ALKYL ESTERS OF PHOSPHORIC ACID CARROLL A. HOCHWALT, J. €LUM, I. AND J. E. MALOWAN Central Research Department, Monsanto Chemical Company, Dayton, Ohio
C. P. DYER Merrimac Division. Mollaanta Chemical Company, Everett, Maas.
The properties and applicatione of alkyl esters of. phosphorie acid are discussed. From a commercial standpoint the esters of greatest interest are mixtures of monoalkyl and dialkyl hydrogen phosphates. In these acid esters hydrogen is replaced by various basic groups including sodium, potassium, ammonia, and amines. Data are presented on sueh physical properties as solubility, freezing point, specific gravity, viscosity, and conductance of solutions. Chemical properties inrlude stability t o hydrolysis and corrosiveness to metals. The outstanding property of mixed lower alkyl phosphates is their high solubility in water. Their water solutions exhibit low
IN RECENT years a number of new aliphatic estem of phosphoric acid have been introduced. The stimulus for the development of these new compounds has come in part from the in& production of elemental phosphorus which has led to larger output at lower prices of such compounds as phosphorua oxychloride and phosphorus pentoxide; them are eaeantial magenta for the production of esters. The eaters of orthophosphoric acid may he represented by the type formulas: (tertiary ester) (RO) \
(RO)/
/OH
\ 0
(secondary ester)
freezing points, good humectancy, high conductivity, and good stability. Furthermore, they are not particularly corrosive. The properties of concentrated water solutions of several of the alkyl phosphates are of advantage for certain industrial applications. Several esters are antistatic agents in the spinning of textile fihers. Ammonium alkyl phosphates are useful in flameproofing cloth and paper. They possess an advantage over inorganic phosphates as flameproofing agents in that they can be exposed to lower relative humidities without crystallization. Other possible applications for the alkyl phosphates are indicated.
~tmdantefor plastics, particularly for the cellulom eaters. Triphenyl phosphate is also an important article of commerce. It occurs in the form of white Wes and is used in the fireproosng and stabilizing of cellulose esters and as an additive to lubricants. Newer tertiary eaters are the trimethyl and triethyl phosphates which are colorless liquide, are stable at mom temperature, but tend to hydrolym at elevated ternperatmw. Same specialid applications have been d e veloped for them compounds. The pure monoalkyl and didkyl esters have been prepared and described (f.9). This article wilI be con6ned to the mixturea of primary and seoondary eaters obtained by the mm tion of the lower aliphatic dcohols with phwphorua pentoxide. The unreadedhydroxyl groups may be neutralired by various baaea.
Methods of Production Mte of a disuryl and monoslkyl phosphate are easily ob-
where R may he any aliphatic, aromatic, or cycloaliphatic radical. The hydrogen of the unrescted hydroxyl group may be rephed by various metals, particularly those of the alkali and alkalin4esrth groups, ammonia, or aminerr. The tettiary or neutral mtem are well known commeroial pmduote; their properties and applications have bepm completely described (6,7, fa, I@. Commercially useful eatern 8re tributyl and tricmyl phosphate which are colorlea liquids and which find their chief application as plasticimrsand as fire
tained by heating a trialLyl phosphate with a strong b:
This procedure is costly, as the trialkyl phosphate are expensive raw matmiah. The partial estera of orthophaephoric acid 818 resdily prepared by the d o n of phosphonnr pentoxide and the conmponding alcohol or ether:
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
The alkyl eaters can also be prepared by the reaction of alcohol and phosphorus oxycbloride: 3ROH
+ POCL 4(R0)Z
-
0
+ aHCl
(6)
AB shown by the above equations,the product of the reaction of an alcohol and phosphorus p t o x i d e is a mixtm of the primary and secondary eaters; the proportion of primary to secondary ester will depend primarily upon the amount of water preaent or formed during the reaction. With anhydrous alcohol the resotion proceeds according to Equation 5 although with higher diphatic alcohols more of the m o n d y l ester will he formed. ¶tion of the alkyl eaters can be effeoted by the merent solubilities of their barium or calcium d t a (6,14). The monoalkyl calcium and barium phosphate ara only slightly soluble and can be s e p t e d from the easily soluble dialkyl calcium and barium phosphate of the lower alcohols by filtration. From the standpoint of low cost, the mixture of primary and secondary alkyl eatem mnlting from the reaction of phosphorus pentoxide and alcohols is of greater c0mmeroi.d interest than the pure primsry or pure secondary alkyl eeters. In addition to the amount of water present, the ratio of the reactants will also influence the composition of the product. The molal ratio of alwhol to phosphorus pentoxide can be varied over the range 2: 1to 4: 1 in order to obtain varying propertim. Under such conditions the content of m P 0 , in the eaters will vary from 35-66 per cent and the FtH,PO. from 65-35 per cent. In all the eaters there will he a trsce of phosphorus pentoxide as &PO, and a certain amount BB the alkyl eaters of pyrophosphoric and metaphosphoric aide. The temperatureat which the alcohol and phoephorus p t a i d e are reacted streds the speed of the reaction but not the composition of the product. The rate of addition of the resctsnta does not strect the wmposition of the product and is governed by the ability of the v d to U p a t e the heat of reaction. Figure 1 shows the alkyl phosphate pilot plant.
- *
/I
A
II
I I
21
Properties of Acid &tens UnWre the neutral alkyl phosphate, the acid esters have limited usefulness becam of instsbiliy to heat, readJr hydrolyain, and poor c o r d o n charaderisties. To determine the stability of the ethyl eaters of phosphoric acid to hydmlynis, a solution of mixed diethyl and monoethyl hydrogen p h w phatea was diluted to a 6 per cent solution and allowed to Btand at mom temperatnre. From Table I it is apparent tbat about 6 per cent of the esters were hydrolysed to phosphoric acid after the &pee of 89 days and that there WBB a gradual conversion of diethyl to monoethyl eater. T
'
D I. ~BTm-
Frfahly diluted Ntar4day. After 11 day8 Aftar 18 day. AI& ao day. Aftsr 32 day. ~
t asadam
or
~ c nPnAepnomc , EBTBBB % of Total ROI Preent UI: Diethyl Monoathyl atsr aster &PO. 40.3 50.0 0.7 30.7 48.0 ia.3 ao.1 50.0 13.0 a4.3 50.0 16.7 31.4 53.3 i6.a ai.? 63.4 15.4 as.a 54.7 10.1
The instability to heat of the mixed mono- and diethyl eaters was shown by boiling under a vacuum of 8 mm. At first alcohol W e d over. At 150" C. the eaters began to boil vigorously and a condensate was obtained which amounted to 15 per cent of the eaters used. At 200' C. dewmpition started with evolution of ethylene. The condensate was nearly neutral and soluble in water, and had a boiling point of 208" C. This identified the distillate 88 triethyl phosphate. The reaidue from the diswlseion wnsiated of pyrophosphoric and metaphosphoric acid esters.
Properties of Alkyl Phosphates
Interesting products are obtained by the neutralisation of mixed mono- and M y 1 phosphoric acids by both organic and inorganic bases. The outatandw property of most of
these alkyl phosphate is their high solubility in water. Thwe points, good humectant water solutions exbibit low propertiea, high conductivity, and good &ability. Furthermore they are not particularly corrosive. S o ~ m m .Many of the akyl p h w Dbatea are readilv soluble in water. 88 shown k Table 11. 1; determining th& valuea, concentrated wlutiona were prepared either by concentrating aqueous solutiona under vacuum until crystals appesFed on cooling or by adding water to the exce89 of the d i d d t a . After the solution and the crystsls had bean prmitted to stsnd several days, the amount of solids in the solution wan determined. It was diffiout to obtain 8ccmt.e values on account of the propensity of the compounds to form either gda or supereatwated solutions. Neither the potaesium nor the sodium dialkyl pbosphatea gave de& nite clyetah. Experience has shown that a 60 per cent solution of nearly all of the potersiumneutralired &l estenr may b made with little if any danger of cryatdimtion taking place#even under *tm Storage mditionu The crystdisinppoint of more wcenhtd sohtionsis difhcut to memm, and ~ c 60a per cent solutions may be handled aatkfw. toav them IIW been no attempt except in a
fe
I N D U S T R I A L A N D B N G I N E E R I N G CHEMISTRY
2a relutively few c w.
8 8 to ~ ~make up
a t r o w solutions for general
~ ? J N QPorn W D V~scosrry.
Vol. 34. No. 1
Tasm 111. Splpcmc G~avrrx,pH, rn &WE
.
Fmzing pointa and Vis
&ties for some of these solutions at Vanous concentrutions are shown in lQum 2 and 3. V i t i e a wem m e a a d by the Feneke modification of the Oatwdd viscometer. Table III lists the specific gsvity and color of concentrated d u tions of a variety of alkyl phosphoric d& and alkyl phob phates wmmercinlly availsble. The products of Table III were produced by the regotion of 2.8 molas of unhydmue alcohol with 1 mole of phosphorus pentoride except where noted otherwise; the mixed ethyl and methyl estare of Figure8 2 and 3 were prcducta of the reaction of 4 m o h of anhydrous dcohol with 1mole of phosphorus penhide.
PH
0 7.6 7.b 7.5 7.5 7.6 7.5 7.5 7.6 7.5 7.6 7.5 7.5 7.5 7.5 0
7.6 0 7.5 0
7.b
cd.r N& NOM
NWl. Nono None
... ... ... ... ...
... ...
N&
... ... ... ... &ht
doohol .nd 1.0
-4
46 -a -24 TEMPERATURE 'E.
4
42
FlOWB
2.
Cwvw
01
-
-28
&NCENTBATlON-hZINQ
-32
-36
POmT
Aarwoos 8 o ~ o n mOF Emrr. Eslaae
The properties of the mixed alkyl phosphates are determined ,by the properties of the monoalkyl phosphates and dialkyl pbospbntes present in the mixture. Table I1 shows that dimethyl and diethyl phosphates, whether neutrdkd by sodium or potassium, exbibit high solubility in water.,- On the other hand, monoethyl or monomethyl phosphate8,wiU have d8erent properties when neutralized by sodium or potassium. Thus, momthyl dipotsmium phosphate has the high water solubility of the diethyI phosphutee, and ita nque ou8 solutions are fsirly fluid. Monoethyl disodium phosphate exhibita greatly diminisbed dubility in wnter, and ita q u e OUB solutions show i n m d viscosity.
high viscosity can be obtained by neutralisation of the monoakyleetsr wntent of the mixed eatera by both d u m and potsmium. By this procedure a monoethyl sodium potsssium phosphate, for exnmple, can be formed with high sohbfity and high viscosity. The content of diethyl wid aster will be n e u W e d , of c o w , by the 6mt base 4. Mixed eatenr formed by neutralization by both sodium and p o h mum ure listed in Tables I1 and 111. & ~ I L I T T . The neutralised esters are much leassusceptible to hydrolysis than nre the acid esters. hlutiona of the neutraliaed eaters were duxed and the formation of inorganio phosphate and change in the pH of the sdutiona were measured. The dnta in Table IV show that little change &ta from this trentment. C o a ~ o s r vACTION. ~ Although the alkyl mid estem of phospboric acid ure c o d v e to metnls, esters neuhdined by slkali metals such 88 potaasum are stable compoundn which bnve little corrosive tendency. Table V shows the m d t a of Bxposing various metals to a 40 per cent solution of mixed ethyl potsmium phosphate d e by the reaction of 4 molea of anhydrous ethyl dcohol with 1 mole of phosphom pentoxide. The eamples were i m m d in the alkyl phos phate solution which wm ciroulated by a pump and muintained at 88' C.; sir wm continuously bubbled through the &Uti?
Y
Table V includes three seta of data on mixed ethyl p o d mum phosphate eblutions with initid pH values of 7.6,8.76, 76.5 3a4.a and 9.65. Use of sodium dicbmmnte m an inbibitm reduces 61.0 1M.a the c o d o n rutes in Table V to negligibledw. 71.5 262.6 ao.9 s 26.4 H m m m m PaoPwTlge. Blgurea 4 and 5 &ow speoific 405.6 8o.a 30.6 a3.4 gsvitiea of various dutiona and humeotsnt properties .fe71.4 am5 prea~edas the of s~lutionin equilibrium wi& 67.5 40.8 n.8 am.9 at various relative humiditiea and 25%C. These data *ere 27.8 38.4 68.0 i77.a obtained by a conventiod dynnmic metbod. The mixed ai8.8 68.1 allryl phosphate8 of Flgum 4 and 5 were p r o d u d by &e 18'* e o n of 2.8 moles of anhydrous alcohol with 1 &orus pentoxide; the amyl phosphate of c dmhol with 1 male of phosphom the c q for 100 mole per cent d u m Tbis is the explanation for the Merences in solubfity and d u m repmsnt, reaptWy, complete viscosity shown in Figma 2 and 3 for the mixed alkyl phob n e u a o n by d u m hydroxide or complete neutnrlisaphnte8 neutralid by sodium or potsmium. SoIuWty and tion by &hanoLunine. The'intmnediate curves r e p d t visecaity cbaractsristica of the mixed eatera vary, depending neutreJhtion by vacyhg proportions of the two baees. upon whether the mon&yl phosphate p w n t is neutralid by sodium or potne8ium. Thus, the mixed ethyl potsmiwri Application of Neutraliasd Algyl Phosphates phosphate solutions exbibit lower freesing pointa and lower D e propertias of concentrated water so~utio& of enviscositias than do the mixed ethyl sodium phosphate solu*inn. of the alkyl phosphites ure ndvnntageous for certain interesting industrinl applications. For instSnce,several are antiIt hss been found that ~ 0 1 d t i 0of~low fnming point and
mt-
INDUSTRIAL A N D ENGINBERZNG CHEMISTRY
Jammy, 1942
44% min. mirad ethyl h i u m phqhnb 46% mol?. diethyl ot-um phcaphab 42%. -1% mired matby1 potyulum phapbata
0.1
1.6
8.411
..
None
0.6
8.46
7.65
None
None
8.45
8.85
p E of (lolution at 8 t u t of 1st Period. 7.6
...........
p E o! d n paled
. at and of
PslJatntiOn om./& C u t iron Mild *bel coppa BZW Aluminum
x
XOL
7.5
+2.4 +i.b +1.8 +1.5
-2.4
-0.84
-a.a
-a.4 -0.11 -0.82
+o.ai -0.24 +o.w +o.ai
-1.2 +0.08
-4.6
-a.i
+a.a
-0.14
The &I phosphate may be used for the procesajng of worsteds and woolens and in the manufactum ofrugs. WINTmo P m . Inorganic phosphateu have been suggested in the past 88 humectant substitutes for glycerol in vat printing pastes, but hae shown that they fall down in two important particulara. In the fvst place they tend to OBW the paste to “liver”, i. e., the viscosity of the printing paste will incresae exceasivelyon a few dam standing. Secondly, they give poor color yields. The work of Glarum (4) has demonstrated conclusively the importanc&of maintainingconstant via&@ in the printing operation in order to get clarity of print and constant depth of &de. change in v i % d t y Mt Only aftects tha with which the paate flows into the engraved portiona of the printing roll, but also the weight of the paste that is picked up by the roll, which in turn detemineu the ammt of &or d e m c ited on the cloth.
7.6
7.45
-0.24
Zk.0
7.a
a3
-0.26 -0.88
+o.aa
PE of Edution a t Strrt of 1st Period, 8.75
...........
pH of .ole at a d of Park”i POU&l*tio?3 cm./d& X 1D C u t iron Mild steel COPPr. B-
Aluminum zino
7.00
8.0
7.8
In +0.87 +0.8 0.0
+0.14
+om
+2.14
-1.b -1.8
-0.a
-0.74 -0.64
-0.11
-0.05 -0.00
-0.20
+o.%
-a.a
+a40
PEof Bdutiw st E t u t of 1.t Period. 8.56 p E o[ *oh. at and of m d 8.1 8.111 8.1 PSnOtr.th om./d& X ID Cut iron +1.50 -1.6 -0.67 Mild ~ t d +o.m -1.6 -0.81 coppa +o.ia -0.06 -o.aa BlU + o . m +o.ia -0.0s~ Aluminum +0.80 +0.41 -0.a2 Zk.0 +2.6 -0.008 -0.008
...........
8.1
+i.a5 -1.1 -0.1s -0.07 -0.44 +o.a4
8.2 -0.71 -0.117 -0.08 -0.045 -0.21
W
F
3U I t
>
8 L“ >
+0.2
v1
&tic agents in the spinning of W e fibers, one is a meisfactory substitute for glycerol in the printing of vat colors, o t h m are of Borne inheat for ttSmeprw6ng cloth and paper, and a few offer possibilities 88 refrigerating brines. Other poesible u ~ e 8of a varied nature are discussed Mow. SpnuhmrO AQENTS.Since alkyl phosphates are eledrolyta which are highly soluble, noncorrosiVe, and c h e m i d y stable, they are weH suited 88 antistatic agente for the spinning of wool and other fibers. They eliminate static in spinning and do not oxidise or discolor on aging (Figure 6). Being water soluble they are easily removed without the aid of soap. The wide range of pmperties of the alkyl phosphateu 88 a class makes it possible r e d l y to dect the phosphate beat suited for each sat of conditions. The methods of Murphy and Walker ( 3 , U ) wem adapted to demomhte the d e o t of the alkyl phosphatea on the conductance ofwool. Rgure 7 Shows the tremendcm increase in conductance which may be obtained by impregnsting wool with alkyl phosphates. The alkyl phosphate increase the oondudance much more than inoganio d t e of high d u b$ty aUch 88 dipotaesum pbospbate. The mixed ethyl “di~potassi~phosphateofFzgune7wssmsdebyraaction of 2.8 m O h of anhycLons eth alcohol with 1 mole of phw phoruapentodda &&#
: W
F z W v I
>
t VI
ou5
>
0 2 0 4 0 6 0 8 0 TEMPERATURE --‘C
Actual Viseosjty messurements on a M s C M i c h a e l h Bter show that diptaaim phosphate (a good example of an inorganic phosphate with good humeotant propertias) c a w appreciable livering of a staadard vat printing psata. The alkyl phcephatea, how-for instance, methyl aodim
V d 34, No. 1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
potsasium phosphate and particularly amyl sodium potassium p h o s p h a w r e sati8fdmy in this respect. The primary iniluence of inorganic phosphates on color yield 8eem8 to be a coagulating efiect wbich induces a change in the particle size of the insoluble vat dyeatutr. Obviously, if the dyetuff is aggregated by the presence of any chemical, the rate of reduction is dower because of less particle surface being svailshle for the reduction resction. The inorganic phosphates aa e.xempIi6ed by dipotaasiUm phosphate are bad offendersin this direction. The alkyl phosphates, pnrticuM y again the amyl sodiumptsasium type, seem in no way to alter adversely the particle size of the vat pigments and are aa good in this respect aa g l p r o l . Mimcopic examination of a printed fabric before, during, and after aging, disclased further information in regard to the action of various humectants on color yield. It appeara evident that both glycerol and amyl sodium potansium phosphate become fluid enough at aging temperatures to permit good penetration of the paate and therefore of t h e print color, but under the cold oxidising conditions they are viscoiis enough to be slowly soluble and thedore permit full oxidation of the reduced color before the paate is removed from the cloth. Diptsssium phosphate and even ethyl sodium potassium phosphate, on the other band, although perhaps fluid enough at aging temperatures, diesolve rapidly in the cold oxidizing solution so that poor color yields result. ~ p ~ ~ p n Interest r o . in the heproofing of textilea and paper is perennial. The literature on this subject is extensive and complete. Ethyl ammonium phosphate is a good h e p m o h n g agent. It p~laesses one distinct advantage over inorganic phosphates such aa diammonium phosphate in that it ramaine liquid at lower relative humidities than does the inorganic type. This means that a piece of cloth h p m o f e d with ethyl ammonium phosphate is softer in fed. There are a ndmber of theories in respect to the action of a h p m o 6 n g agent. However, it would aeem that n w l y dl inorganic h e p m o f i n g chemiosla are solids which, upon heating, either melt readily or decompose into compounds which do melt d y . The pceeence of the molten solid in the fnbric prevents the h e fromspreading. If a mallsample of a solution of diammonium phosphate is put into a crucible and heated with a b e , the end pmduct is a molten liquid, undoubtedly a phosphoric acid. Ethyl
ammonium phosphate behavea in a similar manner. Since the flamepmfing ability of an &yl phosphate depends on the phosphoric acid formed after thermal breakdown, the alkyl ammonium phosphate containing the maximum amount of P,Os should be superior. The &yI phosphates derived from the lower aliphatic alcohols, methyl and ethyl, have higher PI0s contents than those derived from alcohols of a bigher number of carbon atom at the same degree of egteriEcation. Ethyl mmonium phosphate, for example, cont9ius 53.5 per cent Pros aa against 42 per cent for the c o m p n d i n g amyl type. The higher alcohol derivatives are at a further disadvantage because of their higher arbon content. I
I
I
I
I
I
I
9 R I , c 6
I
2 w
t
5 w
i MI~CF~ANEOW. Monc- or m y 1 phosphateg, particularly t h m containing at least four carbon atom, are recommended aa auidic sademtors for urea-formaldehyde alkyd resin enamels. Baking schedules can be shortened and baking temperatures lowered. Even airdrying enamel8 are made d b l e thmugh their use (10).
~~~,1942
I N D U S T R I A L A N D E N D I N E E R Q N0 C H E M I S T R Y
Alkyl acid phosphate, such as monoamyl phosphate, are stated to be of intemt in soldering because no obnoxioue fumes are given off when the work is done in a confined space, the spattering cbaracteristies of 8om8 of the fluxes are eliminated,and c o r d v e residues are avoided. It is indicated that they are of particular value in welding zinc, magnesium, and aluminum (28). Mono-, di-, and triesters of phosphoric acids, particularly those whicb are miscible with oil, are stated to belnhibitom of c o m i v e action on metal surfaces and can be applied in oils or other carrying vehidea to provide a thin coating on such a surface (26). Akyl acid phosphates--for example, diethyl acid phcephate-can be used in place of concentrated sulfuric acid, aluminum chloride, or zinc chloride magenta for polymerizing unsaturated hydrocarbon compounds,sueh as tung oil. The action of t h e e organic Dh,haeDhatm is miid and chamiw . . - does not occur (1).
25
The neutralired alkyl phosphatee, partiwlssly. mixed ethyl or methyl potaeaium pkmapbatq exhibit high solubilityin water, low freedng pointa for their squeous solutim, low vi~cositieaat low temparstures, m m * v 0f inhibited solutiom, Q and freedom from foaming. BzIluacteristies desired in hrinea formfrigeratingsyetems. Accordinglysome neutralired &yl phosphates may be conBidered as substitutes for such mfrigeranta 88 r&um chloride,methanol, and ethylene glycol solutiom. The alkyl phosphates have bwn used 88 lubricanta in such operatiom of metal working as deep drawing and lap grinding. In contrast to oils they have the advantgse of easy m o v d from the metal parte by washing with water (0). There haa been considerable intereat in the use of watchsoluble phwphate 88 fertilizers which would not beaome insoluble by d o n with the soil. The calcium d t a of the lower aliphatic eatera of phosphoric acid have hem -tsd for thispurpose(17,18). Raporteouthevalue of theee wmpoands Bs fertiliRos are conui* (8). As an insecticide, the mercury d t of ethyl phosphoric acid ester has bwn d & M (8). conclusion Although the alkyl wid phosphatee and their d t a am comparative newcornera to the W d of indwtrial chemistry, their interesting pmpertieu had one to believe that they may evenWY become ae well known and 88 widely used 88 the older and better known @eeterified derivativea of phwphoric acid.
Literature Cited (1) Caplsn. U. 8. Patent 2,223,648 (DW.a, 1840). (a) DU pont G., public ~elrrti~ns Dapt.. b.NSW *, 7. eo73. si-a (1ea-a). (3) Dyer. C. P., Am. DveaWRsph.. 30, 110-22P (1941). (4) Glwm,8. N.. lbid.. 25. 1W-m(1988). (6) Om-, P. H,. “Unit Pmaaaaa in O d e 89ntbaais”. 2nd 4.. p. 664. New York, Mi% Graw-HiU Book Ca., 19%. (6) Hsrlqy, V.. J . pbm. Ah.. m.160-7 (1984). (7) H&, R., BW.. 16, im-70 (ma). (8) Hillmrh. G. E.,Pin& L. 1..Sherman. M. 8.. and Tremeame,T. H., S d Sei., 4 6 No. 6, 409-18 (18%). (9) Hochdt. C. A. (to Mollllanto Chemical Ca.). U. 8. Patent %19a.886( M d19,1940). T. 8.. and H o w , A. Q., IND. E m (10) E+, Cnur.,Js,612-16 (1941). (11) Murphy, E. J.. and Walker, A. C., J . PAW. Chsm.,32, 1 7 8 1 4 (1828). I dm . C h . (12) Nollar, C. R.. .nd Dutton. 0. R.. . &., 56.424-5 (19aa). , iae (1833). (la) P&W~.A ~ B .6. (14) Plimmer. R. H. A,, and Bumh, W. J. N., J . C b . sw., 1w8. asaiwo. (16) F’rutton. U. 8. Patent 2,334,696 (Dw. 10,
