804 
before, separating it thus into a solution (A), 
and an insoluble residue (B). 
(A.) Potash —The solution rarely contains any 
but the alkaline salts. If, however, any of the 
earths are present, they must first be separated 
in the form of carbonates, by adding a mix- 
ture of carbonate and caustic ammonia; the 
filtered liquid is evaporated to dryness, the 
residue ignited to expel ammoniacal com- 
pounds and re-dissolved in water, which then 
contains only salts of potash and soda. If 
sulphuric or phosphoric acids be present, it is 
necessary for a quantitative determination of 
each alkali to convert the mixed sulphates or 
phosphates into chlorides. The method for 
accomplishing this object is rather circuitous : 
chloride of barium in slight excess is added to — 
the solution, which is filtered from the sulphate 
or phosphate of baryta that then precipitates ; 
the filtered liquid is heated with a mixture of 
caustic and carbonate of ammonia, again fil- 
tered, evaporated to dryness, and ignited ; the 
bases are thus obtained in their desired con- 
dition of chlorides; they are then carefully 
weighed, re-dissolved in a small quantity of 
water; bichloride of platinum in solution is 
added, and the whole evaporated to dryness on 
a water-bath. The dry residue is digested with 
rectified spirit, and the washing continued as 
long as the liquid passes coloured through the 
filter; the precipitate, consisting of anhydrous 
double chloride of platinum and potassium, is 
dried and weighed ; 100 grs. indicate 19.43 of 
tash. 
Soda.—After the potash has been determined, 
the corresponding quantity of chloride of pot- 
assium is deducted from the weight of the mixed 
chlorides, and the deficiency inferred to be chlo- 
ride of sodium; 100 grs. of chloride of sodium 
correspond to 53.33 of the anhydrous alkali. 
The platino-chloride of sodium, which the 
alcoholic solution contains, crystallizes in bold, 
well defined, flattened prisms readily soluble 
in water. 
Ammonia, when present in organic fluids, 
cannot be quantitatively determined with ac- 
curacy. Its presence is easily recognized by 
the characteristic pungent fumes which are 
given off when the residue of evaporation is 
mixed with caustic potash and gently warmed. 
(B.) Iron.—The precipitate by carbonate and 
caustic ammonia from A and the insoluble re- 
sidue B are dissolved in hydrochloric acid. 
When no phosphates are present, the acid 
solution is nearly neutralized by caustic am- 
monia; then an excess of hydro-sulphuret of 
ammonia added; the iron falls as a black sul- 
phuret. This is collected on a filter, washed, 
re-dissolved in! hot hydrochloric acid, and the 
iron thrown down as sesquioxide by ammonia 
in excess. It is thus completely separated from 
lime and magnesia.* 
* In the rare instances in which alumina presents 
itself in the animal fluids, this earth would pre- 
cipitate along with the sulphuret of iron, and would 
again be thrown down with the sesquioxide. It is 
however easily separated by digesting the oxide 
while still moist in a solution of caustic potash ; 
the oxide of iron alone remains behind. ‘To sepa- 
rate alumina from the alkaline liquid, it is feebly 
ORGANIC ANALYSIS. 
If the earthy phosphates are present in mix- 
ture with iron, the process already described, 
when speaking of phosphoric acid, must be 
employed. 
ime—The acetic solution of the phos- 
phates filtered from the iron, or if no iron be — 
present, the acid solution supersaturated with 
ammonia and the precipitate re-dissolved in 
acetic acid, (a precaution indispensable, as 
‘oxalate of lime is soluble in nitric or hydro- — 
chloric acids,) is treated with solution of ox- 
alate of ammonia in excess. A white precipitate — 
of oxalate of lime falls; it is allowed to 
some hours in a warm place (the ieee would 
otherwise pass turbid through the filter), sepa- 
rated by filtration, ignited, and then moistened 
with a saturated solution of carbonate of am= 
monia, after which it is thoroughly dried ata 
temperature short of redness. Carbonate of 
lime is thus obtained; 100 grs. contain 56 of 
pure lime. ‘ 
Magnesia.—The filtered liquid is super 
saturated with ammonia, well agitated, and : 
lowed to stand for some hours; if any mag: 
nesia be present, it separates as a crystallin 
precipitate, which must be washed with 
weak solution of phosphate of ammonia; it” 
dried and ignited ; the residue contains 35.7 
of magnesia in every 100 grs. , 
Our ordinary analysis terminates here. 
Lead is sometimes found as a morbid ca 
stituent of certain parts, more particularly ¢ 
the soft solids; the fluid or part to be examin 
is dried and incinerated, (if bulky, in a ele 
earthen crucible,) and the c 2c 
as far as may be; the residue is digested 
nitric acid diluted with thrice its bulk of wi 
filtered, nearly neutralized by ammonia, ai 
current of sulphuretted hydrogen transmit 
through the liquid. The gas is easily g 
rated for this purpose by adapting to a e¢ 
mon phiat a glass tube bent twice at f 
angles, one limb being considerably le 
than the other; the short limb aint 
through the cork of the phial, and the ‘ 
lunges nearly to the bottom of the liqui 
he examined. In the phial 100 or 200 
of coarsely bruised proto-sulphuret of 
are placed, and an ounce or two of | 
sulphuric acid (1 of acid and 5 or 6 of w 
abundant effervescence arises from 
engagement of the sulphuretted 
If lead be present in the tested liquid, a 
or black precipitate of sulphuret of 
and the liquid becomes milky from the 
decomposition of the gas; when it” 
strongly of the sulphuretted hydrogt 
liquid is filtered, the precipitate is tre 
nitric acid, to which a few drops of su 
acid have been added, and the whole 
a white residue of sulphate of lead is ol 
which contains 68.42 per cent. of 
lead. Sulphate of lead is insoluble i 
acid, but is completely dissolved by 
solution of acetate of ammonia. __ 
supersaturated with hydrochloric , a 
rendered slightly alkaline by ammonia ; thea 
precipitates, is collected on a filter, th 
washed, ignited, and weighed. 
