ORGANIC 
mains, as the phosphate of irou is insoluble in 
acetic acid. The absence of iron must be 
determined by dissolving the precipitate in 
nitric acid, nearly neutralizing with ammonia 
and adding hydrosulphuret of ammonia; the 
iron, if present, would fall as a black sulphuret, 
mixed with oxalate of lime. Oxalate of lime 
dissolves in dilute nitric acid, and, on super- 
saturating with ammonia, is thrown down un- 
changed. By converting the oxalate of lime 
into the carbonate or sulphate, as directed when 
speaking of the estimation of lime, the quan- 
tity of oxalic acid may be inferred—100 grs. 
of the carbonate indicate of anhydrous oxalic 
acid 72 grs., and 100 of the sulphate 51.94 of 
the acid. 
2. For the inorganic constituents. 
To ascertain the nature and proportion of 
the saline matters incineration is resorted to in 
the manner already described. This process, 
however, only tells us what the fixed ingre- 
dients are, and their quantity, in the form of 
oxides, chlorides, sulphates, phosphates, or 
carbonates. All the ammoniacal salts are ne- 
cessarily dissipated, frequently carrying off 
portions of sulphuric acid and chlorine. The 
organic acids that may have been combined 
_ with the bases are entirely decomposed and 
their place supplied by carbonic acid, which 
renders it difficult to decide whether any car- 
bonate actually existed as such in the com- 
pound ; and moreover the metals, as iron, cal- 
cium, and magnesium, with other bodies, as 
sulphur and phosphorus, are for the most part 
estimated, not (as is sometimes probable, and 
at others certain, that they existed) in the me- 
tallic or unoxidized form, but as oxides or 
acids. The information we derive from inci- 
neration is therefore incomplete, and the mere 
deduction of the weight of ashes from the 
entire weight of the body burned by no means 
furnishes us with a correct estimate of the pro- 
portion of volatile ingredients ; generally speak- 
ing, however, it is the nearest approximation 
we can obtain. ’ 
_ I shall here describe very briefly the means 
t adapted to the qualitative and quantitative 
rmination of the saline matters, referring 
those requiring more ample instruction on this 
Subject to Rose’s Manual of Analytical Che- 
Mistry, and the various systematic treatises on 
the science. 
_ Although during incineration portions of 
aline matter, and especially of chlorine, are 
arried off, and the sulphates are sometimes 
reduced to sulphurets, we find it the only 
method by which any thing like an accurate 
estimate of the inorganic constituents can be 
obtained, inasmuch as many of these bodies 
cur in the form of chemical compounds 
‘ith organic matter, and are thus prevented 
rom forming precipitates with the ordinary re- 
gents: iron is particularly liable to be thus 
fiected. When practicable, we should usually 
ake an analysis of the solution for the inor- 
fanic acids before evaporation, and afterwards 
second examination of the fixed residue after 
ynition. 
The inorganic materials for which we shall 
VOL, III. 
ANALYSIS. 
have in general to search are comparatively 
few in number; among the acids, hydro- 
chloric, sulphuric, phosphoric, and carbonic, 
with traces of silica, will be those of most fre- 
quent occurrence. Occasionally we may have 
to seek for iodine, fluorine, and unoxidized 
sulphur. Potash, soda, ammonia, lime, mag- 
nesia, and oxide of iron, are the bases that will 
be most frequently the objects of experiment, 
and now and then we may have to look for 
copper, lead, and some other metals. 
Qualitative examination. 
a. The saline residuum, after ignition, is 
boiled with a little water (solution A) and fil- 
tered from the insoluble residue (B). 
A. b. The solution, except in special cases, 
will only contain sulphates of potash, soda, lime, 
and magnesia, as well as chlorides of the same 
bases, and phosphates and carbonates of potash 
and soda. When the alkaline carbonates are 
present, lime and magnesia need not be looked 
for; nor need we search for either of these 
bases if the solution contain phosphates, unless 
the liquid reddens litmus paper. The liquid 
is, therefore, in the first place tested with blue 
and with reddened litmus paper, by which 
acidity, alkalinity, or neutrality is rendered 
evident; we then proceed to determine what 
acids are present. The absence of a precipitate 
should not be too hastily decided on. As a 
general rule the tests should be allowed to 
stand twelve hours before a negative result is 
recorded. 
c. A portion of the liquid is acidulated with 
nitric acid, and to a smal! quantity of it a drop 
or two of solution of chloride of barium added ; 
a white cloud indicates sulphuric acid. 
d. Into another portion of the acidulated 
fluid nitrate of silver is dropped in slight excess ; 
a bluish white flocculent precipitate shews the 
presence of chlorides. 
e. The solution (d) is filtered from the chlo- 
ride of silver, is boiled for a few minutes, then 
saturated exactly withammonia. If phosphoric 
acid be present, a yellow precipitate of phos- 
phate of silver, very soluble in excess of ammo- 
nia, is produced. 
801 
J. A little of the aqueous solution is evapo- - 
rated to dryness, and a drop of nitric acid added 
to the residue : effervescence indicates carbonic 
acid, due in all probability to the decomposition 
of some organic acid by ignition. 
We have next to test for the bases in solution. 
g- The liquid is rendered slightly alkaline 
by ammonia free from carbonate.* A white 
precipitate shews phosphate of lime or magnesia, 
or both. 
h. The filtered liquid is tested by oxalate of 
ammonia; if lime be still in solution, a white 
cloud falls. 
i. The oxalate of lime is separated by filtra- 
tion and phosphate of soda or ammonia added ; 
brisk stirring with a glass rod causes a white 
* The absence of carbonic acid is easily ascer- 
tained by adding some lime-water to the solution 
of ammonia; it ought to remain perfectly transpa- 
rent; opalescence indicates the existence of carbo- 
_ hic acid, 
3 F 
