402 MR HENRY HOW ON MECONIC ACID, 
out by strong pressure, and the cake of salt redissolved twice or thrice in as small 
a quantity of boiling water as is found sufficient, the mother liquors being always 
pressed from the crystallised salt. By proceeding in this manner a perfectly 
white salt is obtained, from whose solution in hot water an excess of strong hy- 
drochloric acid throws down the meconic acid in colourless brilliant scales; these 
require but a little washing with cold water, and one resolution in the smallest pos- 
sible quantity of hot water, to be obtained on cooling of the fluid absolutely pure. 
This is another advantage in the use of ammonia, for the potass salt requires, at 
the least, three treatments with acid to abstract the alkaline base entirely. 
Bibasic Meconate of Ammonia.—The ammonia salt obtained in the above given 
process, crystallises from tolerably dilute fluids left at rest, in groups of radiated 
fine silky needles: they have an acid reaction. In the following analysis the 
nitrogen was determined by adding hydrochloric acid to a solution of the salt, 
evaporating the filtrate with some bichloride of platinum, collecting the residue 
on a filter, and washing with alcohol and ether; the per-centage of nitrogen was — 
calculated from the platinum remaining on ignition of the undissolved ammonia 
salt. This method was preferred in one or two other cases of ammonia salts, as 
more convenient than a combustion with soda lime, and less liable to loss ; for it 
is not easy always to mix these salts with soda lime so quickly as to avoid the 
escape of ammonia. 
5: a grains, dried at 212°, gave 
6: a ... carbonic acid, can 
2°20 water. 
{: 5-285 grains, dried at 212°, gave 





4505 ... metallic platinum. 
Calculation. 
Carbon, . . 85°51 3589 ©, 84 
Hydrogen, . é 4:73 4:27 1a AY a) 
Oxygen, : t Jon 47°88 O7 S12 
Nitrogen, . “ 12:09 11:96 N 28 
100-00 100°00 234 
The hydrogen is rather above the calculated result, but the substance, when 
dried at 212°, is extremely hygroscopic: the numbers lead to the formula 
HO, 2. NH,0, C,, HO,, 
as representing the constitution of bimeconate of ammonia in the dry state; the 
crystals appear to contain varying amounts of water of crystallisation, as num- 
bers were obtained in drying different specimens indicating a loss of between six 
and sixteen per cent. of water. An aqueous solution of this salt may be boiled 
without any change; but when kept for a considerable time boiling with an ex- 
cess of ammonia, it becomes altered. 

