US1991410A - Process for crystallizing borax from solutions - Google Patents

Description

Patented Feb. .19, 1935 moms roa CRYSTAIJJIZ-I NGaBORAXI FROM SOLUTIONS r (Alfred Newman, Long Beach," Calif; assignor' 'to Pacific Coast Borax Company, a corporation-of Nevada J "No Drawing. Application lulyl30, 1932, I f

. d :lSerialNo. 627,133 y 6 Claims. (eras- 59) :Thisinvention has to do ina general way with the art of crystallizatiomiand is more particu-j larly related to the production of borax crystals from agitated aqueous solutions of borax. v

--Itis well known to those familiar with the art, that if any aqueous solution of borax, which, by way of illustration, may contain 20 to 30% crystal vborax in solution, is placed in a tank and is agitated in any suitable manner and rapidly cooled by any suitable means, 'suchas-contact with ,pipe coils through which a refrigerant, cooler than the borax liquid, is flowing, or by. rapidly evaporating the water from the borax solution in aso-called vacuum cooler, the borax crystals which precipitate from the solution are chiefly aggregates of small crystals, the individual particles having no definite form or shape.v For convenience-I define such crystals as type one. [Beingof irregular shape the crystals readily cohere-and upon packing the mass-of crystals often becomes (compact {and hard and thus as commonly defined becomes caked. Although borax crystals formed-in this'way arej -adapted for many uses it has been found advantageous for some purposes to form acrystalline borax, the

individual ,3 particles of which are of definite crystalform'with distinct, crystal faces characteristicofborax or NazBiOmlOHzO. For convenience Idefine such crystals as type two. I Such crystals, on account of their definite crystal form and distinct'crystal faces, do not cohere or cake tothe same degree as crystals of type one.

The trade having cometo demand larger crystals it'has been founddesirable to produce by rapid cooling crystalline borax" of a size larger than type one. Ithas been foundthat the typeone-crystals hitherto produced-by rapid cooling have approximately the following meshz- ,Tyler' Cumulative Tyler Cumulativemesh ,7 percent 'mesh percent 14 0.30 v 149.27 20 3.53 86179 28 30i83 -l50 I 91.52 35 57.15 200 94.82; 48 70. 40 200 '100. 00

By the process herein described it hasbeen found possible to produce crystals of type two having the following mesh:

yl r T ler' Cumulative y Cumul t standar a We mesh percent gh pfrcent The'productionof boraxgcrystals of type two has hitherto been .caccom'plished, first by very slow. cooling .of the ,borax solution, and second,

by adding a small amountof soap, fatty acid, or

other emulsion colloidflof similar nature tothe hot boraxsolution.eitherprior to. or during the step of rapid cooling and agitation. V i Thejprocess of slow cooling obviously has marked disadvantages in the commercial process,

since the time, from 6 to 7 days and equipment required for the production ofl-a given amount of this typeiof borax is muchgreater than that which is necessary in a process ,that. canbe car- The use of soap, fattywa'cid, or other emulsion colloids v often results. in :aquantityrof the agent beingentrained 'or entangled in the borax crystal, This quantity is suflicient to yield adiscolored-glass when the 'borax is fused, .and'when the borax is placed in warm water and the mixture ried out by rapid cooling,:say frame to. 5 hours. a

shaken the quantity is sufficient to produce a foam onlather similar; tothat'whensoap isadded to warm; water. I l It,-is a primary :object'of my invention to.-produceborax crystals of -typetwoaand at thesame time vto avoid the. undesirable results noted above I- have discoveredthat thegobj ectcontemplated by my invention can be attainedsimply by seeding a hot }b orax solution with a suitable quantity of borax crystals formed by the process of-slow cooling anotherhot .borax solution. L It is preferable that the borax'usedfas] seed crystals be deposited from solution without agitation; Byslowcoohng. Ikrefertothe type of process first enumerated above in which the hot boraxsolution is -cooled merely by radiationtothe atmosphereover .a

substantial periodof time. Aspointed out above,- the: borax crystals .formed by -such a cooling process areof well defined crystallineform and shape and I have'discovered that they have the peculiar property, whenadded as seed" crystals to another hot borax solution, of causing-the crystalsiformed from the latter-solution'to also be of wellidefined'crystal formsand shape with distinct crystalfaces. This property; seems to be -peculiar tothecrystalsformedbythe slow cooling process,

and the. '15 act is of particular ,value; in'that'the seeded solution can be rapidly,;cooled;-;and;gagitated during crystallization without in any way interfering with the formation of the individual crystals. I

The following example is given for the purpose of more clearly illustrating the process contemplated bymy invention. First, four thousand gallons, of hot aqueous solution of borax containing, say thirty, per cent crystal borax, placed in a tank and allowed to cool by radiation of heat into the atmosphere for a period of six days. This time may be greater or less within certain limits without in any way affecting the results of the process. The crystal borax'thus formed is separated from the liquor and the crystals are crushed to a suitable size for use as seeds. I have found that the best results are obtained if the seed crystals are larger than what will pass a sixty-five mesh Tyler standard screen, or a screen having an opening of .0082 inch.

After a suitable quantity of these seed crystals has been prepared, in the manner described.

above, another suitable quantity, say four thousand gallons of hot aqueous solution of borax of approximately 185 F., containing, say twentyeight per cent crystal borax, is placed in a tank, agitated, and rapidly cooled in any suitable manner until a temperature of substantially 135 F.-

' limits by controlling the time over which the agitation and cooling takesplace. 7 It has been found that proceeding in the above described manner crystals of the aforementioned characteristics are produced. 7

I have found that the mother liquor can be removed much more easily from crystals formed in the process contemplated by this invention than from the aggregation type of crystals 'ordinarily produced by rapid cooling a hot borax solution. 3 As a further advantage of producing larger size crystals, a given weight of the material when packed for shipment, occupies a volume of approximately eighty percent the volume occupied by the same weight of borax of the aggregation crystal type. My process, therefore, has the advantage of reducing the cost of production, (as

compared with borax produced by the slow cooling;process) reducing the cost of packing T and shipping, (as compared'with the aggregate type of crystal) and supplying to the trade crystals ofborax which do not readily cake, and of a size suitably larger;

It will be noted from the foregoingdescription that 'Ihave used four thousand gallons as the quantity of solution from-which the seed crystals are prepared and have also, referred-to four thousand gallons" asthe quantity of solution which is rapidly cooled. It is to be understood of course that the quantity of seed 'ory'stals' added to the second solution is a comparatively. small percentage of the total quantity of seed crystals produced during the slow cooling step. It is to' be understoodthat the term concen-' tratedsolution as used herein has reference to a borax solution'of a temperature'andtconcentration suitable for seeding without dissolving the seed crystals. 1

It is to be understood that, while I have herein referred to one preferred method of practicing this process, the invention is not limited by the precise terms of the foregoing description but includes within its scope whatever changes fairly come within the spirit of the appended claims. I claim as my invention:

1. A process of crystallizing borax of definite crystal form and with distinct crystal faces from aqueous solution which comprises slow cooling a hot aqueous solution of borax to crystallize borax therefrom; pulverizing and screening borax crystals thus obtained to a fineness such that it will be retained on a screen of .00082 inch opening; seeding a second hot concentrated solution with the pulverized crystals; and rapidly cooling the second solution.

2. A process of crystallizing borax of definite crystal form and with distinct crystal faces from aqueous solution which comprises slow cooling a hot aqueous solution of borax to crystallize borax therefrom; pulverizing and screening the borax crystals thus obtained to' a fineness such that it will be retained on a screen of .0082 inch opening; seeding a second hot concentrated solutionwith the pulverized crystals; and rapidly cooling the'second solution with agitation.

3. A process of crystalliz'ing borax of definite form with distinct crysta'lfaces from a concentrated'a'queous solution which comprises rapidly cooling said solution and seeding the same with borax crystals obtained by slow cooling another borax solution, said seed crystals being of a size such that they will be retained on a screen having an opening 'of .0082 inch. 7

4. A processof crystallizing' borax of definite crystal form withdis'tinct "crystal faces from a concentrated aqueous solution which comprises rapidly cooling said solution and seeding the same with borax crystals obtained by slow cooling another borax solution, said seed crystals being of a size-such that they will produce particles of well defined crystalline form and shape.

5'. A process of crystallizing borax of definite form with distinct crystal faces from a concentrated aqueous solution which comprises rapidly cooling and agitating said solution and seeding the same with boraxcrystals obtainedby slow cooling another borax solution, said seed crystals being of a size such thatthey will be retained on a'screen having an opening of .0982 inch.

'6. A process of crystallizing borax of definite crystal'form with distinct crystal faces from a concentrated aqueous solution which comprises rapidly cooling and agaitating said solution and seeding the same with borax crystals obtained by slow cooling another borax solution, said seed crystals being of a size such that they will produce particles of well defined crystalline form and shape. I

' ALFRED NEWMAN.