Action of Sodium Amide on Silicates and Refract ories P. VICTORPETERSON AND F. W. BERGSTROM, Stanford University, Calif.
S
ODIUM amide, as is well A large variety of silicon-containing substances, The furnace used in the present known from the work of investigation consists of a sheet including feldspar, bauxite, serpentine, soapmonel m e t a l can (5 inches in Franklin (6) and his colstone, soda-lime and Pyrex glasses, burnt refracdiameter, 6 inches high) around l a b o r a t o r s , i s a base of the the circumference of which are tories, and clay, are completely decomposed by ammonia system, analogous not spot-welded six 6-inch (300-watt) fused sodium amide. The aqueous solution of only structurally but also chemichromolox s t r i p h e a t i n g units, parallel t o the axis of the cylincally to sodium hydroxide. It the fusion contains all of the silica as sodium drical can. The number in operahas frequently been o b s e r v e d silicate, and silicon may therefore be determined tion at any one time is controlled that sodium amide is more reby means of a t u m b l e r switch accurately by the usual methods of quantitative active chemically than sodium which is placed underneath the analysis. The optimum conditions for the futransite board box that contains hydroxide and a rather extenthe asbestos insulation of the fursions have been determined, and it is pointed out sive literature has grown up in nace. The current consumption which many confirmations of that the use of nickel crucibles eliminates the can also be varied by a rheostat this statement may be found ( I ) . placed in the supply line. A heavy much more costly platinum crucibles necessary in cover of monel metal (or nickel) is The great reactivity of sodium fusions of silicate ores with sodium carbonate or placed over the top of the furnace a m i d e , coupled w i t h i t s and the surrounding insulation. hydroxide. relatively low melting point of Through this c o v e r asses an 210" C., suggests that it mag ammonia inlet tube, wEose depth advantageously replace sodium hydroxide or carbonate in of immersion into the molten sodium is adjustable, a thermometer alkaline fusions designed to open up silicate ores or refrac- well, likewise long enough to dip into the melt, and an exit tube ammonia gas, all made of nickel. Sodium is contained in a tories prior to analysis. Furthermore, the use of sodium for spacious nickel crucible placed within the monel metal can of the amide will permit the replacement of the expensive platinum furnace. crucibles required for the sodium hydroxide fusions with the After the conversion of the sodium to sodium amide by a much cheaper and fully as satisfactory ones constructed of nickel. It was with these considerations in mind that the stream of ammonia gas a t 350" C., and after cooling, also in a current of ammonia, the crucible is placed mouth down in a present investigation was undertaken.' large mortar, and the bottom and sides are tapped with a TABLEI. COMPARISON OF ANALYSESBY SODIUM AMIDEAND mallet until the sodium amide separates from the metal. The larger pieces are coarsely broken with a pestle, and CONVENTIONAL ALKALINBFUSION METHODS rapidly transferred to bottles with tightly fitting ground SILICON DIOXIDE Eodium Alkaline stoppers, greased a t the top. These bottles should contain amide fusion an atmosphere of ammonia. (Sodium amide exposed to the DESIQNATION methoda NAME methodb % % atmosphere for any length of time should not be used because 75 4 75.6d 75.6 Ferrosilicon B58C of the danger of explosion, 2). 96 : 9 , ' 96.73d 96.8 Silicon B57
6.4,6.44 6.32 B69 Bauxite 66.55, 66.69 66.66 B70 Felds ar 73.9, 74.1 74.1 B8O Soda-{me glass 99 3 99 3 99.26 B81 Glass sand 65:2b, 65.39 65.4 B89 Lead-barium glass 67.65, 67.65 6 7.6 B91 Opal glass 80 2 80 07 80.1 Pyrex glass 54:7' 54'6 54.68 By6 Burnt refractory 32.3k, 32.31 32.38 Burnt refractory B77 46.7,46.6 46.9 Caeohoslovak clay 20.6, 20.63 20.69 Burnt refractory B78 61.1, 61.0 61.0 Asbestine 29 0 28 9 29.0 Calamine 35'4l35'1 35.2 Serpentine 4012: 40:2 40.26 .. Soa stone 65 7 65.6 65.6 Fedspar 36:5: 36.5 36.6 Soapstone a Fused 2 to 3 hours a t 330° C.,a time usually longer than necessary (silicon and ferrosilicon, see Table 111). b silicon and ferrosilicon were fused with NanOl; the remainder with NanCOa. C Bureau of Standards standard analyzed sample No. 68 etc. d Per cent of sillcon element. Here and elsewhere, dupiioste analyses of the same specimen are given.
EXPERIMENTAL METHOD
The silicate mineral or refractory to be analyzed is thoroughly sampled and then ground until the desired degree of fineness is obtained, after which it is thoroughlydried a t 110" to 140" C. Analysis should not as a rule be attempted on a sample which does not pass through a ZOO-mesh screen. The rather tedious reduction of the sample to this state of division ... . .. is circumvented by the use of a mechanical grinding device. .. .. The fusion is carried out in 100-cc. nickel crucibles, with the use of approximately 20 grams of sodium amide and 0.5 gram of the silicate ore. Half of the sodium amide is first placed in the em ty crucible, and the specimen for analysis is spread over its surice and then covered with the remainder of the amide. The 100-cc. crucible is placed within one of 150 cc. capacjty to guard againat the loss of material by the creeping of the fusion over the sides of the containing vessel. The two crucibles, together with a number of other similarly arranged pairs, are then introduced into an PREPARATION OF SODIUM AMIDE electrically heated muffle furnace, previously heated to the temThe sodium amide required in the present experimental perature at which the fusion is to occur (Table 11). A stream of gas is passed through during the fusion and the subwork was prepared by a method that differs in slight detail ammonia sequent cooling of the melts to room temperature. Crucibles are from that already described by Dennis and Brown (3). removed from the furnace at definite intervals and the contents Briefly, dry ammonia is passed through molten sodium a t a analyzed, if it is desired to determine the minimum time necestemperature around 350 " C. until complete conversion to sary for complete decomposition of the ore. At a temperature of 330" C., this time is generally about 20 to 30 minutes, although amide has taken place. it is usually advisable t o continue the fusion for an additional period to be certain of com lete decomposition. Material of 1 The methods of analysis described in the present article have been sucunknown behavior should be ieated for 2 to 3 hours at 330' c. cessfully used a t the San Jose State Teachers College for a number of years. 136
March 15, 1934
INDUSTRIAL AND ENGINEERING
CHEMISTRY
137
TABLE11. INFLUENCE OF TIME, TEMPERATURE, AMOUNTOF SODIUM AMIDE,AND SIZE OF PARTICLES ON RATE OF DECOMPOSITION OF SILICATES AND REFRACTORIES TIMEOF
HBATING~ Min.
WEIGHTOF SAMPLE Gram
UNDISSOLVED
Gram
%
FELDSPAR, 200 MESH AND FINER
FELDSPAR, 200 MESH AND FINER
20 grams 45.5 37.9 10.2 8.5 4.3 2.7
FELDSPAR, 200 ME0H AND FINER
20 grams 5i.o 39.5 13.3 6.5 3.4 1.8
FELDSPAR, 200 MESH AND FINER
Fusing temperature, 270° C.; amount of NaNHz, 16b 0.5028 0.2296 18.5 0.5003 0.1714 21 0.5018 0.0857 26 0.5020 0.0434 36 0.5011 0.0292 46 0.5008 0.0125 56 0.5024 0.0059
Fusing temperature, 330' C.; amount of NaNHz, 20 grams 8b 0.5010 0.2762 55.1 10.5 0.4977 0.0106 2.1 13 0.4955 0.0045 0.9 18 0.5040 0.0023 0.45 28 0.4990 0.0003 0.06 FELDSPAR, 200 MESH AND FINBR
FELDSPAR, 200 MESH AND FINER
Fusing temperature, 330' C.; amount of NaNH2, 10 grams 6b 0.4999 0.2550 49.0 8.5 0.4984 0.0212 4.3 11 3.2 0.5007 0.0162 0.4996 16 0.0095 1.9 0.5000 26 0.5 0.0027 0.5018 46 0.0000 0.0
Fusing temperature, 240° C.; amount of NaNHa, 21b 0.5006 0.2566 0.1986 0.5026 23.5 31 0.0665 0.5003 41 0.0326 0.5022 61 0.0170 0.5000 101 0.5030 0 * 0090
UNDISSOLVED %
Gram
FELDSPAR, 200 MESH AND FINER
Fusing temDerature. 330" C.: amount of NaNHt. 5 grams 6b 0.5026 0.2737 54.3 0.5011 7.5 8.7 0.0438 0.4997 10 5.9 0.0294 0.5028 15 0.0180 3.6 0.5034 25 0.0090 1.8 0.5019 45 0.0050 1.0
Fusing temperature, 210° C.; amount of NaNHz, 30b 0.5022 0.2285 35 0.5035 0.1910 40 0.5016 0.0512 50 0.5004 0.0426 70 0.5061 0.0218 110 0.5083 0.0137
TIMEOF WEIGHTOF H E A T I N G ~ SAMPLE Min. Gram
20 grama 45.7 34.3 17.1 8.6 5.8 2.5 1.2
Fusing temperature, 360' C.; amount of NaNHz, 20 grams 7b 0.5010 0.2744 55.1 9.5 0.5000 0.0080 1.6 17 0.5025 0.0033 0.6 27 0.5010 0.0005 0.1 FEIIDSPAR, 116 TO 150 MESH
Fusing temperature, 330' C.; amount of NaNHz, 18 grama 8b 0.4495 0.2320 51.6 13 0.4334 0.0418 9.6 28 0.4422 0.0153 3.5 68 0.4939 0.0074 1.5 188 0.4558 0,0028 0.6 FELDSPAR, 160 TO 170 ME1SH
Fusing~. temperature, 330° C.; amount of NaNHz. 16 grams 9 0.3864 0,0899 23.1 17 0,3835 0.0287 7.4 67 0.3767 0.0040 1.1 FELDSPAR, 160 TO 170 MBISH
.
Fusing temperature, 330" C amount of NaNHz, 16 grams; amount of N d H , 0.4 gram (2.6%) 9 0.3864 0.08ss 22.9 17 0.3823 0.0273 7.1 67 0.3823 0.0030 0.8 GLASS-SAND, 200 MESH AND FINBR
Fusing temDerature, 330' C.: amount of NaNHz, 20 grama 0.5005 0.0020 0.4 8b 10.5 0.5048 0,0018 0.36 13 0.5000 0.0013 0.26 18 0.5050 0.0009 0.18 28 0.4993 0 0000 0.00
F m D S P A R , 200 MESH AND FINBIR
Fusing temperature, 300" C.; amount of NaNHz, 20 grama 12b 0.5032 0.2623 52.3 14.5 0.5000 0.0427 8.5 22 0.5034 0.0166 3.3 32 0.5004 0.0049 1.0 42 0.5040 0.0027 0.3
ALUNDUM, 160 TO 2W MESH
Fusing temperature, 360' C.; amount of NaNHz, 20 grama 13 0.5085 0.5020 98.7 577 0.4980 0.4167 84.1 ALUNDUM, 200 MESH AND FINER
Reokoned from time a t which the orucibles were introduced into previously heated muffle. b Sodium amide has just melted a t this point.
Fusing temperature, 330° C.; amount of NaNHz, 20 gram8 12 0.4995 0.4483 89.8 427 0.5001 0.1776 35.4
I t is possible to avoid the use of a muffle, provided the inner crucible be fitted with a nickel cover carrying a nickel tube through which a slow stream of ammonia passes during the fusion. The cooled inner nickel crucible and its contents (and also the outer crucible, if sodium amide has crept into it) are placed in a 500-cc. casserole, which is partly filled with 95 per cent alcohol and then covered with a watch glass. Small quantities of water are added from time t o time as the reaction subsides. The subsequent analysis of the dissolved fusion is carried out according to the usual methods (8). The muffle furnace, to which reference has been made, consists of a rectangular monel metal box (15 X 8 X 6 inches, inside dimensions) closed b a hinged door. To the outside of this box are spot-welded eigxt 14-inch chromolox heating units, the whole being well insulated against heat losses with asbestos. The top of the furnace carries three holes which are used, respectively, for a thermometer well and for the introduction and removal of ammonia. It is permissible to use an ordinary gas-fired muffle, but it is recommended that it be lined with a monel metal or nickel box, through which a current of ammonia can be passed.
con, ferro-silicon, feldspar, bauxite, soda and Pyrex glasses, burnt refractory, and at least in one variety of clay, after fusion for varying periods of time with sodium amide a t a temperature of 330" C. (Higher temperatures may cause undue volatilization of sodium amide.) The specimens for analysis must be finely ground, preferably to 200 mesh per inch or finer (Table 11). I n the case of an easily fusible silicate, feldspar, the minimum fusion time, a t the end of which sensibly complete decomposition of the 200-mesh material has taken place, is about 30 minutes. It is recommended that the time of fusion of material of unknown behavior be 2 to 3 hours a t 330" C. Alundum (Table 11)is not completely broken down by fused sodium amide under the optimum conditions in 9 hours, and it therefore cannot be analyzed by the methods described without an undue expenditure of time. The fact that a substance containing alumina is slowly attacked by fused sodium amide is of some interest, since pure alumina has been reported by Fernelius (4) to remain unattacked a t 375" C. The alumina used in the latter experiments was not ground. Zirconia of 200 mesh is slowly and completely attacked by fusing with sodium amide for 4 hours a t 330" C. It is rarely necessary to eliminate traces of nickel from the aqueous solutions of the sodium amide fusions, since a number of blank determinations showed this to be present in amounts of 0.3 mg. or less per analysis (dimethylglyoxime test),
CONCLUSIONS The foregoing work definitely shows that fused sodium amide may be used to open up silicates, glasses, and certain refractories as a preliminary step in their quantitative analysis. The temperature and time of fusion, the size of the particles of the substance to be analyzed, and other factors play a very important part in the course of the reactions. The experimental findings may be summarized as follows: Silicon can be determined accurately in commercial sili-
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Vol. 6, No.2
TABLE111. COMPARISON OF ANALYSISOF SILICON AND FERROI n all the fusions which have been considered in this article, SILICON FUSED WITH SODIUM AMIDE AND WITH SODIUM it is probable that mixed aquo-ammono silicates, aluminates, CARBONATE etc., are primary products of the reactions, but whether these SODIUM CARBONATEare further converted to sodium ammono silicates, alumiFUSION SODIUM AMIDEFUSION FUSION nates, etc., is a matter of conjecture. TIMEAT WBIQHTOF Weight of Per cent Per cent
B U B S T A N C E ~ 330° C. Hours Ferrosilicon 9
SAMPLE
of Si
of Si
0.8027 0.7996
76.4 76.6
75.6
(1) Bergstrom and Fernelius, Chem. Rev., 12, 75-6, 90, 92, 106, (2) Bergstrom and Fernelius, Ibid., 12, 75,83. 84 (1933).
8102
Gram
Grams
0.4980 0.4944
151-2 (1933).
Ferrosilicon
4
0.6033 0.4998
0.7709 0.7667
71.9 71.7
76.6
Ferrosilicon
6
0.2001
0.3083
72.0
75.6
Silicon
9b
0.4887 0.4968
1.0353 1.0268
96.9 96.73
96.7
Silicon
4
0.4871 0.4980
0.9258 0.9252
87.06 86.8
96.8
0
b
LITERATURE CITED
200 mesh. 20 grams of NaNHz used per analysis. 6 per cent NaNs added.
(3) Dennis and Browne, J . Am. Chem. Soc., 26,587-600 (1904). (4) Fernelius, Dissertation, Stanford University, 1928. (5) Franklin, J . Am. Chem. SOC.,27, 820-51 (1905); Franklin and Kraus, Am. Chem. J.,21,8-14 (1899); Franklin, Ibid., 47,285 (1912); Proc. Eighth Intern. Congress Applied Chem., 6, 119 (1912); J . Am. Chem. Soc., 46, 2134-51 (1924). (6) Hillebrand, U.8. Geol. Survey, Bull. 700 (1919). RECEIVED August 26, 1933. From the master’s and doctoral theaes of P. Victor Peterson, Stanford University, 1923 and 1930. The maater’n thesis was prepared under the direction of E. C. Franklin.
Inclusion of Rarer Metals in Elementary Qualitative Analysis I. Inclusion of Tungsten and Molybdenum in Groups I and I1 LYMANE. PORTER, University of Arkansas, Fayetteville, Ark.
D
URING more than a hundred years (3) the list of
metals found in the general scheme of elementary qualitative analysis has remained practically unchanged. In the light of the growing commercial importance of some metals not found in the original list, it has seemed advisable to introduce a few of the more important rarer metals by modifying and simplifying certain procedures from schemes for the analysis of the rare elements (1, 2, 4) and incorporating them into the scheme for the commoner ones. The detection of tungsten in group I and of molybdenum in group I1 is described in this paper, and detection of titanium and vanadium in group I11 will be described later. Stock solutions of the common ions are made up in the customary manner. For tungsten and molybdenum, the alkali salts of the tungstate and molybdate are dissolved in water and diluted to the proper concentration.
DETECTION OF TUNQSTEN IN GROUP I The sample, which may include a BUS ended precipitate, is treated with dilute h drochloric acid untifprecipitation appears complete, and 5 cc. o?the acid are added in excess. This mixture is warmed just below the boiling point for 2 or 3 minutes, and cooled, in order t o make the recipitate of tungstic acid or tungstic oxide more complete. :1 the material is boiled, some or all of the mercurous ions will be oxidized, provided nitrates are also present. The cooled mixture is filtered two or three times through the same pa er if necessary to obtain a clear filtrate which is reserved for rater groups. Certain acid ions-namely, arsenate, arsenite, phosphate, borate, oxalate, tartrate, vanadate, and to a less extent acetate-interfere with the completeness of the tungsten recipitation, so that combinations of these with tun sten shourd be avoided. The separation of the lead chloride by f o t water and the identification of mercurous mercury by the use of ammonium hydroxide are accomplished in the customary manner. The ammoniacal filtrate from the mercury will contain the silver and the tungsten, This solution is then made nearly neutral with dilute hydrochloric acid, and enough ammonium hydroxide is added just t o redissolve any precipitate that may have appeared, The silver may now be identified and separated by the addition of a soluble iodide followed by filtration. In the presence of a large excess of ammonia, the precipitated silver
iodide i s colloidal, and it is difficult to remove it by filtration. This test for silver has been shown to be fully as sensitive as the usual one using nitric acid t o precipitate the silver chloride. After filtration, the solution is evaporated to a small volume, acidified with dilute hydrochloric acid, and treated with 3 cc. of stannous chloride. After the mixture has been heated to boiling, 3 cc. of concentrated hydrochloric acid are added, and the mixture is again boiled. The formation of tungsten blue proves the presence of tungsten. Test solutions were run by this method using widely varying concentrations of the constituent ions. Tungsten was found correctly in all cases where there was as much as 10 mg. of this metal in the solution, in the presence of even as much as 400 mg. of other metals of group I. I n the hands of a class, satisfactory results were obtained with samples in which the concentration of each constituent present was approximately tenth normal,
DETECTION OF MOLYBDENUM IN GROUPI1 Molybdenum belongs in the arsenic division of the hydrogen sulfide group. I n order to effect a satisfactory separation of the molybdenum sulfide, however, the procedure for the precipitation of the group should be modified. The filtrate from grou I is neutralized with ammonium hydroxide and is made sightly acid with dilute hydrochloric acid. To this are added 2.5 cc. of concentrated hydrochloric acid, 1 gram of ammonium iodide, and enough water t o make a total volume of 100 cc. This mixture is then saturated with precipitation flask hydrogen sulfide in the cold in a and the flask, loosely sto pered, is p aced in a beaker of boiling water. When the water [as again reached boiling temperature, boiling is continued for 4 or 5 minutes, after which the mixture is cooled, resaturated with hydrogen sulfide, and filtered.
fressure
This procedure has been shown to precipitate satisfactorily all the members of this group. Of the commonly mentioned ions that interfere with the precipitation of molybdenum sulfide, the presence of phosphate must be avoided, because of the formation of a complex compound that prevents
