94 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[July 30, 1870. 
( c .) By passing ammonia through a strong solution of 
the commercial carbonate until it becomes charged with 
the gas, when crystals of the ammonium carbonate, simi¬ 
lar to those produced by method ( b ), will form in small 
quantity, either while the gas is passing, if the solution 
he kept cool, or afterwards, on allowing the solution to 
stand in a closed vessel in a cool place. 
(cl.) By dissolving a sufficient quantity of the com¬ 
mercial carbonate in warm, dilute solution of ammonia, 
best in a closed or nearly closed vessel, when ammonium 
carbonate crystallizes out on cooling. If the free am¬ 
monia be present in large quantity, the crystals are 
small; if it be present in very small quantity only, the 
salt next to be described crystallizes out; while if it be 
present in not much more than sufficient quantity to 
prevent this, the crystals of ammonium carbonate are 
large. I have found this one of the best methods for 
getting large crystals. 
(e.) By adding dilute spirit to a solution of commer¬ 
cial carbonate in ammonia-water (or to any solution 
equivalent to this prepared in any other way), in quan¬ 
tity somewhat less than enough to cause a precipitate, 
when the ammonium carbonate slowly crystallizes out in 
long, flat prisms. As with the last method, the size of 
the crystals is generally less in proportion to the quan¬ 
tity of free ammonia. When strong spirit is added to a 
concentrated ammoniacal solution of the carbonate, the 
whole soon partially solidifies through the formation of 
minute crystals of ammonium carbonate, large prisms 
sometimes shooting across the mass when the mixture is 
not too strong in free ammonia. 
(/.) By dissolving ammonium carbamate in sufficient 
quantity in water at a gentle heat (30°-35°) in a closed 
vessel, when, on cooling the solution, and standing it 
aside for some time, a little ammonium carbonate crys¬ 
tallizes out. 
(g.) By dissolving ammonium carbamate in sufficient 
quantity in strong ammonia solution at the ordinary 
temperature in a closed vessel, and setting the solution 
aside with the vessel only imperfectly closed, that am¬ 
monia may slowly escape, when ammonium carbonate 
crystallizes out. 
(h.) By passing carbonic anhydride into strong am¬ 
monia-water for some time, taking care to leave large 
excess of ammonia, and setting the solution aside in a 
closed vessel, when the carbonate separates in small, 
usually minute crystals. 
(i.) By dissolving good commercial carbonate, crushed 
small, in water at a gentle heat,—best in a closed, or 
nearly closed vessel,—setting the solution aside to cool 
and crystallize, decanting the mother-liquid on to a fresh 
quantity of commercial carbonate, again effecting solu¬ 
tion by heat, cooling, and crystallizing, a second time 
decanting the mother-liquid, and so on, repeating these 
solutions and crystallizations a sufficient number of 
times, when, according to the extent to which the water 
has been treated with the commercial carbonate, either 
the last solution, after depositing crystals for one or two 
days, will, on being decanted, and left for a further time 
in a closed vessel in a cool place, deposit large prismatic 
crystals of ammonium carbonate, or the solution will, in 
one night’s crystallization, form over the first crop of 
crystals a second of the ammonium carbonate, and con¬ 
tinue for some time to yield more of this substance.* 
If, instead of waiting for the solution to crystallize, it be 
treated with ammonia-water, a precipitation of minute 
crystals of the salt will take place, and convert the 
whole into a semi-solid mass. This and method (d) are 
the best for obtaining large crystals. The crystals are 
relatively short and broad when this solution is allowed 
to crystallize slowly at medium temperatures; but when 
the solution which has thus been left standing for some 
* Details of the action of wa L er on the commercial carbo¬ 
nate will be given further on. It would be inconvenient to 
go into them here. 
days is exposed to the sky for a night in clear cold 
weather, long flat prisms generally form. 
Dalton's Method of producing the ammonium carbo¬ 
nate by the wet way has only indirectly succeeded in 
my hands. 
Dalton's Method by the Dry Way. —Dalton gives no 
further account of this method than that I have set 
down in the historical notice of his paper. 
Sensible Properties. —Ammonium carbonate gives out 
an exceedingly strong ammoniacal odour, due presum¬ 
ably not to itself, but to ammonia as a product of its de¬ 
composition. It has an extremely pungent taste, and at 
once affects the tongue as a caustic to a marked degree. 
Form. —Ammonium carbonate takes the form of elon¬ 
gated plates or flattened prisms. Their shape is roughly 
indicated by the annexed cuts. 
The inclination of the side-face 4 to the face 2 does not 
appear to be the same as that of the side-face 3 ; nor am 
I decided whether the side-face 5 is parallel or not to 
the side-face 3 ; but the two faces, 4 and 5, I have found 
it difficult to observe satisfactorily. The faces of the 
crystals lose their lustre when the mother-liquor is wiped 
off, and the edges are rapidly destroyed. From the 
general inclination of the side-faces to the broad face 2, 
the crystals look like half-forms, or as if the crystal had 
been formed with its face, 1, on the bottom of the vessel, 
which is indeed a common position of the crystals. The 
crystals have, however, the same appearance when 
formed with both surfaces of the plate free. The end 
faces, 6 , 7 , are always hollowed out, and give a distinc¬ 
tive appearance to the crystals. 
When large crystals are formed by slow growth, they 
are so broad in proportion to their length, that they can 
hardly be described as prisms. But when large crystals 
are produced in a single night, they are often of great 
length, shooting across the solution like nitre crystals. 
One of these I measured, and found it to be 50 mm. 
long, 6 mm. broad, and about 0 - 5 mm. thick. Crystals 
growing over the bottom of the vessel take the broad, 
short, tabular form; while those produced in the body of 
the solution assume the slender, flat, prismatic form. 
When solitary crystals are first seen suspended in the 
solution, they have a narrow breadth, no sensible thick¬ 
ness, and a considerable length relatively to their minute 
bulk, and are hardly, if at all visible, except when in a 
position to reflect light to the eye from one or other of 
their broad surfaces. A very small absolute bulk of such 
crystals is sufficient to convert the whole solution into a 
semi-transparent magma, forming, as they do, equally 
through all parts of it. When they are very minute, 
and in not too great quantity, the network they form 
can be shaken by gently jolting the vessel into a smaller 
bulk, retaining more or less the shape of the interior of 
the vessel. Shaken up on to the sides of the vessel, they 
form masses looking like jelly. Violently shaken up, 
they subside afterwards to the lower part of the vessel. 
When the solution filled with these crystals is left un¬ 
disturbed, the crystals grow, and form a closely inter¬ 
lacing network of slender, apparently four-sided prisms. 
The ends of small crystals, whether proportionately short 
or not, are terminated by almost exclusively one face, the 
