436 
PHARMACEUTICAL MEETING. 
ON OXYGENNESIS. 
BY MR. ROBBINS. 
The subject I have the honour to bring before you this evening is the 
description of a new and easy method for the production of oxygen gas. The 
discovery of oxygen was made just ninety years ago by Priestley, who, in 
1774, succeeded in separating it, and determining the nature of the atmo¬ 
sphere. In the following year the discovery was again made by Scheele (to 
whom Priestley’s experiments were then unknown). 
Oxygen is the most abundant of all known substances. It constitutes at 
least one-third of the solid mass of the earth, which, so far as we are ac¬ 
quainted with it, is mainly composed of metallic oxides and oxygen salts. 
In 100 parts, water contains 89, and atmospheric air 23, of their weight of 
this substance; it is likewise found in most organic compounds. 
Prom the time of the discovery to the present, perhaps no subject has so 
much engaged the attention of chemists as the production of oxygen at a 
cost sufficiently low to be employed in the arts, for the reduction of metals, 
and other operations requiring a high temperature ; and also for the purposes 
of illumination, the light obtained by it vying in splendour with the sun’s 
rays. This desirable object has yet to be accomplished, and may be regarded 
as a prize to be won by some future happy discoverer. It does seem surprising, 
since nature has provided us so bountifully with this substance, and presented 
it in such a variety of combinations, that up to the present time there should 
be no known method of separating it, excepting at such a cost as excludes 
it for the purposes just enumerated. 
In Gmelin’s ‘ Chemistry ’ six processes are given for the production of 
oxygen. 
1st. By heating chlorate of potash to low redness, 1 eq. of the salt yielding 
6 eq. of gas, leaving a residue of 1 eq. chloride of potassium. As this process is 
slow and tedious, a small quantity of oxide of manganese is usually mixed with 
the salt, which greatly facilitates the decomposition, and the evolution of gas 
is both rapid and abundant. According to the authority just named, manga¬ 
nese is often mixed with carbonaceous matter, which passes over as carbonic 
acid ; but another impurity I may mention is the presence of chlorine, which, 
I believe, may always be detected when oxygen is obtained by this method. 
2nd. By ignition of red oxide of mercury. Oxide of mercury by strong igni¬ 
tion is resolved into mercury vapour and free oxygen. On account of the high 
temperature necessary for this experiment, it is recommended to first coat the 
retort with clay mixed with horsehair. Unless the oxide of mercury be very 
pure, the presence of hyponitric acid may be feared in the product. 
3rd. By strong ignition of oxide of manganese. Three atoms binoxide of 
manganese Mn 3 O c are resolved into Mn 3 0 4 and 2 oxygen, which escape. 
4th. By heating manganese with an equal weight of oil of vitriol. When 
manganese is heated alone, it is converted into Mn 3 0 4 ; but when mixed with 
sulphuric acid the product is MnO, S 0 3 ; by the presence of that acid, there¬ 
fore, the product is increased one-half as much more. Practically, this method 
is not so economical as theoretically it appears. Glass vessels must be used, 
which invariably become fractured before the end of the operation. 
5th. By ignition of nitrate of potash. This salt, when heated above its 
melting-point, is converted by the loss of 2 eq. of oxygen into nitrite of 
potash. On a further increase of temperature both nitrogen and oxygen pass 
off, consequently the product is always contaminated with nitrogen, which 
increases as the action proceeds. 
6th. By the action of sulphuric acid on bichromate of potash. Three parts 
