). Determination of DBP absorption DBP absorption (DBP number) is determined as follows by a method based on the standard DIN 53601, and is a measure of the absorbency of the precipitated silica: Method 12.50 g of silica in powder or bead form with 0-10% moisture content (the moisture content being adjusted, where appropriate, by drying at 105°C in the drying cabinet) are placed in the kneader chamber (item no. 279061) of the Brabender "E" Absorptometer (with no damping of the output filter of the torque sensor). In the case of pellets, the sieve fraction from 3.15* to 1 mm (Retsch stainless-steel sieve) is used (by using slight pressure from a plastics spatula to press the pellets through the 3.15 mm-pore-width sieve). While the material is constantly mixed (rotation rate of kneader paddles: 125 rpm), dibutyl phthalate is added dropwise at a rate of 4 ml/min at room temperature into the mixture by way of the "Brabender T 90/50 Dosimat". Incorporation by mixing is achieved with only low power consumption, and is followed by means of the digital display. Toward the end of the determination, the mixture becomes pasty, and this is indicated by a steep rise in the power consumption. When the display shows 600 digits (0.6 Nm torque) , both the kneader and the DBP feed are switched off via an electrical contactor. The synchronous motor for the DBP supply has coupling to a digital meter, thus permitting read-off of DBP consumption in ml. Evaluation DBP absorption is stated in g/(100 g) , and is calculated from the measured DBP consumption by using the following formula. The density of DBP at 20 °C is typically 1.047 g/ml. DBP absorption in g/(100 g) = ((DBP consumption in ml) * (DBP density in g/ml) * 100)/(12.5 g) . Defined DBP absorption relates to the anhydrous, dried silica. If moist precipitated silicas are used, the value is to be corrected by means of the following correction table. The correction value, corresponding to the water content, is added to the DBP value determined experimentally; by way of example, an addition of 33 g/(100 g) for DBP absorption would be implied if the water content were 5.8%. Correction table for dibutyl phthalate absorption -anhydrous - pH determination The method, based on DIN EN ISO 787-9, serves for determination of the pH of an aqueous suspension of silicas at 20°C. To this end, an aqueous suspension is prepared from the specimen to be studied- After brief shaking of the suspension, its pH is determined by means of a previously calibrated pH meter. Method Prior to making the pH measurement, daily calibration of the pH tester (Knick 766 Calimatic pH meter with temperature sensor) and of the pH electrode (Schott N7680 combination electrode, is required, using the buffer solutions, at 20°C. The calibration function is to be selected in such a way that the two buffer solutions used include the expected pH of the specimen (buffer solutions having pH 4.00 and 7.00, pH 7.00 and 9.00, and, where appropriate, pH 7.00 and 12.00). If pellets are used, 20.0 g of silica are first comminuted for 20 s by means of a mill (Krups KM ,75, item No. 2030-70). 5.00 g of silica in powder or bead form, with 5 ± 1% moisture content (where appropriate, the moisture content being adjusted by drying at 105°C in the drying cabinet or by uniform wetting prior to any comminution) are precisely weighed out to 0.01 g on a precision balance into a previously tared wide-necked glass flask. 95.0 ml of deionized water are added to the specimen. An automatic shaker (Gerhardt, LS10, 55 W, level 7) is then used to shake the suspension in the sealed vessel for a period of 5 minutes at room temperature. The pH is measured directly after shaking. To this end, the electrode is rinsed first with deionized water and then with a portion of the suspension, and then dipped into the suspension. , A magnetic stirrer bar is then added to the suspension, and the pH measurement is made at a constant stirring rate with formation of slight vortex in the suspension. When the pH meter displays a constant value, the pH is read off from the display. The method when hydrophobic silica is used is similar, but in that case 5.00 g of the specimen, after comminution where appropriate and with 5 ± 1% moisture content, are weighed out precisely to 0.01 g on the precision balance into a previously tared wide-necked glass flask. 50.0 ml of analytical grade methanol and 50.0 ml of deionized water are addec, and an automatic shaker (Gerhardt, LS10, 55 W, level 7) is then used to shake the suspension in the sealed vessel for a period of 5 minutes at room temperature. The pH is likewise measured with stirring, but after precisely 5 min. Determination of solids content of filter cake This method is used to determine the solids content of filter cake via removal of the volatile content at Method 100.00 g of the filter cake are weighed out into a dry, tared porcelain dish (diameter 20 cm) (specimen weight E). Where appropriate, the filter cake is comminuted, using a spatula, in order to obtain separate fragments of not more than 1 cm3. The specimen is dried to constant weight at 105 ± 2°C in a drying cabinet. The specimen is then cooled to room temperature in a desiccator cabinet, using silica gel as drying agent. The material is weighed to determine the final weight A. The solids content in % is determined as 100% - (((E in g - A in g)*100%)/(E in g)). Determination of electrical conductivity The electrical conductivity (C) of silicas is determined in aqueous suspension. Method If pellets are used, 20.0 g of silica are first comminuted by means of a mill (Krups, KM 75, item No. 2030-70) for 20 s. 4.00 g of silica in powder or bead form, with 5 ± 1% moisture content (the moisture content being adjusted, where appropriate, by drying at 105°C in the drying cabinet or uniform wetting prior to any comminution) are suspended in 50.0 ml of deionized water, and heated for 1 min to 100°C. The specimen cooled to 20°C is made to precisely 100 ml and homogenized by rotary shaking. The measurement cell of the LF 530 (WTW) conductivity tester is flushed with a small amount of specimen before the LTA01 measurement cell is dipped into the suspension. The value displayed corresponds to the conductivity at 20°C, because the TFK 530 external temperature sensor automatically compensates for the temperature. Both this temperature coefficient and the cell constant k are to be checked prior to each series of tests. The calibration solution used comprises 0.01 mol/1 potassium chloride solution (C at 20°C = 1278 µS/cm). Determination of solids content of precipitation suspension The solids content of the precipitation suspension is determined gravimetrically after filtration of the specimen. Method 100.0 ml of the homogenized precipitation suspension (Vsuspension) are measured out at room temperature with the aid of a measuring cylinder. The specimen is filtered off with suction by way of a round filter (Schleicher & Schuell 572) in a porcelain suction filter funnel, but not sucked dry, so as to avoid cracking of the filter cake. The filter cake is then washed with 100.0 ml of deionized water. The suction-filtration of the leached filter cake is then completed, and the filter cake is transferred into a tared porcelain dish and dried to constant weight at 105 ± 2°C in a drying cabinet. The weight of the dried silica (mspecimen) is determined. The solids content is determined as: solids content in g/1 = (mspecimen g) / (Vsuspension in 1). Determination of alkali value The alkali value (AV) determined is the consumption in ml of hydrochloric acid (using a specimen volume of 50 ml, 50 ml of dist. water, and a hydrochloric acid concentration of 0.5 mol/1) during direct potentiometric titration of alkaline solutions ' or alkaline suspensions as far as pH 8.30. The result reveals the free alkali content of the solution or suspension. Method The pH device (Knick, Calimatic 7 66 pH meter with temperature sensor) and the pH electrode (Schott N7680 combination electrode) are calibrated at room temperature with the aid of two buffer solutions (pH = 7.00 and pH = 10.00). The combination electrode is dipped into the test solution or test suspension, the temperature of which has been controlled to 40°C, and which is composed of 50.0 ml of specimen and 50.0 ml of deionized water. Hydrochloric acid solution whose concentration is 0.5 mol/1 is then added dropwise until a constant pH of 8.30 is obtained. Because the equilibrium between the silica and the free alkali content is established only slowly, a waiting time of 15 min is required before final read-off of the acid consumption. For the amounts and concentrations selected, the read-off of hydrochloric acid consumption in ml directly corresponds to the alkali value, which is a dimensionless quantity. The following examples are intended to provide further illustration of the invention but not to limit its scope. Example 1 Preparation of silicas Example 1.1 1550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02, 8.05% Na20) form an initial charge in a reactor made from stainless steel with a propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0.65 kg/min of sulfuric acid (density 1.83 kg/1, 96% H2S04) are then metered in with vigorous stirring at 92 °C over a period of 80 minutes. This metering of sulfuric acid is regulated in such a way that the alkali value prevailing in the reaction mixture is 20. The water glass addition is then stopped, and the addition of sulfuric acid is continued until a pH of 5.0 (measured at room temperature) has been achieved. The resultant suspension is filtered, using a membrane filter press, and the product is washed with water. The filter cake, with 21% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed with 18% solids content and with a pH of 4.0 is then spray-tower dried with addition of ammonia. The resultant microbead product has a BET surface area of 123 m2/g and a CTAB surface area of 119 m2/g. Example 1.2 1550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02, 8.05% Na20) form an initial charge in a reactor made from stainless steel with a propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0.65 kg/min of sulfuric acid (density 1.83 kg/1, 96% H2SO4) are then metered in with vigorous stirring at 88.5°C over a period of 80 minutes. This metering of sulfuric acid is regulated in such a way that the alkali value prevailing in the reaction mixture is 20. The water glass addition is then stopped, and the addition of sulfuric acid is continued until a pH of 4.5 (measured at room temperature) has been achieved. The resultant suspension is filtered, using a membrane filter press, and the product is washed with water. The filter cake, with 19% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed with 19% solids content and with a pH of 3.0 is then spray-tower dried with addition of ammonia. The resultant microbead product has a BET surface area of 168 m2/g and a CTAB surface area of 148 m2/g. Example 1.3 1550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02/ 8.05% Na20) form an initial charge in a reactor made from stainless steel with a propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0.65 kg/min of sulfuric acid (density 1.83 kg/1, 96% H2SO4) are then metered in with vigorous stirring at 93°C over a period of 80 minutes. This metering of sulfuric acid is regulated in such a way that the alkali value prevailing in the reaction mixture is 20. The water glass addition is then stopped, and the addition of sulfuric acid is continued until a pH of 5.0 (measured at room temperature) has been achieved. The resultant suspension is filtered, using a membrane filter press, and the product is washed with water. The filter cake, with 21% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed with 18% solids content and with a pH of 4.0 is then spray-dried with addition of ammonia and roller-granulated. The resultant granulated product has a BET surface area of 126 m2/g and a CTAB surface area of 118 m2/g. Example 1.4 1 550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02, 8.05% Na20) formed an initial charge in a stainless steel reactor with propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0,65 kg/min of sulfuric acid (density 1-83 kg/1, 96% H2S04) are then added at 92°C over a period of 100 minutes, with vigorous stirring. This sulfuric acid addition is regulated in such a way that the AV prevailing in the reaction mixture is 20. The addition of water glass is then stopped, and the supply of sulfuric acid is continued until a pH of 5.0 (measured at room temperature) has been reached. The resultant suspension is filtered, using a membrane filter press, and washed with water. The filter cake, with 22% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed, with 19% solids content and with a pH of 3.8, is then spray-dried with ammonia feed and roller-granulated. The resultant granular product has a BET surface area of 130 m2/g and a CTAB surface area of 113 m2/g. Example 1.5 1 550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02, 8.05% Na20) formed an initial charge in a stainless steel reactor with propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0.65 kg/min of sulfuric acid (density 1.83 kg/1, 96% H2S04) are then added at 92.0°C over a period of 100 minutes, with vigorous stirring. This sulfuric acid addition is regulated in such a way that the AV prevailing in the reaction mixture is 20. The addition of water glass is then stopped, and the supply of sulfuric acid is continued until a pH of 5.0 (measured at room temperature) has been reached. The resultant suspension is filtered, using a membrane filter press, and washed with water. The filter cake, with 21% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed, with 19% solids content and with a pH of 4.0 is then spray-tower dried with ammonia feed. The resultant microbead product has a BET surface area of 110 m2/g and a CTAB surface area of 108 m2/g. Example 1.6 1 550 1 of water and 141.4 kg of water glass (density 1.348 kg/1, 27.0% Si02, 8.05% Na20) formed an initial charge in a stainless steel reactor with propeller-stirrer system and jacket heating. 5.505 kg/min of the abovementioned water glass and about 0.65 kg/min of sulfuric acid (density 1.83 kg/1, 96% H2S04) are then added at 88.0°C over a period of 100 minutes, with vigorous stirring. This sulfuric acid addition is regulated in such a way that the AV prevailing in the reaction mixture is 20. The addition of water glass is then stopped, and the supply of sulfuric acid is continued until a pH of 5.0 (measured at room temperature) has been reached. The resultant suspension is filtered, using a membrane filter press, and washed with water. The filter cake, with 22% solids content, is liquidized, using aqueous sulfuric acid and a shearing assembly. The silica feed, with 20% solids content and with a pH of 3.0 is then spray-tower dried with ammonia feed. The resultant microbead product has a BET surface area of 143 m2/g and a CTAB surface area of 131 m2/g. Further physico-chemical data for the abovementioned silicas are given in the following table. 9 Example 2 Example 2.1 The precipitated silicas 1.1 and 1.3 of the invention from Example 1 were studied in an SBR emulsion rubber mixture. The silica Ultrasil VN2 GR from Degussa AG with a CTAB surface area of 125 m /g was selected as prior art and reference. The mixing specification used for the rubber mixtures is given in Table 2.1 below. The unit phr here means parts by weight, based on 100 parts of the untreated rubber used. Polymer Buna 1712 is an emulsion-polymerized SBR 5 copolymer from Buna DOW Leuna with a styrene content of 23.5% by weight and with an oil content of 37.5 phr. X50-S is a 50/50 blend of Si 69 [bis (3-triethoxysilylpropyl) tetrasulfane] and carbon black obtainable from Degussa AG. Vulkanox 4020 is 6PPD from 10 Bayer AG, and Protektor G 3108 is an ozone-protection wax from HB-Fuller GmbH. Vulkacit D/C (DPG) and Vulkacit CZ/EG (CBS) are commercially available products from Bayer AG. 15 The rubber mixtures are prepared in an internal mixer using the mixing instructions in Table 2.2. Table 2.3 gives the methods used for rubber testing. The mixtures are vulcanized at 160°C for 18 minutes. Table 2.4 shows the results of testing on the vulcanized rubber. The dispersion coefficient was determined using the surface topography inc. Medalia correction (A. Wehmeier, "Filler Dispersion Analysis by Topography Measurements" Technical Report TR 820, Degussa AG, Advanced Fillers and Pigments Division). The dispersion coefficient thus determined correlates directly at reliability level > 0.95 with the optically determined dispersion coefficient, for example as determined by the Deutschen Institut fur Kautschuktechnologie e. V. [Germany Institute for Rubber Technology], Hanover, Germany (H. Geisler, Bestimmung der Mischgiite, presented at DIK Workshop, 27-28 November 1997, Hanover, Germany). As can be seen from the data in Table 2.4, with the mixtures A and B the silicas of the invention have a lower vulcanization time t90% than the reference mixture. In addition to the lower vulcanization time, advantages are to be found in particular in a higher 500% stress value and the increased reinforcement factor. The ball rebound values at 0 and 60°C are comparable, and no shortcomings in the hysteresis behavior of the mixtures are therefore to be expected. The dispersion of the silicas of the invention is very good. Example 2.2 The precipitated silica 1.2 of the invention from example 1 was studied in an SSBR/BR rubber mixture. The prior art and reference selected was the silica Ultrasil 3370 GR from Degussa AG with a CTAB surface area of 160 m2/g. The mixture used represents a model mixing specification for a car tire tread mixture. The mixing specification used for the rubber mixtures is given in Table 2.5 below. The unit phr here means parts by weight, based on 100 parts of the unprocessed rubber used. The polymer VSL 5025-1 is a solution-polymerized SBR copolymer from Bayer AG with a styrene content of 25% by weight and a butadiene content of 7 5% by weight. The copolymer comprises 37.5 phr of oil and has a Mooney viscosity (ML l + 4/100°C) of 50 ± 4. The polymer Buna CB 24 is a cis-1,4-polybutadiene (neodymium type) from Bayer AG with cis-1,4 content of at least 97% and a Mooney viscosity of 44 ± 5. X50 S is a 50/50 blend of Si 69 [bis(3-triethoxysilylpropyl) tetrasulfane] and carbon black obtainable from Degussa AG. The aromatic oil used comprises Naftolen ZD from Chemetall. Vulkanox 4020 is a 6PPD from Bayer AG, and Protektor G 3108 is an ozone-protection wax from HB-Fuller GmbH. Vulkacit D/C (DPG) and Vulkacit CZ/EG (CBS) are commercially available products from Bayer AG. Perkazit TBZTD is obtainable from Akzo Chemie GmbH. The rubber mixtures are prepared in an internal mixture, using the mixing specification in Table 2.6. In addition to the methods indicated in Table 2.3 for rubber testing, the methods given in Table 2.7 were used. The mixtures were vulcanized at 165 °C for 15 minutes. Table 2.8 shows the results of testing on the vulcanized rubber. As is seen from the data in Table 2.8, the advantages also found in example 2.1 are confirmed in the vulcanization kinetics and a higher level of reinforcement for the mixture C, using the silica of the invention. In addition, advantages are found in the hysteresis behavior of the mixture C. There is an increase in the loss factor tan 5 (0°C) , indicating improved wet skid performance, and there is a decrease in tan 8 (60°C), indicating reduced rolling resistance. The dispersion quality of the silicas of the invention is moreover exceptionally high, with resultant advantages in road abrasion. What is claimed is: A precipitated silica which has the following physical and chemical properties: CTAB surface area 100-160 m2/g BET surface area 100-190 m2/g DBP value 180-300 g/(100 g) Sears value V2 15-28 ml/(5 g) Moisture level 4-8%. The precipitate silica as claimed in claim 1, wherein the BET surface area is 100 to 170 m2/g. The precipitated silica as claimed in claim 1 or 2, wherein the CTAB surface area is from 100 to 150 m2/g. The precipitated silica as claimed in any of claims 1 to 3, wherein the Sears value V2 is from 20 to 28 ml/(5 g) . The precipitated silica as claimed in any of claims 1 to 3, wherein the Sears value V2 is from 22 to 28 ml/(5 g) . The precipitated silica as claimed in any of claims 1 to 5, wherein the DBP value is from 200 to 250 g/(100 g). The precipitated silica as claimed in any of claims 1 to 5, wherein the DBP value is from 250 to 280 g/(100 g). The precipitated silica as claimed in any of claims 1 to 7, wherein the ratio of Sears value V2 to the BET surface area is from 0.140 to 0.280 ml/(5 m2). The precipitated silica as claimed in any of claims 1 to 8, wherein the BET/CTAB ratio is from 0.9 to 1.2. A process for preparing precipitated silicas, which comprises a) taking an aqueous solution of an alkali metal silicate or alkaline earth metal silicate and/or of an organic and/or inorganic base with an alkali value from 7 to 30 as initial charge, b) metering water glass and an acidifier simultaneously into this initial charge at from 55 to 95 °C, with stirring, for from 10 to 120 minutes, in such a way that during the precipitation the AV remains constant at from 7 to 30, c) using an acidif ier to acidify to pH of from approx, 2.5 to 6, and d) filtering, washing and drying. The process as claimed in claim 10, wherein the AV is from 15 to 25. The process as claimed in claim 10 or 11, wherein after step a), the steps carried out comprise b') stopping the feed for from 30 to 90 minutes while maintaining the temperature, and b") then, at the same temperature, for from 10 to 120 minutes, preferably from 10 to 60 minutes, simultaneously adding water glass and an acidifier in such a way that the AV remains constant during the precipitation. The process as claimed in claim 10 or 12, wherein during step b) and/or b') and/or b") an organic or inorganic salt is added. The process as claimed in any of claims 10 to 13, wherein for the drying process use is made of a pneumatic drier, spray drier, disk drier, belt drier, rotating-tube drier, flash drier, spin flash drier, or spray tower. The process as claimed in claims 10 to 14, wherein after the drying process, a roller compactor is used for pelletizing. The precipitated silica claimed in any of claims 1 to 9, or prepared as claimed in any of claims 10 to 15, wherein the surface of the silica has been modified with organosilanes of the formulae I to III [SiR1n(OR)r(Alk)m(Ar)p]q[B] (I) , SiR1n(OR)3-n(Alkyl) (II) , or SiR1n(OR)3-n(Alkenyl) (III) , where B is -SCN, -SH, -Cl, -NH2, -OC(0)CHCH2, -OC(0)C(CH3)CH2 (if q = 1), or -Sw- (if q = 2), B being chemically bonded to Alk, R and R1 are an aliphatic, olefinic, aromatic, or arylaromatic radical having 2-30 carbon atoms, optionally with substitution ' by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate, or organosilane radical, where the meaning or substitution of R and R1 may be identical or different, is 0, 1, or 2, is a bivalent unbranched or branched hydrocarbon radical having from 1 to 6 carbon atoms, is 0 or 1, is an aryl radical having from 6 to 12 carbon atoms, preferably 6 carbon atoms, which may have substitution by the following groups: the hydroxyl, amino, alcoholate, cyanide, thiocyanide, halo, sulfonic acid, sulfonic ester, thiol, benzoic acid, benzoic ester, carboxylic acid, carboxylic ester, acrylate, methacrylate or organosilane radical, is 0 or 1, with the proviso that p and n are not simultaneously 0, is 1 or 2, is a number from 2 to 8, is 1, 2, or 3, with the proviso that r + n + m + p - 4, is a monovalent unbranched or branched saturated hydrocarbon radical having from 1 to 20 carbon atoms, preferably from 2 to 8 carbon atoms, is a monovalent unbranched or branched unsaturated hydrocarbon radical having from 2 to 20 carbon atoms, preferably from 2 to 8 carbon atoms. The precipitated silica as claimed in any of claims 1 to 9 or as prepared in any of claims 10 to 15, whose surfaces have been modified with organosilicon compounds whose composition is SiR24_nXn (where n = 1, 2, 3, 4), [SiR2xXyO]z (where 0 < x < 2; 0 < y < 2; 3 < z < 10, where x + y = 2) , [SiR2xXyN]z (where 0 < x < 2; 0 < y < 2; 3 < z < 10, where x + y = 2), SiR2nXm0SiR2oXp (where 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 < p < 3, where n+m=3, o + p = 3) , SiR2nXmNSiR20Xp (where 0 < n < 3; 0 < m < 3; 0 < o < 3; 0 < p < 3, where n+m=3, o+p=3), and/or SiR2nXm[SiR2xXyO]2SiR20Xp (where 0