August 4, 1911] 



SCIENCE 



141 



This result was in itself insufficient to 

 prove the metallic nature of ammonium, 

 since free hydrogen was always present in 

 the amalgam, and may have been the active 

 substance in the reaction. To remove any 

 doubt, Coehn then showed that not only 

 are cadmium and zinc precipitated by the 

 cold amalgam, but that barium amalgam 

 results from the action at zero of am- 

 monium amalgam on a solution of barium 

 chloride. This fact was independently 

 discovered later by G. M. Smith, who also 

 obtained sodium and potassium amalgams 

 in a similar manner. Thus the experi- 

 ments of LeBlanc, Coehn and G. M. Smith 

 furnish indisputable evidence of the metal- 

 lic nature of ammonium in ammonium 

 amalgam. 



It is often stated that metals are insol- 

 uble in a physical sense, in all solvents 

 excepting other metals. This state- 

 ment can scarcely be upheld in view of the 

 recent work of Kraus, on solutions of so- 

 dium, potassium, calcium, etc., in liquid 

 ammonia. These very unique solutions, 

 discovered by Weyl in 1864, seem to have 

 many distinctive metallic properties. 

 They are practically opaque, except when 

 very dilute; even in this respect they re- 

 semble gold, which is transparent in very 

 thin layers. They also show metallic 

 luster, and reflection, and while they con- 

 duct the electric current, the conduction 

 seems to be metallic rather than electrolytic 

 in character. Upon evaporation, they de- 

 posit the pure metal in crystalline form. 

 All such solutions, if sufficiently dilute, 

 have a characteristic deep blue color. 

 Now Palmaer has shown that by the elec- 

 trolysis of tetraalkyl ammonium salts dis- 

 solved in liquid ammonia, unstable blue 

 solutions are formed about the cathode. 

 These blue solutions were thought to eon- 

 tain the organic radical in metallic form 

 dissolved in ammonia. These facts have 



been confirmed by Kraus, who also concurs 

 in the explanation. 



LeBlanc 's experiments on the polariza- 

 tion of mercury in solutions of ammonium 

 salts, were also extended to include a sim- 

 ilar study of salts of a number of substi- 

 tuted ammonias. Mono-, di- and tetra- 

 methyl and mono-ethyl ammonium ions 

 gave results more or less like those of 

 ammonium ions, from which facts Le- 

 Blanc concluded that in these cases also 

 amalgams were formed, although none of 

 the supposed amalgams were isolated. 

 When attempts were made by Dr. Moore 

 and myself to obtain an amalgam by the 

 electrolysis of aqueous solutions of tetra- 

 methyl ammonium salts the results were 

 complete failures; not a trace of amalgam 

 could be isolated. But when we substi- 

 tuted absolute ethyl alcohol for water, as 

 solvent, the amalgam resulted at once.- 

 This amalgam differs greatly from ammo- 

 nium amalgam in both appearance and 

 stability. It is a crystalline solid of metal- 

 lic luster, closely resembling sodium amal- 

 gam. It can be kept for days at tempera- 

 tures below -j- 10 degrees and does not 

 have any tendency to become inflated. Its: 

 density is somewhat less than that of mer- 

 cury, but still many times greater than that 

 of ammonium amalgam. Its electrical con- 

 ductivity is comparable to that of a metal. 

 Chemically, it resembles the alkali metal 

 amalgams, but is far more active than that 

 of sodium. It reacts with water with great 

 energy and rapidity, giving hydrogen and 

 the corresponding base, tetra-methyl ammo- 

 nium hydroxide. From solutions of salts 

 of copper and zinc, these metals are pre- 

 cipitated at once; while from solutions of 

 salts of sodium and potassium the corre- . 

 spending amalgams are formed. With 

 solutions of ammonium salts the charac- 



= McCoy and Moore, Science, 30, 315 (1909); 

 J. Amer. Chem. Soc, 33, 273 (1911). 



