238 
ON THE COMBUSTION OF IRON IN COMPRESSED OXYGEN. 
at which the vapour-densities of these compounds are observed, the bodies are tempo¬ 
rarily decomposed, and, instead of forming one homogeneous vapour, are at the. time 
of the observation really composed of a mixture of vapours. In certain cases this ex¬ 
planation is probably the true one; but its general acceptance has been disputed by 
Deville himself, though his results on dissociation seem, to cursory observation, to be 
in its favour; and it must be admitted that, up to the present tiuie, the arguments and 
experiments which he has brought forward in opposition to the views of Kopp and Can¬ 
nizzaro have not been satisfactorily answered. No sufficient proof, for example, has yet 
been adduced that the well-known anomalous cases of nitric oxide, chlorous anhydride, 
hvdrosulphide of ammonium, cyanide of ammonium, and various other salts of ammo¬ 
nium and the volatile bases, are due to dissociation of their components. This subject 
is one, however, too intimately connected with the molecular theories at present under 
discussion to remain long in its actual state. New experiments and evidence will, no 
doubt, be forthcoming, which will throw further light upon the cause of these outstand¬ 
ing exceptions.” 
ON THE COMBUSTION OF IRON IN COMPRESSED OXYGEN. 
BY E. FRANIvLAND, F.R.S. 
Whilst oxygen was being compressed into a Natterer’s apparatus, recently supplied to 
the Royal Institution from Vienna, an accident occurred, which deserves to be placed on 
record,"owing to the interesting relations of iron to highly compressed oxygen revealed 
by it. The accident occurred in the following manner:—Oxygen was liberated from 
pure chlorate of potash, heated in a Florence flask, and was collected in a floating bell- 
gasholder, whence it was drawn through a flexible tube, and pumped in a strong wrought- 
iron receiver, of ‘62 litre capacity, and weighing 2-775 kilogrammes. When about 25 
atmospheres of oxygen had thus been introduced into the receiver, a sharp explosion oc¬ 
curred, followed by a shower of brilliant sparks, which lasted for several seconds. On 
examining the apparatus, it was found that the union-joint connecting the pump with 
the receiver had given way, allowing the compressed gas to escape from the latter. The 
pump-head, containing the valve, was slightly scorched internally. The steel tube con¬ 
necting this head with the receiver was very hot, and had obviously been in a state of 
active combustion, as it was coated internally with a layer of fused oxide of iron, whilst 
its bore had increased to at least three times its original size, and in two places the tube 
was even perforated. The receiver was also heated, although not to such an extent as 
to be unbearable to the hand. On examining its interior, it was found that the com¬ 
bustion had been propagated to the steel cap, the narrow passage in which was hollowed 
out into a capacious chamber, whilst the steel screw-valve had been completely consumed. 
The combustion had not, however, stopped here, but, extending into the receiver itself, 
had seized upon the internal walls of the latter, and covered them with fused globules 
of magnetic oxide of iron, and there can scarcely be a doubt, that, had the union-joint 
not given way, and thus furnished an outlet for the compressed oxygen, the latter would, 
in a few seconds more, have converted the receiver into a most formidable shell, the 
almost inevitable explosion of which would have scattered fragments of intensely ignited 
iron in all directions. 
Regarding the primary cause of this explosion, there can scarcely be two opinions. 
The piston and valves were lubricated with olive oil, and the latter, becoming ignited by 
the heat of the compressed gas, had communicated its combustion to the steel and iron 
of the apparatus. Although the pump and receiver were not artificially cooled, yet this 
circumstance did not in all probability contribute materially to the ignition, because the 
oxygen was very slowly pumped into the receiver, the operation having to be frequently 
interrupted, to wait for the necessary quantity of gas which was being contemporaneously 
generated. Moreover, I had ascertained, immediately before the explosion, that the re¬ 
ceiver was quite cold, and the head of the pump only just perceptibly warm. A few 
days previously, GO atmospheres of oxygen had been with impunity rapidly pumped 
into the same receiver, and equally without any external refrigeration. How, then, is 
this difference of result to be accounted for ? The answer to this question is not dif¬ 
ficult when an apparently trivial alteration of the condition of the apparatus, in the two 
