ON OXYGENNESIS. 
437 
bichromate of potash and four parts sulphuric acid are heated together in a 
capacious retort, an evolution of oxygen gas easy to regulate is the result. In 
this experiment we might congratulate ourselves if the process is conducted 
to the end without a fracture of the retort. 
On glancing over the six processes just described, I think we may say that 
two only are now used, viz. chlorate of potash with and without manganese, 
and manganese alone: the latter is selected only for cheapness when a con¬ 
siderable quantity of the gas is required ; chlorate of potash, with manganese 
for facility of operation; and chlorate of potash alone when purity is the prin¬ 
cipal object to be attained. More recently other processes have been recom¬ 
mended, one of which, by heating together a mixture of nitrate of soda and oxide 
of zinc, has been patented ; from this mixture oxygen is said to be produced at 
a cheaper rate than by any other method at present known, Unfortunately 
for the value of this discovery, the produce is contaminated with a considerable 
percentage of nitrogen. Mr. Kuhlman, of Lille, discovered and published an 
ingenious and beautiful process for the production of oxygen by means of 
baryta. He found that by passing a current of common air through caustic 
baryta, heated to dull redness, peroxide of barium was formed, which, on an 
increase of temperature, is resolved into oxygen gas and caustic baryta, the 
latter ready again to perform its part in a similar operation. The idea natu¬ 
rally suggested itself that the means were now at hand for getting oxygen 
from the atmosphere in any quantity at a small cost. This method, although 
so promising, has been for the present abandoned. It was found that after a 
few operations, either from a molecular change or from the silica or other 
impurities, a sort of glass or fusion resulted on the surface, the baryta then 
refusing to act again. 
We now come to the consideration of the new method for the generation of 
oxygen recently introduced by myself; the process, or the compound em¬ 
ployed in it, has been named Oxygennesis. It will have doubtless been ob¬ 
served by you that in all the processes hitherto known a high temperature is 
necessary, and until that point is reached, no product whatever is obtained; 
this fact we may consider as the chief difficulty experienced in the prepara¬ 
tion of oxygen, and more especially so when sulphuric acid is used. If, for 
example, by the mere addition of sulphuric acid to bichromate of potash in 
the cold we could get the same results which are obtained by the application 
of heat, this process, instead of being thrown in the rear, would have taken 
front rank. Oxygennesis therefore stands alone as a novel and the only mode 
we possess for producing oxygen without the application of heat. The mode 
of using this compound is extremely simple. We have only to take some of 
this powder, place it in a glass flask or bottle provided with an exit tube, pour 
on either of the dilute mineral acids, and we have immediately oxygen evolved 
in a similar way, and with as much facility as hydrogen is obtained from 
zinc, or carbonic acid from a carbonate. 
The composition of this compound is extremely simple, merely a mixture 
of peroxide of barium and bichromate of potash; not so the chemical changes 
resulting from the addition of an acid. Peroxide of barium on addition of sul¬ 
phuric acid is resolved into sulphate of baryta and peroxide of hydrogen, and 
it is from this sometimes so-called oxygenated water we get this curious and 
interesting chemical reaction. Whenever peroxide of hydrogen and chromic 
acid are brought in contact with each other, instantaneous decomposition is 
the result; the chromic acid is reduced to sesquioxide of chromium, and the 
peroxide of hydrogen to water, at the same time pure oxygen derived from 
both those substances is disengaged. The theory of this very interesting re¬ 
action is not, I believe, well understood, and I know only one way of explain¬ 
ing it, that is, on the ozone and antozone theory of Brodie. According to that 
