IN GASES: HYDROGEN, CARBONIC OXIDE, AND OXYGEN. 
633 
Dr. Botsch* in a dissertation read at Tubingen has denied the fact (briefly 
announced by me in 1880) that the absence of steam prevents the combination of 
carbonic oxide and oxygen by the spark. He states that he has repeated the experi¬ 
ment, and the mixture exploded, “ even when dried by phosphoric oxide.” He found 
that by sufficiently reducing the pressure he could prevent the propagation of the 
explosion, both in the wet and dry gases. He suggests as an explanation of my results 
that the dry gases were tested under a less pressure than the wet gases. From the 
detailed account I have given above, it is evident that Dr. Botsch’s explanation does 
not account for the facts observed. I conclude that he failed to obtain the same result 
by not leaving the mixture long enough in contact with dry phosphoric oxide. I may 
add that during the last two years, several of my pupils have repeated the experiment 
in the Balliol College laboratory, so that the fact of the non-inflammability of the dry 
gases when submitted to an electric spark under ordinary pressure and temperature, 
may fairly be considered beyond the possibility of doubt. 
Experiments have already been described in which the addition of water to a non¬ 
explosive mixture of carbonic oxide and oxygen has rendered it explosive. Into one 
of the explosion tubes above described a piece of potash (previously fused and heated 
to redness in a silver boat, and allowed to cool in a desiccator) was introduced. It 
was fused to the glass at the top of the tube above the platinum wires. The phos¬ 
phoric oxide was then introduced, the tube was drawn out to a capillary end 
in the blowpipe and charged with the mixture. It was then sealed up in the flame 
and allowed to stand. After two days the gases were tested with a succession of 
sparks without exploding. The potash was then gently warmed by applying a 
Bunsen flame to the top of the tube. On passing a spark, a flame passed up from 
the platinum wires to the top of the tube. After standing an hour it was again 
tested with a spark. No explosion took place. On heating the potash rather 
strongly and passing another spark a flame passed up from the platinum wires to 
the top of the tube, and downwards about half the length of the tube. After the 
tube had stood about two hours longer, a third flame was produced on reheating 
the potash and passing a spark. 
To try what effect the admixture of small quantities of different gases had on the 
determination of the explosion, some of the mixture of carbonic oxide and oxygen 
previously used was brought over into the eudiometer of McLeod’s apparatus, which 
had been dried at 100° C. Under 300 millims. pressure the mixture did not explode on 
passing through it a succession of sparks. A little carbonic acid gas, dried over 
phosphoric oxide, was introduced. The spark was passed without causing an explosion. 
A fresh charge of carbonic oxide and oxygen was brought into the eudiometer, and a 
small quantity of cyanogen, dried over phosphoric oxide, introduced. The spark did 
not cause an explosion under 300 millims. pressure. A fresh portion of the same 
mixture, with a small quantity of dry air, was tested under the same pressure with 
* Liebig’s Annalen, 1882. 
4 M 
MDCCCLXXXIV. 
