T H E CHEMICAL REACTIT’ITY OF T H E FUSED BASES I. The Action of the Alkali Amides upon Electropositive Metals‘ BY
w. C O N A R D FERNELICS? A N D
F.
n-. BERGSTROM
In an earlier series of investigations3one of us has examined the action of liquid ammonia solutions of the amrnono bases, potassium and sodium amides, upon a number of elements. I t was found that an electropositive metal, such as magnesium, reacts in the sense of the equation,
+
ZNHQ AIg
+ zI~KHz
=
XIg(KHK)? 2XH3
+ Hz
to form potassium ammono magnesiate and hydrogen, just as zinc reacts with an aqueous solution of potassium hydroxide to form potassium zincate and hydrogen, Zn zKOH = Zn(OK)n H 2
+
+
Whereas such a reaction in water is fairly rapid, the analogous reaction in liquid ammonia is slow, enabling the observer to gain an idea of the steps involved and the intermediate products. Thus it was found that magnesium first reacts with a liquid ammonia soiution of potassium amide to liberate potassium, which is detected by the opaque blue color of its dilute solution and the coppery lustre of the highly concentrated solution,* the reaction probably proceeding in accordance with the equation, Mg
+ 2KXHz
XIg(NHz)n
+ zK.
To understand this apparently anomalous displacement of one metal by a less electropositive metal, one has but to recall that dilute solutions of the alkali metals in liquid ammonia are ionic in character,j the positive ions being the normal ions of the alkali metal while the negative ions are solvated electrons, e-. Since potassium amide forms potassium, K+, and amide, NH2-, ions, the reaction of a solution of this substance with magnesium is but a reaction between four ions, K+, XH,-, Mg++ and e-, in accordance with the equation, zK+
+ 2NHz- + Mg++ + ze- e XIg(NH2)2+ zK+ +
28-
This paper is a portion of a dissertation submitted to the department of chemistry and the committee on graduate study of Stanford University by Mr. W. C. Fernelius in partial fulSllment of the requirements for the degree of Doctor of Philosophy. Presented a t the Swampscott meeting of the American Chemical Society, Septemher 1928. 2 Royal1 Victor Fellow in Chemistry, 1927-8. 3Bergstrom: J. Am. Chem. Soc., 45, 2788 (1923); 46, 1545 (1924); 47, 1836 (192j); 48, 2848 (1926); 50, 652 (1928); J. Phys. Chem., 30, 1 2 (1926). 4 Although magnesium dissolves slightly in liquid ammonia, the color intensity of the solution is so much less than that of a solution of potassium that there can be no confusing the two. Furthermore, a concentrated solution of potassium has a very coppery luster. Cf. J. Am. Chem. SOC.,45, 2789 (1923). 5 Kraus: J. Am. Chem. Soc., 43, 749 (1921) and previous articles.
CHEMICAL REACTIVITY O F THE FCSED BASES
741
Since magnesium amide, Prlg(NH,),, has a very low solubility in ammonia, it is precipitated and there remains in solution only Kf and e- ions, which together constitute a solution of metallic potassium. The potassium resulting from the equilibrated condition noted above reacts with the solvent to regenerate potassium amide,
ZK+ z N H ~= z K K H ~$- Hz the magnesium serving as a catalyst for this reaction. Furthermore, the amide of the less electropositive metal, being an amphoteric base reacts with the alkali metal amide to form an ammono metallate,l in accordance with the equation, ?*Ig(KHZ)z z K S H = ~ M~(NHK)~.zNH~.
+
Purpose of the Investigation In view of this interesting behavior of the alkali metal amides in liquid ammonia solution it was deemed worth while to extend the study of such reactions to the fused state where the temperature and concentration of the amide would be much greater and where solubility or insolubility in liquid ammonia would not be a factor influencing the course of the reaction. Furthermore, there is at the present time no really satisfactory or comprehensive theory of fusions in the alkali bases and any study pointing toward the formulation of such a theory is valuable. This work was stimulated by an observation of Professor E. C. Franklin that a piece of magnesium ribbon plunged into molten sodium hydroxide has drops of a blue liquid adhering to it upon withdrawal. Such behavior indicates the liberation of metallic sodium in accordance, probably, with the equation, RIg
+ zSaOH
zNa
+ Rlg(OH)2.
Historical: The Action of the Amides upon the Elements Following the discovery of sodium and potassium amides by Gay-Lussac and ThCnard, these investigators found that several metals were attacked by potassium amide., Davy, working contemporaneously, studied in a superficial manner the reaction of potassium amide with tellurium and a r ~ e n i c . ~ Ephraim4 examined the reactions of sodium amide with sulfur, bromine, iodine and magnesium as well as with a large number of oxides, sulfides, chlorides and ternary salts. Winter5 observed that an energetic reaction occurred when yellow phosphorus was warmed with sodium amide. Kohler One will recall that the phenomenon of amphotericity of the basic amides is much more general than the similar property of the basic hydroxides. N o t only is there an aluminate, zincate, plumbite, stannite and stannate of potassium, but also a cuprite, a cadmiate, a magnesiate, a calciate, a bariate and even a sodiate in the ammonia system. Furthermore these compounds are for the most part definitely crystalline and easily obtained in a pure condition. * Gay-Lussac and ThBnard: “Recherches physico-chimiques,” 1, 341 (1811). 3 Davy: Phil. Trans., 1810, 27. Ephraim: Z. anorg. Chem., 44, 185 (1905). J. .4m. Chem. Soc., 26, 1484 (1904).
742
W. CONARD FERNELIUS AND F. W. BERGSTROM
and Stang-Lundl have electrolyzed fused sodium and potassium amides and determined their specific conductivity and decomposition voltages. McGee2 has also determined the specific conductance of molten sodium amide.8
Apparatus and Manipulation In designing an apparatus for studying fusion reactions there were numerous factors which had to be taken into consideration. I t can safely be said that no single technique so far employed has been entirely satisfactory in all
FUSION CHLRECR
FIG.I
of its details. The apparatus finally chosen for this investigation is shown in Fig. I . It was designed so that the amide fusions could be carried out in a current of ammonia in the complete absence of air and moisture. The fusion chamber (DEFG) consists of a pyrex tube ( 2 7 mm. diameter by 60 cm. long, with side arms of 12mm. tubing, as shown) wound with number 2 7 chrome1 wire to serve as a heating unit4 and insulated with 8 5 c ; magnesia pipe covering. A length of three quarter inch monel metal tubing, S, is inserted in the Wohler and Stang-Lund: 2. Elektrochemie, 24, 261 (1918). J. Am. Chem. Soc., 43, 586 (1921). Other important references dealing Kith the fused alkali amides are Beilstein and Geuther: Ann., 108, 88 (1858)' Baumert and Landolt: 111, I (18j9); Drechsei: J. prakt. Chem., (2) 16, 201 (1877); Vv'ikcenus: Ber., 25, 2084 (1892);Titherly: J. Chem. Soc., 65, 504 (189 ); 71, 69 (1897); De Forcrand: Compt. rend., 121, 66 (1895); Dennis and Browne: J. Am. Ahem. hoc., 26, j 8 7 ( I 04);Ruff and Goerges: Ber., 44, joz (1911); Miles: Proc. Roy. Soc., Edinburgh, 35, 134 ?I91 j);Kraus and Cuy: J. .4m. Chem. SOC.,45, 7 1 2 (1923); Gunts and Benoit: Bull., (4) 41, 434 (1927). There exists also a voluminous literature on the use of sodium amide in organic chemistry. The pgrex tube was wound for the entire length covered by the magnesia iflsulationincluding the section E. These windings are not shown in Fig. I . The two terminals of the wire mere tied to glass knobs fused to the glass a t the ends of the insulated portion.
* McGee:
CHEMICAL REACTIVITY O F THE FUSED BASES
7 43
furnace to serve as a sheath to protect the glass from the corrosive amide which is often spattered or spilled from the fusion boat, X, during the course of a reaction. The upper part of the monel tube on the right was milled away to a depth of about one third its diameter and over about half of its length, to enable the observer to view the molten amide in the boat. Likewise, there is a hole in the metal directly underneath the glass tube F through which materials are introduced into the fusion boat. A short length of one eighth inch monel rod, inserted through the tight rubber sleeve, D’, and through a small hole drilled in the metal sheath served to keep the sheath in position. A long monel rod H (118 inch in diameter) hooked at one end and working through the rubber sleeve C’ is used to place the fusion boat, a nickel combustion boat 13x7 j mm. in size, at any desired position within the fusion chamber. The space E of the insulation is arranged so that it may be removed to enable one to view the interior of the chamber. h resistance heating unit is wound on F, and the side tube G , sealed to F, may also be used for the introduction of materials into the furnace. J is a mercury bubbler which gives a visual pleasure of the amount of gas passing through the apparatus. The large tube AI is filled with dilute air-free sulfuric acid and serves both as an ammonia scrubber and as a gas collector. The apparatus for gas analysis is connected through a capillary with the top of the gas collector, &.I. The technique employed when using this apparatus is perhaps best described by giving the log of a typical run. After thoroughly cleaning and drying both the chamber and the sheath, the latter is inserted in the furnace and locked in position. The boat, previously cleaned inside and outside with emery cloth’ is attached to the manipulative rod, H, placed in the chamber and then moved directly beneath the vertical filling tube, F. *Ill stoppers are now fitted into position and the inlet tube C connected to the pure ammonia line,2 A-B’, and a slow tream of ammonia admitted to sweep out foreign gases within the system. topcock li is open during this time PO that all gases are vented t o the waste. The heating current for the main furnace is now turned The ammonia stream is continued for twenty minutes and during this time the stoppers F and G are removed for a sufficient length of time to insure the removal of all air that may be in these tubes. 1 Neither fused amides themselves nor the products of their reaction with the strongly electropositive elements attack or discolor the nickel boats to anv noticeable extent. The reaction products of the more electronegative elements, however, exhihit a definite corrosive action upon the nickel. Particularly is this true of tin, lead, arsenic and antimony fusions which leave a rather tightly adherent film of brown-blaek material clinging to the boat. Phosphorus and the elements of the sulphur group give reaction products which discolor the nickel to a considerable extent, but do not appear t o attack it seriously. * The ammonia used is the commercial anhydrous product dried over sodium according to the method of Franklin and Kraus: Am. Chem. J., 23, z8j (1900). The amount of current passing through the furnace is regulated by means of a lamp resistance. The maximum temperature attained by the furnace is a function of the heating rurrent. Having determined therefore the relation between the maximum temperature and the heating current once and for all, it was possible to dispense with temperature measuring instruments during the course of a n experiment. This allowed the use of a smaller furnace.
744
W. CONARD FERNELICS AND F. K. BERGSTROX
The alkali metal can now be introduced into the fusion boat. For this purpose an injector tube, I, was prepared by sealing a fine capillary to a wider tube which snugly fits the interior of F. Freshly cut alkali metal a little in excess of the quantity it’ was desired to introduce into the boat (about a gram) is placed in the injector tube and this latter is connected by means of a rubber tube to the pure ammonia line at B. By closing B’ and opening B air in I was displaced with ammonia. After this was accomplished, ammonia was again directed through the furnace by closing B and opening B’. The tube I was placed inside of F with the end of the capillary about on a level with the top of the boat, and a current passed through the externally wound resistance to melt the alkali metal. After the metal was molten, I was tapped a few times to disengage the melt from the oxide crust. Then, by closing B’ and slowly opening B, the pure molten metal was forced by ammonia pressure through the capillary into the fusion boat, leaving the oxide behind. The injector was then weighed with rubber caps over both ends. Subtracting this weight from the weight of the same when it contained the alkali metal gave the weight of the metal in the boat. This process completed, the vertical heating unit is shut off, the injector removed and F once more tightly stoppered. The boat is now withdrawn to the fusion space-that portion of the chamber between F and the removable cover, E. This region is the hottest and also the only one where there is absolutely no danger of any spattered material reaching the glass walls. Here the metal is quickly converted to the amide-usually within a half hour. X clear light yellow melt is sufficient indication that the reaction is complete, although, when gases are being collected it is better to run the exit ammonia stream through the acid tower for a time t o see that no acid insoluble gases are present in the line. If the reaction that is to be carried out is very vigorous, or if it is desired to collect the gases given off during the reaction quantitatively the amide is allowed to cool, the boat moved under F and the reacting substance added through F or G, the entrance of air into the tube of course being prevented by the current of ammonia passing through F or G into the atmosphere. Then, with F and G tightly stoppered, the boat is withdrawn into the fusion space, stopcock K closed, and the furnace heated to the desired temperature. If a quantitative collection of the gases given off during the reaction is not desired, the solid reactant is added directly to the molten amide in a similar fashion. Following the completion of the fusion the boat is withdrawn to the cooler part of the furnace-that portion outside of the insulation-and permitted to solidify. Unless otherwise specified, all reactions were carried out at 375°-4,000. The nickel boat containing the cooled melt was now sealed in an ammonia reaction tube according t o the methods previously developed by Franklin and co-workers’ and the products there washed with liquid ammonia and pre’Franklin: J. Am. Chem. SOC., 27, 831 (1905);29, 127j (1907)‘35, 1460 (1913); J. Phys. Chern., 15,jro (1911);16,694 (1912);Fitzgerald: J. Am.Chern.’Soc., 29, 1694 (1907); Bohart: J. Phys. Chern., 19, j39 (191jj,
CHEMICAL REACTIVITY O F THE FUSED BASES
745
pared for analysis. In those cases where all of a solid element does not react with the amide, the difference in density of the element and the insoluble reaction product is usually sufficiently great to enable one to carry the precipitate in suspension to the opposite leg of the reaction tube without carrying over any of the unreacted element. In order to transfer the boats to the ammonia tube, a “conveyor”, made by sealing a stopcock on the closed end of a wide test tube, was slipped over the end of the pyrex furnace tube, after removal of the stopper, T. Then, with a current of ammonia passing through the conveyor, the end of the furnace was lowered to allow the boat to slide from the furnace into the conveyor, which was at once tightly stoppered. ;\mmonia pressure to the extent of about twenty centimeters of mercury was allowed to build up within the tube before the stopcock was closed. S o apparent harm results if the fusion products be preserved for several days in such containers. The technique just described for conducting amide fusions and treating the reaction products has several distinct merits: i I ) chemically pure amides nre used; ( 2 ) the temperature of the fusion chamber can be regulated at will by varying the amount of current passing through the heating unit; (3) any gases other than ammonia evolved during the reactions are quantitatively collected: (4) the melt can be examined optically at any time and the color changes, formation of precipitates, intensity of reaction, etc. determined: ( 5 ) the atmosphere in which the fusion is carried out can be changed at will: ( 6 ) at no time does the melt come in contact with glass or air and suffer contamination and ( 7 ) the use of liquid ammonia, the parent solvent of these nitrogen compounds, to extract the melt does not destroy the reaction products as does water. The disadvantages of the apparatus are ( I ) the small size of the boats employed prevents one from obtaining any but the smallest xmounts of reaction products; ( 2 ) the spattering of the melt during some reactions clouds the window after a time, and ( 3 ) long time fusions in such an apparatus are inconvenient and wasteful of amrn0nia.l Furthermore, the sloiv decomposition of the fused amides into their elements introduces a somewhat uncertain blank correction into the analyses of gases evolved during the fusion process. Since the decomposition of the amides produces an alkali metal which reacts with the ammonia atmosphere in the furnace to form an amide and hydrogen, the net reaction should amount to a decomposition of the ammonia into three volunies of hydrogen and one of nitrogen. The heated metal of the sheath may also decompose some ammonia catalytically into its elements. In blank runs the ratio of hydrogen to nitrogen approximated the theoretical value of 3 to I . The second objection is removed by enlarging the furnace sufficiently to allow a thin pyrex tube t o be placed around the milled portion of the monel sheath. This tube can be readily replaced when it becomes clouded. It was found convenient also to move the filling tubes, F and G, t o the edge of the uninsulated portion, E. This permitted one to see the fusion at the moment the solid reactant was introduced.
746
W. CONARD FERNELIUS AND F. W. BERGSTROM
Discussion In general it can be said that' the reactions of the fused alkali amides resemble very closely their reactions in liquid ammonia solution. I n some cases, however, there are very interesting differences. The reaction of magnesium with fused potassium amide will serve as an admirable example of the reaction of an electropositive metal with a fused alkali amide. Immediately upon adding magnesium to fused potassium amide, the melt becomes blue' and globules of potassium form and float about on the surface of the melt. A white precipitate, visible through the clear melt, and disappearing on subsequent heating indicates the presence of magnesium amide. On continuing the fusion in an atmosphere of ammonia, the potassium is converted into amide and the melt becomes clear. When the potassium amide is dissolved by liquid ammonia, potassium ammono magnesiate, Alg(KHK)z z S H ~ , remains behind, The extent of the displacement of sodium from the molten amide by magnesium was approximated by conducting the reaction in an atmosphere of nitrogen and extracting the cooled melt with liquid ammonia. In order to arrive at a relationship between the liberat,ed sodium and the magnesium entering the reaction, it was necessary to apply a number of relatively large corrections to the actual weight of extracted sodium, so the values in the fifteenth column of Table I (Experimental part) are to be regarded as more or less close approximations. Nevertheless it will be seen that almost two atoms of sodium are liberated for each atom of magnesium entering the reaction. The only other metals to liberate alkali metal in sufficient quantity to color the melt blue were calcium and aluminum. Calcium does not react as vigorously with fused potassium amide as might be expected. h heavy white precipitate of potassium ammono calciate, C a S K 2SHg, remains after the excess of potassium amide is washed away with liquid ammonia. Aluminum in the form of wire is not attacked as vigorously by fused potassium amide as is magnesium. Nevertheless, very small globules of potassium could occasionally be seen darting about the surface of the bluish1 Practically every investigator who has repared the amides of the alkali metals by passing ammonia gas over the fused metals gas reported the formation of a blue colored solution which loses its color when acted upon by an excess of ammonia. Davy: Phil. Trans., 1809, 2 , Beilstein and Geuther: Ann., 108, 89 (1858); Baumert and Landolt: 109, 3 (1859); TitheAe;: J. Chem. SOC.,65, j04 (1894); 71, 469 (1897); Rengade: Compt. rend., 140, 1184 (190 ), Wohler and Stang-Lund: 2. Elektrochemie, 24, 261 (1918); Guntz and Benoit: Bull., 54; 41, 434 (1927). McGee: J.,Am. Chem. SOC.,43, 586 (1921) did not observe this color although the present investigation has repeatedly shown it. From the analogy to the blue colored solutions of the alkali metals in liquid ammonia and the amines, Titherley: J. Chem. SOC., 65, j I o (1894), argued that this color was due to a solution of the alkali metal in the fused amide and this view appears to be correct: * Ephraim (2. anorg. Chem., 44, 185 (19oj)) studied the reaction of magnesium with fused sodium amide and concluded that magnesium nitride, sodium, and hydrogen were formed. His experimental technique would not have distinguished between magnesium nitride and potassium ammono magnesiate. The question of whether or not the ammono magnesiate exists in the anammonous form in the molten amide cannot be settled without further experimentation. I t seems possible that the salt exists as Mg(NHK)*, since the evolution of ammonia has been observed upon adding magnesium to fused sodium amide in an atmosphere of nitrogen.
CHEMICAL REACTIVITY O F THE FUSED BASES
747
green molten amide and the aluminum was slowly converted into a white or gray mass insoluble in the fusion. This precipitate, which remained when the potassium amide was dissolved out with liquid ammonia, did not prove to be definite in composition. It is perhaps best to regard it, provisionally, as consisting of ammonous aluminum nitride which has adsorbed potassium amide, since the known compound resulting from the action of potassium amide on ammonous aluminum nitride,' potassium ammono aluminate, is readily soluble in liquid ammonia.* Beryllium is dissolved slowly by fused sodium amide with the production of sodium ammono berylliate, BeXXa 2iXH3, which may be readily extracted from the melt by liquid ammonia. Zinc slowly reacts with fused potassium amide to give potassium ammono zincate, Zn(XHIi)*'2XH3, which is sparingly soluble in liquid ammonia. Impure cerium is slightly attacked by fused potassium amide. Finely divided metallic germanium3 reacts readily with fused potassium amide to liberate hydrogen and form a product insoluble in liquid ammonia which may be either potassium ammono germanate, SGeKHK, or potassium ammono germanite, Ge = T\'K.SH3, since the percentage of potassium, nitrogen and germanium in the two compounds is almost identical. The atomic ratio of hydrogen evolved to the germanium added is about 3 : I , indicating that the ammonia-insoluble reaction product consists of a mixture of germanate and germanite in the approximate ratio of I : I , formed in accordance with the equation^,^ Ge Ge
+ KYH? + K H 3 NGeSHK + 2H2 + P X H a + S H 3 = G e = S I i , S H 3 + H2. =
In this connection, it may be recalled that when carbon is fused with sodium amide, either sodium cyanide or sodium cyanamide is formed, according to the conditions.6 Fused potassium amide converts mercury into a dilute potassium amalgam. Apparently the mercury itself is not attacked, but merely dissolves the potassium resulting from the very slow decomposition of potassium amide into its elements6 Thorium and manganese are attacked slightly by fused potassium amide over a period of ten hours, but the reaction products were not obtained in Berpstrom: J. Phys. Chem., 32, 436 (1928). Bergstrom: J. Am. Chem. Soc., 45, 2788 (1923); 46, 1548 (1924). The germanium oxide, from which the germanium was prepared by reduction, was a gift of the S e w Jersey Zinc Company. An ammono germanate of the approximate composition, N G e S H K , has been prepared in liquid ammonia by the action of potassium amide upon the product of ammonolysis of germanium tetrabromide. (Bergstrom: unpublished ohservations.) Sodium ryanide, asodium ammono carbonite: Franklin: J. Phvs. Chem., 27, 167 (1923); sodium cvanamide, a sodium ammono carbonate: Franklin: J. Am. Chem. Soc., 44,1495 (1922). h g l i s h patents, 1 2 , 2 1 9 ;2 1 , 7 3 2 (1894); German patents, 117,623; 124,977; 126,241 (1900); 148,04j (1901). Cf. Zentrallblatt, 75, I, 411 (1904). e At temperatures much above 400°, the fused aikah amides acquire a pale bluish-green color, because of the presence of free alkali metal in solution. This color does not persist a t lower temperatures in a n ammonia atmosphere. Wohler and Stang-Lund (Z. Elektrochemie, 24, 261 (1918))found that mercury has no action upon molten sodium amide. 1
2
3
748
W. CONARD FERNELIUS AND F. W. BERGSTROM
amounts sufficient for identification. Copper, cadmium, thallium, titanium, zirconium, tantalum, chromium, nickel, platinum and iridium were not attacked by fused potassium amide. Of these metals, zirconium alone was in the form of a powder.' Other metals which have been reported as unattacked by fused potassium amide are iron, silver and gold.? Sodium Hydroxide Fusions In order to follow the parallelisms between the fused alkali bases of the water and ammonia systems, a few reactions were carried out in fused sodium hydroxide at a temperature of 400' in the amide-fusion apparatus. Sodium dissolves to a slight extent in fused sodium hydroxide, imparting a blue color to the melt. At first the major portion of the sodium floats on the melt, but with lapse of time the two appear to react and form an insoluble solid. The cooled melt was very hard and reacted vigorously with water to form a small amount of gas. This latter behavior would suggest the formation of sodium h~dride.~ Magnesium under similar conditions gives a blue color to the solution near the strips of the metal and then dissolves completely within a short time. Le Blanc and co-workers4 have examined the action of sodium and potassium hydroxide on a number of metals and have formulated the reaction with magnesium as one of the type reactions, thus
+ +
+
llg zKOH = ?*lg(OH)? Z K RIg(OH)2 = RIgO H2O zHZO 2K = zKOH H2
Had they written in place of RIg(OH)2
(2)
+
+
above the following,
+ zKOH = llg(OK)s + z H ~ O
which is as strongly supported by the experimental results, then the course of the reactions of the aquo and ammono bases on magnesium is the same. Calcium reacts with fused sodium hydroxide in an atmosphere of nitrogen to form a blue melt and, with lapse of time, a white precipitate that is insoluble in the fused mixture. Since liquid ammonia fails to extract any soluble metal from the cold fusion, free sodium and calcium must be present in very low concentrations in spite of the bluish-green color of the melt a t Platinum is attacked very noticeably over long periods of time. Titherley: J. Chem. Soc., 65, 505 (1894); Dennis and Browne: J. Am. Chem. Soc., 26, 590 (1904); McGee: 43, 590 (1921). *Silc.er, Miles: Proc. Roy. SOC. Edinburgh, 35, 134 ( 1 9 1 5 ) ;Ruff and Goerges: Ber., 44, 502 (1911); Wohler and Stang-Lund: Z. Elektrochemie, 24, 263 (1918,. Gold, Franklm: unpublished observations. I r o n : Wohler and Stang-Lund: loc. a t . ; Titherley: loc. clt.; De Forcrand: Compt. rend., 121, 66 (1895)' Winter: -7. Am., Chem. Soc., 26, I 86 (1904). Carbon in the iron, however, introduces cyarhdes into the amide. Szarvasy, J. dhem. Soc., 77, 606 (1900); Dennis and Browne: loc. cit. p. 589. Hevesy: Z. Elektrochemie, 15, 529 (1909), has shown that sodium dissolves,in sodium hydroxlde to the extent of twent percent (by weight) at 480". Thls high solublllty may be due, in part a t least, to hydride Lrmation. ' Le Blanc and Bergmann: Ber., 42, 4728, 4743 (1909); Le Blanc and Weyl: 45, 2300, 2312 (1912).
CHEMICAL REhCTIVITY OF THE FUSED BASES
749
the completion of the reaction. As hydrogen is formed when the cold fusion is hydrolyzed, a portion, at least, of the calcium appears to have been converted into hydride. Aluminum wire does not appear to be attacked at all by fused sodium hydroxide in five hours time. I t seems worthy of mention at this point that the reactions of the fused alkali amides considered in the present paper do not require for their interpretation any assumption of acidic dissociation as has been made for the alkali hydroxides.' Rather, it would appear more logical to assume a normal dissociation into alkali metal ions and amide ions, SaKH@Xa+ XH2-.
+
Experimental Calcium a n d Potasszuni A4nizde. Preparation 1 . X freshly cut piece of calcium ( 0 . 2 g ) was added to molten potassium amide and the fusion continued for six and one half hours. The white fusion product, which was disintegrated under liquid ammonia only after long and patient shaking, was thoroughly washed with fresh solvent. One half of 0 . j 1 4 1 g. gave 0.0723 g. nitrogen, while the other half gave 0.1089 g. CaO and 0.1892 g. KsSO1. The specimen was dried in a vacuum at 20'. Preparation 2. was in all essentials a duplicate of the preceding. The specimen taken for analysis weighed 0. j 7 6 4 g. when dried in a vacuum at 20' and 0.5749 g. when heated in a vacuum at 115'. One half of 0.5749 g. gave 0.0820 g. nitrogen while the other half gave 0.1287 g. CaO and O . Z I O Og. K2SO1. Calc. for
CaNX.zNH3
Ca N
K
Found
I 31.5 33 ' 1 30 8
I1
30.3 28.1
31.9 28.j
33
32.7
.0
The results are in better agreement with a formula, C a X K . I . j S H a . Beryllium and Sodium Amide. The product of the fusion of metallic beryllium with sodium amide was washed several times with large volumes of liquid ammonia to remove the very soluble sodium ammono berylliate. In this operation some sodium amide was necessarily transferred in solution to the other leg of the reaction tube since its solubility is of the order of a gram a liter at ordinary temperatures. The leg of the reaction tube containing the boat was then opened, cleaned out and resealed with the other leg maintained at -40' in a bath of liquid ammonia.2 The extracted material was then concentrated to a volume of a few cc. to precipitate the major portion of the sodium amide, and then the clear supernatant liquid was decanted into the clean leg of the reaction tube. The solid left after evaporation of the ammonia Fry and others: J. Am. Chem. SOC.,46, 2268 (1924);48,958 (1926);49, 864 (1927); 50, 1 1 2 2 , 1138(1928);52, 153 (1930). Cf. Strain: 52, 1 2 1 7(1930). ZFranklin: J. Phys. Chem., 15, 510 (1911).
750
TV.
CONARD FERNELIVS AND F. W. BERGSTROW
from this solution was prepared for analysis in the usual manner. The sodium analysis, as expected, runs a little high. One quarter of 0.7133 grams (dried in vacuum at 20’) gare 0.08 j6 g. nitrogen. A second quarter gave o 0 8 5 0 g. nitrogen while the remaining half gave 0.1062 g. Re0 and 0.3474 g. X a ? d 0 4 ’ Calc. for Be(KH2)?;HXa.SH,, Be 1 1 . 2 , S j z . 5 , Ya 28.8. Found, Be 10.8, N 48.0, S a 31.5.
Fic.
2
The Initial Equilibrium between Sodium A m i d e and Jfaqriesiiim. .1 weighed amount of polished magnesium ribbon was added to fused sodium amide in an atmosphere of nitrogen. I n the resulting rapid reaction, metallic sodium was formed and floated in the form of a globule on the surface of the melt. The fusion was now quickly cooled and extracted with liquid ammonia until the washings were no longer colored blue-that is, until all of the alkali metal had been washed over. During these washings some sodium was converted to sodium amide and hydrogen by the combined catalytic action of the nickel of the boat and the solid sodium amide. To collect and measure this hydrogen the ammonia in the reaction tube was evaporated into a nitrometer containing dilute acid. The washings of the fusion, which contained metallic sodium, sodium amide and magnesium amide [the latter in the form of sodium ammono magnesiate, Mg(h”2)2.zNaSH2]were sealed off from the rest of the reaction tube and weighed, after drying in a vacuum. When water was admitted to the specimen tube to hydrolyze its contents, considerable hydrogen pressure was developed. If this gas were allowed to
CHEMICAL REACTIVITY O F THE FUSED BASES
751
escape into the atmosphere, some ammonia would be lost, and since the esact amount of this ammonia was necessary in the calculations to follow, the released hydrogen was bubbled through dilute acid. The hydrolysate was then sucked from the reaction tube through this same dilute acid' (See Fig. z ) , which was analyzed for nitrogen and magnesium. The weight of the sodium extracted is equal t o the weight of the washings (Xt. of tube sample, dried in a vacuum, less weight of tube empty and evacuated.) less the magnesium amide (calculated from the magnesium analysis) and the sodium amide (calculated from the nitrogen in excess of that present as ?\Ig(SHd?) . The total amount of sodium liberated by the magnesium is equal to the amount extracted plus that converted to sodium amide during the washing. (Item I j ) The following table is a summary of three determinations.
+
TABLE I K t , S a converted t o amide ( 2 ) \Yt. X g introduced (3) Equivalent weight S a (4) Wt. solids extracted ( 5 ) Volume hydrogen, oo, 760mm., cc. (6) Corresp. wt. ?r'a ( 7 ) Xitrogen analysis (grams) (8) Mg Analysis (hIg&'207) (9) Magnesium amide, wt. (IO) Sitrogen in I I g ( S H ? ) ? ( 1 1 ) Sitrogen in XaKH, ( i ) - ( ~ o ) ( 1 2 ) Sodium amide, wt. (13)Total amides, wt. (9)+(12) ( 1 4 ) Wt. Ka extracted (4)-(13) ( I j ) Wt. S a liberated (6)$(14) (3) Wt. K a equivalent to IIg (I)
I
I1
excess
2 . j882
2
I11 .zoj9
o ,0833 O.ISj6 0 . I024 36.7
0
09i9
o.ojo0 0.1324 0.2431 34.0
0.1852 0.17;+
21.9
0.0697
o
0.0800
o 0069 0 oojo
0.0450 0 .OIjz o.oz,$8
0 0025
0.0120 0.0060
o 0426
o 0013 o 0056 o 01j6 o 0181 0 0843
O.II23
0
0.1148 0.0581 0.028~
0.0511
0.1424 0.2ooj
0.1324
0752
159.5 o 1 j ~ 6
o ,0092
o.ozj6 0.0376 0.1308
0.1848 1852
o
Magnesium and Potassium Amide. Four preparations were made by fusing small amounts of clean magnesium ribbon (0.08 g. in Prep. I to 0.40 gram in Prep. 11) with an excess of potassium amide for periods of time ranging from one hour, Prep. I, to six hours, Prep. 11. The high magnesium and low nitrogen analyses of preparation I1 are perhaps to be accounted for by an incomplete reaction of the primarily produced magnesium amide with the potassium amide, since there still remained some precipitate in the boat at the end of the fusion period. 1 In Fig. z is pictured the apparatus customarily used for removal of solutions from an ammonia tube (Franklin: J. Phys. Chem., 15, 516 (191 I ) , with the exception that the tube C terminates underneath the dilute acid in the flask. In operation, suction is applied a t D and the solution in d is slowly drawn through the acid in E . E , C and D are then closed; A is removed and partly filled with water by opening stopcock B, with the end of the stopcock capillary under water. This solution is drawn through E in the same manner and the process repeated to ensure the complete removal of the specimen from A . The partial vacuum in E is released by slowly opening C and then D to the atmosphere.
W. CONARD FERNELICS AND F. W. BERGSTROM
752
Preparation 1. One half of 0.2660 gram g:tve 0.0442 g. nitrogen while the other half gave 0.0930 g. MgzPzOi. The preparation was dried in a vacuum at 2 0 ' . Preparation 2 . One fifth of 2.0944 g. gave 0.1364 g. nitrogen. +Isecond fifth gave 0.3009 g. lIg,P2Oi and a third fifth gave 0.7765 g. of a mixture of RIgSOa and KzS04. Dried in vacuo at zoo. Preparation 5. The analytical data for this specimen has been lost. The analyses though are correctly reported. Preparation 4. One quarter of 0.7162 g. (dried in a vacuum at 2 0 ' ) gave 0.0560 g. nitrogen, while a second quarter gave 0,1347 g. llg,P20r. Calculated for Mg(NHK), z N H J
I '5.3 33.2
I4 5 33 7 47 0
llg
s K
I1 15.7
Found
I11 '5.9
IV
16 . A
.6 33,2 48.3 (indirect)
31.4
32
Zinc and Potassium Amide. Preparation I . Four tenths of a gram of fine zinc shot was added t o fused potassium amide, but no immediate reaction occurred, other than a darkening of the color of the fusion. Some of the zinc was still unattacked after two hours. The washed specimen, insoluble in liquid ammonia, was light grey in color. The specimen, dried in a vacuum at zoo, weighed 0.0748 g. From this 0.0197 g. nitrogen was obtained. Preparation 2. This was a duplicate of the preceding, except that the fusion was continued for four hours. The specimen, dried in a vacuum at' ZOO, weighed 0 . 6 7 2 2 g. One quarter gave 0.0446 g. nitrogen and a second quarter gave 0.1247 g. ZnzPzOi. Calculated for Zn(NHK)* zKH8
S Zn
27
I .o
31.4
26.3
Found
I1
26.6 31.8
Cadmzum and Potassaum Anazde. Cadmium in the liquid form (temperature of fusion 400°!) is very slightly attacked by fused potassium amide in a period of two hours. ,4luminum and Potassium Amzde. Preparatzon 1. Upon adding 0.29 g. of aluminum wire to molten potassium amide there was an immediate reaction with the production of a blue melt. After five hours of heating there still remained a good deal of the aluminum. I n an ammonia tube the white insoluble matter was separated from the aluminum wire and the former prepared for analysis. Subs., dried in vacuo at zoo, 0.1954 g. Heated in vacuo at 130°, 0.1943 g. One half gave 0.0323 g. nitrogen and the other half gave 0.1060 g. A1203and o.ozo8 g. KzS04. Preparation 2. I n this experiment-a duplicate of the preceding-small globules of potassium could be seen on top of the melt after addition of the aluminum. During the fusion a grey precipitate appeared in the melt and
CHEMICAL REACTIVITY OF THE FUSED BASES
753
with time increased in amount. Time of fusion, five hours. The specimen, dried in a vacuum at ZIO', weighed 0.2499 gram. One half gave 0.0400 g. nitrogen, while the other half gave 0.1334 g. A1203 and 0.0372 g. KzSOI. Preparation 3. One half of 0.1056 g. (dried in a vacuum at 20') gave 0.0164 g. nitrogen while the other half gave 0 . 0 5 0 2 g. A1203and 0.0261 g. K2S04. Calculated for N Al K X1S 34.2 65.9 0.0 Al(KH 2) S H K Found
37.1
23.9
31,6
I I1
33 . o
57.5 56.6
13.4
50.4
22.2
111
32 . o 31.0
9.6
Cerium and Potassium Amide. A half gram fragment of cerium dissolved in part in molten potassium amide (blue solution) and the liquid ammonia extraction gave a small amount, of a grey precipitate, whose analysis did not correspond to a definite compound. Thallium and Potassium Amide. Thallium, molten at the temperature of the fusion, 400'~ was not attacked in four and one half hours. Titanium, Zirconium, Thorium and Potassium Amide. Of these elements, the first two were not attacked at all in four hours. A short length of thorium rod (0.64 g) lost 2 0 mg. after five hours contact with fused potassium amide. (;ermanium and Potassium Amide. Thirty and three tenths milligrams of germanium powder, prepared by reducing germanium oxide with hydrogen at joo', was added to cold potassium amide and the mixture heated. Shortly afterward there was a vigorous evolution of gas which continued more slowly for one and one half hours and then ceased. The boat was examined at this time and found to contain a yellow solid with a clear supernatant liquid. The cooled melt was white and disintegrated readily in liquid ammonia to give a copious fine white precipitate. This was washed well with liquid ammonia but during the process it appeared to undergo a slight ammonolysis, as was inferred from the continued pale yellow or green color of the washings. (potassium amide in solution). Subs., dried in a vacuum at 2 0 ° , o.j1;4 g. Heated in a vacuum at I IO', 0 . ~ I I g. I One quarter gave 0.0243 g. nitrogen. One half gave 0.1439 g. K2S01. The germanium was separated by the method of Johnson and Dennis.' 190.2 cc of gases (standard conditions), collected during the fusion, consisted of hydrogen and nitrogen in the ratio of 13.69 to I . Since the nitrogen was formed by the decomposition of ammonia in the presence of nickel and the fused amide, we must subtract the corresponding volume of hydrogen (3xS'ol. N2) plus the volume of nitrogen from the collected gases (190.2 cc) in order to find the hydrogen actually formed in the reaction bemeen germanium and potassium amide. (138.4 cc.) Johnson and Dennis: J . Am. Chem. Soc., 47, 790
(192j).
W. CONARD FERNELIUS AND F. W. BERGSTROM
754
Preparation 2. This was a duplicate of the preceding experiment except that 0.332 g. germanium was used. The preparation, dried in a vacuum at zoo,weighed 0,3433 g. Heated in a vacuum a t 210’ it) lost 0.0082 g. One fifth of the heated specimen gave 0.0107 g. nitrogen, a second fifth gave 0.0109 g. nitrogen, and two fifthsgave 0.0851 g. &SO4. The gases (348.3 cc.) collected during fusion consisted of hydrogen and nitrogen in the volume ratio of 6.918 to I , that is, there was I 72.3 cc. or O . O I ~g.~hydrogen in excess of that arising from the decomposition of the amide. Calc. for GelNH)SK) ” ” GelNK).SHR Found I ”
Ge
3-
51.6
19.9
jo.8
I1
K 27.8
H:Ge’ 4:1
19.6
27.4
2 :I
19.8
25.0
z.96:1
17.7
27.8
3,36:1
The analyses refer to the specimens dried in a vacuum at room temperatures. Tantalum and Potaissiuni Amide. Sheet tantalum was not attacked at all by fused potassium amide in six hours. Chromium and Potassium Amide. In two experiments chromium in the form of small lumps was fused with potassium amide for three hours, but the solutions obtained by hydrolyzing the melt and then acidifying gave no tests for chromium. Manganese and Potassium Amide. Fused potassium amide attacks manganese (prepared by the thermite process) rather superficially over a period of six hours. The melt is colored a light brown. A small amount of precipitate, sparingly soluble in liquid ammonia, blackened in contact with the air, a behavior characteristic of potassium ammono hypomanganite,’ PrIn(NHK)2.2SH3. Manganese and Sodium Amide. Manganese is only slightly attacked by fused sodium amide, but the cooled melt imparts a yellow color to liquid ammonia indicating the formation of some sodium ammono hypomanganite. summary
A n apparatus and technique have been developed for studying the reactions of the fused alkali amides. In general, the reactions of the electropositive elements with the (2) fused amides are similar to the same reactions in liquid ammonia at room temperatures. The strongly electropositive elements react initially with the fused amides to liberate free alkali metal. 13) Magnesium, beryllium, zinc and calcium dissolve in the alkali amides to give the corresponding ammono metallate. (Le. compounds analogous to (I)
(Ratio of hydrogen evolved to the germanium reacting.) Bergstrom: J. Am. Chem. SOC.,46, 1553 (1924). It is better to call this derivative of divalent manganese a hypomanganite, rather than a manganite as was done in the article ref erred to. 1
CHEMICAL REACTIVITY OF THE FUSED BASES
755
potassium zincate, Zn(OK)*.) Germanium appears to be converted to a mixture of potassium ammono germanite and germanate by fused potassium amide. Cerium, thorium and manganese are slightly attacked by fused potassium amide, while copper, cadmium, mercury, thallium, titanium, zirconium, tantalum, chromium, nickel, platinum and iridium are not attacked after several hours fusion. (4)
Sodium dissolves in fused sodium hydroxide to give a blue colored
melt. ( 5 ) The course of the reaction of the strongly electropositive metals with the fused alkali hydroxides appears to be essentially the same &s that with the fused alkali amides. Stanfwd University, Cdifurnia.
