50G 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [December 24, 1870. 
water in addition to that in the formula, this is just its 
calculated loss by exposure. In cold moist weather the 
commercial carbonate appears to be slightly deliquescent, 
but in consequence of other changes it is difficult to de¬ 
cide this point conclusively. 
Behaviour when Heated .—The commercial carbonate 
gets moist when heated; it is, of course, gradually dissi¬ 
pated. The products of its distillation will be after¬ 
wards described. 
Behaviour with Water .—It dissolves in four parts of 
water at 15°, according to my experiments. Perfectly 
clean lumps were weighed and dropped into a weighed, 
quantity of water (fresh boiled and cold) in a stoppered 
bottle; the bottle was kept in a place at a temperature 
always very near 15°, and was often agitated. In dif¬ 
ferent experiments varying proportions were used. On 
cooling slightly the saturated solution, it deposited crys¬ 
tals of acid carbonate. Cooled in ice the deposit of 
crystals was still more copious, and consisted always of 
acid carbonate ; although it has been stated* that the 
half-acid carbonate then crystallizes out. As above de¬ 
termined, its solubility accords with that of the acid 
carbonate it contains, namely, about half its weight. 
The solubility of the carbonate which used to be in com¬ 
merce has been variously stated as lying between that of 
1 in 2 of water, and 1 in 4 of water; I think it must 
Rave been less than this. A saturated solution, unlike 
one of the acid carbonate, or of the half-acid carbonate, 
does not act like a saturated solution of carbonic anhy¬ 
dride. The strongest hot solution I have been able to 
make is that of 1 in 1|- of water. This was made by 
■dropping this proportion of the carbonate, crushed small, 
suddenly into the hot water contained in a wide-mouthed 
bottle fitted with a caoutchouc stopper, then closing the 
bottle and keeping it hot in the water-bath at a tem¬ 
perature of about 65° C. Only a little carbonic anhy¬ 
dride was lost. When made, the stopper of the bottle 
containing it could be withdrawn without anything more 
than a very slight escape of bubbles. The old carbo¬ 
nate of commerce is stated in Berzelius’s ‘ Lehrbuch’t 
to be soluble in twice its weight of water at 49° C. 
A cold saturated solution of the old carbonate was 
stated by Griffiths^ to boil at a temperature of 82° C. 
John Davy found such a solution to decompose at a 
lower temperature than this, bubbles beginning to ap¬ 
pear at 49° 0. I have tested the modern carbonate, and 
find a solution of it of 1 in 4 begins to effervesce, though 
only slightly, at 60° C., effervesces copiously at 75°, and 
continues to do so as the temperature rises, which it does 
rapidly. At 85°, or a little below, the products of effer¬ 
vescence, which before consisted almost entirely of car¬ 
bonic anhydride, contain much ammonia, and begin to 
condense on the neck of the flask or retort. At 100° C. 
the solution has given off all the carbonate it contained, 
and is nothing but water (Griffiths). I have just stated 
that the cold saturated solution differs from the saturated 
solution of half-acid carbonate, in not behaving like a 
saturated solution of carbonic anhydride ; and there can 
be no doubt that this fact, and that of the point of inci¬ 
pient effervescence in the two solutions when heated 
being- different, are due in part to the difference in the 
ratio of the ammonia to the carbonic anhydride in them. 
The following experiment shows the effect of dilution 
upon the production of effervescence. Some of the same 
solution as that used in the previous experiment was 
mixed before heating with an equal bulk of water 
(freshly boiled and cooled), and then did not begin to 
effervesce until about 70° C., was only in full effervescence 
at 80 C. or higher, and only at 90° C. began to yield pro¬ 
ducts of effervescence, which condensed in the neck of 
* Pelouze et Fivhny. ‘ Traite de Chimie,’ vol. ii. p. 483 
(1861). v 
t Vol. iii. p. 313. 
X ‘Quarterly Journal of Science’ (1826), vol. xviii. p. 91. 
“ On the Boiling-points of Saturated Solutions.” 
the flask. In both these experiments the heat was applied 
by a water-bath. Griffiths’ statement must not be sup¬ 
posed to be so much at variance with that of J. Davy 
as the latter seemed to consider it; for Griffiths meant 
apparently by the boiling-point of this solution the point 
at which Jhe products of the effervescence begin to bo 
such as undergo condensation, and this would probably 
occur with the old carbonate at about 82° C. 
The action of a saturated solution upon more commer¬ 
cial carbonate is well known to be the production of a 
sort of skeleton of the pieces of carbonate, consisting of 
the acid carbonate. I have only to add that by prolonged 
digestion I have found the particles of this mealy skele¬ 
ton to grow into, or be replaced by, transparent crystals 
of the same substance. 
I have examined the effects of heating the commercial 
carbonate with a little water, and have found that bub¬ 
bles of carbonic anhydride escape through the solution 
from the undissolved lumps at a lower temperature than 
they escape from a cold saturated solution heated alone. 
Thus, from about 40°-45° C. very slight effervescence 
was visible, due probably to an escape of the air en¬ 
tangled in the pores of the carbonate. At 47° decided 
effervescence commenced; this became copious at from 
54°-56°, and at tins temperature crystals began to form 
in the neck of the flask. (In this and the preceding ex¬ 
periments the mouth of the flask, as I should have men¬ 
tioned before, was loosely closed so as to prevent dif¬ 
fusion of the vapours given off.) Cooled down to 51° the 
escape of bubbles ceased. Heated again and kept at 
from 56°-60° effervescence went on again, the condensa¬ 
tion of the vapours appeared to be complete, and the 
lumps which had originally been barely covered with 
water disappeared entirely in a couple of hours. During 
their solution they seemed to dissolve entire, for no tem¬ 
porary residue of acid carbonate or any loss of trans- 
lucency in the lumps was seen. The products of the 
distillation were examined, and the results of the ex¬ 
amination will be found among those of the examination 
of the products of distillation. The solution on cooling- 
deposited crystals first of acid carbonate, and then of 
half-acid carbonate, determined to be such by their 
form. The mother-liquor was a very concentrated solu¬ 
tion of normal carbonate, with a very little acid carbo¬ 
nate. Tested for carbamate the result was negative. 
A modification of this treatment of water with the com¬ 
mercial carbonate, by which the three ammonium car¬ 
bonates can be obtained, has been several times referred 
to in this paper. 
Behaviour with Alcohol .—It is well known that recti¬ 
fied spirit dissolves out carbamate from the commercial 
carbonate, leaving undissolved the acid carbonate. Hfine- 
feld,* in 1836, heated the commercial carbonate with 
spirit of 90 per cent., and found that at 47'o°C. some 
bubbles began to rise from the lumps, that this pheno¬ 
menon became quite evident at 50°, and that from 56° 
to 62° there was copious effervescence of nothing but 
carbonic anhydride. Above this temperature the gases 
escaping condensed in the neck of the retort as a neutral 
compound, and the distillate which now formed was a 
neutral solution. I have repeated the experiment of 
heating the carbonate at present in commerce with spirit 
of about 90 per cent., with somewhat modified results. 
Of the products of distillation I shall say nothing at 
present. Minute bubbles began to escape from the 
lumps at 41°; at 45° there was very evident effervescence 
from the lumps ; at 50° there was copious effervescence 
with a simmering- noise ; at 51° the products of the effer¬ 
vescence began to condense; while at 53° the efferves¬ 
cence was exceedingly great. The temperatures ob¬ 
served by me as marking the stages of this phenomenon 
are, therefore, lower than those observed by Hiinefeld. 
The heat was applied by means of a water-bath, and the 
flask was loosely closed by a caoutchouc stopper to pre- 
* Journ. fur prakt. Chemie, vol. vii. p. 25. 
