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Full text of "Reactions in Liquid Ammonia"


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, By Edwaed Cubtis Feanklin, Leland Stanford Jr. University, California. 
Read (by title) before the Academy, at Topeka, December 31, 1904. 

HPHE striking parallelism between the general properties of liquid 
-*- ammonia and water has been emphasized by Franklin and his 
coworkers in previous papers. Water, among solvents, is character- 
ized by its high boiling-point, its high specific heat, its high heat of 
volatilization, its high critical temperature and pressure, its high asso- 
ciation in the liquid condition, its high dielectric constant, by its low 
boiling elevation constant, by its power to unite with salts as water of 
crystallization, by its wide solvent power, and by the fact that, with 
the possible exception of hydrocyanic acid, it is the most powerful 
ionizing solvent known. Aqueous solutions of salts are generally ex- 
cellent conductors of electricity. 

Of all well-known solvents ammonia most closely approaches water 
in all those properties which give the latter its unique position among 
solvents. While the boiling-point of liquid ammonia is thirty-three 
degrees below zero, it still appears abnormally high when compared 
with the boiling-points of such substances as methane, ethylene, hy- 
drogen sulfide, phosphine, arsine, hydrochloric acid, 1 etc. The spe- 
cific heat of liquid ammonia is greater than that of water, while its 
heat of volatilization, with the exception of water, is the highest of 
any known liquid. Its critical temperature is abnormally high, and 
especially the critical pressure, which is the more characteristic con- 
stant, is second only to water among solvents. Ammonia is an asso- 
ciated liquid, and its dielectric constant, while much below that of 
water, is still high. Its boiling-point elevation constant is the lowest 
of any known liquid, namely, 3.4, and it quite equals water in its 
power to unite with salts as ammonia of crystallization. As a solvent 
for salts it is inferior to water, though some salts, for example, silver 
iodide, dissolve much more abundantly in ammonia than they do in 

1. The abnormally high boiling-point of liquid hydrofluoric acid, its evident association, 
even in the gaseous condition, its power of uniting with fluorides, and the fact that Moissan 
has found a hydrofluoric acid solution of potassium fluoride to be a good conductor of elec- 
tricity, have led the writer to suspect that hydrofluoric acid is to be classed with water and 
liquid ammonia as an electrolytic solvent. 

Some preliminary experiments on hydrofluoric acid have shown it to possess strong solvent 
powers. Potassium fluoride, sodium fluoride, potassium chloride, sodium bromide, nitrate, 
and chlorate, potassium bromate, acetamide, urea and potassium sulfate are abundantly 
soluble ; silver cyanide, barium fluoride and copper chloride appear to dissolve to some extent ; 
while calcium fluoride, copper sulfate, copper nitrate, ferrous chloride, mercuric oxide, lead 
fluoride and metallic magnesium are insoluble. 


water, and it far surpasses this solvent in its power to dissolve the com- 
pounds of carbon. Finally, it exhibits very marked power as an 
ionizing solvent. The more dilute ammonia solutions are much bet- 
ter conductors than aqueous solutions of equal concentration. 

Metallic Derivatives of the Acid Amides, Compounds Belated to 
Ammonia as the Ordinary Metallic Salts are to Water. ( "Am- 
monsalts," "Amidesalts," "Acidamidesalts." Suggest a good name.) 
In view of the close general resemblance between ammonia and wa- 
ter, the writer, collaborating with Mr. O. F. Stafford, was led to study 
the reactions between acid and basic amides in ammonia solution. 
The result of this work was to show that these substances behave in 
ammonia in a manner entirely analogous to the action of acids and 
bases in water. Franklin and Stafford have shown that the acid 
amides, which discharge the red color of a solution of phenolphtha- 
leine in ammonia, react with the soluble basic amides, which give the 
characteristic red color with the same indicator, to form metallic de- 
rivatives of the acid amides, in accordance with the following general 
equations : 

MNH 2 + AcNH 2 = AcNHM + NH 3 
and 2MNH 2 + AcNH 2 = AcNM 2 + 2NH 3 . 

Acetamide and potassium amide, for example, react with each other 
as follows : 

CH 3 CONHK+ KNH 2 = CH 3 CONK 2 + NH 3 

Carbamide and potassium amide, as follows : 

NH 2 NH 2 

/ / 

CO + KNH 2 = CO + NH 3 

\ \ 



/ / 

CO + KNH 2 =CO + NH 8 

\ \ 


Metallic Amides, Imides, and Nitrides. ( Basic Amides, Basic 
Imides. "Ammon Bases.") Continuing in the direction suggested 
by the above- outlined analogy between water and ammonia, the writer 
now finds that the soluble basic amides react with the salts of the 
heavy metals in solution in ammonia to form amides, imides or ni- 
trides of the heavy metals. For example, potassium amide reacts 
with silver nitrate to form silver amide, with lead nitrate to form lead 
imide, and with mercuric iodide and bismuth iodide to form mercury 


nitride and. bismuth nitride, respectively. The reactions are repre- 
sented by the following equations : 

AgNOs + KNH 2 = AgNH 2 + KNOs 

Pb(NOs)2 + 2KNH 2 = PbNH + 2KNO3 + NH 3 

3HgI 2 + 6KNH2 = Hg 3 N 2 + 6KI + 4NH 3 

BiI 3 + 3KNH 2 = BiN+3KI + 2NH 3 . 

These substances are precipitated when potassium amide and the 
salts are brought together in ammonia solution. Silver amide is pure 
white, lead imide is orange, bismuth nitride is dark brown, and mer- 
cury nitride is chocolate brown. All of these compounds are very ex- 
plosive. So sensitive, indeed, is silver amide that only with great 
difficulty was the analysis of the compound accomplished. 

Compounds Related to Ammonia as the Ordinary Basic Salts Are to- 
Water. ( "Ammonbasic Salts," " Basic Amide Salts." Suggest a good 
name.) In some cases when the metallic salt is in excess, the result 
of the action of the alkali amide on the salt is a compound related to 
ammonia as the ordinary basic salts are to water. Examples of these 
compounds are HgClNEh, Hg = N — Hg — Brand Hg = NHg — I, 
which are formed when mercuric chloride, bromide, and iodide, re- 
spectively, are treated with potassium amide. The reactions take 
place in accordance with the equations : 

HgCI 2 + NaNH 2 = HG^ + NaCl 
2HgI 2 + 3KNH 2 = Hg = N — Hg — 1 + 3KI + 2NH 3 . 

HgClNEb is the well-known infusible white precipitate, which is 
usually considered to be mercuriammonium chloride, Hg = NH2.CI, 
but by the writer looked upon as a compound related to ammonia as 
a basic salt is to water, with the formula given above. This formula, 
originally proposed for mercury chloramide by Kane some sixty years 
ago, has, in recent years, been discredited on the authority of Kani- 
melsberg. The other two compounds are less well known. They are 
described in the literature as having been prepared from aqueous so- 
lutions, while their existence has also been denied. According to 
Rammelsberg, they are dimercurammonium salts; the iodide, for ex- 
ample, having the formula Hg = N.I. The author's formulation is 
given above. These basic compounds dissolve in liquid ammonia so- 
lutions of ammonium salts, in a manner analogous to their solution in 
dilute aqueous acids, as indicated by the equation 

Hg = N — Hg — I + 3NH 4 t = 2HgI 2 + 4NH 3 . 

Phenomena in Liquid Ammonia Analogous to Hydrolysis in 
Water. ("Ammonolysis," "Amidolysis," "Ammolysis." Suggest a 
good name.) The salts of mercury, arsenic, antimony, tin, aluminum 
and probably salts of other metals react with pure dry liquid am- 
monia in a manner analogous to ordinary hydrolytic action in water. 


For example, mercuric choride gives a small amount of mercury 
chlor-amide, and mercuric iodide gives Hg — N — Hg — I, both of 
which dissolve in excess of ammonium salts. Bismuth nitrate 1 and 
aluminum iodide give white precipitates of their respective basic 
salts, both of which are soluble in ammonium salts. The reversible 
equation representing the action of ammonia on mercury iodide is 

2HgI 2 + 4NHs s=s Hg = N — Hg-I + 3NH 8 .HI. 

TheMercury Ammonium Bases. In the light of the above outlined 
relations.it would seem that certain of the so-called mercury am- 
monium bases are to be looked upon as mixed compounds containing 
residues basic to both ammonia and] water, while others are simply 
mercury salts with ammonia of crystallization. For example, the fu- 
sible white precipitate is to be formulated HgCl2.2NH3, and not as a 
double salt of mercury ammonium iodide and ammonium iodide, 
Hg = NH2LNH4I, nor as the double salt of dimercurammonium- 
iodide and ammonium iodide, Hg2NI.3NH4l, nor yet as mercury diam- 
monium diodide, Hg(NH3)2l2, although it may be that the latter 
formula represents the manner in which ammonia of crystallization 
associates itself with the salt. 

The chloride of Millon's base, instead of being oxydimercuram- 


monium chloride, O NH 2 .01, or dimercurammonium chloride 

with water of crystallization, N(Hg2)Cl.H20, is better formulated as 
a compound or mixture of salts basic to ammonia with salts basic to 
water. Of the half-dozen or more possible formulas, the following 
are given: HgO.HgClNH2; NH 2 — Hg — O — Hg — 01; 2HgO.Hg 
(NH2)2.HgCl 2 

Compounds Related to Ammonia, as the Plumbates, Aluminates, 
etc., are to Water. Certain metallic amides, the lead and aluminum 
derivatives, for example, dissolve in excess of potassium amide, just as 
metallic hydroxides and oxides dissolve in potassium hydroxide, form- 
ing compounds presumably of the type PbNK or Pb(NHK) 2 . Sev- 
eral amides have been found to dissolve in this way, but so far only in 
the case of the lead compound has the attempt been made to isolate 
and analyze the salt formed. The analysis indicates the compound 
PbNK, but the difficulty of separating the pure substance from the 
other products of the reaction has thus far rendered attempts to ob- 
tain concordant analyses futile. 

1. Not the ordinary salt with water of crystallization, but the salt formed eleotrolytically 
at a bismuth electrode in ammonia solution. 

Note. — One further matter deserves mention, namely, a new instance of the catalytic action 
of platinum and certain metallic oxides. The potassium amide used in the above-described ex- 
periments is made by the action of liquid ammonia on metallic potassium. The action is a slow 
one, a fraction of a gram of metallic potassium, with large excess of ammonia, being completely 
converted into potassium amide only after the lapse of days. The writer finds that the pres- 
ence of spongy platinum or of the oxide of iron greatly accelerates the reaction. The addition 
of a very small quantity of spongy platinum brings the action to-completion in the course of 
about fifteen minutes.