528 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[January 4,1873» 
effected in the case of a few experiments made with pro¬ 
tochloride of tin, under conditions carefully considered 
and regulated so as to ensure a trustworthy result. And it 
was found in these few experiments that the weight of the 
matter of oxygen absorbed from the ozonized gas by the 
tin-salt was almost exactly three times the weight of the 
matter of oxygen absorbed from the same gas by iodide 
of potassium,—the volume occupied by the weight of 
oxygen absorbed by the tin-salt being almost exactly 
twice the volume proper to the weight of oxygen ab¬ 
sorbed by the iodide of potassium. 
Independently of the importance attaching to the 
actual determination of the density of ozone, Sir B. 
Brodie’s result has a further interest for chemists, which 
it would be difficult to exaggerate. The principal of the 
elementary bodies known to chemists in the gaseous or 
vaporous state, are hydrogen, chlorine and its congeners, 
oxygen, sulphur, nitrogen, phosphorus, arsenic, mer¬ 
cury, and cadmium. Now it is a fact that the weight of 
phosphorus or arsenic contained in any volume of phos¬ 
phorus or arsenic vapour is four times the weight of 
phosphorus or arsenic contained in the same volume of 
phosphoretted or arsenetted hydrogen, and of a host of 
other phosphoretted or arsenetted gases or vapours. It 
is also a fact that the -weight of hydrogen, chlorine, 
oxygen, or nitrogen contained in any volume of each 
of these elementary gases is twice the weight of hy¬ 
drogen, chlorine, oxygen, or nitrogen contained in the 
same .volume of a variety of hydrogenous, chlorinous, 
oxygenous, or nitrogenous compound gases. It is also a 
fact that the weight of mercury or cadmium contained 
in any volume of the vapour of either element, is iden¬ 
tical with the weight of the element contained in the 
same volume of the vapour of all its hitherto examined 
volatile compounds. But now a variety of oxygen is 
shown to exist, the weight of any given volume of which 
is three times the weight of oxygen contained in the 
same volume of the simplest of oxygenous compounds 
respectively, thus:— 
Unit-volumes. 
I’"i 0 3 Hg 
PC1 3 CO NO HgCL. 
The question, then, naturally arises, how long will it be 
before another variety of oxygen is recognized, the 
weight of any given volume of which, like that of a given 
volume of phosphorus vapour, shall furnish the weight 
of the element contained in four such volumes of its 
several simplest compounds ? And again, how long will 
it be before yet another variety of oxygen is recognized, 
the weight of any given volume of which, like that of 
any given volume of mercury vapour, shall furnish but 
the weight of the element contained in the same volume 
of its several simplest compounds ? There is the 
strongest indirect reason for believing in the existence 
of such a unitary oxygen. For in its reactions, oxygen 
behaves as a sort of more active electro-negative counter¬ 
part of electro-positive mercury Hg ; and like mercury 
Hg, and unlike hydrogen H 2 and chlorine Cl 2 , it enjoys 
the property of adding itself to a pre-formed unit of 
substance by an indivisible proportion. 
THE ESTIMATION OF NITROGEN.* 
BY L. KESSLER. 
Experience has convinced the author that the soda- 
lime process for the estimation of nitrogen does not, with 
certain organic substances, give nearly the quantity 
which they contain, the error with cutaneous matters 
dissolved in sulphuric acid being sometimes more than 
fifty per cent. Even when operating volumetrically 
upon not more than one or two decigrams, carbides of 
hydrogen and volatile nitrogenous bodies are produced, 
which by their coloration, insolubility, and more or less 
feeble basicity, interfere with the ascertainment of the 
exact point of saturation. When calcination of the 
* ‘ Moniteur Scicntifique Quesneville/ xiv. 343. 
platinum salt, after washing with alcohol and ether, is 
adopted, the washings arc nearly always turbid, and de¬ 
posit incessantly platinum compounds which escape 
weighing. If it be considered, also, how easily gaseous- 
ammonia is decomposed at a high temperature into its 
elements, it is surprising that in a process where the 
ammoniacal gases issuing from the reaction have to 
filter slowly through a long row of substances brought 
;o a red heat, a greater loss does not take place. Such a 
want of exactness, the author considers, renders this- 
method, nearly the only one at present adopted by com¬ 
mercial analysts, unsuited to be the basis upon which 
' ,he manure trade should be carried on; since being 
founded upon the ultimate production of a compound- 
'ammonia), itself decomposible under the conditions of 
ffie experiment, it does not present the characters of 
exactness usually found in elementary analysis. 
With this conviction he has sought to simplify the 
processes for the measurement of nitrogen disengaged in a 
::ree state, employing by preference that of Dumas, by 
oxide of copper, except that instead of collecting the 
gases yielded by the combustion over mercury, he receives 
;hem in an india-rubber bag. This bag is formed of two- 
disks of supple india-rubber, free from sulphur, one milli¬ 
metre thick and from twelve to fifteen centimetres in 
diameter, joined together at the edges, and having issuing 
from one side an india-rubber tube of [the same size 
as the delivery tube of the combustion apparatus, and 
from the other a glass tube graduated in cubic centi¬ 
metres. The india-rubber tube is made to close with a 
small stop-cock or compressor. 
For the examination of the carbonic acid gas used to 
sweep out the combustion tube, bags similarly made- 
may be used, but without the graduated tube. The bag 
is filled with water, then emptied and closed under 
water. The delivery tube of the combustion apparatus 
is then introduced into the end of the india-rubber tube 
beyond the stop-cock, without lifting it out of the water- 
The stop-cock is opened quickly and the gas introduced. 
When the bag is full, the india-rubber tube is closed and 
the delivery tube removed; then, without bringing the 
opening of the tubing above the water, the end of 
a pipette filled with a solution of soda is thrust into it. 
The carbonic acid is absorbed, and by the volume of the 
residue it may be judged whether the air has been suffi¬ 
ciently removed from the combustion apparatus. In 
order to estimate this residue more conveniently, it may 
be transferred under water to a test tube. 
When the air is considered to be sufficiently removed, 
the first-mentioned bag is attached in the same manner,. 
first introducing into it fifteen to twenty grams of concen¬ 
trated solution of caustic soda. If the bag be too much 
inflated, it should be agitated. M. Kessler prefers to 
keep the absorption apparatus under water to prevent 
the unnoticed escape of any gas. When no more gas is 
disengaged, the combustion tube is again swept out with 
carbonic acid gas, and the bag is removed, the india- 
rubber tubing being pinched progressively so as to drive 
int© the bag any nitrogen present. After the removal 
the carbonic acid gas may be examined as before. 
In measuring the nitrogen the bag should be shaken 
until the gas in the graduated tube no longer diminishes 
in volume. Then pinch the end of the flexible tube with 
the fingers, open the stop-cock, place the bag under 
water, keeping the graduated tube above the sur¬ 
face, and the caustic soda will run away. Lastly, bring 
the surfaces of the liquids, inside and outside, to the 
same level, and note the volume of nitrogen, the tem¬ 
perature of the water and pressure of the atmosphere.. 
If the quantity of nitrogen should exceed the capacity 
of the tube, or if it be desired to obtain a more exact 
measurement in a narrower tube, the gas should be 
transferred to another vessel before running off the soda. 
In this case the delivery tube should be carried to the 
top of the fresh graduated tube to prevent loss by absorp¬ 
tion while passing through the water. 
