ORGANIC 
The presence of copper is determined in the 
same way by incineration, treatment with nitric 
acid and sulphuretted hydrogen ; the resulting 
sulphuret is dissolved in nitric acid, and the 
oxide thrown down from the boiling solution 
by excess of caustic potash: it is ignited and 
weighed; 100 parts contain 80 of metallic 
copper. If the nitrate of copper be treated 
with ammonia instead of potash in excess, a 
beautiful transparent blue solution is obtained, 
which, when procured as just mentioned, is 
characteristic of the presence of copper. 
Mercury, arsenic, antimony, and a variety 
of other substances may occasionally be met 
with after poisoning with these bodies; but 
abundant directions for their discovery are 
given in the works on Toxicology, and to these, 
and in particular to the excellent treatise of 
Dr. Christison, the reader is referred. 
_B. ANaLysIs OF ANIMAL SOLIDS. 
Solid matters, as tumours, concretions, and 
sediments, are best subjected to a preliminary 
test by the action of heat; the sediments are 
separated by filtration from the liquids in 
which they are deposited ; by ignition on plati- 
num foil of a few small fragments we observe 
either, 
1. It is wholly or almost wholly dissipated, 
in which case it consists of, 
Cholesterin, which fuses and burns with 
flame ; 
Uric acid, or which are gradually dissi- 
Urate ammonia, § pated, producing transient 
blackening of the foil around ; 
Cystic oxide, which is consumed with a pe- 
culiar odour; 
_ Albumen, fibrin, or hairs, which swell up 
and burn with flame: 
__ 2. Or it blackens, leaving a less bulky re- 
idue ; 
_ In which case it may be 
_Urate of soda, potash, . they leave an alka- 
_ Lime, or magnesia, ‘§ line ash, which in 
the two first fuses at a red heat, or it may arise 
Tom a mixture of some of the preceding list 
with some of those that follow. 
_ 3. Or, lastly, it undergoes little or no change 
n bulk, when it is composed of 
Phosphates of the earths ; 
Carbonate of lime, or magnesia ; 
Oxalate of lime, which generally decrepi- 
_ Having by these simple trials acquired some 
mowledge of the nature of the substance we 
ave to deal with, we proceed to a more spe- 
jal examination. 
a. Cholesterin is the principal constituent of 
lliary calculi in the human subject, mixed 
ith variable proportions of colouring matter. 
ese calculi, when numerous, generally pre- 
facettes more or less flattened and po- 
hed ; when solitary, they often attain consi- 
able bulk, and are usually crystalline and 
mitransparent on the surface. Before the 
owpipe they fuse and burn with a bright 
noky flame, leaving but little ash. Boiling 
hol dissolves the cholesterin, and on cool- 
3 deposits the greater part in pearly glisten- 
ANALYSIS. 805 
ing scales. Caustic potash dissolves. the co- 
louring matter and leaves the cholesterin. This 
last reaction distinguishes it from other fats, 
and particularly from lithofellic acid, recently 
discovered as an occasional constituent of be- 
zoars and of gall-stones in the inferior animals ; 
the lithofellic acid fuses at a higher tempera- 
ture than cholesterin, and separates from its 
alkaline solution as an insoluble fat on neu- 
tralizing by a stronger acid. 
b. Uric acid generally assumes the form of a 
reddish-brown crystalline sand, or of lighter- 
coloured rounded masses. Before the blow- 
pipe it blackens and burns away, leaving only 
a minute trace of ash, usually alkaline, owing 
to the presence of a very small quantity of lime 
or soda. The manner of applying nitric acid, 
so as to produce the characteristic colour from 
the decomposition of uric acid, has been al- 
ready mentioned. When powdered it dissolves . 
completely in solution of potash by the aid of 
heat, and if the solution be supersaturated 
with hydrochloric acid, uric acid again preci- 
pitates in minute white crystals. 
The urates are much more soluble in hot 
water than uncombined uric acid: they form 
amorphous deposits usually of a light brown 
colour. 
Urate of ammonia before the blowpipe pre- 
sents phenomena resembling uric acid; when 
rubbed with solution of caustic potash, ammo- 
niacal fumes are emitted. In its other reac- 
tions, except that it is more soluble in boiling 
water, it closely resembles uric acid. 
Urate of soda is distinguished by the large 
proportion of fusible alkaline ash left on igni- 
tion after the application of a red heat; the 
residue dissolves with effervescence in hydro- 
chloric acid and gives no precipitate when this 
solution is treated with an alcoholic solution of 
chloride of platinum. If potash were present, 
it would be indicated by the formation of crys- 
tals on adding this test. 
Urate of lime occasionally accompanies uric 
acid ; the residue by incineration then yields the 
usual reactions of lime, such as a precipitate 
with oxalate of ammonia when added to a 
solution of the ash in acetic acid. 
c. Cystic oxide is wholly dissipated by heat, 
emitting a peculiar odour. - It is soluble readily 
both in acids and alkalies, and is deposited in 
hexagonal plates by spontaneous evaporation 
of its ammoniacal solution. The peculiar form 
of its crystal is at once recognized by the em- 
ployment of the microscope. 
d. Albumen and fibrin are discovered by 
their solubility in diluted alkalies and in acetic 
acid. Neutralization causes a flocculent preci- 
pitate soluble in excess of acetic acid or of the 
alkalies ; the acetic solution gives a precipitate 
on adding ferrocyanide of potassium. Before 
the blowpipe they swell up, leaving a bulky 
coal which burns with difficulty to a small 
white or yellowish ash; they always contain 
saline matter. Albumen and fibrin, in com- 
mon with all the compounds of protein, are 
further characterized by dissulving slowly in 
the concentrated acids; with sulphuric acid a 
