ORGANIC 
___ Sulphuric acid may be precipitated from the 
filtered liquid or from any fluid suspected to 
contain it by acidulating (if not already acid), 
not too strongly, with nitric acid, and preci- 
pitating with nitrate of baryta. The preci- 
pitate should be well washed with boiling 
water as long as any thing is dissolved, then 
ignited and weighed. Boiling nitric acid is 
without effect upon it; 100 grs. contain 34.19 
of sulphuric acid. 
(B.) The insoluble portion consists of carbo- 
nates and phosphates of the earths, and per- 
haps of iron. We bring them into solution 
by means of nitric acid, and supersaturate 
with caustic ammonia to separate the phos- 
phates; filter if necessary, and add oxalate of 
ammonia; collect and ignite the precipitate, 
moisten with solution of carbonate of am- 
monia; it is once more heated to incipient 
redness, and it then consists of carbonate of 
lime: the carbonic acid is estimated in the 
manner already directed. The filtered liquid 
is boiled with solution of carbonate of am- 
monia; the magnesia, if any, precipitates and 
must be strongly ignited; 100 parts indicate 
110 of carbonic acid, which must be added to 
that combined with the lime. 
Phosphoric acid—The quantitative estima- 
tion of this body is attended with some dif- 
ficulty, as it cannot be effected by direct oe 
cipitation, but is inferred from the loss. e 
precipitate by caustic ammonia just obtained 
consists entirely of earthy phosphates and phos- 
phate of iron. It is ignited and the weight 
ascertained. It is then brought into solution 
by means of concentrated hydrochloric acid, and 
ammonia’added until the precipitate from the 
Still acid solution is no longer perfectly re- 
dissolved. Acetic acid is now added and then 
More ammonia, taking care that the liquid is 
still strongly acid. Phosphate of iron alone 
precipitates; this is separated by filtration, and 
after strong ignition consists of 57.44 phos- 
phoric acid and 42.56 sesquioxide of iron. 
From the filtered liquid the lime and mag- 
hesia are separated by oxalate of ammonia and 
austic ammonia, as will presently be de- 
ribed ; then deducting the united weight of 
he oxide of iron, lime, and magnesia from that 
of the ignited mixed phosphates, the remainder 
$ phosphoric acid. 
+ order to bring the tests for analogous 
odies together, I shall here interrupt the course 
f the analysis to describe the methods of pro- 
eeding with those substances for which occa- 
ionally, though more rarely, we have to look. 
Todine, in organic fluids, always occurs in 
née form of an iodide, and is not met with in 
ne human body in its normal condition. We 
ust evaporate to dryness and treat the residue 
ith alcohol. The iodide will be dissolved ; 
® again evaporate to dryness and re-dissolve 
water: (if the quantity be not very minute, 
is preliminary process may be dispensed 
ith, merely concentrating the liquid and 
Owing it to cool;) iodine may now be 
tected by adding a little cold solution of 
, and pouring into the mixture a few 
ps of solution either of chlorine or of chlo- 
ANALYSIS. 803 
ride of lime (bleaching liquor), when a blue 
colour, more or less intense, is produced. The 
quantitative estimation of iodine in these ana- 
lyses is seldom required ; when it is, a neutral 
solution of chloride of palladium is added to 
the solution, accurately neutralized, and the 
whole set aside in a warm place for twenty- 
four hours, a black precipitate of iodide of pal- 
ladium forms: it should be collected on a 
weighed filter and dried at a very gentle heat, 
otherwise part of the iodine escapes. 100 grs. 
of iodide of palladium contain 70 of iodine. 
By suspending this iodide in water and adding 
starch and a little chlorine water, the blue 
colour is produced as usual. 
Fluorine, when present, and it appears to be 
a universal constituent of bones, is always in 
exceedingly minute quantity. To discover it 
we incinerate the dried matter, pulverize and 
make it into a thin cream with oil of vitriol in 
a shallow platinum crucible; instead of its 
usual cover the mouth is closed by a piece of 
flat glass, the under surface of which has been 
covered with a film of melted bees’ wax or 
some resinous varnish ; when firm or dry, a few 
characters are traced with a sharp point to 
expose the glass underneath; the glass: is 
pressed upon the crucible so as completely to 
close it, and the whole heated over a spirit- 
lamp for a quarter of anhour. The glass 
is kept cool by a piece of moistened paper. 
If any fluorine be present, the traces upon the 
glass from which the wax has been removed 
will be more or less corroded ; the superfluous 
wax may be removed by oil of turpentine, and 
the corrosion may be rendered distinct by 
rubbing a little powdered charcoal over the 
surface. If any marks are produced, it is an 
unequivocal proof of the presence of fluorine. 
This method, however, is not very delicate. 
Free sulphur is detected by boiling the sub- 
stance with solution of potash; if this element 
be present in the unoxidized state, a black pre- 
cipitate of sulphuret of lead is formed on add- 
ing a few drops of acetate of lead. 
If we desire to know the quantity of free 
sulphur, we first satisfy ourselves of the ab- 
sence of sulphuric acid, or determine its quan- 
tity accurately by the method already de- 
scribed ; then deflagrate the substance or dry 
residue with eight parts of pure nitre and two 
of pure carbonate of potash, throwing the mixture 
in successive small portions into a platinum 
crucible heated to redness; the sulphur is thus 
converted into sulphuric acid at the expense of 
the oxygen of the nitre, and its quantity may 
be determined by dissolving the saline residue 
in water, supersaturating with nitric acid, and 
precipitating by a salt of baryta as usual: the 
process is one requiring more than ordinary 
care to ensure accuracy. 
To resume the usual process of analysis, we 
now proceed to determine the bases. Most 
of the acids may be determined with consi- 
-derable exactness before the organic matter has 
been destroyed by ignition; it is not so with 
the bases. Incineration should always precede 
an attempt to estimate them. The second por- 
tion of saline matter is dissolved in water as 
3 F2 
