DE. MAECET ON THE IMMEDIATE PEINCIPLES OE HUMAN EXCEEMENTS. 409 
a third crop of excretine could be obtained ; but as soon as the thermometer rose above 
the fi'eezing-point, the alcoholic extract ceased to deposit crystals, and those which had 
formed were rapidly dissolved. It was also observed that the crystallization occurred 
more rapidly when the alcoholic solution was left in an open vessel ; which is accounted 
for by the circumstance that the evaporation of the alcohol increased the proportion of 
water in the alcoholic fluid, and consequently the excretine acquired a favourable con- 
dition for assuming the solid form ; the cold temperature moreover reduced its solubility 
in alcohol, and it was therefore induced to crystallize. The amount of crystallized 
excretine was apparently proportional to the intensity of the cold. Each crop of crystals 
was collected upon the same filter, and allowed afterwards to become comparatively dry 
by exposure to air in the funnel. The filter was next washed with ether or boiling 
alcohol, which dissolved out the whole of the crystals, and the solution by standing 
for a night yielded an abundant crop of nearly pure excretine ; more or less of the 
impurities which had precipitated with the excretine were left on the filter, being 
insoluble in ether or in boiling alcohol. For the purpose of obtaining excretine in a 
perfectly prue and colourless condition, the impure substance resulting from the spon- 
taneous evaporation of the ether solution, or from the exposure of the alcoholic extract 
to cold, was separated from its mother-liquor (the latter being decanted), then washed 
in a capsule with a little cold alcohol, which dissolved the colouring matter and a 
very small proportion of excretine ; the cold coloured alcohol was decanted, and after 
repeating this operation four or five times, and collecting the washings^ the excretine 
was dissolved in a little hot alcohol ; on cooling, it was obtained colourless and beautifully 
crystallized ; if the crystals were not yet pure, the above operation was repeated. The 
washings yielded another crop of crystals, which were purified by the same process ; and 
the operation was repeated on the successive series of washings until the coloured alco- 
holic solution contained but very little excretine ; by this method much less of the sub- 
stance was lost than by repeated crystallizations in ether, and drying the impure crystals 
on filtering-paper. 
In order to submit this new substance to analysis, it was necessary to prepare it on a 
large scale, and the cold weather not lasting long enough for the purpose of allowing 
me to extract it in sufficient quantity, I was obhged to adopt the following method, 
which is a modification of that described in my first paper. The clear alcoholic extract 
of eight or nine evacuations was mixed with lime-water and then filtered. I washed the 
precipitate with water, and then dried it perfectly on a water-bath ; this substance being 
transferred to a flask, was now agitated \vith a mixture of alcohol and ether, and filtered 
after having stood for some hours. The residue left on the filter was w'ashed with ether, 
dried in the open air, or in a retort (with the view of recovering the alcohol and ether), 
and again treated 'with a mixture of alcohol and ether. The solutions were but little 
coloured, and after twenty -four hours yielded a beautiful crop of excretine. The mother- 
liquor, separated by filtration or decantation, deposited some hours afterwards a second 
crop of crystals. The substance was purified by repeated solutions in alcohol and ether, 
MDCCCLVII. 3 H 
