US3227755A

US3227755A - Quaternary ammonium borohydrides and purification thereof

Info

Publication number: US3227755A
Application number: US254395A
Authority: US
Inventors: Robert W Bragdon; Edward A Sullivan
Original assignee: Metal Hydrides Inc
Current assignee: Metal Hydrides Inc
Priority date: 1963-01-28
Filing date: 1963-01-28
Publication date: 1966-01-04
Anticipated expiration: 1983-01-04

Description

Jan. 4, 1966 R. w. BRAGDON ETAL. 3,227,755

QUATERNARY AMMONIUM BOROHYDRIDES AND PURIFICATION THEREOF Filed Jan. 28, 1963 AYAVA A VV V7( VV vllYl/AVAVAVAVAVAVAVAVA AQYAYAVAVAVAVYAVAVAVA United States Patent O 3,227,755 QUATERNARY AMMONIUM BOROHYDRIDES AND PURIFICATIGN THEREOF Robert W. Bragdon, Marblehead, and Edward A. Sullivan,

Beverly, Mass., assignors to Metal Hydrides Incorporated, Beverly, Mass., a corporation of Massachusetts Filed Jan. 28, 1963, Ser. No. 254,395 20 Claims. (Cl. 260-567.6)

This invention relates to the purification of impure quaternary ammonium borohydrides of the group having a total number ofvcarbon atoms from to 15 inclusive in the organic substituents to the nitrogen atom, such as tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyl trimethyl ammonium borohydride, etc., containing certain impurities in certain amounts. The invention also related to the preparation of such borohydrides in substantially pure form.

The United States patent to Banus, Gibb and Bragdon No. 2,738,369 describes the preparation -of quaternary ammonium borohydrides by reacting a quaternary ammonium hydroxide with sodium -borohydride or potassium borohydride in water, the reaction being illustrated by the equation:

Since both the quaternary ammonium borohydride 'and the alkali metal hydroxide are highly soluble in water, the quaternary ammonium borohydride recovered usually contained a considerable amount of alkali metal hydroxide as an impurity.

We have discovered that, subject to certain limitations, when certain quaternary ammonium borohydrides containing as an impurity one of the salts sodium hydroxide, potassium hydroxide, potassium iluoride, potassium carbonate, potassium citrate, potassium tartirate, sodium carbonate, potassium sulfate or sodium sulfate, are extracted with an amount of water sulcient to dissolve substantially all the impurity but not substantially more than the amount required to dissolve both the impurity and the quaternary ammonium borohydride, a liquor is formed which, when permitted to settle, separates in two separate liquid layers. The upper layer is essentially a saturated aqueous solution of the quaternary ammonium borohydride containing only a small 'amount of the impurity and the lower layer is an aqueous solution of the impurity containing only a small amount of quaternary ammonium borohydride. The upper layer may be separated from the lower layer and substantially pure quaternary ammonium borohydride recovered therefrom by crystallization or by removing the water by evaporation. If too great an amount of water is used the resulting liquor, when permitted to settle, will not separate in two separate liquid layers.

If the amount of water used is not substantially more than that required to dissolve the impurity, the liquor formed is a solution of substantially all the impurity and some of the quaternary ammonium borohydride with a solid residue which is substantially pure quaternary ammonium borohydride. The solution, when permitted to settle, separates in two separate layers. The upper layer is essentially a saturated aqueous solution of the quater- 4nary ammonium borohydride and the lower layer is essentially an aqueous solution of the impurity containing a small amount of the quaternary ammonium borohydride.

The impure quaternary ammonium borohydrides which may be treated by the method of the invention are those having from 5 to 15 carbon atoms inclusive in the organic substituent to the nitrogen atom and in which the impurity is essentially one of the salts previously menice tioned. Illustrative examples of such quaternary ammonium borohydrides are tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyl trimethylammonium borohydride, triethylmethylammonium borohydride, ethylpyridinium borohydride, and methylisoquinolinium borohydride. The method is not operative for treating an impure quaternary ammonium borohydride containing less than a certain amount of the quaternary ammonium borohydride, the amount depending upon the solubility of the quaternary ammonium borohydride treated, the solubility of the impurity, and the temperature used for extraction as indicated more fully hereinafter.

The invention willbe more clearly understood from the following description in conjunction with the accompanying drawings, in which:

FIG. 1 shows two phase diagrams of the ternary systems water-tetraethylammonium borohydride-sodium hydroxide illustrating areas representing liquid compositions within the scope of the invention obtained by extracting solid mixtures of tetraethylammonium borohydride and sodium hydroxide at temperatures of 25 C. and 80 C.; and

FIG. 2 shows a phase diagram of the ternary'system water-tetrapropylammonium borohydride and potassium hydroxide illustrating areas containing liquor compositions within the scope of the invention obtained by extracting solid mixtures of tetrapropylammonium borohydride and potassium hydroxide at a temperture of C.

Referring to FIG. l of the accompanying drawings, the apexes A, B, and C of the large triangle represent percent tetraethylammonium borohydride, 100 percent sodium hydroxide, and 100 percent water respectively, each by weight. Any selected point P on the side AB of the triangle represents the amounts of tetraethylammonium borohydride and sodium hydroxide in percent by weight in a solid impure tetraethylammonium borohydride.

The full line and dotted line diagrams were established empirically by extracting impure borohydrides having varying amounts of sodium hydroxide and tetraethylammonium borohydride with varying amounts of water at 25 C. and 80 C. respectively. The most important phase changes, viz. the rst appearance of two liquid phases and the reversion to a single liquid phase on further dilution, are readily detected visually by the opalescence exhibited by systems containing two liquid phases, when agitated vigorously. Titration with water of a single known mixture of quaternary ammonium borohydride and an alkali metal hydroxide can, then, determine three points on a ternary phase diagram such as those shown in FIG. l: l-the point at which all of the alkali metal hydroxide has been dissolved (irst appearance of two liquid phases), 2-the point at which all of the quaternary ammonium borohydri-de has been dissolved (absence of undissolved solids) and 3-the point at which only a single homogeneous phase is present (disappearance of two liquid phases). From the Weights of the known mixtures and-of the quantities of water required to reach these three points, the ternary compositions of the points can be calculated and plotted. Titration of several known mixtures of divergent composition permits rapid outlining of the ternary phase diagram. Referring to FIG. l, the area bounded by the full straight lines AF, AD, and the full curved line DEF` represents aqueous liquor compositions of tetraethylammonium borohydride and sodium hydroxide obtained by extraction of solid mixtures of the borohydride and hydroxide with wa'ter at a temperature of 25 C. These compositions fall within the scope of the invention; that is, when the solution -is permitted to settle at a temperature of 25 C. it separates in two separate layers, the upper layer being essentially a saturated aqueous solution of the quaternary ammonium borohydride and a small amount of the alkali metal hydroxide and the lower layer being an aqueous solution of the alkali metal hydroxide containing a small amount of borohydride. The remaining areas within the large triangle ABC represent liquid compositions obtained by extraction at 25 C. which fall outside the scope of the invention; that is, when the solutions are permitted to settle only a single liquid layer is formed. The line CI, drawn from the apex C through the point F, intersects the line AB at the point J. The point I represents a solid impure tetraethylammonium borohydride containing about 5 percent by weight of the borohydride and indicates that, when extracting7 impure tetraethylammonium borohydride at 25 C., the method of the invention is not operative if the solid impure tetraethylammonium borohydride contains less than about 5 percent by weight of borohydride.

The area within the full line triangle ADF represents aqueous liquor compositions formed by extracting impure solid tetraethylammonium borohydrides at 25 C. with suicient water to dissolve substantially all the sodium hydroxide but not all the borohydride, the solid residues being substantially pure tetraethylammonium borohydride. If the solution is removed from the solid residue and permitted to settle, two separate liquid layers are formed, the upper layer being essentially a saturated aqueous solution of tetraethylammonium borohydride and a small amount of the alkali metal hydroxide and the lower layer being an aqueous solution of sodium hydroxide containing a small amount of borohydride.

The area bounded by the full straight line DF and the full curved line DEF represents aqueous liquor compositions formed by extracting solid impure tetraethylammonium borohydrides at 25 C. with suicient water to dissolve all the borohydride as well as all the sodium hydr-oxide to form a liquor which, when permitted to settle, separates in two separate layers, the upper layer being essentially a saturated aqueous solution of the borohydride containing a small amount of sodium hydroxide and the lower layer being an aqueous solution of sodium hydroxide containing a small amount of borohydride.

It will be apparent from the above that any impure tetraethylammonium borohydride represented by the point P on the line AB in FIG. 1 may be treated by the method of the invention if a line drawn from the point P to the apex C of the triangle ABC passes through the area bounded by the full straight lines AF, AD, and the full curved line DEF. The line PC in FIG. l intersects the line AF at the point K and intersects the curved line DEF at the point L. Any point on the portion KL of the line PC represents the amounts in percent by weight of tetraethylammonium borohydride, sodium hydroxide and water in a liquor composition which, when permitted to settle at a temperature of 25 C., separates in two separate liquid layers, one of which is essentially a saturated aqueous solution of tetraethylammonium borohydride which is from about 0.001 to about 0.15 molar in sodium hydroxide, the other layer consisting essentially of an aqueous solution of sodium hydroxide.

If the extraction temperature is increased both the size and position of the area representing liquor compositions within the scope of the invention is changed slightly. This is shown by comparing the dotted line diagram in FIG. l with the full line diagram. The area bounded by the dotted straight lines AF', AD', and the dotted curved line DEF represents aqueous liquor compositions obtained by extracting solid mixtures of tetraethylammonium borohydride and sodium hydroxide with water at 80 C. The line CI', drawn from the apex C through the point F', intersects the line AB at the point J'. The point J' represents a solid mixture of sodium hydroxide and tetraethylammonium borohydride containing about 18 percent by weight of the borohydride and indicates that, when extracting impure tetraethylammonium borohydride at C., the method of the invention is not operative if the solid impure borohydride contains less than about 18 percent by weight of borohydride.

Both the size and position of the areas in the diagram of the ternary systems water-quate-mary ammonium borohydride-alkali .metal hydroxide representing liquor compositions within the scope of the invention change with the water solubility -of the quaternary ammonium borohydride and the alkali metal hydroxide impurity. In FIG. 2 of the accompanying drawings, the a-pexes A', B and C' of the large triangle represent 100 percent tetrapropyl ammonium borohydride, percent potassium hydroxide, and 100 percent water respectively, each by weight. The area bounded by the straight lines AF, AD, and the curved line D, E", and F" represents aqueous liquor `compositions of tetrapropylammonium borohydride and potassium hydroxide within the scope of the invention obtained by extraction of solid mixtures of the borohydride and hydroxide with water at 80 C. The line C'J", drawn from the apex C" through the point F", intersects the line AB' at the point J. The point I" represents a solid impure tetrapropylammonum borohydride containing about 36 percent by weight of the borohydride and indicates that, when extracting impure tetrapropylammonium borohydride at 80 C., the method of the invention is not operative if the solid impure tetrapropylammonium borohydride contains less than about 36 percent by weight of borohydride.

It will be understood by those skilled in the art that a triangular phase diagram of any ternary system water, any salt selected from sodium hydroxide, potassium hydroxide, potassium fluoride, potassium carbonate, potassium citrate, potassium tartrate, sodium carbonate, potassium sulfate, and sodium sulfate, which for convenience we designated as splitting agents, and any quaternary ammonium borohydride selected from the group having a total number of carbon atoms from 5 to 15 in the organic substituent to the nitrogen atom may be established empirically in the manner as described in connection with FIG. 1 having a closed area similar to that shown in FIG. 1 representing the contents in percent by weight -of water, the selected salt, and the selected quaternary ammonium borohydride of liquor compositions which, when permitted to settle, separate in two irnmiscible liquid layers, the upper layer of which is essentially a saturated aqueous solution of the selected quaternary ammonium borohydride which is from about 0.001 to about 0.15 molar in the selected salt and the other is essentially an aqueous solution of the selected salt.

When the selected salt in the above mentioned saturated aqueous solutions of quaternary ammonium borohydride is either sodium hydroxide or potassium hydroxide, these aqueous solutions are unexpectedly more stable toward hydrolysis than those of other borohydrides under comparable conditions. At 60 C. a three molar solution of tetraethylammonium borohydride which is 0.12 molar in sodium hydroxide hydrolyzes fourteen times slower than a three molar aqueous solution of sodium borohydride which is 0.12 molar in sodium hydroxide. This significantly higher stability makes such solutions attractive for long term and/or high temperature applications, such as a storable and portable source of hydrogen for remote location fuel cells.

These aqueous solutions of quaternary ammonium borohydrides, particularly the aqueous solutions of tetraethylammonium borohydride, are very useful as nuclear shielding components, maintaining a high concentration of hydrogen atoms per unit volume in a stable, nonammable aqueous system. Being liquid, such solutions uniformly lill complex structural shapes without the danger of void formation. Furthermore, the shield solution can be forcibly circulated to provide heat exchange as well. In these respects such solutions are unique in providing such a combination of properties. bility of the solutions is an added feature.

The present invention also provides a means for purifying quaternary ammonium borohydrides which contain salts other than those designated as splitting agents. For example, sodium metaborate can be separated from a quaternary ammonium borohydride by adding one of the splitting agents t-o the impure borohydride and then extracting the mixture with water. In such case, when the liquor is permitted `to settle, the metaborate will be `found in the aqueous solution of the splitting agent.

The method of the invention may be embodied as a purification procedure in the preparation yof tetraethylammonium borohydride or other quaternary ammonium borohydrides having a total number of carbon atoms from 5 to 15 in the organic substituents to the nitrogen atom. Thus, tetraethylammonium hydroxide may be reacted with sodium borohydride or potassium borohydride in water as illustrated by Equation l above to form an aqueous solution of tetraethylammonium borohydride and the alkali metal hydroxide. The amount yof water in the solution then may be adjusted to produce a liquor having a composition such that, when it is permitted to settle, it separates in two separate liquid layers, the upper layer of which is essentially a saturated aqueous solution of tetraethylammonium borohydride containing a small amount of the alkali metal hydroxide. If desired, sodium borohydride may be used in the above reaction in the form of a stabilized aqueous solution of sodium borohydride and sodium hydroxide. Such a stabilized aqueous solution is described in the patent to Robert W. Bragdon, No. 2,970,114, dated January 31, 1961, and may contain from about 5 to 12.9 percent by weight of sodium borohydride and from about 35 to 46.9 percent by weight of sodium hydroxide based upon the weight of the solution.

Similarly, the invention may be embodied as a puriiication procedure in the preparation of any quaternary ammonium borohydrides having a total number of carbon atoms from 5 to 15 in the organic substituent to the nitrogen atom. Thus, an aqueous solution of the quaternary ammonium borohydride and a salt selected from sodium hydroxide, potassium hyd-roxide, potassium fluoride, potassium carbonate, potassium citrate, potassium tartrate, sodium carbonate, potassium sulfate, or sodium sulfate may be formed in which .the quaternary ammonium borohydride and at least a portion yof the selected salt is obtained by reacting either sodium borohydride or potassium borohydride with an equimolar amount of quaternary ammonium hydroxide, fluoride, carbonate, citrate, tartrate, or sulfate. The amount of water in the solution then may be adjusted to produce a liquor having a composition such that, when permitted to settle, it separates in two separate liquid layers, the upper layer of which is essentially a saturated aqueous solution of the quaternary ammonium borohydride and a small amount of the selected salt and the lower layer is essentially an aqueous solution of the selected salt.

The invention is illustrated further by the following specific examples.

The sta- Exam ple 1 Extraction of 31.2 grams of 67.6 percent pure tetraethylammonium borohydride containing sodium hydroxide as an impurity with 25 ml. of water at 60 C. resulted in complete dissolution of the solids. The resulting liquor, when permitted to settle, separated in two immiscible layers. Crystallization occurred when the upper layer was cooled. Filtration and drying of the crystals resulted in recovery of 6.7 grams of 99.3 percent pure tetraethylammonium borohydride. The yield can be improved by recycling the upper layer to subsequent purication.

Example 2 40 grams of 52.9 percent pure tetraethylammonium borohydride containing potassium hydroxide as an impurity was extracted with 25 ml. of water at 60 C. and the resulting liquor was treated as above described to recover 2.7 grams of 95.7 percent pure tetraethylammonium borohydride.

Example 59 grams of 41.0 percent pure benzyl trimethylammonium borohydride containing sodium hydroxide as an impurity were extracted with 58 ml. of water at 60 C. Thirteen grams of 88.2 percent pure benzyl trimethylammonium borohydride was recovered from the resulting liquor when processed as described in Example 1.

Example 4 44 grams of 38.9 percent pure tetrapropylammonium borohydride containing sodium hydroxide as an impurity were extracted with 32 ml. of water at 60 C., resulting in complete dissolution of the solids. The resulting liquor, when permitted to settle, separated into two immiscible layers. Separation and vacuum drying of the top layer resulted in the recovery of 12.4 grams of 88.9 percent pure tetrapropylammonium borohydride.

Example 5 Addition of 17.7 grams of 99.5 percent pure sodium borohydride (0.467 mole) to 110 grams of an aqueous solution containing 44 percent by weight of tetraethylammonium hydroxide resulted in complete dissolution of the sodium borohydride and the formation of two immiscible layers at room temperature. When the Itop layer was separated and taken to dryness under vacuum, 49 grams of 97.1 percent pure tetraethylammonium borohydride were recovered.

Example 6 Forty pounds of 98.5% pure sodium borohydride (1.04 lb.mole) were .added to 366 pounds of 40.25% aqueous tetraethylammonium hydroxide (1.00 lb.mole) in pilot plant equipment. The mixture was stirred and allowed to settle, whereby two immiscible layers were formed at room temperature, The top layer was separated physically and dried under vacuum at C. A total of 141.5 lbs. of 99.0% pure tetraethylammonium borohydride were recovered, representing a 97.5% yield.

We claim:

1. In a method for purifying a quaternary ammonium borohydride containing as an impurity a salt selected from the group consisting of sodium hydroxide, potassium hydroxide, potassium uoride, potassium carbonate, potassium citrate, potassium tartrate, sodium carbonate, potassium sulfate and sodium sulfate, said borohydride being selected from the group consisting of tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethylammonium fborohydride, triethylmetihylamrnonium borohydride, ethylpyridinium borohydride, and methylisoquinolinium borohydride, said impure quaternary ammonium borohydride containing substantial amounts of said impurity and quaternary ammonium borohydride, the step comprising extracting the solid impure quaternary ammonium borohydride with -an amount of Water to form two immiscible layers, one of which is essentially an aqueous solution of the quaternary ammonium borohydride and the other is essentially `an aqueous solution of said salt.

2. The method as claimed by claim 1 wherein the selected quaternary ammonium borohydride is tatraethylammonium borohydride.

3. The method as `claimed by claim 1 wherein the selected quaternary ammonium borohydride is tetrapropylammonium borohydride.

4. The method as claimed by claim 1 wherein the selected quaternary ammonium borohydride is benzyltrimethylammonium borohydride.

5. In a method for preparing a quaternary ammonium borohydride selected from the group consisting of tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethylammonium borohydride, triethylmethylammonium borohydride, ethylpyridinium borohydride, and methylisoquinolinium borohydride, the steps which comprise forming an aqueous solution of sodium hydroxide and the quaternary ammonium borohydride in which the quaternary ammonium borohydride and at least a portion of the sodium hydroxide is obtained by treacting sodium borohydride with substantially an equimolar amount of a quaternary ammonium hydroxide, adjusting the amount of Water in said solution such that two immiscible layers are formed, one of which is essentially an aqueous solution of the quaternary ammonium borohydride and the other is essentially an aqueous solution of sodium hydroxide.

6. The method as claimed by claim wherein the selected quaternary ammonium borohydride is tetraethylammonium borohydride.

7. The method as claimed by claim 5 wherein the selected quaternary ammonium borohydride is tetrapropylammonium borohydride.

8. The method as claimed by claim 5 wherein the selected quaternary ammonium borohydride is benbyltrimethylammonium borohydride.

9. In a method for preparing a quaternary ammonium borohydride selected from the group consisting of tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethylammonium borohydride, ethylpyridinium borohydride, and methylisoquinolinium borohydride, the steps which comprise forming an aqueous solution of the quaternary ammonium borohydride and a salt selected from the group consisting7 of sodium hydroxide, potassium hydroxide, potassium uoride, potassium carbonaite, potassium sulfate, potassium citrate, potassium tartrate, sodium carbonate, and sodium sulfate in which at least a portion of said salt is obtained by reacting an alkali metal borohydride selected from the group consisting of sodium borohydride and potassium borohydride with a substantially equimolar amount of a quaternary ammonium salt, adjusting the amount of water in said solution such that two immiscible layers are formed, one of which is essentially an aqueous solution of the quaternary ammonium borohydride and the other is essentially an aqueous solution of said salt.

10. The method as claimed by claim 9 wherein the selected quaternary ammonium borohydride is tetraethylammonium borohydride.

11. The method as claimed by claim 9 wherein the selected quaternary ammonium borohydride is tetrapropylammonium borohydride.

12. The method as claimed by claim 9 wherein the selected quaternary ammonium borohydride is benzyltrimethylammonium borohydride.

l13. The method as claimed by claim 9 wherein said 8 selected alkali metal borohydride is sodium borohydride and said selected salt sodium hydroxide.

14. The method as claimed by claim 9 wherein said selected alkali metal borohydride is sodium borohydride and said selected salt is sodium carbonate.

15. The method as claimed by claim 9 wherein said selected alkali metal borohydride is sodium borohydride and said selected salt is sodium sulfate.

16. In a method for purifying an impure tetraethylammonium borohydride containing sodium hydroxide as an impurity in an amount not exceeding about percent by weight which comprises extracting the impure borohydride with an amount of water at a temperature of about 25 C. to form a liquor in which the amounts of tetraethylammonium borohydride, sodium hydroxide and water in percent by weight based upon the weight of the liquor are represented by a point within the area AFEDA shown in FIGURE l, and permitting the solution portion of said liquor to settle at a temperature of about 25 C. thereby forming two separate immiscible layers, one of which consists essentially of an aqueous solution of tetraethylammonium borohydride and the other consists essentially of an aqueous solution of sodium hydroxide.

17. As a composition of matter an aqueous solution consisting of a quaternary ammonium borohydride selected from the group consisting of tetraethylammonium borohydride, tetrapropylammonium borohydride, benzyltrimethylammonium borohydride, triethylmethylammonium borohydride, ethylpyridinium borohydride, and methylisoquinolinium borohydride and a salt selected from the group consisting of sodium hydroxide, potassium hydroxide, potassium uoride, potassium carbonate, potassium citrate, potassium tartrate, sodium carbonate, potassium sulfate and sodium sulfate and having two immiscible layers, one of which is essentially an aqueous solution of the quaternary ammonium borohydride and the other is essentially an aqueous solution of said salt.

18. A composition of matter as claimed by claim 16 wherein the selected quaternary ammonium borohydride is tetraethylammonium borohydride.

19. A composition of matter as claimed by claim 16 wherein the selected quaternary ammonium borohydride is benzyltrimethylammonium borohydride.

20. A composition of matter as claimed by claim 16 wherein the selected quaternary ammonium borohydride is tetrapropylammonium borohydride.

OTHER REFERENCES Bonus et al.: I.A.C.S., Vol. 74, pp. 2346e2348 (1955).

CHARLES B. PARKER, Primary Examiner.

FLOYD D. HIGEL, Assistant Examiner.

Claims

1. IN A METHOD FOR PURIFYING A QUATERNARY AMMONIUM BOROHYDRIDE CONTAINING AS AN IMPURITY A SALT SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE, POTASSIUM HYDROXIDE, POTASSIUM FLUORIDE, POTASSIUM CARBONATE, POTASSIUM CITRATE, POTASSIUM TARTRATE, SODIUM CARBONATE, POTASSIUM SULFATE AND SODIUM SULFATE, SAID BOROHYDRIDE BEING SELECTED FROM THE GROUP CONSISTING OF TETRAETHYLAMMONIUM BOROHYDRIDE, TETRAPROPYLAMMONIUM BOROHYDRIDE, BENZYLTRIMETHYLAMMONIUM BOROHYDRIDE, TRIETHYLMETHYLAMMONIUM BOROHYDRIDE, ETHYLPYRIDINIUM BOROHYDRIDE, AND METHYLISOQUINOLINIUM BOROHYDRIDE, SAID IMPURE QUATERNARY AMMONIUM BOROHYDRIDE CONTAINING SUBSTANTIAL AMOUNTS OF SAID IMPURITY AND QUATERNARY AMMONIUM BOROHYDRIDE, THE STEP COMPRISING EXTRACTING THE SOLID IMPURE QUATERNARY AMMONIUM BOROHYDRIDE WITH AN AMOUNT OF WATER TO FORM TWO IMMISCIBLE LAYERS, ONE OF WHICH IS ESSENTIALLY AN AQUEOUS SOLUTION OF THE QUATERNARY AMMONIUM BOROHYDRIDE AND THE OTHER IS ESSENTIALLY AN AQUEOUS SOLUTION OF SAID SALT.

17. AS A COMPOSITION OF MATTER AN AQUEOUS SOLUTION CONSISTING OF A QUATERNARY AMMONIUM BOROHYDRIDE SELECTED FROM THE GROUP CONSISTING OF TETRAETHYLAMMONIUM BOROHYDRIDE, TETRAPROPYLAMMONIUM BOROHYDRIDE, BENZYLTRIMETHYLAMMONIUM BOROHYDRIDE, TRIETHYLMETHYLAMMONIUM BOROHYDRIDE, ETHYLPYRIDINIUM BOROHYDRIDE, AND METHYLISOQUINOLINIUM BOROHYDRIDE AND A SALT SELECTED FROM THE GROUP CONSISTING OF SODIUM HYDROXIDE, POTASSIUM HYDROXIDE, POTASSIUM FLUORIDE, POTASSIUM CARBONATE, POTASSIUM CITRATE, POTASSIUM TARATRATE, SODIUM CARBONATE, POTASSIUM SULFATE AND SODIUM SULFATE AND HAVING TWO IMMISCIBLE LAYERS, ONE OF WHICH IS ESSENTIALLY AN AQUEOUS SOLUTION OF THE QUATERNARY AMMONIUM BOROHYDRIDE AND THE OTHER IS ESSENTIALLY IN AQUEOUS SOLUTION OF SAID SALT.