V O L U M E 21, N O . 1, J A N U A R Y 1 9 4 3
173
Mead, J. F., and Bartron, E. A,, J . Am Chem. Soc., 70, 1286 (1948).
Miller, J. F., Hunt, H., Hass, H. B., and McBee E. T., ANAL. CHEM.,19,146 (1947). Miller, J. F., Hunt, H., and McBee, E . T., I b i d 19, 145 (1947). Newman, L., Phillip, J. F., and Jensen, A. R., Ibid.. 19, 451 (1947).
Nichols, M. L., and Olsen, J. S.,Ibid., 15, 342 (1943). Nicolet, B. H., and Poulter, T. C., J . Am. Chem. SOC.,52, 1186 (1930). CHEM.,20, Ogg, C. L., Willits, C. O., and Cooper, F. J., A N ~ L 83 (1948). Prigot, M., and Pollard. C. B.. J . Am. Chem. S o c , 70. 2758 (1948). Reithel, F. J., and West, E. S., I b i d . , 70, 898 (19481 Rooney, H. A , , ANAL.CHEY.,19, 475 (1947). Rosenmund, K. W.,and Kuhnhenn. W.,2. C'ntersuch. .Yahr. u. Genussm., 46, 154 (1923). Saffer, A . , and Johnson, B. L., Ind. Eng. Chem.. 40, 538 (1948).
Scafe, E. T., Herman, J., Bond, G. R., Jr., and Coopcrntors, ANAL.CHEM.,19, 971 (1947). Seaman, W., Woods, J. T., and Massad, E. A , . Ibid., 19 250 (1947).
Shaeffer, W.E., and Becker. W.IT.,I b i d . , 19, 307 (1917) Siggia, S., Ibid., 19, 1025 (1947). Siggia, S., and Edsberg, R. L., I b i d . , 20, 762 (1948). Siggia, S.,and Maisch, M.,I b i d . , 20, 235 (1948). Sisido, K., and Yagi, H., I b i d . , 20, 677 (1948).
(58) Sobel, A. E., Hirschman, A , , and Besman, L., Ibid., 19, 927 (1947). (59) Sobel, A. E., Hirschman, A., and Besman, L., J . Biol. C h a . , 161,99 (1945). (60) . . Sobel. A. E.. Mever. A. M..and Gottfried. S. P.. Ibid.., 156., 355 (1944). (61) Steyermark, A., Baas, E., and Littman. B., ANAL. CHEM.,20, 587 (1948). (62) Swern, D., Findley, T. W Billen, G. N., and Scanlan, J. T.. Ibid., 19, 414 (1947). (63) Swern, D., and Jordan, E. F., J . Am. Chem. Soc., 70, 2334 (1948). (61) Thomas, P. R., Donn, L.. and Beckei H. C., AYAL CHEM.,20, 209 (1948). (65) Trafelet, L., Ibid., 20, 68 (1948). (66) Unteraaucher, J., Be?., 73B,391 (1940). ANAL. (67) Vaughn, T. H., and Nieuwland J. A,, IND. ENG.CHEM., E D . ,3, 274 (1931). (68) Wagner, C. D.. Riown, R. FI an(i Peters, E. D.. J . A m . Chem. Sic., 69,2609 (1947) (69) Ibid.. 69. 2611 (1947) (70) Wagner, C D.. Siiiitn R H., and Peters, E . D., ANAL CHEM., 19, 976 (1947) (71) I b i d . , 19, 982 (1947). (72) Warner. E. C., and Miles, S €1. Ibid., 19 274 (1947). (73) Widmaier. O., Luftfahrt-Forsch., 20, 181 (1943) 1
I
I
.
RECEIVED November 1, 1948.
[End of Review Section]
Determination of lithium in Rocks by Distillation hIARY H. FLETCHER', Bureau of Mines, U . S . Department of the Interior, Washington, D. C .
A method for the quantitative extraction and recovery of lithium from rocks is based on a high temperature volatilization procedure. The sample is sintered with a calcium carbonatevalcium chloride mixture at 1200' C. for 30 minutes in a platinum ignition tube, and the volatilization product is collected in a plug of Pyrex glass wool in a connecting Pyrex tube. The distillate, which consists of the alkali chlorides with a maximum of 5 to 40 mg. of calcium oxide and traces of a few other elements, i s removed from the apparagus by dissolving in dilute hydrochloric acid and suhjected to standard analytical procedures. The sinter residues contained less than 0.0005% lithium exide. Lithium oxide was recovered from synthetic samples with an average error of 1.1%.
T
HE accurate determination of lithium in rocks is not easy, even after the alkalies have been obtained in a comparatively pure solution. The analysis is further complicated by the laboriousness of the classical methods for isolating the alkalies, which is chiefly due to the large amounts of reagents that must be used for purposes of decomposition. Although unsatisfactory from various viewpoints, the ancient methods of Berzelius (2) and Smith (8, 9) and their recent modifications (5, 8, IO) are the best now available for accurate x-ork. The inadequacies of the well-known methods for separating the alkali chlorides before determination of lithium in rocks have been ably discussed by Kallmann ( 5 ) , who has pointed out the losses inherent in each step of the various procedures. He has combined the best features of the Berzelius method (2) as modified by Koenig (6) and of the J. L. Smith method (8, 9) and has overcome most of the error by careful reworking of all residues and precipitates. Severtheless, these methods suffer from the disadvantage of requiring separation of large amounts of impurities in the solid state from small amounts of alkalies in the filtrates. The method deccribed beloxy is a radical departure from current procedures. It utilizes high-temperature volatilization for an immediate and relatively clean separation of lithium and other alkalies from the sample. I t is an adaptation for analytical purposes of the Fraas-Ralston (3) commercial process for the
* Present address, Geological Survey, U. S. Department of the Interior, WLahington, D. C.
production of lithium salts from spodumene. In the proposed procedure, the sample is sintered with a calcium carbonatecalcium chloride mixtiire a t 1200' C. for 30 minutes in a platinum ignition tube through which a cuirent of air is drawn. The volatilization product is collected in a plug of glass wool in a connecting Pyrex tube, which is then washed out with dilute hydrochloric acid. The resulting solution is subjected to standard proeedures for the determination of lithium. This paper is aoncerned primarily with the quantitative extraction and recovery of lithium from its various minerals, although use of the method in determining other alkalies is also proposed. Because lithium is accompanied by other ions in the volatilization step, the composition of the distillates is discussed. However, the separation of these ions and the final determination of the lithium are of secondary interest, as both may be accomplished by standard procedures. REAGENTS AND APPARATUS
Calcium carbonate, c.P., lithiumfree. Calcium chloride, lithium-free. The apparatus is shown in Figures 1 and 2. A is a platinum-lO% rhodium ignition tube (0.3-mm. wall thickness) with small end tapered to fit inside B, a Pyrex standardtaper female interjoint 9/14, with small water condenser sealed on exit end. C is a plug of Pyrex wool. D is a platinum-lO% rhodium boat, 15 X 83 X 7 mm., 0.3-mm. wall thickness. E , crystal corundum pedestals for boat, were made from sections of a boule of synthetic corundum. c.P., anhydrous,
ANALYTICAL CHEMISTRY
114
Figure 1. Unagsembled Apparatus
F is a platinum-wound furnace with Variac (Type 100 Q) and ammeter. Its over-all length was 30 om. (12 inches), and inside diameter 0.875 inch. An Alundom tube was used on which 5
- _ .
wound 10 turns per inch. The optical pyrometer is not shown in the photographs METHOD
Mix 2.9 grams of cslcium carbonate, 1.000 gram of sample ground to -100 mesh, and 0.56 gram of calcium chloride in a n agate mortar, transfer quantitatively to the platinum boat to which corundum pedestals have been affixed with a n organic cement, and insert into the ignition tube. Apply full suction from a water pump to the exit end of the condenser tube and a current of cooling air to the platinum-glass joint. Start the furnace, and after a temperature of 1200" C. has been reached, maintain i t for 30 minutes. Then turn off the electric current, and in ahout 15 minutes when the furnace has cooled to approximately 700' C. remove the boat and sinter residue. Discontinue the suction and the air current, remove the ignition tube from the furnace, and allow t o 0001. Disconnect the nlatinum and elass parts and rime the corun-
~~~
~
water, police weiL abd rinse several times with a stre& i f water The lass portion is most easily rinsed in the same test tube
removal of all the salts. Filter t h i combined solutions to sena-
Filter. evanorste 'the filtrate to drvness. dhsol;e
the eesidue in
isolatidn of lithiurh. beter&e^ lithium in the mixed alkalies by any standard procedure. These methods have been recently reviewed by Kallmann (6),and the analyst may Qhoosethe one best suited to his needs. DISCUSSION AND EXPERIMENTAL
The volatilization reaction upon which this procedure is based occurs below the boiling point of lithium chloride and depends upon the high partial vapor pressure exerted by this substance a t elevated temperatures (5). Hence, as high a temperature as is practicable should be used. A strong current of air is necessary to remove the products from the zone of deromposition as they are formed in order to drive the reaction to completion. A platinum assembly is required, because ceramic ware is attacked by thc volatilised chlorides at the working temperatures. Hnwever, because platinum sticks to platinum a t these temperaturm, i t is necessary to employ small corundum pedestals to sepmate the platinum b a t from the platinum tube. An Nundum boat was used to hold the platinum boat in earlier experiments, hut because i t absorbed about 7 mg. of lithium oxide during each
Table I.
Composition of Volatiliwtion P r o d u c t s from Mineral Samoles
Mineral
Platinum
MB
M*.
Smdumene
None
12.5
Lepidolite Amblygonite Petaiite Zinnwhldite Triphylite
0.45 6.6 1.2
2.4 0.69
5.9 5.3 13.2 8.1
CaO
5.8
Other I m w r i t i e s Weight Computed f&m Speotrogrwhio Analysis M8. About 0.4 or less Pb. Mn. Zn, Fecombined ' ' . About 0.1 P b About 0.1 Pb. Fe oombined About0.4 Pb. Zn,Mn combined About 0.3 Zn, Mn combined About 0.3 Pb, Zn combined
run, its use was discontinued. The corundum pedwstals are small and positioned well under the boat, so that the fumes apparently do not come in contact with them. In assembling the apparatus, the pedestals are stuck to the platinum boat with an organic cement which is destroyed during the ignition. It is not necessary to remove the boat and pedestals as a unit, for the host is not taken from the ignition tube until the furnace has cooled below the sticking point of platinum. When a run is made, the sample begins to decompose hetween 750" and 800' C., a8 evidenced by the initial appearance of fumes. Although the decompasition is rapid between 850" and 950" C., i t is necessruy to raise the temperature to 1200' C. to remove the last traces of lithium. The temperatures listed above were measured with an optical pyrometer by sighting directly ou the charge. The volatiliaation product collects 8s s white fume in the plug of glass wool, in the glsss connecting tube, and in the small end of t.he platinum ignition tube where there is usually a small fused portion as well. The smokelikc product dissolves immediately, but the fused portion requires policing to assist its solution. The spectroscope was "sod to determine the completeness of the extraction of lithium from the gangue and sinter mixture, and provided a test which was simple, rapid, and a great deal more sensitive than a chemical determination. The volatilization method was tried on samples of spodumene, lepidolite, amblygonite, petslite, ainnwaldite, and triphylite m d the sinter residues were examined spectroscopically for lithium; in each case the residues contained less than 0.0005% lithium oxide. The spectroscopic determinations were made on 20. mg. samples, which were completely volatilized in. a carbon arc. The duration of the visibility of the 6707.9 A. line was measured mith a stop watch. Synthetic standards of approximately the sane composition were used to obtain a standard ourve. No claim for high accuracy is made for these determinations, and errors of 100 to 200% probably occurred; however, o invalidate much larger enom than these would be necesssry t the results. The residual lithium content was so small that i t could not be determined chemically. Of the samples tested, zinnwrtldite fused at 1200' C., and amblygonite between 1240" and 1270" C . ; but even in cases where fusion occurred, the lithium was completely removed. The volatiliastion product from the minerals was collected and converted to thc sulfate, and subjected to spectrographic and-
V O L U M E 21, N O . 1, J A N U A R Y 1 9 4 9
175
gsis to determine the impurities present (Table I). Calcium and platinum were found to be the chief contaminants and so were determined gravimetrically. Bll other ions, such as aluminum, silicon, magnesium, and titanium, were found to occur in insignificant amounts. The platinum was higher in the distillates obtained from zinnwaldite and lepidolite, both of which had a relatively high potassium content. Potassium salts may be the source of the attack on the apparatus, as high platinum volatilization also resulted when a sample of Bureau of Standards potash feldspar was ignited according to the procedure. The analyses given in Table I show lead, manganese, and zinc the chief minor impurities present in such small amounts that in most cases they can be ignored. Occasional iron would be removed with the calcium. The quantities of iron and manganese remain the same, irrespective of their original concentrations in the minerals. In the rare instances where the sample might have a high lead or zinc content, the amounts of lead and zinc found in the distillate would increase, and they would have to be removed by appropriate means, such as the ammonium sulfide method for both or the &hydroxyquinoline method for zinc. Inasmuch as no direct method was available for checking the completeness of the recovery of the volatilized lithium and there were no standard samples a t hand with a known lithium content, synthetic samples were prepared. To minimize errors that were not unique to the volatilization procedure itself, C.P. chemicals (A1201, 0.1885 gram; SiOa, 0.5620 gram; and Li2C03, 0.2495 gram) were used. The purity of the lithium carbonate used was determined by analyzing six control samples for lithium by the Palkin method ( 7 ) as modified by Wells and Stevens (11). This method was also used for determining lithium in the volatilization products. The lithium carbonate wvas found to be 99.1% pure. Hence the amount of lithium oxide used in preparing the synthetic samples was calculated on the basis of a 99.1% pure lithium carbonate. The final lithium sulfate products obtained from the control samples were compared spectrographically with those obtained by the volatilization procedure. The products were found to be of comparable purity. The recovery of lithium oxide from the synthetic samples as determined by the volatilization procedure is reported in Table 11. The extent to which the other alkalies are volatilized has not been thoroughly tested. However, samples of Bureau of Standards analyzed soda and potash feldspars have been treated by the volatilization procedure and the residues examined with the spectrograph. Potassium could not be detected in the residues. Sodium was found to the extent of about O . O O l ~ osodium oxide. The limit of detection of potassium is about 0.05% potassium oxide. Platinum was removed from the solutions of the volatilization products from these feldspar samples, suitable aliquots were taken, and sodium was determined by the triple acetate method ( 1 ) . Results of drterminations appear in Table 111.
Table TI.
Recovery of Lithium Oxide from Synthetic Samples Error,
LizO Present
MQ.
MQ.
100.0 100.0 100.0 Mean
98.7 98.5 99.6 98.9
Table 111. Sample
B.S.99 B.S. 70 a
Liz0 Found
% of LizO Present 1.3
1.5 0.4 1.1
Recovery of Sodium from Standard Feldspars S a t 0 Present
NazO Found
% 10.73
10.sa
2.38
Corrected for reagent blank.
Error,
% of Liz0 Present
%
2.30a
0.9 3.4
If these resuIts are typical for alkali minerals in general, the method could be extended to include analyses of all the other alkalies, for sodium chloride has the lowest partial vapor pressure of the five elements. The partial vapor pressures of rubidium and cesium chlorides are well above that of lithium chloride (8). In the treatment of the feldspars, fumes were first observed a t 850" to 900" C. and the evolution of fumes wm heavy a t 1020" to 1080" C. A maximum temperature of 1300" C. was used for these volatilizations. The total time consumed for the volatilization step in general was approximately 4 hours, about 2.5 hours of which were required to reach the decomposition temperature. All these ignitions were started with a cold furnace. The time could probably be lessened without injury to the furnace, or a furnace preheated to 500" to 600" C. could be used. If many lithium determinations were required, it would be advisable to construct a multiple-type furnace and ignite a number of samples simultaneously. SUMMARY
A high-temperature volatilization procedure using a platinumwound furnace has been developed for the quantitative extraction of lithium from rocks. The sample is sintered with a calcium carbonate-calcium chloride mixture a t 1200" C. for 30 minutes in a platinum ignition tube through which a current of air is drawn. The volatilization product is collected in a plug of Pyrex wool in a connecting Pyrex tube and is dissolved from the apparatus iyith dilute hydrochloric acid. The resulting solution is then treated by standard procedures for determining lithium. The removal of lithium from the gangue and sinter mixture is quantitative; sinter residues from spondumene, lepidolite, amblygonite, petalite, zinnwaldite, and triphylite all contained less than 0.0005~olithium oxide. Lithium was quantitatively recovered in the distillate within the range of experimental error. In a series of experiments an equivalent of 100.0 mg. of lithium oxide was added as the carbonate to synthetic samples, and 98.7, 98.5, and 99.6 mg. of lithium oxide mere recovered. ACKNOWLEDGMENTS
The investigation reported in this paper was completed under the general direction of Paul RI. Ambrose, chief, College Park Branch, Lletallurgical Division, Bureau of Mines, and the immediate supervision of Alton Gabriel, to whom the author is indebted for helpful advice and criticism. She also wishes to acknowledge the kind amistance of her associates in the conduct of this work, and especially to thank Howard F. Carl for construction of the platinum-wound furnace and assistance in designing the apparatus, Maurice J. Peterson for spectrographic analyses of the volatilization products, Howard Jaffe for spectroscopic examination of many precipitates, Walter Slavin for photographs of the apparatus, and Morris Slavin and Foster Fraas for many helpful suggestions. LITERATURE CITED (1) Barber, H. H., and Kolthoff, I. M., J . Am. Chem. SOC.,50, 1625-31 (1928). (2) Beraelius, J. J.. Pouu. Ann., 1. 169 (1824). (3) Fraas, F., and Ralston, 0. C., Bur. Mines, Rept. Invest. 3340 (1937).
Hillehrand, W. F., and Lundell, G. E. F., "Applied Inorganic Analysis," pp. 497-8, New York, John Wiley & Sons, 1929. Kallmann, S., IND.ENQ.CKEM.,ANAL.ED., 16, 712-17 (1944). Koenig, E. W., Ibid., 7, 314-15 (1935). Palkin, S.,J.Am. Chem. Soc., 38, 233 (1916). Smith, J. L., Am. Chemist, 1, 404 (1871). (9) Smith, J. L., Am. J . Sci. (31, 1, 269 (1871). (10) Stevens, R. E., IND. ENG.CHEM.,ANAL.ED., 12, 413-15 (1940). (11) Wells, R. C., and Stevens, R. E., Ibid., 6, 440 (1934). RECEIVED M a y 5 , 1948. Presented before the Section of Inorganic and Analytical Chemistry a t the 600th meeting of the Chemical Society of Wash. ington, May 13, 1948.
