ORGANIC 
This specimen of healthy saliva therefore 
contained, 
Le ae 
{ Fatty and odorous 
matter .....6 
Alcoholic extract 
and salts ..... 
Mucus and epithe- 
lium 1.36 
Ptyalin, watery ex- 
: 2.38 
994.98 
0.06 
_ Organic matter, 1.22 
{ 3.04. 
_ Fixed salts, 1.98. 
tract, salts and 
traces of mucus 
. 
1000.00 
If mercury were sought for, the best plan 
liva, evaporate to dryness, mingle the dry mass 
with well-dried carbonate of soda, to place the 
_ mixture ina fine glass tube sealed at one end, 
_ and apply the heat of a spirit lamp. If the 
_ metal were there, it would sublime and condense 
__ asa dew of metallic globules on the cool part 
_ of the tube. 
; IJ.—Uttimare Anatysis. 
__ Organic bodies consist principally of carbon, 
hydrogen, oxygen, and nitrogen, with occa- 
_ sionally small quantities of sulphur, phos- 
phorus, and various metallic, earthy, and saline 
_ Matters in minute proportions. In cases where 
_ the four first elements only are present, the 
aualysis is comparatively easy; and if, as some- 
times occurs, the substance to be analysed is 
_ capable of assuming a crystalline form, its 
oe is a matter of little difficulty, 
_ When, however, saline compounds enter es- 
" sentially into its constitution, as in most animal 
aa crystallization is never found to take 
place. 
_ This general absence of crystalline form in 
| animal principles, and the consequent difficulty 
of ascertaining that they are free from all mois- 
ture, which does not chemically enter into their 
constitution, have, by rendering us uncertain 
of the purity of the substances analysed, mainly 
_ contributed to the slow and uncertain progiess 
of this department of chemistry, and have 
given rise to the numerous 
Contradictory statements 
with which it abounds. By 
“Multiplied researches and 
ee we are, how- 
. ever, at length arriving at 
“results on the accuracy of 
which tolerable confidence 
ogy laced. 
_ The determination of the 
four elements, carbon, hy- 
n, Oxygen, and nitro- 
as they constitute the 
d of most organic sub- 
‘Stances, is that part of the 
process which now claims 
ur attention. It is to Gay 
} Lussac and Thenard that we 
| are indebted for the funda- 
| mental principle that re- 
gulates our operations. The 
Process proposed by them 
would be to mix a little nitric acid with the sa-_ 
ANALYSIS. 813 
has subsequently been modified and improved 
by many chemists, especially by Berzelius, 
Prout, and Liebig,.and in the hands of the lat- 
ter eminent philosopher it has acquired a de- 
gree of facility and accuracy hitherto unap- 
proached in any other department of analytical 
research. 
Our object being to determine the relative 
proportion in which each of the ultimate ele- 
ments exists, it becomes necessary to the success 
of any analytical process that we should pro- 
cure them in the form of definite compounds 
that can easily be collected; and it has been 
found most convenient, by supplying the sub- 
stance to be analysed with a sufficient quantity 
of oxygen, to convert the carbon into carbonic 
acid, which may be absorbed by potassa and 
weighed, and the hydrogen into water, which 
may likewise, by passing over a substance that 
has a powerful attraction for it, such as chloride 
of calcium or sulphuric acid, be collected 
and weighed, whilst the nitrogen escapes 
as gas, which is collected over mercury and 
measured. 
In cases where nitrogen is present, it has re- 
cently been proposed to heat the substance to be 
analysed along with hydrate of soda or potash; 
all the nitrogen is thus converted into ammonia, 
in. which form, like carbonic acid and water, it 
admits of being weighed. By calculation it is 
easy to find the weight of the carbon, hydrogen, 
and nitrogen respectively contained in the car- 
bonic acid, water, and ammonia collected. Car- 
bonic acid contains three-elevenths of its weight 
of carbon; water, one-ninth of hydrogen, and 
ammonia fourteen-seventeenths of nitrogen. 
When by incineration of a portion of the mass 
the proportion of saline matter has been deter- 
mined, the quantity of oxygen the substance 
contains may be known by deducting the united 
weight of the carbon, hydrogen, nitrogen, and 
salts from the total weight of the body ana- 
lysed; the deficiency (supposing sulphur and 
phosphorus not to have been present) is oxygen. 
Scrupulous attention to the purity of the 
matter submitted to analysis is of course of 
primary importance, a very slight admixture 
Fig. 429. 
zl 
enn | 
Apparatus for desiccation of organic substances. 
A, tube containing chloride of calcium resting on the support B; 
c, bent tube containing the matter to be dried and plunged in the bath 
D; d,d, caoutchouc connectors; E, vessel containing water, which flows 
out gradually by the stop-cock f to maintain a current of air through the 
apparatus, 
