Патент USA US2368042код для вставки
Patented lien. 23', 1945 ‘ - T 2,368,042 um'rso STATES '- PATENT 0mm 2,368,042 PROCESS FOR PRODUCING NEUTRAL CALCIUM HYPOCHLQBITE _ ‘ - Homer Louis Robson, Lewiston, N. Y., assignor to V The Mathieson Alkali Works, Inc., New York, vN. Y., a corporation of Virginia No Drawing. Application January 21, 1942, ‘ Serial No. 427,589 , 11 Claim. This invention relates, to the production of neutral calcium hypochlorlte and provides an ; improved method of preparing slurries thereof ‘ ‘ (on. 23-86) f of the neutral compound formed by the procedure just outlined is the tendency of the slurry to, becomesupersaturated and then to form many j very small crystals of the neutral hypochlorlte The general method of producing calcium hy~ 5. which cannot vbe grown to satisfactory size ‘for ?ltering during the completion of the chlorina pochlorites consists essentiallyv of chlorinating tion. To reduce this tendency, it has been pro lime slurries whereby the lime is converted to posed to form the neutral compound in the pres hypochlorite which crystallizes to form slurries ence of previously formed crystalsof the neutral ' oi’ hypochlorite crystals. The hypochlorite crys this are customarily recovered from the mother 10 compound. Following this procedure, it has been found necessary to employ very large amounts liquor by ?ltration; or centrifuging. ' Though this of seed crystals in order to avoid the formation‘ method has long been known, its practical ap of small crystals due to spontaneous crystalliza plication to the production of neutral calcium tion. Amounts of seed crystals exceeding the ‘ hypochlorite has presented many difficulties. For example, it has been known that milk of is expected yield have been suggested. It has further been suggested that better crys lime can be chlorinated at ordinary tempera tals of the neutral hypochlorite may be obtained However. under such conditions, basic ' tures. ’ by thinning the slurry in which the precipitation, hypochlorite compounds are formed which have oi the neutral compound is to occur, as by dilut been found objectionably to thicken the slurry so that chlorination could not be carried on 20 ing it with ?ltrate obtained from the ?ltering 0! a previous portion of the slurry. Because of the satisfactorily. The usual procedure is to con solubility relations, thinning the slurry with water duct the ?rst stage of the chlorination at an is uneconomical due to solution of the neutral elevated temperature, for example 30 to 45° C., compound and its-loss in the increased amount at which temperature the dlbasic calcium hy pochlorite compound, Ca(OCl2.2Ca(OH)2, is 25 of ?ltrate. The use of‘several volumes of ?ltrate per volume of chlorinated milk of lime slurry formed. The dibasic compound crystallizes in has been suggested. Such procedure calls for hexagonal plates and does not objectionably a considerable increase in tank capacity and in thicken the slurry. volves the-handling of large amounts of ?ltrate If the chlorination is carried further toward ‘ completion at such elevated temperatures, a pre so which is corrosive to pipes and pumps. One di?lculty of operating in the above de cipitation oi’ the hemibasic hypochlorit'e com scribed manner is the small proportion of the pound occurs. This compoundhas been vari chlorinating time during‘ which the neutral com ously termed “monobasic,” "two thirds basic,” pound is being crystallized. If the slurry formed etc. However, I have found the composition of this compound ~to be in accordancev with the 35 by chlorinating the milk of lime until the lime has been substantially converted to the dibasic formula, 2Ca(OCl)z.Ca(0H)2. This hemibasic compound is cooled to 15 to 25° C., and further compound forms in pointed lath-like crystals and ‘chlorinated to form the neutral compound, so these interfere with the growth 0! crystals oi the lution of the‘ di-basic compound takes place'ior a neutral calcium hypochlorite, Ca(OCl)2.2(H2O>), 40 considerable period. For a brief interval the so- . upon iurther chlorination. lution then becomes saturated, and subsequently m some operations the chlorination is stopped supersaturated with rapect to the neutral com while the solids present in the slurry are pre pound, and spontaneous crystallization of many dominantly the hemibasic compound which has ?ne crystals will occur unless a large amount oi’ been found to be generallymore ?lterable than having advantageous ?lterability characteristics. the neutral compound resulting from further 46 neutral hypochlorite seed crystals is present. Then follows a period during which growth of chlorination oi the hemibasic slurry. By other the crystals of the neutral compound'takes place. procedures the partly chlorinated slurry in which the solids present are predominantly the dibasic , This period is but a small portionwoi the entire compound, is cooled to 15 to 25° C. and the chlorination period. For example, ‘it the milk of chlorination continued toward completion. While so lime slurry is made up or 1 part ‘lime to 2.6 parts a slurry of the neutral compound may be ob- ‘ tamed by this latter procedure, the neutral com water, less than one-?fth oi the chlorine will be I added during the period of growth of the neutral compound crystals. Consequently, the neutral crystals do not have su?lcientv timet'o grow. talc and the slurry thereofv is diincult to ?lter. One reason tor the small size 01' the crystals, “ Poorly'?lterable slurries are objectionable be pound thus produced is in the form of ?ne crys- ~ 2 2,388,042 cause they formcakes containing large amounts of mother liquor. This mother liquor is rich in calcium chloride. Because of its hygroscopic properties, calcium chloride resists drying and causes considerable loss of hypochlorite by de-> the dibasic slurry used should not exceed 47' Twaddell and‘ preferably should be between 40 and 44° Twaddell. The free lime content of the composite slurry is advantageously maintained at a value below 1.5%, byv weight, throughout its composition during the drying operation. When ' chlorination. the milk of lime is chlorinated, equimolecular portions of calcium chloride and calcium hypo l the calcium hydroxide present in the dibasic slur In this chlorination, the chlorine reacts with chlorite are formed in the solution. One-half or ry as indicated by the equation more of the calcium hypochlorite formed is usu 10 ally precipitated as the neutral compound while Ca( 001) z.2Ca( OH) =+2Clz—>2Ca(OCi) z+CaCh all of the calcium chloride stays in solution. The ' In other words, two moles of chlorine are required amount of calcium chloride remaining in the cake to react with each mole of the dibasic hypochlo decreases as ?lterability increases. rite. one mole of chlorine being required to react To reduce the calcium chloride content, it has with each mole of Ca(OH):, to form the neutral been proposed to prepare crystals of the dibasic calcium hypochlorite. Reference herein and in compound and to separate these as by centrifug the appended claims to equivalent quantities of ing or ?ltration. The separated crystals of the chlorine and dibasic hypochlorite slurry will be dibasic compound may then be suspended in wa understood to have reference to this reaction. I ter and the chlorination continued until neutral 20 The process of the present invention has the calcium hypochlorite is formed. By this sepa distinct advantage of being adapted to continu ration of the dibasic compound crystals from ous operation. For example, a supply of the di the mother liquor in which they are formed, a basic slurry may be maintained and a portion of considerable proportion of the calcium chloride this slurry constantly supplied to and admixed is vremoved and therefore the ?nal slurry of neu 25 with the neutral slurry with simultaneous chlori tral calcium hypochlorite contains a smaller pro nation. However, if desired, the addition of the portion of calcium chloride. Consequently, for dibasic slurry to the neutral slurry may be in the same size of crystals and equal ?lterability, termittent. the amount of calcium chloride in the ?ltercake In the continuous operation of this process a will be less so that drying thereof is simplified. 30 quantity of the neutral slurry is maintained in It has also been claimed that larger crystals of the mixing and chlorinating chamber. In the the neutral compound can be crystallized from , batch type of operation a quantity of the neutral solutions of lower calcium chloride content than slurry from a previous run may be used. For ex would be obtained by ordinary chlorination. ample, a portion of the neutral slurry from a Separation and resuspension of the dibasic com 35 previous run may be allowedto remain in the pound crystals are, however, objectionable as a mixing and chlorinating chamber for use in start plant procedure because of the greatly increased ing the following run. In either type of opera tank capacity required and because of the in tion the neutral slurry for the initial run may creased losses of calcium hypochlorite in the ?l be prepared in a conventional manner, for in trates. Also, the ?ltrate resulting from ?ltra stance by the chlorination of a lime slurry or of tion of the neutral compound slurry is higher in a slurry of the dibasic compound, advantageously calcium hypochlorite content than that obtained to a point where its free lime content is below by ordinary chlorination. To make such opera 1.5% by weight and usually about 0.5% by weight. tion economical, it is necessary to treat this ?l depending upon the operating conditions to be trate with lime to effect the recovery of basic 45 employed. ' hypochlorite therefrom which can be ?ltered oil! The dibasic compound slurry used in accord and returned to the process. If this recovery step ' ance with the present invention may be prepared, is practiced with both the ordinary and with the for instance, by chlorinating a milk of lime slurry basic compound separation and resuspension type until the clear liquor, on separation from the slur of chlorination, the loss of calcium hypochlorite 51 ry, shows the desired gravity. It is not neces is greater in the latter-case due to the larger sary to ?lter or centrifuge the dibasic compound volume of ?ltrate from the recovered basic hypo ~ and resuspend it, as has been previously sug chlorites. Further, since water enters the second gested, though such procedure may be followed if stage of such chlorination processes with the desired. Likewise, a portion of the mother liquor separated dibasic compound, less water may be 55 from the dibasic slurry may be removed by set added' to the lime in preparing the initial milk. tling and drawing of! part of the clear super of lime slurry, if an excessive amount of ?ltrate is natant' liquor at a favorable stage in the chlori ' to be avoided, and this would necessitate the nation. Such variations may be advantageous. handling of objectionably thick milk of lime particularly if the ?ltrate from the neutral com-. slurries. Oil pound is treated with lime to recover basic hypo In accordance with my improved process, slur chlorite compounds which are addedto the milk ries of neutral calcium hypochlorite of excellent of lime slurry prior to or during its chlorination, ?lterability may be prepared while avoiding the so as to avoid the accumulation of calcium chlo above-mentioned di?iculties of the previously pro ride in the system. posed methods. One satisfactory method of preparing the di '05 Brie?y, I have discovered that slurries of neu basic compound slurry is as follows: A milk of tral calcium hypochlorite crystals of excellent lime slurry is chlorinated until substantially all ?lterability may be prepared by adding, prefer the calcium hydroxide has been converted to the ably at a uniform rate, a slurry of dibasic calcium dibasic compound. At this point, if desired, the hypochlorite to a previously prepared slurry of 70 chlorination may be stopped, the slurry settled neutral calcium hypochlorite with simultaneous and a portion of the supernatant liquid discard chlorination by injecting chlorine into the com posite slurry at a rate approximately equivalent, chemically, to the rate at which the disbasic slurs ry is added. The gravity of the liquid phase of ed. The remaining 'slurry is then chlorinated until the ‘clear liquor on separation .from the slurry shows a gravity of 40 to 44' Twaddell. The chlorination of the milk of lime may be started 2,388,042 at ordinary room temperature and the tempera ture allowed to rise to 35 to 45° C. and held there during continued chlorination until the .clear liquor separated from the slurry reaches the de sired gravity. My present invention is not dependent upon the use of any particular method of preparing the di 3 in the size or shape of the crystals of the dibasic compound. Likewise, I have found‘ that the slurry of neutral calcium hypochlorite may be stored without alteration providing the free lime content is not over 0.5%. For short periods such as one hour, the neutral slurry having higher lime con tents, for instance up to 1%, may be stored with. out change, and for still shorter periods the lime basic slurry used in accordance therewith. How content may be up to 1.5%. Slurries of the di ever, best results have been obtained where the crystals of the dibaslc slurry were relatively larg 10 basic compound, the solutions of which are of more than 47° Tw. gravity, should not be stored, and ‘well formed. ‘ as they may alter, the dibasic compound changing In experimental runs I have found it possible into the hemibasic compound. Similarly, a slurry and advantageous to continue the chlorination of the neutral compound containing more than of the dibasic slurry until the clear liquor sepa rated from the slurry-shows a gravity of 47° Twad 15 1.5% freelime should not be stored at any tem perature, as fine crystals of the hemibasic com dell. As precipitation of the hemibasic compound pound may form and seriously impair the ?lter may occur at slightly higher gravities, We pre ability. These ?ne crystals could be partly re fer to stop the chlorination at 44° Tw. or pref moved by slow, careful chlorination of the mixed erably to proceed to this point, stop the chlorina tion and continue stirring for a short period. The 20 slurry but the ?nal slurry of the neutral com pound would be less ?lterable than one formed gravity of the liquid 7 phase will fall slightly as without such storage period. equilibrium with respect to the dibasic compound By reason of the fact that these slurries of suit is established. If the gravity should fall below able gravity and free lime content may be stored 40° Tw., for instance, the slurry‘ may be further chlorinated to bring the gravity above 40° Tw. 25 without change in the size or character of their In preparing the neutral hypochlorite slurry ~ solid constituents, a supply of the dibasic slurry may be maintained for the operation of the proc in accordance with my present method, the pres ess and interruption of the process by failure of vlously prepared dibasic slurry is passed, pref-_ the chlorine supply or of the pumps or cooling erably at a constant rate, into a chamber or tank equipmentdoes not result in poorer ?lterability of partly ?lled with a previously prepared slurry of the ?nal neutral slurry. Partly chlorinated milk neutral calcium hypochlorite, the free lime con of lime slurries, the solution phase of which has a tent of which is advantageously less than 1.5% gravity of less than 30° Tw., should not be stored, and preferably about 0.5% by weight. Simul due to the formation of undesirable basic com taneously, chlorine is added to the slurry in the pounds which become serious at temperatures be mixing and chlorinating chamber, which for con _ low about 23° C. and may result in complete block venience is herein sometimes referred to as the age of tanks and lines. composite slurry, at a rate dependent upon the In accordance with my invention, I have found composition of the dibasic slurry and the rate at it particularly advantageous to use dibasic slur which the dlbasic slurry isiadded, and such that the alkalinity of the composite slurry is main tained substantially constant. During the chlori ' nation and addition of the dibasic slurry. the com posite slurry is cooled and preferably kept at a . temperature between 15 and 20° C. A tempera ture as high as 25° C. may be maintained provid ries which consist of crystals of the dibasic com- _ pound and liquid solutions of 40 to 47° Tw. gravity. However, my improved process has been suc cessfully operated using dibasic slurries, the grav ity of the liquid solution of which was as low as 34-“ Tw. The use of such low gravity slurries in troduces difficulties and ordinarily the slurry of the neutral compound obtained by their use is not as ?lterable as that obtained by use of dibasic tendency of the slurry to foam and foaming in slurries having a liquid phase of 40° to 47° Tw. terferes with the circulation and hence the growth of the crystals of the neutral compound. Simi 50 gravity. Dibasic slurries, the liquid phase of which has gravities as lowas 30° Tw., may be larly, I have found that temperatures as low as used with advantage but the ,dibasic crystals pres 10° C. may be employed but that at lower tem ent in dibasic slurries, having a liquid phase of peratures the solution tends to become super 35° Tw. gravity or less, have sharp edges which saturated to an undesirable degree with the neu tral compound so that unsatisfactory slurries may 55 may provide nuclei for undesirable small crystals or the neutral compound during the subsequent result unless the rate of chlorination is quite slow. chlorination. When the liquid phase of the di In the‘ batch-type of operation, when the mixe basic slurry has a gravity of 40° to 47° ‘Tw., and ing and chlorinating chamber is substantially particularly if the gravity is above 44° Tw., these filled, the addition of the dibasic slurry.is dis; edges have been dulled by solution of part of the continued and the neutral slurry therein may-be dibasic crystals during the chlorination required further chlorinated, for instance, to a lime con to attain such gravity. tent of 0.1 to 0.2%, at which point a portion of There is a further advantage in employing the neutral slurry may be transferred to storage, slurries of the dibasic-compound, the liquid phase leaving in the chamber sumcient neutral slurry for the resumption of the operation. The opera 85 of which is of 40° to 47° Tw. gravity. This is the advantage of easier mixing of such dibasic slur tion is resumed by the addition of further dibasic ries with the neutral slurry and a more uniform slurry with simultaneous chlorination, as just concentration in the mixing and chlorinating described, until the chamber is again ?lled or un chamber. Precipitation of the neutral compound 7 til the desired quantity of neutral slurry has been prepared. ' 70 may be effected, for example, from solutions of 50 to 55° Tw. gravity. The addition of a dibaslc 1 have found that a dibasic slurry, the clear slurry having a gravity of 80 to 35° Tw. to such liquid of which upon separation from the slurry neutral slurry may cause serious dilution locally, has a gravity of 40 to 47° Tw., may be stored at ordinary temperatures without formation of un so that the concentration of dissolved ‘salts may desirable basic compounds or appreciable change 75 vary seriously throughout the mixing and chlori ing the alkalinity is kept above 0.5% but such higher temperatures are inadvisable as there is a 4 escapes nating chamber. By the addition of a dibasic slurry of 40 to 44° Tw. gravity, this dilution prob‘ _to be advantageous for commercial operation; With this throughput the capacity of the system lem is lessened to a point where it is no longer troublesome. The dilution problem is more di?i cult because of the fact that crystals of the neu tral compound are relatively thin and fragile and ~ per unit of tank volume is considerably in excess suflicient to maintain the gravity of the liquid prepared neutral calcium hypochlorite slurry hav ing a calcium hydroxide content of approximately 0.1% by weight. The free lime content of the neutral slurry was allowed vto increase to 0.5% of that obtainable with processes which involve the separation of the dibasic compound and its resuspension in water. This is an important ad violent stirring cannot be employed during their vantage of my improved process, particularly so precipitation as such stirring would tend to break since all equipment must be constructed of cor the crystals into small fragmentsand seriously rosive-resistant material and is consequently reduce the ?lterability of the ?nal neutral slurry. 10 quite expensive. Vigorous stirring would also tend to introduce The following speci?c example is given as a de foam into the slurry which would seriously im tailed illustration of the improved process of my pair the ?lterability. . present invention as applied to the discontinuous or batch-type of operation. 3500 pounds of lime Instead of preparing the dibasic slurry in ad vance and storing it for subsequent use, the prep of 95% Ca(OH)z content and 8900 pounds of aration oi the dibasic slurry, and its subsequent water were made into a milk of lime slurry and use in preparing the neutral slurry, may with charged to a 1500 gallon tank equipped with a slow speed turbine type agitator. 2230 pounds of advantage be combined in a unitary continuous operation. For example, I have found that such chlorine was added, the temperature being al continuous operation may advantageously be car 20 lowed to rise to 37° C. and held thereby circu lating cooling water through coils located within ried on in four tanks constructed of corrosion resistant materials. Milk of lime and chlorine the tank. When all the chlorine had been added, are fed continuously to the ?rst tank, the amount ‘ the solution was stirred for ten minutes and the of chlorine being sufficient to maintain the grav clear liquor was found to have a gravity of 44° Tw. ity of the solution therein between 22 and 26° Tw. This dibasic slurry was then pumped at the rate The slurry from this tank, which is normally of 8 gallons per minute into a mixing and chlo fairly thin, then ?ows or is pumped to the second rinating tank also having a capacity of 1500 gal tank to which chlorine is also admitted at a rate ions and which was half-?lled with previously phase of the dibasic slurry at 40 to 47° Tw. In - the ?rst tank the temperature is allowed to rise to about 30' to 40° C., and in the second tank it is preferably held between 35 and 40° C. by suitable cooling. The division of this chlorinating opera tion into two stages tends to equalize the chlori and at this point the introduction of chlorine into the tank was started at a rate equal to approxi mately. 300 pounds per hour. The chlorine was natlng load and to facilitate proper temperature added in the liquid form, being passed through a rotormeter tube calibrated at 50 to 1500 pounds per hour and then through a needle valve into the slurry. The rate at which the chlorine was added ing the neutral slurry previously described, 40 was adjusted so as to hold the free lime content of the slurry at 0.5%. I wherein it is chlorinated at a rate sufficient to keep the free lime content of the composite slurry At the end of 90 minutes half of the dibasl-c control. v . The dibasic slurry from said second tank may‘ be passed continuously to the third tank contain under 1.5% and preferably between 0.5 and 1.0% by weight. The neutral slurry may be passed continuously from the third tank to the ?nal tank to which a slow stream of chlorine is admitted which reduces the remaining lime to the desired residual which may be from, say, 0.05 to 0.25% by weight. slurry and 450 pounds of chlorine had been added. ‘ At this point addition of the dibosic slurry was stopped and the addition of chlorine continued for about 10 minutes at a slightly reduced rate so as to reduce the alkalinity of the resultant neutrtl slurry to 0.1%, expressed as calcium hydroxide. v‘720 gallons of the resulting neutral slurry were In the third tank the temperature is advan 50 then discharged to storage and the cycle repeated, tageously kept between 15 and 25° C., and prefer converting the remaining 720 gallons of dlbasic ably between 15 and 18° C., by suitable cooling. slurry to neutral slurry. The temperature of the The temperature maintained in the ?nal tank neutral slurry was maintained between 15 and 17° will depend upon the intendeddisposition of the C. during addition of the chlorine by circulatin¢ low alkalinity neutral slurry therein. If this 55 brine through cooling coils positioned therein. slurry is to be used promptly, as by continuous \ The resulting slurry of the neutral compound was ?ltration or centrifuging,‘ the temperature may i found to be of good ?lterability. with advantage be from 15 to 25° C. If, however, The following is a specific illustration of my the slurry from this fourth tank is to be stored improved method of preparing slurries of neutral for an extended period of time, it should be cooled 80 calcium hypochlorite as applied to the continuous type of operation. A dlbasic slurry, the liquid While the above-mentioned temperatures have phaseof which had a gravity of 43 to 44° Tw., been found. particularly suitable for this type of prepared by chlorinating a slurry of 3500 pounds ‘operation of my improved process, other tempera of lime of 95% Ca.(OH)z content and 8900 pounds' tures may be used. However, the use of tempera 66 of water, as previously described, was charged at tures other than those within the speci?ed range the rate of 8 gallons per minute into a mixing and - down, for instance, to 0° C. prior to storage. ' is apt to lead to reduced capacity of the opera tion and to poorer fllterability of the ?nal slurry . chlorinatlng tank of 1500 gallons capacity half ?lled with a previously prepared slurry of neutral calcium hypochlorite having a‘ lime content of. In continuous operation such- as described 70 0.5% to 1.0% by weight. Simultaneously there above, the throughput may be varied widely ac with chlorine was added at the rate of approxi cording to the chlorine supply available and the mately 300 pounds per hour. The temperature of desired .?lterability of the ?nal slurry. A the neutral slurry was held down to 15 to 17° C., throughput of one-half of one per cent of the by circulating refrigerated brine through cooling volume of each tank per minute has been found 76 coils submerged therein. Samples of the neutral ' of neutral compound. 9,368,042 slurry were taken from time to time and tested for free lime content and the rate of chlorine ad- ' 5 . Twaddell and simultaneously chlorinating the composite slurry by adding chlorine thereto at dition adjusted to keep the lime content of the neutral slurry between 0.5% and 1.0%. It was , a rate such‘as to maintain the free lime content found that the alkalinity could be kept within this 5. A continuous process for the production of readily filterable slurries of neutral calcium hypo chlorite crystals comprising adding to a previ ously prepared slurry of neutral calcium hypo range with infrequent adjustment of the chlorine ?ow, for instance one adjustment per hour. of the composite slurry substantially constant. As the operation continued, the neutral slurry chlorite at a uniform rate a slurry of dibasic was permitted to over?ow from the mixing and chlorinating tank into a second tank. Gaseous 10 calcium hypochlorite, the liquid phase of the lat ,ter having a gravity within the range of 30° to 47° chlorine under approximately 20 pounds pressure was supplied to this second tank at an average rate of about 20 pounds per hour to complete the chlorination of the neutral slurry, the lime con tent being reduced to approximately 0.1% by weight. In this second tank the slurry was cooled to 0°-+5° C. and from this tank the ?nal slurry was drawn o? to storage. Twaddell, while chlorinating the composite slurry by passing chlorine thereto at a rate substantially equivalent, chemically, to that at which the di basic calcium hypochlorite slurry is added so as to maintain substantially constant the free , C8.(OH)2 content of the composite slurry. 6. A continuous process for the production of readily ?lterable slurries of neutral calcium hypo as above described, over a period of 10 hours a 20 chlorite crystals comprising maintaining a quan tity of neutral calcium hypochlorite slurry in a portion of the ?nal slurry was withdrawn from mixing and chlorinating chamber, continuously storage and was found to be of good ?lterability. passing thereto a slurry of dibasic calcium hypo A portion thereof was ?ltered through a rotary chlorite, the liquid phase of the latter having a vacuum ?lter and without using the water spray the resultant cake had the following analysis: 25 gravity within the range of 30° to 47° Twaddell, while chlorinating the composite slurry by con Per cent tinuously passing chlorine thereto at a rate sub After the continuous operation of this process, Ca<OCDz _____________________________ __-_ 53.6 stantially equivalent, chemically, to that at _________ __ _____________________ __ 1.0 which the dibasic calcium hypochlorite slurry is Ca(Ol-I)2 ______________________________ __ 0.4 added, continuously withdrawing neutral calcium CaCl-z _________________________________ .._ 7.0 CaCOa hypochlorite slurry from the chlorinating and mixing chamber to a second chamber and fur ther chlorinating the withdrawn‘ neutral slurry. By using alight spray of wash water during the in the said second chamber. ?ltration the calcium chlorine content of the cake 7. A process for the production of readily ?l was reduced to 3-496. 35 I claim: terable slurries of neutral calcium hypochlorite crystals which comprises simultaneously adding 1. A process for the production of readily ill to a previously prepared slurry of neutral calcium terable slurries of neutral calcium hypochlorite crystals comprising adding to a previously preé hypochlorite chlorine and a slurry of dibasic cal pared slurry of neutral calcium hypochlorite a 40 cium hypochlorite, the liquid phase of the latter slurry of dibasic calcium hypochlorite,'the liquid having a gravity within the range of 30° to 47° phase of the latter having a gravity within the Twaddell, the chlorine being added at a rate sub stantially equivalent, chemically, to the rate at range or‘ 30° to d7“ Twaddell, while chlorinat ing the composite slurry at a rate such as to which the slurry of dibasic calcium hypochlorite Water __________________________________ __ 38.0 maintain the free lime content thereof below 1.5% by weight. is added. 8. A process for the production of readily fil 2. A process for the production of readily ?l terable slurries of neutral calcium hypochlorite crystals comprising adding to a previously pre~ terable slurries of neutral calcium hypochlorite crystals which comprises simultaneously adding to a previously prepared slurry of neutral cal . pared slurry of neutral calcium hypochlorite a 50 cium hypochlorite chlorine and a slurry of dibasic slurry of dibasic calcium hypochlorite prepared calcium hypochlorite, the liquid phase of the la‘ by chlorinating milk of lime and composed of a ter having. a gravity within the range of 40° to solid phase consisting essentially of dibasic cal 47° Twaddell, the chlorine being added at a rate cium hypochlorite and a liquid phase having a substantially equivalent, chemically, to the rate gravity within the range of 30° to 47° Twaddell, - at which the slurry of dibasic calcium hypo while chlorinating the composite slurry at a rate chlorite is added. such as to maintain the free lime content thereof 9. A process for the production of readily ?l below 1.5% by-weight. terable slurries of neutral calcium hypochlorite 3. A process for the production of readily ill crystals which comprises simultaneously adding terable slurries of neutral calcium hypochlorite 60 to a previously prepared slurry of neutral cal— crystals comprising admixing with a slurry of cium hypochlorite chlorine and a slurry of di neutral calcium hypochlorite a slurry of dibasic basic calcium hypochlorite, the liquid phase of calcium hypochlorite, the liquid phase of which the latter having a gravity within the range of has a gravity within the range of 30° to d7° 30° to 47° Twaddell, the chlorine being added at Twaddell and simultaneously chlorinating the 65 a rate substantially equivalent, chemically, to the composite slurry by adding chlorine thereto at a rate at which the slurry of dibasic calcium hypo rate such as to maintain the free lime content chlorite is added, and maintainingv the com of the composite slurry substantially constant. posite slurry at a temperature of between about 4. A process for the production of readily fil 10° to 25° C. while the chlorine and slurry of di terable slurries of neutral calcium hypochlorite 70 basic calcium hypochlorite are being added crystals comprising admixing with a slurry of thereto. neutral calcium hypochlorite having a free lime 10. A process for the production of readily ?l terable slurries or’ neutral calcium hypochlorite crystals which comprises simultaneously adding has a gravity within the range of 30 to 47° 75 to a previously prepared slurry of neutral cal content below 1.5%, by weight, a slurry of dibasic ' calcium hypochlorite, the liquid'phase of which 6 ohm hypcchlorite chlorine and a slurry of di cium hypochlorite chlorine and a slurry oi’ dibasic basic calcium hypochlorite prepared by chlorinat ing milk of lime and composed of a solid phase consisting essentially of dibasic calcium hypo calcium hypochlorite, the liquid phase of the lat chlorite and a liquid phase having a gravity with in the range of 30° to 47° Twaddell, the chlorine being added at a rate substantially equivalent, substantially equivalent, chemically, to the rate ter having a gravity within the range of 30' to 47° Twaddell, the chlorine being added at a rate at which the slurry of dibaslc calcium hypo chlorite is added, and thereafter discontinuing ehemicall , to the rate to which the slurry of the addition of the slurry of dlbasic calcium hy dibasic calcium hypochlorite is added. pochlorite while continuing the chlorination fur "11. it process for the production of readily ?l 10 ther to reduce the calcium Mdroxide content of terable siurries of neutral calcium hypochlorite the resultant neutral slurry crystals which comprises simultaneously adding to a previously prepared slurry of neutral cal LUEJZEE ROBSON.