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XXV.—On Meconic Acid, and some of its Derivatives. By Mr Henry How, 
Assistant to Dr ANpErson. Communicated by Dr T. ANDERSON. 
(Read 5th January 1852.) 
In a paper on Comenic Acid, read before this Society in April of last year, and 
since honoured with a place in its Transactions, I mentioned my being engaged 
in an investigation on Meconic Acid; the details of the experiments referred to 
form the matter of the present communication. 
My object in undertaking this subject was to ascertain if products correspond- 
ing to those described as derived from comenic acid were formed under similar 
circumstances in the case of meconic acid. Lalso thought it probable, that as the 
former is itself a derivative of the latter, the changes undergone by meconic acid 
in some reactions, would be found to result in substances apparently the imme- 
diate derivatives of comenic acid. This remark refers to the action of heat on 
meconate of ammonia; and it will be seen that the expectation was realised. A 
similar result was found in other instances, where it had not been anticipated. 
The experiments I am about to detail were performed in the laboratory of Dr 
T. ANDERSON. 
The process employed for the purification of meconic acid was that given 
by Grecory in his “Outlines,” excepting that ammonia was substituted for 
potass as the solvent of the crude acid. As in the case of comenic acid the vola- 
tile alkali was preferred, because, although in both cases a great deal of acid 
‘remains in the highly coloured mother liquors, from which it can only be reco- 
vered in a pure state at the expense of much time and labour, it was found that 
if ammonia was used, the whole of the mother liquors could be employed under 
circumstances where their impure state did not affect the results of the experi- 
ment. A considerable saving was thus effected. This point is of some import- 
ance, because the numerous solutions requisite for the purification of meconic 
acid occasion so much loss, that seldom much more than a fourth part of the 
_ weight of the crude acid started from, is obtained as the result of a careful pre- 
paration. 
The process consists in dissolving crude meconic acid in hot water by aid of 
caustic ammonia. The crude acid is obtained from meconate of lime by treating 
it three successive times with twenty parts boiling water and three parts strong 
muriatic acid. The mixture of the acid so obtained, and about twice its weight 
of water, is kept hot in a water-bath and constantly agitated, till, by the addition 
of caustic ammonia, solution is complete; the salt formed is extremely soluble in 
hot water, and the fluid cools to a solid mass. The black mother liquor is squeezed 
VOL. XX. PART III. 5Q 
