Patented Jan. 12, 1937. 2,067,227

UNITED STATES PATENT OFFICE 2,067,227 METHOD OF PRODUCING CRYSTALLIZED ANYDEROUS SODUMI METAS LICATE Chester L. Baker, Berkeley, Calif., assignor to Philadelphia Quartz Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application November 25, 1933, Serial No. 699,705 3 Claims. (C. 23-110) This invention relates to the production of a large amount in freight and carrying charges. crystalline anhydrous sodium metasilicate and its For instance, sodium metasilicate pentahydrate principal object resides in the provision of a carries approximately 41% of water, all of which method for the production of such material in weight is saved in the anhydrous product. In a form which is easily and quickly dissolved in addition, the anhydrous product, upon solution Water. in Water, gives off heat, whereas the hydrated It is also an object of the invention to pro material absorbs heat. The heat thus liberated vide a method of preparing anhydrous crystal helps to raise the temperature of the Water and, line Sodium metasilicate from an aqueous solu therefore, aids in the solution of the material, tion of the metasilicate. and since Solutions of detergents are often used O A further object of the invention resides in at high temperatures, this fact helps to gain the provision of a method of making various in the temperature desired. timate mixtures of Crystalline anhydrous sodium My present-invention involves the discovery metasilicate with other compatible substances. that if a Solution of Sodium metasilicate be suf The mixtures so produced are so intimate in ficiently evaporated it will become Supersaturat character as to result in distinct advantages ed in respect to anhydrous sodium metasilicate not obtainable by the simple expedient of me at any temperature above 72 C. Which is ap chanically mixing the two ingredients separately proximately the melting temperature of sodium formed. For example, a mixture with caustic metasilicate pentahydrate. More specifically I Soda can be made in accordance with the pres have found that an aqueous solution containing 20 ent invention which is less dangerous to those at least 50% and preferably in the neighborhood using it and is less likely to injure the work of 57% or upwards of sodium metasilicate will which is being cleaned. The intimate mixtures yield crystals of anhydrous sodium metasilicate of the present invention behave in practice quite if heated to temperatures above 72° C. differently from mixtures that are not so inti In carrying out the invention, therefore, I may 25 mate. first prepare a solution of sodium metasilicate Before proceeding with a more detailed de by any convenient method such as, for example, Scription of my invention I should like to point by mixing a solution of commercial Silicate of out that in my United States Patent No. 1898,707 Soda with sufficient caustic Soda so that the re and in my copending United States applications Sulting solution contains silicon dioxide and Sod 30 Serial Nos. 551,785, filed July 18, 1931 and 652 ium oxide in equi-molecular proportions. (It 418, filed January 18, 1933, have disclosed will be understood, of course, that the require various methods for the production of crystalline ments of phase equilibrium permit Some varia hydrates of Sodium metasilicate in acceptable tion from the equi-molecular proportions of sili commercial form. More specifically the above con dioxide and sodium oxide in the Solution, the 35 patent and applications disclose means for pre criterion of the permissible variation being that paring four Crystalline hydrates of Sodium meta the solution yield anhydrous sodium metasilicate silicate, namely, the pentahydrate, Na2SiO3.5H2O; crystals as a stable solid phase.) Such a Solu the hexahydrate, Na2SiO3.6H.O; the octahydrate, tion is then concentrated by evaporation until Na2SiO3.8H2O, and the nonahydrate, it contains preferably 57 or more percent of Sodi um metasilicate, at which point, as stated, it is supersaturated with respect to anhydrous Sodium In addition the anhydrous salt, Na2SiO3, has metasilicate at temperatures above 72 C. At been shown to crystallize in water free silicate this temperature, however, crystals will not read of Soda glasses of suitable chemical composition. ily form spontaneously. Indeed, at any tempera 45 Vitreous glasses of this composition can be made ture under about 100° C. the solution may be by melting silica Sand and SOdin carbonate to held for many hours and sometimes for days gether in equimolecular proportions. Such prod without the formation of any crystals of anhy ucts, however, dissolve in water much more slow drous sodium metasilicate. Furthermore, if Such ly than most crystalline salts and this fact great a solution is subjected to the usual crystallizing 50 ly limits their usefulness. procedure of cooling with or without agitation, The anhydrous character of the material of it will yield hydrated crystals only but never an the present invention permits a greater concen hydrous crystals. It is apparent, therefore, that tration of the active principles than is obtain the methods of crystallaation heretofore adopted able in the hydrated product and, therefore, saves by the art, or such, for example, as are described 2 2,067,227 and claimed in my patent and in my applications as this water is required for the formation of the above referred to will not result in the produc desired Sodium hydroxide monohydrate. The tion of crystalline anhydrous sodium metasili material is then discharged into a soap frame or Cate. - other suitable container. Upon cooling, the ma But in accordance with the present invention, if the solution be heated to a temperature higher terial will transform into a hard brittle cake that 3. than the melting temperature of sodium meta can be ground to a free-flowing stable condition. silicate pentahydrate (i. e., approximately 72 C.) It is also quite possible to use other alkaline and preferably to about 120° C. or slightly higher, salts, soaps or substances of a similar compatible O nature for the purpose of chemically absorbing Small crystals of anhydrous sodium metasilicate a certain proportion of the water in order to re O will rapidly appear in great numbers, as evidenced move it from the solution and permit the forma by the fact that the solution which was at first tion of the ultimate crystallized product. The clear and transparent becomes white and milky result is an integrally crystallized mixture of in appearance. The microscope also may be used 5 markedly improved characteristics. The possi to detect the presence of the crystals. After they ble number of such mixtures is, of course, very 5 are formed the excess Water may be disposed of great, and the conditions for producing them are by combining it with some suitable substance dependent to Some extent upon the individual compatible with the metasilicate, such, for exam-4 peculiarities of the added substance and its possi ple, as sodium carbonate or sodium hydroxide, as 20 ble reaction with the metasilicate. will appear more fully hereinafter. In fact, quite In the examples given above, it is not 20 a number of Substances can be used for this pur necessary to evaporate all of the residual water pose and, indeed, the substances mentioned in because the added substance is capable of taking the examples appearing hereinbelow may be con up or absorbing Water with the formation of an sidered as having the ability to chemically absorb 25 apparently dry product. Sodium hydroxide has the excess water. Incidentally, Substances which been found to be particularly useful in this re 25 are suitable for the purpose are such as will pro spect. Furthermore, I have found that the for duce a solid when combined with water if other mation of crystals is either absent or slight at wise compatible with sodium metasilicate. temperatures in the neighborhood of 90° C. or With the foregoing in mind, I Will now give 30 lower and abundant at 120° C. or higher. the following preferred examples of Suitable The Crystals produced in accordance with my 30 methods for carrying out my invention, although invention are microscopic in size and dissolve I wish it to be distinctly understood that I do quickly in cold Water so that they may be used not wish to be limited to the exact procedure out directly as an alkaline salt. For example, they lined may be added directly to a laundry wash wheel Eacample in uphich sodium carbonate is used to for Washing clothes. 35 absorb the eaccess Doter What I claim is:- 1000 pounds of a solution of silicate of soda 1. The method of making anhydrous crystalline having 8.9% Na2O and 28%. SiO2 is run into a Sodium metasilicate which comprises preparing graining kettle equipped with a steam jacket and a solution of sodium metasilicate containing up Wards of approximately 50% of sodium meta 40 Some Suitable agitating means. 263 pounds of silicate, agitating and heating the solution to a caustic Soda containing 76% Na2O is added and temperature upwards of 90° C. until crystals of dissolved by mixing. Steam is then turned into the jacket of the kettle and agitation continued anhydrous sodium metasilicate appear, and dry s ing the mass by continuing the heat and adding until the mass becomes fairly white and thick. a compatible alkali metal compound capable of 45 300 pounds of anhydrous Sodium carbonate are absorbing excess water to form a solid. then added and mixed in. Upon continued heat ing and agitation the mass crumbles to a fine 2. The method of making anhydrous crystalline white powder comprising an intimate mixture Sodium metasilicate which comprises preparing a of anhydrous sodium carbonate and anhydrous Solution of sodium metasilicate containing up wards of approximately 50% of sodium meta 50 sodium metasilicate crystals. Silicate, agitating and heating the solution to a Eacample in which sodium hydroacide is used to temperature upwards of 90° C. until the mass absorb the eaccess water becomes fairly white and thick, and drying the 400 pounds of silicate of Soda glass containing mass by continuing the heat and adding sodium 23.5% Na2O and 76%, SiO2 is placed in a steam carbonate to absorb excess water. 55 jacketed heavy paste mixer. This material should 3. The method of making anhydrous crystalline be previously ground preferably to pass a sieve sodium metasilicate which comprises preparing a having 200 openings to the inch. 95 pounds of Solution of sodium metasilicate containing up water are then added followed by 500 pounds of wards of approximately 50% of sodium meta caustic soda containing 76% Na2O. The mass is silicate, agitating and heating the solution to a 60 further mixed and heated until it becomes smooth temperature upwards of 90° C. until the mass in consistency, and starts to thicken up slightly. becomes fairly white and thick, and drying the This should require about an hour, and care mass by continuing the heat and adding sodium 65 hydroxide to absorb excess water. should be exercised not to raise the temperature 65 to such a point that Water is lost from the mass, CHESTER L. BAKER.