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Lord Rayleigh (1842-1919, born John William Strutt)
Density of Nitrogen
Nature 46, 512 (1892) [from Scientific Papers, vol IV (Cambridge, UK: Cambridge Press, 1903)]
I am much puzzled by some recent results as to the density of nitrogen, and shall be obliged if any
of your chemical readers can offer suggestions as to the cause. According to two methods of
preparation I obtain quite distinct values. The relative difference, amounting to about 1/1000 part,
is small in itself, but it lies entirely outside the errors of experiment, and can only be attributed to
a variation in the character of the gas.
In the first method the oxygen of atmospheric air is removed in the ordinary way by metallic copper,
itself reduced by hydrogen from the oxide. The air, freed from CO2 by potash, gives up its oxygen
to copper heated in hard glass over a large Bunsen, and then passes over about a foot of red-hot
copper in a furnace. This tube was used merely as an indicator, and the copper in it remained bright
throughout. The gas then passed through a wash-bottle containing sulphuric acid, thence again
through the furnace over copper oxide, and finally over sulphuric acid, potash and phosphoric
anhydride.
In the second method of perparation, suggested to me by Prof. Ramsay, everything remained
unchanged, except that the first tube of hot copper was replaced by a wash-bottle containing
liquid ammonia, through which air was allowed to bubble. The ammonia method is very convenient,
but the nitrogen obtained by means of it was 1/1000 part lighter than the nitrogen of the first
method. The question is, to what is the discrepancy due?
The first nitrogen would be too heavy, if it contained residual oxygen. But on this hypothesis,
something like 1 per cent. would be required. I could detect none whatever by means of alkaline
pyrogallate. It may be remarked that the density of the nitrogen agrees closely with that recently
obtained by Leduc using the same method of preparation.
On the other hand, can the ammonia-made nitrogen be too light from the presence of impurity?
There are not many gases lighter than nitrogen, and the absence of hydrogen, ammonia, and water
seems to be fully secured. On the whole it seemed the more probable supposition that the impurity
was hydrogen, which in this degree of dilution escaped the action of the copper oxide. But a special
experiment seems to preclude this explanation.
Into nitrogen prepared by the first method, but before its passage into the furnace tubes, one or
two thousandths by volumes of hydrogen were introduced. To effect this in a uniform manner the
gas was made to bubble through a small hydrogen generator, which would be set in action under
its own electro-motive force by closing an external contact. The rate of hydrogen production was
determined by a suitable galvanometer enclosed in the circuit. But the introduction of hydrogen
had not the smallest effect upon the density, showing that the copper oxide was capable of
performing the part desired of it.
Is it possible that the difference is independent of impurity, the nitrogen itself being to some
extent in a different (dissociated) state?
I ought to have mentioned that during the fillings of the globe, the rate of passage of gas was very
uniform, and about 2/3 litre per hour.

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density 密度 nitrogen 窒素 oxygen 酸素 copper 銅 hydrogen 水素 oxide 酸化物
potash 炭酸カリウム Bunsen ブンゼンバーナー furnace 炉 indicator 指示薬 sulfic acid 硫酸
phosphoric anhydride リン酸無水物 ammonia アンモニア alkaline アルカリ性の
pyrogallate ピロガロール impurity 不純物 generetaor ガス発生装置 electromotive force 起電力
galvanometer 検流計 circuit 回路 dissociated 解離した globe 秤量級
HO
OH
OH
pyrogallate ピロガロール
レイリーは1894年、 ラムゼーと一緒に、 貴ガスのアルゴンも発見します。
アルゴンはギリシャ語で怠け者という意味。