SOME QUATERNARY AMMONIUM SILICATES
187
effect obtained with the derivatives of ethylamine is not due to the size or shape of the inhibiting substance, but can be explained on the basis of those factors that are altered in such manner as to enhance adsorbability. REFERENCES (1) ARDAGH, G. E., ROOME,R. M. B., AND OWENS,H. H.: Ind. Eng. Chem. 26,1116 (1933). R.: Compt. rend. 176, 838 (1923). (2) AUDUBERT, E. L., ROETHELI,B. E., AND MCCARTHY, B. Y.: Ind. Eng. Chem. 20, 582 (3) CHAPPELL, (1928). (4) CHIAO,SHIH-JEN, A N D MANX,C. A , : Ind. Eng. Chem. 39,910 (1947). (5) FORREST, H . O., ROBERTS,J. K . , A N D ROETHELI,B. E . : Ind. Eng. Chem. 20, 1369 (1928). G . : Organic Chemislrv, 2nd edition, Vol. I, p. 375. John Wiley and Sons, Inc., (6) GILMAN, New York (1942). (7) GLASSTONE, S.: Tezlbook of Physical Chemislry, p. 375. D . Van Nostrand Company, Inc., New York (1940). (8) ISGARISHEW, N . , AND BERKMAN, S.: Z. Elektrochem. 28, 49 (1922). (9) JENCKEL, E . J., AND BRAWKER, E . : 2.anorg. allgem. Chem. 221,249 (1934). (10) JIMENO, E., GRIFOLL,I., AND MORRAL, F. R.: Trans. Electrochem. SOC.69, 105 (1938). (11) LEJEUNE,G . : Compt. rend. 199, 1396 (1934). (12) MA", C. A , : Trans. Electrochem. SOC.69, 115 (1936). (13) MANN,C . A., LAUER,B. E., AND HULTIN,C. T.: Ind. Eng. Chem. 28, 159 (1936). (14) Reference 13, p. 1049. (15) MUNGER,H. P . : Trans. Electrochem. SOC.69, 85 (1936). (16) PRIAK,H., A N D WENZEL,W.: Korrosion u. Metallschuts 10, 29 (1934). F. H . , AND KUHN,W. E . : Ind. Eng. Chem. 21.1066 (1929). (17) RHODES, I?. L.: Chem. & M e t . Eng. 34,421 (1917). (18) SPELLER,F. N., AND CHAPPELL, A , , AND KAYSER,C.: Z . physik. Chem. 170A, 407 (1934). (19) THIEL, (20) WARNER, J. C . : Trans. Electrochem. SOC.66, 287 (1929).
SOME QUATERNARY AMMONIUM SILICATES REYKOLD C. MERRILL
AND
ROBERT W. SPENCER
Philadelphia Quartz Company, Philadelphia, Pennsulvania Received January 9, 1960
Various forms of silica dissolve in strong organic bases, such as the quaternary ammonium hydroxides and more alkaline amines, and from at least some of these solutions crystalline quaternary ammonium silicates can be obtained (3). This paper reports the amounts of silica dissolved in some organic bases under specific conditions and records the preparation of several new crystalline quaternary ammonium silicates not previously reported in the literature. EXPERIMENTAL
Materials Most of the work was done with a micronized silica gel containing 90.2 per cent SiOr, 9.4 per cent K O , plus a total of 0.4 per cent impurities not volatilized
188
I t l i Y S O L D C . XERRILL AND .ROBERT \V, SPEXCEIt
hy hydrofluoric acid. l’hc hases include 20.4 per cent (1.33 JY) phenyltrimethylammonium hydrosidc (sp. gr. 1.0393 a t 20°C., Monsanto Chemical Company), 30.8 per cent (2.38 .Y)benzyltrimethylammonium hydroxide (Rohm and Haas), 48.7 per cent (2.26 J - j methanolic tetraethanolnmmonium hydroside (Carbide and Carbon Chemicals Corporation), 10 per cent t,etramethyl- and tetraethylammonium hydrosides (Eastman Iiodalc Company), and guanidine carbonate (American Cyanamid Corporation). Guanidine solutions mere made hy dissolving guanidine rnrhonate in wat,er and adding sufficient calcium hydroxide slurry to precipit,at,eall of the carbonate. Since quaternary ammonium hydroxides decompose at eierated t,empcratwes,the most, concentrated solutions \\-ere made by cJraporation undcr vacuum a t 40°C.
Jlethods Analyses for the amouiit of R20,where R is the basic radical such as sodium or tr.1 ~:~mct,hylammouium, v-ere made by direct titration with standardized hydrochloric acid to either the methyl red endpoint or that shown by electrometric titratmion. Bilic:i \vas determined grai.imetrically and the amount of water ol)t.nined by difference. SOLVTIOK O F SILICA IX ORGANIC B.\SF,S
l’rcliriiinary esperiments slio\\-edt,hat the amounts of 28- to 100-mesh Wedron quart ir, band dissolved h y quatenlary ammonium hydroxides were comparable to those dissolved by sodium and potassium hydroxides of equivalent normalities. IIo\rcver, iri no cnsc was t,he amount of silica dissolved from the quartz sand a t ort1in:ii-y temperatures great,cr than 0.1 per cent. Amounts of silica dissolved by : L ( ~ I I C ~ UI)asea S after revolving 2 moles of silica gel per mole of base on a ball mill for 48 hr. at r6om temperature (-25°C.) are summarized in table 1. Quaternary : ~ m n i o n i u mhydrosides dissolve about, as much silica gel as do sodium or potassium hydroxides at equivalent concentrations. Guanidine dissolves less than O W t,hird as much silica as the other bases. Except for the results with benzyltrinict~hylammoniumhydroxide, the dissolved silica increases with concentration. ‘rhe a,mount of silica dissolved by various organic amines at room temperature mid ;Itl their boiling points increases with their basicity from 0.1 to 1.5 per cent for tlietlianolaminc, triethanolamine, ethylenediamine, diethylenetriamine, aminoethylethanolamirie, di-n-butylamine, cyclohexylamine, octylamine, and morpholine. Less t,han 0.1 per cent silica was dissolved a t room temperature by monoct,hanolamine, propylenediamine, t,riethylamine, triet,hylenetctramine, I)iit,ylsmine,and di-n-butylamine. The amounts of silica dissolved are not always grc:tter ut elevated temperatures. Aisolution of 1.89 per cent silica in a 1.80 N solution of benzyltrimethylamnionium hydroxide in methanol was made by rotating on a ball mill a t room tempctxtiire for 48 hi. an ~ S C C S Sof anhydrous silica gel with the methanol solution of the h s e .
189
SOME QUATERNARY .kMMONIUM SILICATES CRYSTALLINE QUATERNARY .IMivIObXJM SILICATES
Tetramethylammonium silicate
A solution containing 7.91 per cent silica in I.G3 N tetramethylammonium hydroxide w&s further concentrated by evaporation under vacuum a t 40°C. and then placed in an ice box. After two recrystallizations from hot water and drying to constant weight in a vacuum desiccator, the fine white crystals which formed contained 39.81 per cent tetramethylnmmonium hydroxide and 26.38 TABLE 1 Solution of micronized silica gel in aqueous bases ajter 48 hr. at 26%".
~
NaOH.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
~
KOH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NHiOH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C sHs (CHj)3NOH. . . . . . . . . . . . . . . . . . . . . . . . . CaHsCHz(CHj)aNOH., . . . . . . . . . . . . . . . . . .i .
i
H ~ N C ( = N H ) N H .~. . . . . . . . . . . . . . . . . . . . . .
I
(CHs)dNOH . . . . . . . . . . . . . . . . . . . . . . . . . . . . (C2Hs)rNOH.. . . . . . . . . . . . . . . . . . . . . . . . . . (CsHsOH)rNOH, . . . . . . . . . . . . . . . . . . . . . . . .
* Average
l
.I ~
2.36 1.28 2.40 1.27 2.38 1.33 2.02 2.27 2.3s 3.11 3.39 2.39 2.76 1.11 1.63 0.76 1.46 1.33 2.26 2.63
i I
1
,
I ~
~
,
I
I
per ccn1
>20 1' >20 14 0.3 7.9* 12 13 6.2"
4.1 2.5 1 2 2.3 8.4* 7.9 6.2*
>s. 10 18
I
>21
of two to four determinations
per cent silica, corresponding to the composition 1.00IiOH :1.OOSiO,: 4.30HD. After a short exposure to air these crystals contained G.34 moles of water. After two recrystallizations and drying, the composition of crystals obtained from a solution of 7.8 per cent silica in 1.11 N tetramethylammonium hydroxide \vas 1.00ROH: 1.09SiO2:4.67H2O.
Tetraethylammonium silicate Crystals were also obtained on cooling a solution originally containing 5.76 per cent silica in 0.76 N tetraethylammonium hydroxide which had been further concentrated under vacuum at 4OoC. Sufficient crystals were not obtained to establish their identity by analysis.
190
REYNOLD C. MERRILL AND ROBERT W. SPENCER
Phenyltrimethylammonium silicates After two recrystallizations from hot water and drying, crystals obtained by concentrating a solution of 13.5 per cent silica in 2.27 N phenyltrimethylammonium hydroxide had the composition 1.00ROH: 1.03Si0~:3.37H20.The composition of another batch from a solution of 7.15 per cent silica in 2.4 N base after two recrystallizations was 1.00ROH:0.98Si02:5.12H20. These crystals melted at 53°C. and had a specific gravity of 1.300. On cooling a solution of 15.9 per cent silica in 2.3 N base crystals were formed which after two recrystallizations and drying analyzed 1.00ROH: 1.43sio2: 5.80H20. Two recrystallizations of a product from a solution of 12.8 per cent silica in 2 N base gave crystals of a composition corresponding to 1.00ROH: 1.32Si02:2.63H20. A third recrystallization gave 1.00ROH: 1.38Si02:2.8TH20. These data suggest the existence of a phenyltrimethylammonium trisilicate with 1.00 ROH to 1.50 SiO2, although the number of molecules of water of hydration TABLE 2 Wel-residue determinations for benzyltrimelhylammonizrm silicates
I
WET CRYSTALS
ROH pn rmt
40.94 68.30 47.15 37.81
I
SiOs
I
SUPEBNAIANI LIQUID
ROH
1
’
I
I
,
I
3.66
8.53 11.97
I
,
I
59.34 46.56 28.64
I
Si09
pn c e l l
4.13 1.72
;:;
is uncertain and the products obtained were contaminated, probably with the disilicate or acid metasilicate. The solubility of the organic silicates a t 0°C. corresponds to about 15 per cent silica in 1.6 N phenyltrimethylammonium hydroxide, 9 per cent silica in 1.9 N base, and 4.5 per cent silica in 2.8 N base.
Benzyltrimethylammonium silicate A solution of 7.66 per cent silica in 2.38 N benzyltrimethylammonium hydroxide formed crystals on cooling. After two recrystallizations and drying in a vacuum desiccator these had the composition l.OOROH:0.96SiO~:6.16H20. The composition of crystals from another solution originally containing 7.66 per cent silica in 2.7 N base corresponded to 1.00ROH:0.94Si02:3.85H20. Schreinemakers’ wet-residue method was used to determine the composition of the bensyltrimethylammonium silicate separating at 0°C. from the results given in table 2. Algebraic solutions for the intersections of straight lines connecting the compositions of the wet crystals with those of the corresponding supernatant liquid gave an average value for the point of intersection of all the lines of 46.9 per cent beneyltrimethylammonium hydroxide and 17.8 per cent silica. This is in better agreement with the theoretical values of 47.2 per cent beneyl-
SOME QUATERNARY AMMONIUM SILICATES
191
trimethylammonium hydroxide and 17.9 per cent silica for benzyltrimethylammonium disilicate with 13 molecules of water of crystallization than with the theoretical values of 47.3 per cent ROH and li.0 per cent SiO, for the benzyltrimethylammonium acid metasilicate, RHSi03.7H20.
Tetraethanolarnrnonium silicate A crystalline product was obtained by cooling a solution of 17.9 per cent silica in 2.26 N aqueous methanolic tetraethanolammonium hydroxide. After two recrystallizations and drying, h e white crystals were obtained which were either monoclinic or triclinic. They occurred in thin rhombic plates and had a strong cleavage parallel to the flat side of the plate or else a marked tabular growth. The plates show the emergence of an optic axis but not of a bisectrix, so its sign could not be determined. Refractive indices of the plates were a = 1,501,p = 1.515, and y = 1.524. The product also contained an opaque brownish material whose refractive index could not be measured. The crystals had a density of 1.578 g./ml. at, 23°C. and softened a t 80-82'C. They were soluble in water but insoluble in alcohol, acetone, ether, benzene, and carbon tetrachloride. The crystals contained 31.6 per cent silica and required 4.31 milliequiv. of hydrochloric acid per gram of organic silicate to reach the titration endpoint at pH 4.5. This is equivalent to 91.4 per cent tetraethanolammonium hydroxide, which with the 31.6 per cent silica gives 123 per cent, an obvious impossibility. A second lot of crystals from a solution of silica in tetraethanolammonium hydroxide after two recrystallizations contained 30.0 per cent silica and required 4.51 milliequiv. of hydrochloric acid per gram to reach the endpoint. This corresponds to 95.4 per cent tetraethanolammonium hydroxide, a result which again is obviously impossible. It s e e m to us possible that the crystalline product obtained was a mixture of tetraethanol- and tetramethanolammonium silicates and perhaps also bases formed by decomposition of the quaternary ammonium hydroxide. Electrometric titrations indicted that they were mainly salts of a monobasic acid but contained some salts of a dibasic acid as an impurity. If the cation is assumed to be tetramethanolammonium, the analyses correspond to 1.00ROH: 1.22Si02: 0.20H20 and 1.00ROH: l.llSiO2:O.OHzO. Guanidine silicates After concentration of a solution containing 3.72 per cent silica in 8.53 per cent guanidine until it contained about 5 per cent silica, fine white crystals were formed in it while standing for several months in an ice box. These were filtered on a sintered-glass filter, washed twelve times with water, and dried to constant weight at 105°C. The crystals were practically insoluble in water at ordinary temperatures and in methyl and ethyl alcohols, acetone, benzene, and carbon tetrachloride,The solubility in water at the boiling point was 0.7 g./lOO ml. and the solutions remained supersaturated on cooling to room temperature sufficiently long so that they could be analyzed. The dissolved crystah corresponded to the composition 1.OOROH :1.O6SiO1:0.14H20. A second and third batch of
192
REYNOLD C. MERRILL .4ND ROBERT W. SPENCER
crystals had compositions of 1.OOROH: l.04Si02:0.13H20 and 1.00ROH: 1.03si02: 0.30H20. I
FIG. 1 . Electrometric titration of (A) 1.DO(CHs),NOH:1.00Si02:6.34H20 and (B) 1.00C sH ~ ( C H J3NOH ) :1.03SiO~: 3.37Hz0.
FIG.2. Electrometric titration of (A) 1.00C(NHz)rOH:1.03Si0~:0.30Hz0, (B) l.OOCsHsCHz(CH~)3NOH:0.96SiO~:6.16Hz0, nnd (C)1.00CsH~(CHs)sNOH:0.98SiOz:5.1ZH~0.
Electrometric titrations Since analyses of most of the crystals obtained agreed about equally well with formulas for acid metasilicates, RHSi03.zH20,as with those for disilicates, RzSi20,.yHzO, or an acid orthosilicate, RH&3iOa.(x - 1)H20, electrometric tilrations were made to distinguish more closely among the various possibilities for the formulas of these compounds. These titrations were made a; room tem-
perature (- 25"C.), using a Beclrman pH meter \vit,li special elcctrotlw for :11kaline solutions and weight burets. Usually about, 0.5 g. of the organic silicate was dissolved in 50 mf. of water and titrated ivith 2 S hydrocliloric acitl. Electromet,ric titrations (e.g., figures 1 antl 2) indicate tlint the tetlnmethylnmmonium, benzyltrimetliylummoniuin, antl guanidine silicates are predominantly salt,
