406 DE. MAECET OjS' THE BOIEDIATE PErN'CIPLES OF HUAIAA’ EXCEIAIENTS. 
margaric acid into a neutral margarate of lime. The quantitative analysis of the 
deposit was effected by boiling it with potash, and decomposmg the soap by means of 
hydrochloric acid, for the pm’pose of precipitating the margaric acid. The whole being 
thrown on a filter, the precipitate was washed until the washings had ceased to exhibit 
an acid reaction and produce a cloudiness in a solution of nitrate of silver ; the fatty acid 
was dried on filtering-paper, and finally dissolved in ether ; the ethereal extract being 
evaporated to dryness in a weighed beaker, the weight of the residue could be easily 
ascertained. The phosphoric acid and hme were determined in the filtrate from the 
margaric acid precipitate, the phosphoric acid with perchloride of iron and sulphate of 
magnesia, and the lime with oxahc acid. The following Table shows the result of the 
analysis, together mth the quantity of margaric acid necessary to combine vdth the 
amount of hme, exceeding that which could possibly have been combined originally with 
the phosphoric acid : these numbers were obtained by calculation, according to the for- 
mula for the neutral margarates, — 
^34 H 33 03 -}- MO. 
round. 
A 
Calculated. 
r . 
Lime. 
Phosphoric acid. 
Margaric acid. 
Margaric acid. 
1. 
0-0021 
0-015 
0-083 
0-074 
2. 
0-040 
0-031 
0-230 
0-112 
3. 
0-058 
0-042* 
0-205 
0-196 
4. 
0-031 
0-023* 
0-100 
0-102 
These results show that the lime, phosphoric acid and margaric acid found in the 
deposit under examination, existed as phosphate of lime and margarate of hme, and 
consequently assumed this form in excrements f. 
From the difficulty of extracting fatty acids perfectly pure and colourless, without 
experiencing more or less loss of substance, when they are mixed up uith animal coloui- 
ing-matters and other impurities, it is next to impossible to obtain mathematicaUy exact 
results in such analysis. In analyses No. 1 and No. 3, the quantities of margaric acid 
found were slightly above the proportion determined by calculation, which resulted from 
the presence of impurities ; these could not have been removed mthout the loss of more 
or less of the acid. In analysis No. 2 the margaric acid was highly coloiu’ed and impure, 
which accounts for its proportion being considerably above what it ought to have been. 
In analysis No. 4, the margaric acid obtained bemg comparatively pure, the result was 
very conclusive. 
The alcohohc extract of excrements filtered from the deposit just described, four or 
* In analyses 3 and 4, the quantity of phosphoric acid was obtained by calculation. 
t It is very remarkable that these salts should have dissolved in the boiling alcoholic extract of fseces, 
and lost their property of dissolving in boiling alcohol, after having been collected on a filter ; which cir- 
cumstance is probably owing to the acid reaction of the alcoholic extract. The same observ'ation applies to 
the margarate of magnesia. 
