December 31,1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
527 
n mixture of water vapour and ammonia and carbonic 
anhydride gases; or, to go a step further, as these sub¬ 
stances do not combine with each other until their tem¬ 
perature is much below the condensing-point of steam, 
and that, therefore, much of the water separates from 
the mixture in the liquid state, the nature of the products 
depends upon the reaction of equivalent quantities of 
moist carbonic anhydride and ammonia, and the beha¬ 
viour of the product of this reaction with liquid water. 
It is always stated that the products of the distillation 
of sal-ammoniac and chalk are the substance 
(C 0 3 ) 3 (0 H 3 ) 2 (N H 3 ) 4 , 
water and ammonia gas; but I am not aware of the 
publication of any investigations on which this state¬ 
ment rests. 
_ It would naturally be made on theoretical considera¬ 
tions, based on the ascertained composition of the car¬ 
bonate as it appeared in commerce. All my own ex¬ 
periments on the subject, direct and indirect, prove it to 
be incorrect, and I am almost fully convinced that this 
statement is an incorrect one, and has been advanced 
upon theoretical grounds only. 
In the distillation of a mixture of chalk and sal- 
ammoniac no ammonia escapes, the evolved gases entirely 
condensing. The carbonic anhydride and the ammonia 
■combine, to form ammonium carbamate, while the water 
is deposited in a free state. The carbamate and the 
water very slowly combine together. On redistilling 
these products, the commercial carbonate and free am¬ 
monia are the new products obtained, unless the distilla¬ 
tion is carried on very slowly indeed. So that it is in 
the refining process that the commercial carbonate is ob¬ 
tained, and not in the primary operation. 
Sal-ammoniac with Potassium or Sodium Carbonate .— 
When sal-ammoniac is distilled with either of these car¬ 
bonates, the products arc the same as when chalk is used, 
•except that in the first part of the distillation some am¬ 
monia escapes. The evolution of the excess of ammonia 
is due to the unchanged carbonate of potassium or so¬ 
dium combining with some of the carbonic anhydride 
•and water, and forming acid carbonate. 
Sal-ammoniac and Pearl-ash distilled with Aqueous 
Alcohol. —When pearl-ash, with fully its equivalent of 
■sal-ammoniac, is distilled with aqueous alcohol, accord¬ 
ing to the directions of the London Pharmacopoeia for 
^preparing- spiritus ammoniae aromaticus, the first portions 
of the distillate soon deposit crystals in the receiver. 
By allowing a sufficient quantity of fluid to distil over, 
these crystals redissolve. The distillate, as a whole, is a 
solution of normal carbonate. The crystals deposited by 
the earliest portions of the distillate are very minute; but 
on letting stand some of the earlier portions of the dis¬ 
tillate of such a strength as only to form crystals slowly, 
u good quantity of very thin, six-sided tables are depo¬ 
sited, which both by their appearance and behaviour on 
•exposure to the air, prove to be half-acid carbonate. 
Acid carbonate is also formed. The mother-liquor is 
basic, or contains more than two atoms of ammonia to 
one of carbonic anhydride. 
The spiritus ammonim aromaticus generally proves to 
contain caustic ammonia, and I think—I cannot speak with 
•certainty—not unfrequently much less carbonate than it is 
intended to contain. By following the directions in the 
British Pharmacopoeia, to use solution of ammonia and 
commercial carbonate instead of pearl-ash and sal-ammo¬ 
niac, the formation of a spirit containing excess of am¬ 
monia is favoured, but to only a small extent. The 
spirit thus obtained is, of course, equally liable, if too 
strong in alcohol, to decompose into a basic solution and 
half-acid or acid carbonate, as I ascertained by prepar¬ 
ing it. During the distillation crystals are apt to deposit 
m the neck of the retort, but they arc soon dissolved 
again as the process goes on. The effects of distilling 
the commercial caibonato with aqueous alcohol and with 
water will be described presently. 
Products of the Distillation of the Normal, the Acid, 
and the Half-acid Carbonates of Ammonium. 
When the normal carbonate is distilled slowly enough, 
the products are carbamate and water, and, when the 
acid carbonate is similarly distilled, the product is the 
acid carbonate again ; but when either the normal, the 
acid,* or the half-acid carbonate is distilled faster than 
the whole of the products of distillation can condense in 
the receiver, partial condensation takes place in such a 
way that the carbonate o f commerce is formed, according to 
the respective equations— 
2[CO*+ 2 0H.,+ 2NH 3 ] 
= (C 0 2 ) 2 CfH 2 (N H 3 ) 3 +30IL + N H 3 
3 [COo + OH„+NH 3 ] 3 
= (C 0 2 ) 2 0 IL (N H 3 ) 3 + 20II, + C 0., 
3 [3C0, + 4 0H,+ 4NH 3 ] 
= 4 [(C 0 2 ) 2 0H, (NH 3 ) 3 ] + 8 0 Ho + C 0.,. 
Products of the Slow Distillation of the Commercial 
Carbonate of Ammonia. 
On distilling the commercial carbonate very slowly, a 
thin film of liquid first condenses, which soon becomes a 
thin layer of crystals, probably of normal carbonate. 
Next, after a cessation in the volatilization, during which 
the temperature rises several degrees, some moist ammo¬ 
nium carbamate deposits. (This is really the first pro¬ 
duct of the distillation, the normal carbonate being only 
the product of the action of moisture—that adhering to 
the carbonate and to the retort and that in the air—on 
the ammonia and carbonic anhydride into which some of 
the carbamate of the commercial salt always passes when 
placed in a fresh volume of air.) After this, slightly 
moist commercial cai’bonate [(CO«) 2 OH 2 (NH 3 ) 3 ] is de¬ 
posited, forming the great bulk of the product s. ' Lastly, a 
very thin layer of moist and more acid carbonate is 
formed either by direct condensation or else by the ac¬ 
tion of water and carbonic anhydride on the superficial 
part of the commercial carbonate already deposited. 
When, therefore, the commercial carbonate is distilled 
very slowly indeed, the product consists principally of 
the same substance ; by a more rapid distillation the pro¬ 
duct consists almost entirely of it. 
Products of the Distillation of the Carbonate formerly in 
Commerce. —These have been examined by Rose. I have 
not succeeded in getting a carbonate of the composition 
the commercial substance used to have. But I have 
already shown that the main product obtained by Rose 
had the composition of the carbonate at present in com¬ 
merce plus water. Unlike, therefore, the present car¬ 
bonate, it yielded a product essentially different from 
itself by slow distillation. The remote part of the de¬ 
posit was neutral. 
Commercial Carbonate distilled with enough Water to 
cover it. —The effects of this distillation carried on at as 
low a heat as possible have been already described, so 
far as the changes in the retort are concerned. The de¬ 
posit was formed by a distilling-heat of about 53° in a 
very warm condenser. It was moist and crystalline, 
and appeared qualitatively to be slightly ammoniacal 
acid-carbonate. Analysis proved it to be so.f 
Commercial Carbonate distilled with Spirit of 90 per cent. 
—Hiinefeld ascertained that by distilling commercial 
carbonate with spirit, a deposit condensed which was 
neutral in composition. I have repeated his experiment 
and have partly described the results. 
It only remains to add here that the deposit, which was 
crystalline and saturated with aqueous alcohol, proved 
to be ammonium carbamate. 
* The formation of the commercial carbonate from the acid- 
carbonate in this way was patented by F. Clarke Hills in 184(1. 
-j- Grossage patented, in 1855, the production of the acid- 
carbonate and a residual solution of the normal carbonate by 
distilling an aqueous solution of the commercial carbonate. 
