DE. MAECET ON THE IMMEDIATE PEINCIPLES OE HUMAN EXCEEMENTS. 407 
five hours after the extract had been prepared, yielded a dark-coloured fluid. When 
this solution was allowed to stand undisturbed in a flask for twenty-four hours, another 
substance subsided and collected at the bottom of the flask; a cold night, favouring 
in a remarkable degree the formation of this second deposit. After decanting the 
clear fluid and filtering the residue, a nearly white and amorphous substance remained 
oji the filter ; boihng alcohol and ether removed from it every trace of colouring matter 
or other impmities, the deposit being insoluble in these fluids. A sample of the siib- 
stance being burnt on the platina knife, it ignited, charred, and finally left a residue 
of white ashes, whilst in the case of the first deposit it was found impossible, even with 
the bloAvpipe, to obtain the ashes otherwise than dark coloured. The inorganic residue 
submitted to analysis, proved to consist entirely of magnesia*', in order to determine 
the nature of the organic substance, combined with magnesia, the compound was 
boiled with potash, when after a short time it dissolved, leaving in the fluid but a hght 
precipitate ; the addition of hydrochloric acid to the mixtm’e induced the separation of 
a white sohd substance, which floated on the hquid ; this substance was collected on a 
filter, thoroughly washed with water, and then dissolved in a little boiling alcohol, 
when on coohng it sohdified, assuming the crystallized form peculiar to margaric acid ; 
its fusing-point was found to be 56° C., and on coohng, the fused mass again crystal- 
lized ; in short, there could be no doubt that this substance was margaric add ; the 
deposit rmder examination being nearly colomdess, I had no difficulty in obtaining the 
fatty acid in a perfectly white and pure condition. Though a qualitative analysis of the 
deposit showed that it contained no other substance than margaric acid and magnesia, 
stih it was important to determine if they were present in such proportion as to form 
the neutral margarate of magnesia, — 
C3,H33 03 + Mg0. 
For this purpose, a sample of the deposit, purified by repeated washings with boiling- 
alcohol and ether, was dried in the water-bath until it ceased to lose weight ; it was then 
ascertained tu weigh 0-088 gramme ; after it had been burnt in a platina capsule, the 
weight, of ashes left amounted to 0-007 ; the result of the analysis may be given as 
follows : — 
On 0-088 gramme. 
Found. Calculated according to formula. 
Margaric acid .... 0-081 0-081 
Magnesia 0-007 0-007 
0-088 0-088 
which shows that the compound can be no other than margarate of magnesia. 
In my previous communication I stated that I had noticed an increase of margaric 
* The carbonate of magnesia resulting from the incineration of a compound of this substance w ith an 
organic acid, had been decomposed by the blowpipe flame, with the evolution of carbonic acid. 
