INDUSTRIAL AND ENGINEERING CHEMISTRY
244
only when the mixture is sufficiently alkaline to react completely with the nicotine salt. A number of oil-soluble nicotine compounds have been proposed, particularly salts of nicotine with high-molecularweight organic acids, in the hope that the nicotine would be kept in the oil layer. Some preliminary experiments have indicated that although most of these acids are insoluble in water, they form salts which are somewhat soluble in water and which, in addition yield some free nicotine to the water by hydrolysis. They have much less effect than might be expected in keeping the nicotine in the oil, and some of them actually favor the water more than free nicotine. T o ensure holding the nicotine in the oil, it is not sufficient to find an oil-soluble compound; the compound must also be insoluble in water and relatively slightly hydrolyzed. The influence of concentration and of constituents of the spray mixture other than acids on the distribution of nicotine is not so great as has generally been assumed. Under practically all ordinary conditions the spray as applied will contain nearly equal concentrations of nicotine in the oil and the water. The ratio will vary little with the type of oil and will be practically independent of the concentration, since the largest amount used in practice is well within the range of constant distribution (Table I). It will not be seriously affected by alkaline fungicides, since saturated lime and sodium hydroxide up to 0.1 molar have practically no effect (Table 111). Emulsifying agents should not produce much change. I n the concentrations which are used, neither the substances themselves nor their possible hydrolysis products are present in sufficient quantity to affect the solubility of the nicotine appreciably. In view of the rapid transfer of nicotine between the oil and the water, no advantage will be gained by dissolving the nicotine in the oil first. I n general, then, practically any nicotine-petroleum oil spray will have approximately equal concentrations of nicotine in the two phases a t the time of application. The situation may be somewhat changed after the spray has been on the foliage for a time. Any material running off
VOL. 32, NO. 2
will cause the same loss of nicotine whether it consists of the unbroken emulsion or only of the water phase, because of the equal distribution. I n the remainder of the spray which remains on the foliage, the water will tend to evaporate more rapidly than the dissolved nicotine, so that the solution will become more concentrated. This increase in concentration will cause some of the nicotine to be transferred from the water into the oil with which it is in contact. After the concentration has exceeded one per cent, the distribution in favor of the water increases, so that further increases in the concentration of nicotine in the water phase will cause proportionally smaller increases in the oil phase. Eventually, however, all of the nicotine which was originally in the water and which has not been lost because of run-off, evaporation, or other agency, will be dissolved in the oil. The effect of rain on the residues will be a reversal of these changes. The extraction of nicotine will be rapid a t first, because of the distribution in favor of the water, as well as the relatively high concentration, and will become progressively less, until from solutions containing less than one per cent, half of the remaining nicotine can theoretically be extracted by each equal volume of water. I n actual practice the extraction will be much less, because most of the water will run off before it has had time to dissolve the maximum possible amount of nicotine from the oil. Literature Cited Cuvilier, B. V. J., 2. anal. Chem., 105, 325 (1936). DeOng, E. R., IND. EX+. CHEM.,20, 826 (1928). Jephcott, H . , J. Chem. Soc., 115, 104 (1919). Kolosovskii, N. A., and Kulikov, F. S.,Acta Univ. Asiae Mediae (Tashkent), VI, No. 8 (1935). Kolthoff, I. M., Biochem. Z., 162, 289 (1925). Lowry, T . M., and Lloyd, W. V., J . Chem. SOC.,1932, 1626. Ratz, F.,Monatsh, 26, 1241 (1905)., Ritcher, P. O., and Calfee, R . K., Ky. 4gr. Expt. Sta., Bull. 370, 47 (1937).
Tsakalotos, D. E., Compt. rend., 148, 1324 (1909). PBEBENTED before the Division of Agrioultural and Food Chemistry at the 97th Meeting of the American Chemical Society, Baltimore, Md. Approved by the Director of the New York State Agricultural Experiment Station for publication an Journal Paper No. 316.
POTASSIUM METAPHOSPHATE A Potential High-Analysis Fertilizer Material S . L. MADORSKY
AND K.
G . CLARK
OLYMERIC modifications of the alkali metaphosphates ranging from mono- to decameric forms have been described in the literature (4, 5, 15-18, 26). The sodium salts-Maddrell’s salt (an insoluble crystalline trimer), Knorre’s salt (a soluble crystalline trimer), Graham’s salt (a very soluble amorphous hexamer), and Kurrol’s salt (an insoluble octamer)-appear to have received more attention than potassium analogs. Graham’s salt in particular has been publicized in connection with recent developments in the treatment of water for industrial purposes (7-10,19). Soluble, insoluble, crystalline, and amorphous forms of the potassium salts have been reported (15, 16). Water-insoluble potassium metaphosphate may be pre-
P
Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Washington, D. C.
pared by a number of reactions, including ( a ) dehydration of monopotassium phosphate or dipotassium pyrophosphate, (6) neutralization of metaphosphoric acid with potassium hydroxide or potassium carbonate followed by dehydration of the product, and ( c ) reaction of potassium chloride with phosphoric acids. Such an insoluble product, composed entirely of the plant foods, potassium oxide (K20) and phosphoric if capable of releasing the potassium and phosoxide (P20s), phorus to growing plants under soil conditions, should possess many of the properties desirable in a high-analysis fertilizer material. Bartholomew and Jacob (3) in a series of pot tests found the fertilizer efficiency of the phosphorus content of water-insoluble potassium metaphosphate, prepared
FEBRUARY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
A praatically water-insoluble and nonhygroscopic form of potassium metaphosphate can be obtained by the action of phosphoric acid on potassium chloride. Analyses made in accordance with the Official Methods of Analysis of the A. 0.A. C. for citrate-insoluble phosphoric acid and for potash in mixed fertilizers indicate that, owing to the solubility of this metaphosphate in ammonium citrate and oxalate solutions, the phosphorus and potassium are available to plants. Vegetative tests support this conclusion. The high plant food concentration of potassium metaphosphate, 39.87 per cent potassium oxide (&O) plus 60.13 per cent phosphoric oxide (P,O5), should permit important economies to be made in bagging, handling, shipping, storage, and tax charges per unit of plant food and thus make it particularly well adapted to economic distribution over wider areas than other fertilizer materials. by dehydration of primary potassium phosphate a t 810" t o 820" C., to be 135.7 in comparison to monocalcium phosphate as 100. Ross (20) studied t h e reaction between potassium chloride and phosphoric acid at temperatures u p to 250" C. Ross and Hazen (11,21),and others ( 2 3 , 2 4 ) avoided the production of the metaphosphates. They ammoniated the product which resulted from the use of a n excess of phosphoric acid and produced a water-soluble product containing both potassiuni and ammonium phosphates in ortho form. dskenasy and Sessler ( 1 ) studied the effect of relative proportions of potassium chloride and phosphoric acid, time, and passage of steam through the reaction mixture for facilitating the volatilization of hydrogen chloride between 120" and 350" C. They obtained products consisting of mixtures of potassium nieta-, pyro-, and orthophosphates with unreacted potassium chloride and free acid. I n a similar study Britzke, Pestov, and Lezhnev (6) passed a stream of air through the reaction mixture and ammoniated to neutralize the residual free acid. A patent ( 2 2 ) describes the preparation of potassium metaphosphate from potassium chloride and phosphoric acid a t a dark red heat. T h e studies reported in the present paper were undertaken to determine the nature and composition of the product's ohtainable by reaction of potassium chloride with phosphoric acid a t temperatures higher t h a n those reported by previous investigators, and some of the physical properties of the hightemperature insoluble crystalline form of potassium metaphosphate.
Procedure and Analysis of Products Mixtures of 65.0 grams of c. P. potassium chloride and 101.5 grams of phosphoric acid (84.22 per cent) in covered glass beakers were heated slowly to avoid frothing and loss of material bv spattering, and were maintained at 120' t o 130' C. on a hot piate for about 18 hours. The loss in iveight resulting from this treatment through volatilization of water and hydrogen chloride was noted. Preliminary experiments indicated the loss of 14 to 16 per cent of the chlorine content and approximately 14 per cent of the free and combined water.
245
Following this initial treatment, the beakers, contents, and covers were transferred to an electric muffle furnace whose rate of heating, as measured by a platinum and platinum-rhodium thermocouple, could be controlled t o reach the desired temperature in 3 hours. Under these conditions the mixtures \?-erevigorously agitated by the evolution of hydrogen chloride and water vapor within the body of the fluid. At temperatures between 300" and 350' C. the mixtures solidified but became fluid again between 700" and 800" C. In general the mixtures were maintained a t the maximum temperature for 1 hour. The reaction rnixture was then cooled in the furnace to 200-300" C., transferred t o a desiccator for further cooling, weighed, and reserved for analysis. When the maximum temperature was to be above 600" C., heating was temporarily interrupted a t about 500" while the materials were transferred to a large platinum dish. The products obtained by these thermal treatments were separated into soluble and insoluble fractions by stirring tffice with m-ater, centrifuging, and decanting. The insoluble material was dried and ignited at 500" C. to constant weight. Analysis showed: K20, 39.82 per cent, and PzOs, 60.48 per cent, in comparison to theoretical values of 39.87 and 60.13 per cent, respectively, for potassium metaphosphate. The soluble fraction was analyzed for total phosphorus by the molybdate method, phosphorus as metaphosphate by a direct gravimetric procedure, phosphorus as pyrophosphate also by a direct gravimetric method, potassium by the perchlorate method, chlorine by the silver chloride-nitric acid method, primary hydrogen by titration with 0.1 N alkali to the methyl orange end point, and primary and secondary hydrogen by titration in the presence of sodium chloride with phenolphthalein as the indicator. The separation of the products into soluble and insoluble fractions, precipitation of the meta- and pyrophosphates, and determination of the primary and of the combined primary and secondary hydrogens were carried out as rapidly as possible in order to minimize possible errors resulting from hydrolysis of the phosphates present; 2.5 to 3 hours were required to complete these operations. The metaphosphate radical (PO8) was determined by ( a ) acidifying the solution to a pH of 2 or less with from I to 2 per cent of its volume of glacial acetic acid supplemented by 0.1 N hydrochloric acid, ( b ) adding a slight excess of a saturated barium chloride solution, (c) adjusting the pH of the solution to 2.2 to 2.3 with 0.1 N alkali, ( d ) collecting the gelatinous precipitate in a fritted glass crucible, ( e ) washing the precipitate twice with a 1t o 3 water-acetone solution, twice with acetone, and twice w-ith anhydrous ether, cf) heating the crucible and precipitat,e slowly a t first to volatilize any residual ether or acetone, and igniting a t 400" C., and (9) weighing the precipitate of barium metaphosphate, Ba(P03)z. In preliminary experiments with known solutions the precipitation of barium pyrophosphate (BrtzP207) was found to be prevented if the pH of the solution did not exceed about 2.3. I t was also found in preliminary experiments that washing the precipitate with water and drying at, 100' C., as suggested by Holt and Meyers ( I Z ) , or washing with alcohol and drying a t the same temperature, did not give concordant results owing to the retention of water in the one case and the tendency of alcohol t o form alcoholates in the other. The pyrophosphate radical (PZO,) was determined by a gravimetric modification of the method of Travers and Chu (27) for determining pyrophosphates in the presence of meta- and orthophosphates. The pyrophosphate was precipitated and weighed as zinc pyrophosphate, ZnzPZ0,,by adjustin a,n aliquot of the sample containing ammonium chloride to a p€f of 5.2-5.3, adding a slight excess of a saturated solution of zinc sulfate, adjusting the pH t o 2.7-2.8 with 0.1 N acid or alkali, and filtering, washing, igniting, and weighing the precipitate as in the case of barium metaphosphate, except that the lmter-acetone wash solution was a 3 to 1 mixture. A mixed solution of previously analyzed sodium metaphosphate, tetrasodium pyrophosphate decahydrate, monosodium orthophosphate monohydrate, and sodium chloride was prepared to cont,ain 4.65 grams of POs, 3.90 grams of P207,4.13 grams of P04, and 6.0 grams of NaCl per liter. The results obt'ained on analysis of 10-ml. portions of this solution for POs and PzO?by the above methods were within 1.0 to 1.5 per cent of theoretical : Analysis No. 1
2
3 4
Grams Found PO1 Pi07 0.0462 0.0385 0.0460 0.0379 0.0460 0.0389 0.0462 0.0388
Analysis
NO. 5 6 Mean Theoretical
Grams Found PO: pro7 0.0467 0.0387 0.0458 0.0384 0.0462 0.0385 0.0465 0.0390
T h e orthophosphate radical (Po4) was taken as the equivalent difference between the total phosphorus and the meta-
246
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 32, NO. 2
and pyrophosphates, the tertiary hydrogen being taken as equivalent to the orthophosphate. Any polyphosphates, if present, presumably would be included with the orthophosphate by this procedure and would result in too high values for the orthophosphate and for the tertiary hydrogen. That this procedure gave substantially correct values for the tertiary hydrogen and consequently for the orthophosphate is shown in the following tabulation by the agreement between the values of the total combined water determined directly on a few of the samples by fusion with lead monoxide according to the method of Jannasch, and the values calculated from the primary and secondary hydrogen and orthophosphate determinations: Total Combined WaterEquivalent t o 1st and 2nd H , By fusion and orthophosphate with PbO
7 -
Temp. of Preparation of Sample
c. 350 500 600
%
%
4.46 2.07 1.77
4.51 2.15 1.73
Reaction between Potassium Chloride and Phosphoric Acid
d
When heated, mixtures of solid potassium chloride and phosphoric acid lose both water and hydrogen chloride by volatilization. The loss of water results from concentration of the acid, conversion of the acid to pyro and meta forms ( d 5 ) , and thermal decomposition of certain ortho- and pyrophosphates (14). Likewise, the volatilization of hydrogen chloride results from reaction of any of the three phosphoric acids with potassium chloride. As long as such mixtures are maintained in a well mixed or fluid condition during reaction, the final products of the heat treatment presumably will be independent of the order in which dehydration and hydrogen replacement reactions occur, but will depend on the relative amounts of potassium chloride and phosphoric acid involved.
3 E
100
90 I
6 &
0
-
80
c
h
I
8
70 60
01
0 L
+
2
g
.+
+
m
50
40
30
5 u 20
2+ H
2 El
10
+
0
X
Mesh
*
3
ANALYSES OF POTASSIUM CHLORIDE FIGURE 1. SCREEN
I n most of the experiments reported here, equimolecular mixtures of c. P . potassium chloride, whose screen analysis is given by curve I of Figure 1, and 84.22 per cent phosphoric acid were employed. Under these conditions complete dehydration and hydrogen replacement is represented by the over-all reaction: KC1 + Hap01 = KPOs HC1 H20
+
I J
+
In a few instances from 2 to 10 per cent potassium chloride in excess of the above amount was used; thus the formation
INDUSTRIAL AND ENGINEERING CHEMISTRY
FEBRUARY, 1940
of normal pyrophosphate as ell as metaphosptrate \vas required for complete reaction:
4KCI t 2HsPOa
=
KPKh
+ 4HC1 + Hs0
The total loss in weight of a mixture and its initial and fiisal chlorine content permit a ready determination of the amount of potassium chloride reacted, and of the frce and combined watcr volatilized. These quantities, however, even in conjunction with the init.ia1 ratio of potassium chloride to pliosphoric acid, do not permit determination of the course of the reaction because within limits tlie observed volatilization of hydrogen chloride and water could be aecoimted for by formation of intermediate products. The various forms of phosphate, therefore, must he determined by direct analysis.
247
H y g r o s e o p i c i i y of Crude Products
A portion of the product prepared from an eqnimolecular mixture a t 800" C. was crushed to pass a 20-mesh screen (0.833-nim. openings) for use in moisturc absorption studies. Samples approxiniating 2 grams each, placed in open 28-mm. wide-moutbcd weighing bottles to a depth of ahout 5 nim., were exposed at room temperature (23-25.5' C.) in a series of desiccators to relativc humidities of 52, 71, 81, and 93 per cent ( I S , page 68), respectively. The increase in weight of these samples was noted at intervals over a period of 30 days. The data ohtained (Figure 2) indicate very little moisture absorption at humidities less than 71 per cent; these samples remained dry in appearance and were free flowing at the end of 30 days. The sample at 81 per cent humidity increased only 2.7 per cent in weight hut appeared slightly moist while that ai 93 per cent was definitely \-et snd caked. P h y s i e a i Properties of Potassinm Metaphosphate
Time, Ooyr
Fluox*; 2. MOIYTUHE ARsoHBED AT 23.0-25.5" c. B Y CEUDE PoTAssIUM METAPKoSPHATE PREPARED .9T 8000
c.
The analyses of the produets obtained by heating mixtures of potassium chloride Rnd plimplioric acid to 300-900" C. are presented in Tahlc I. The products obtained at 700" and below, solidified before attaining the maximum temperatures reported and before reaction had been completed. They were white, porous, apparently amorphous or inicrocrystalline crnstlike niateriala in contrast to those ohtained at 800' and 900' C. which were fluid at these temperatiires but definitely crystalline wlien solidified. ?To large inconsisteiicies attrihutable to incomplete mixing %-erenoted, however, when the lowtemperature products were compared with those which were fluid at the maximum temperatures attained. This was confirmed by experiments made at 350", 500", and 700" C. with smaller potassium chloride cryst.als (screen analysis given hy curve 11, Figure 1) in which only slightly greater volatilizations of hydrogen chloride were noted. At the lower temperatures the products contained considerable free acid and as a result most of the metaphosphate formed was recovered in the water-soluble fraction. At higher temperatures of preparation relatively greater amounts of hydrogen chloride and water were volatilized; consequently tlie freoaoid content of the product was lower and the me& phosphate was found largely in the insoluble portion. Tahle I shows that appreciahle quantities of pyrophosphate were present, hut that this form represented snccessively smaller fractions of the total phosphorus as the temperature of preparation was increased. Acid pyrophosphate, therefore, appears to be one of the intermediate products in t.lsis method of preparation of the metaphosphate. I n those experiments in which an excess of potassium chloride was used, the loss of chlorine indicat.es substantial reaction of tlie secondary hydrogen of phosphoric acid with consequent formation of normal pyrophonpliate as one of the end products. The tesdts indicate that between 700" and 900" C . more than 99 per cent of t.he chlorine content of eqnirnoleciilar mixtures may he volat.ilized t,o produce a product but slightly sohrhle in water and containing only small amounts of free acid.
Pure samples of the insoluble high-temperature form of potassium metaphosphate were prepared by heating equimolecular mixtures of potdssillm chloride and phosphoric acid to 700" arid to 900" C . , ami by heating c . Y. priniary potassium phosphate to 700" C. In each case the products obtained were repeatedly stirred with water to remove any soluble materials, and the final residues were dried a t 500" C . Before these samples were used for solubility determinations they were st,irred twice \vitlr water for several hours and centrifuged, and tlie liquid was decanted to remove the final traces of soluble impurities. About 10 grams of each of the sarnples %wereplaced in 500-ml. Erlenmeyer flasks containing ZOO nil. ni dist,illed water. These flasks were then placed in a w t c r theimostat nsaintained at 25" * 0.1 C. and the liquid ivasstirreil mechanieally for periodsrangingfrom 2 to24hours. A t the completion of this stirring operat,ion, t.he mixtures were cent,rifuged and 100-ml. portions of the clear solutions were evaporated by a stepwisc process in a lii-ml. platinum cnicible. After evaporation to dryiicss the crucihles and contents were igriited to constant weight at 500" C . Since tilank tests with water had shovn no increases, the increases ill weight of the crucibles were takin as t,he arriouot of potassium met.aphosphate in solution.
The results obtained with these three samples are presented in Tahle 11,wliicli slroirs mean value for t.lie solubility of the high-temperature form of potassium metaphospliatc of 0.0041 gram per 100 ml. of solution a t 25' C. The relative const,ancy of the soluhility determinations with respect to time of treatment indicates that hydrolysis to more soluble pyru or ortho forms is exceedingly slow a t this temperat,ure.
INDUSTRIAL AILD ENGINEERING CHEMISTRY
248
TABLE11. SOLUBILITY OF POTASSIUM METAPHOSPHATE IN WATERAT 25' C. KPOa Pre ared by Heating KHzPOI KCP Hap04 KC1 HaPo; to 700" C. t o 700' C. t o 9000 c.
+
7 -
Time of Stirring Hours 2 4 4
6
6 7 12 17 18 22 24
Mean
+
Gram/100 ml.
7
0.0037 0.0043
.... 0.0030 ....
0.0038 0.0040 0.0048 0.0044 0.0040
.... ....
....
0.0027 0.0048 0.0038
0.0050
.... .... .... 0.0040 .... 0.0046
....
0.0038
0.0042
0.0042
....
0.0031
....
....
....
0.0052 0.0039 .
.
I
.
Pure metaphosphate was found to contain 6.30 per cent citrate-insoluble and 15.46 per cent citric-acid-insoluble phosphoric acid (P206),and to be completely soluble in boiling ammonium oxalate solutions when tested in accordance with official methods for fertilizer materials ( 2 ) . A crude product also was completely soluble in the ammonium oxalate solution but analyzed 2.47 per cent citrate-insoluble and 16.63 per cent citric-acid-insoluble. With both samples, washing with water after the citrate solution was filtered off was extremely difficult and required about 20 hours. The melting points of the pure samples were determined by following their heating and cooling curves in the region 770" to 840" C. by means of a calibrated platinum and platinumrhodium thermocouple immersed in the sample contained in a platinum dish. The samples, approximating 130 grams each, were alternately heated and-cooled several times in an electric muffle furnace while temperature readings were made a t 1minute intervals.
VOL. 32, NO. 2
Summary and Conclusions The formation of potassium metaphosphate by reaction of potassium chloride 11ith phosphoric acid was studied over the temperature range 300" to 900" C. Simple methods for the direct determination of meta- and pyrophosphates in mixtures also containing the ortho form were developed and applied to the products of the reaction. Potassium acid pyrophosphate appears to be one of the intermediate products formed in this reaction. Products obtained a t 700" C. or above contained relatively little free acid and unreacted chloride, were low in moisture absorption capacity a t and below a relative humidity of 81 per cent at room temperature, and contained between 87 and 98 per cent of their potassium and phosphorus contents in water-insoluble although plant-available forms. The apparent solubility in water and density a t 25" C. and the melting point of the high-temperature crystalline form of potassium metaphosphate were found to be 0.041 gram per liter, 2.393, and 806 8" C., respectively. Acknowledgment The authors wish to express their indebtedness to J. W. Turrentine under whose direction this work was initiated. Literature Cited Askenasy, P., and Nessler, F., 2. anorg. allgem. Chem., 189, 306
mxn. -,\ - - -
Assoc. Official Agr. Chem., Methods of Analysis, 4th ed., pp. 21, 30, 36 (1935).
Bartholomew, R. P., and Jacob, K. D., J . Assoc. Oficial Agr. Chem., 16, 598 (1933).
Bonneman, P., Compt. rend., 204, 865 (1937). BoullB, A , , Ibid., 206, 1732 (1938). Britzke, E. V., Pestov, N. E., and Leahnev, A. A., J . Chem. Ind. (U. 9. S. R.), 7, 4 (1930). Gilmore, B. H., IND. ENG.CHEM., 29, 584 (1937). Hall, G. O., and Schwarta, C., Ibid., 29, 421 (1937) ; Ibid., 30, 23 (1938).
Hall, R. E., U. S.Patent 1,986,515 (Bpril 24, 1934). Hatch, G. B., and Rice, O., IXD.ENG.CHEM.,31, 51 (1939). Haaen, W., and Ross, W.H., U. S. Patent 1,456,850 (May 29, 1923)
I
Holt, A , , and Meyers, J. E., J . Chem. Soc., 99, 384 (1911). International Critical Tables, Vol. I, Kew York, McGraw-Hill Book Co., 1926. Kiehl, S. J., and Wallace, G. H., J . A m . Chem. Soc., 49, 376 (IYLI).
hlellor, J. W., "Treatise on Inorganic and Theoretical Chemistry'', Vol. 11, pp. 867-9, London and New York, Longmans, Green and Co., 1922. Pascal, P., Bull. SOC. chim., 33, 1611 (1923), 35, 1119, 1131
Time, Minutes
FIGURE 4. TYPICAL HEATING-COOLING CURVEOF POTASSIUM
METAPHOSPHATE
The heating curves showed a distinct break a t the melting point whereas the cooling curves indicated supercooling of 20" to 30" C. below the melting point before crystallization into rather well-defined, fibrous, asbestoslike crystals (Figure 3) occurred. Typical heating and cooling curve cycles are shown in Figure 4. Four determinations gave values of 806.4",806.6", 806.8", and 807.2" C., averaging 806.8", for the melting point in comparison to 810" as reported in the literature (IS,page 155). This crystalline form has a density of 2.393 as d e t e m n e d in benzene a t 25" C. by the pycnometer method.
(1924): Compt. rend., 176, 1398, 1712 (1923), 177, 1298 (1923), 178, 211, 1541, 1906 (1924), 179, 956 (1924). Pascal, P., and Bonneman, P., Ibid., 197, 381 (1933). Pascal, P., and RQchid,Mme., Ibid., 194, 762 (1932); 196, 828 (1933). Rice, O., and Partridge, E. P., IND.ENO.CHEW.31, 58 (1939). Ross, W. H., Trans. A m . Electrochem. SOC.,48,299 (1925). Ross, W. H., and Hazen, W., U. S. Patent 1,456,831 (May 29, (1923).
Socibtb anon. charbons actifs procbdbs E. Urbain, British Patent 288,330 (April 8, 1927). SociQtQanon. manufactures glaces produits chimiques SaintGobain Chauny Cirey, French Patent 641,199 (March 2, 1927). (24) Soci&i produits chimiques terres rares, French Patent 657,307 (Nov. 19, 1927) ; British Patent 300,919 (Nov. 19, 1928). (25) Tammann, G., J . prakt. Chem., 45,417 (1892). (26) Terry, H., Chem. SOC. London, Ann. Rept. Progress Chemistru, 34, 115 (1937). (27) Travers, A4.,and Chu, Y. K., Helw. Chim. Acta, 16, 913 (1933).
PRESENTED before the Division of Industrial and Engineering Chemistry at the 97th Meeting of the American Chemical Society, Baltimore, Md.
