G34 
MR. H. B. DIXON ON CONDITIONS OF CHEMICAL CHANGE 
the same result. Similarly, small quantities of dry nitrous oxide and dry carbon 
bisulphide were found not to render the mixture inflammable. A small quantity of 
hydrogen dried over phosphoric oxide, occupying about g-^o of the total volume of the 
gases, was next introduced into a fresh portion of the dry mixture. On passing a 
spark under 300 millims. pressure, the gases ignited and burnt rather slowly down the 
tube* After the apparatus had been re-dried some of the same mixture of carbonic 
oxide and oxygen was introduced into the laboratory tube, and a portion of it was 
drawn over into the eudiometer and tested by a spark under 300 millims. pressure, 
without ignition. A drop of ether was then passed up into the laboratory tube ; a 
very small quantity of the mixed gases, charged with ether vapour, was drawn over 
into the eudiometer. After the gases had been allowed to interdiffuse for an hour, 
the passage of the spark caused an explosion under 250 millims. pressure. Similarly 
a trace of the vapour of the hydrocarbon pentane rendered the mixture explosive. In 
the same way I have found that both a trace of dry hydric chloride gas and a trace of 
dry sulphuretted hydrogen gas render a non-inflammable mixture of carbonic oxide 
and oxygen explosive. 
From these experiments it appears that the non-explosive mixture of carbonic oxide 
and oxygen is rendered explosive not only by the presence of a trace of steam, but 
by traces of other bodies containing hydrogen which react with oxygen to produce 
steam. Nitrogen, cyanogen, nitrous oxide, carbon bisulphide, and carbonic acid do 
not confer inflammability on the mixture. To test the effect of the presence of steam 
on other gaseous mixtures, I made some comparative experiments on dry and wet 
mixtures of hydrogen and oxygen obtained by the electrolysis of dilute sulphuric acid. 
Into the carefully dried eudiometer of McLeod’s apparatus a mixture of equal volumes 
of air and electrolytic gas, which had been standing for some days over phosphoric 
oxide, was introduced. Beginning at 20 millims., the pressure was increased 
5 millims. at a time until the gases exploded. The dry mixture did not explode under 
70 millims.; it did explode under 75 millims. The residue was run out and a fresh 
portion of the same mixture introduced into the damp tube. Beginning at 20 millims., 
the pressure was increased by 5 millims. at a time until the gases exploded. The 
clamp mixture did not explode under 70 millims. ; it did explode under 75 millims.''' 
The union of oxygen and hydrogen is therefore not affected by the presence or absence 
of water. On the other hand, a mixture of cyanogen with ten volumes of air, which 
had stood over phosphoric oxide, did not explode when the pressure was raised step by 
step from 100 millims. to 800 millims. in the dry eudiometer. On addition of aqueous 
vapour the mixture did not explode under 300 millims., but did explode under 305 
millims. I am inclined to think that cyanogen undergoes oxidation in the same way 
as carbonic oxide, through the medium of steam. 
* Note added Dec., 1884.— Lothar Meyer and K. Seubert (Jonrn. Cliem. Soc., Oct., 1884) find that 
electrolytic gas is only partially burnt when a spark from a IvUUMkokff coil is passed through 
it under a pressure of 70’5 millims. ; at 72 millims. pressure the combustion is complete. 
