2,983,577 United States Patent Office Patented May 9, 1961 2 Thus, contrary to the teachings of the prior art, I have found that kernite can be prepared synthetically from 2.983,577 borax providing certain conditions are maintained. First, an aqueous solution must be used which contains at least METHOD OF PRODUCING SODUMTETRA 28.0% by weight of borax, and secondly, the temperature BoRATE TETRAHYDRATE of the borax solution must be at a temperature of at least Vincent Morgan, Boron, Calif., assignor to United States 57.59 C. Borax & Chemical Corporation, Los Angeles, Calify As stated, kernite must be crystallized from solutions a corporation of Nevada containing at least 28% NaBO-10H2O. This means No Drawing. Filed Apr. 15, 1958, Ser. No. 728,545 i., v 10 that kernite can be crystallized from a 28% solution up to and including a 100% solution of the 10 mol borax. 2 Claims. (C. 23-59). If 10 mol borax is dissolved in its own water of hydra tion this solution can be used for the crystallization of kernite...... This invention relates as indicated to a method for 15 According to the process of the present invention the producing sodium tetraborate tetrahydrate and has more 4 mol hydrate of sodium tetraborate may be prepared particular reference to a method for synthetically pro by first forming the 5 mole hydrate and then redissolving ducing kernite (NaBO'4H2O) from water solution at the 5 mole, hydrate in a solution saturated with respect atmospheric pressure. . . . . to the 5 mol hydrate and then crystallizing out the 4 mol The mineral kernite (NaBO'4H2O) is known to be 20 hydrate, or it may be crystallized directly from aqueous naturally occurring, and at one time was the major borate solution without having the 5 mol present at any time. ore used in the production of borax, boric acid, etc. So that the present invention may be more clearly However, while kernite was used to produce refined borax understood, the following examples are offered by way (NaBO-10H2O), refined substantially pure crystals of of illustration. . . kernite (NaBO'4H2O) have never been produced. 25 - Over the years the kernite deposits have been used less and less and the present principal borate source is now A 60% borax solution was made by heating 300 grams borax (NaBO 10H2O). With the increasing interest of NaBO-10HO with 200 ml. of H2O in a flask. The of supplying a slowly soluble borate material for agricul flask was fitted with a condenser and heated for about tural purposes, a new interest has again been aroused in 30 18 hours at 100 C. kernite. Besides the advantage of slow water solubility, After about 18 hours the 5 mol hydrate, NaBO'5HO kernite has the additional advantages of greater density crystallized from solution. The mixture was then seeded and of only containing 4 mols of water which is quite with about 0.10 gram of natural kernite and the heating obviously a shipping advantage over 10 mol or even continued. 5 Inol borax. 35 At the end of about 62 hours' total heating time a Many futile attempts have been made to synthetically large crystalline mass was formed at the bottom of the produce kernite from borax at atmospheric pressure. flask. The crystals were filtered, washed with hot water The only known synthesis of kernite was accomplished and isopropyl alcohol, and then air-dried. ..., under laboratory conditions by the use of high tempera The crystals were chemically, microscopically analyzed, tures and pressures over long periods of time. Even with 40 and additionally an X-ray powder pattern was made. the foregoing ideal laboratory conditions the resultant The analysis provided conclusively that the product of product contained some 5 mol borax. the aforegoing example was substantially pure crystals The main reason that NaBO-10HO ore is used in of kernite. stead of kernite ore is that kernite is so insoluble and difficult to refine. High temperature and autoclaves are 300 grams of NaBO-10H2O was put into a flask necessary in the dissolution of kernite, whereas relatively 45 with 200 ml, of HO. The flask was fitted with a con simple straightforward hot water solution is all that is denser and stirrer, which turned at about 170 rp.m. necessary to dissolve borax ore. Thus it would be ex When all the borax was put in solution the temperature tremely desirable if kernite could be produced syntheti was maintained at about 84 C. cally at will from borax ore using the same plane equip 50 After 6 hours the solution was seeded with about 0.05 ment. gram of natural kernite. It is therefore the principal object of the present inven At about 23 hours' total elapsed time the solid phase tion to provide a method for producing a substantially consisted almost entirely of 5 mol hydrate. After 48 pure synthetic kernite (NaBO 4H2O) from borax ore. hours' total elapsed time the solid phase was examined A further object of this invention is to provide a meth 55 optically and found to be substantially pure kernite. od for producing kernite at atmospheric pressure. A chemical analysis revealed the following results: Other objects will become apparent as the description proceeds. Percent found Theoretical To the accomplishments of the foregoing and related in Sample 4 no ends, the invention then comprises the features herein after fully described and particularly pointed out in the 50.84 50,96 claims, the following description setting forth in detail 22.67 22.68 certain illustrative embodiments of the invention, these being indicative, however, of but a few of the ways in which the principle of the invention may be employed. 65 Broadly stated the present invention comprises the A solution of 10 mol borax in water was prepared method of synthetically producing kernite which com which assayed 55% borax. The solution was seeded with prises preparing an aqueous solution containing at least about 0.10 gram of natural kernite and the flask was 28.0% by weight of NaBO-10H2O, heating the solu equipped with a condenser and stirrer. The flask was tion to at least 57.5 C., seeding said solution with a 70 heated and maintained at a temperature of 91. C. Sam minor amount of kernite crystals and continuing the heat ples were studied at 18 hours and 25 hours' total elapsed ing until kernite crystallizes from said solution. time. No crystals of 5 mol borax were found in the 2,983,577. 3 4. solution. After. 67 hours the solution was filtered and the following claims or the equivalent of such be, em. the crystals washed and dried. ployed. A chemical analysis gave the following results: I, therefore, particularly point out and distinctly claim as my invention: Percent found Theoretical s 1. The method of synthetically producing kernite which in Sample, 4 mol comprises preparing an aqueous: solution containing at

least 28.0% by weight of NaBO 10HO, heating the 50.94 - 50.96 solution under atmospheric pressure in a temperature 22.70. 22.68 range of from 57.5° C. to about 100° C., seeding said The foregoing experiments illustrate.o that the 4 mol 10 solution with a minor amount of kernite crystals and con hydrate of sodium tetraborate may be prepared directly tinuing the heating until conversion of the: from the 10 mol borax or it can be prepared from the NaBO, •1 OHO 10 mol borax by first going through the 5 mol borax to the tetrahydrate form is substantially complete and stage. - . . . . . 5 the desired synthetic kernite crystallizes out of said solu IV tion. A 300 gram portion of slightly damp 10 mol borax 2. The method of synthetically producing kernite which containing 96.2%. NaBO'10H2O, was heated in a flask comprises preparing an aqueous; solution containing at (without the addition of water) fitted with a stirrer and least 28% by weight of Na2B4O7:10H2O, heating said: a condenser. The temperature was maintained at ap-20 Solution under atmospheric pressure in a temperature. proximately 98 C. The mixture was seeded with a range of from 57.5 C, to about 100°C. until minor amount (0.10 gram) of natural kernite, and heat ing continued while stirring. NaBO'5HO After 24-hours the contents of the flask were examined crystallizes out of solution, seeding the mixture with a and found to consist of a mixture of the 4. and 5 mol. 2 minor amount of NagB4O4H2O, and continuing said. hydrates, and was of a pasty consistency. Heating was heating until the NagBO-5H2Oredissolves and continued until a total of 50 hours had elapsed, when - NaBO'4H.O. the contents of the flask were removed, washed with hot water and isopropyl alcohol, and dried at room tempera crystallizes out of solution. ture. Microscopic (optical) examination, showed the re-. 30 References Cited in the file of this patent covered material to be substantially pure kernite. An UNITED STATES PATENTs. analysis of the recovered material is given below: 2,032,388. Allen ------Mar. 3, 1936 Percent found Theoretical 2,738,254 Suhr ------Mar: 13, 1956 in Sample. 4 mol 35 OTHER REFERENCES 50,84 50.96 "Thorpe's Dictionary of Applied. Chemistry," vol. 2, Na2O. 22.77. 22.68 4th ed., 1938, page 49, Longmans, Green and Co., Ne York, N.Y. Other modes of applying the principle of the invention 40 "Crystallization of Borax," by Donald E. Garrett and may be employed, change being made as regards the Gerhard P. Rosenbaum, Ind; and Eng. Chem, November details described, provided the features stated in any of 1958, vol. 50, No. 11, pages. 1681-1684.