SCIENTIFIC SUMMARY. 
Ill 
A curious compound of manganese with oxygen — permanganic acid — 
has been investigated by Terreil. The most remarkable fact connected 
with this body is its volatility. He prepares this acid by distilling, at a 
moderately low temperature, a solution of permanganate of potash in 
pure sulphuric acid. Violet vapours are evolved, which condense to a 
thick liquid of a greenish-black colour and metallic appearance. It is 
perhaps the most energetic oxidizing agent known : it instantly sets fire 
to paper and alcohol, the latter with explosion ; and, when placed in 
contact with a fatty body, it detonates suddenly, with emission of a 
beautiful white light. A very beautiful effect is produced when a few 
drops of a solution of sulphite of potash are poured upon permanganic acid : 
a vivid disengagement of light is produced, and a large quantity of acid is 
carried off in the form of violet vapours, which are reduced in the air 
and fall down in the shape of brown flocks. 
Wanldyn and Carius have prepared a compound of hydrogen and iron. 
By allowing iodide of iron to react on zinc-ethyl, several gases are evolved, 
and a residue of hydride of iron is left in the tube : it is a black powder 
resembling metallic iron, and gives off pure hydrogen when gently heated. 
When dry, it may be kept unchanged ; but if moistened with water, it gives 
off hydrogen and becomes converted into oxide of iron. Hydrochloric acid 
decomposes it in a similar manner, forming chloride of iron — hydrogen 
being evolved at once from the acid and the hydride. 
Further information on Thallium, the new metal, whose existence was 
first detected by spectrum analysis, has been published by the discoverer, 
Crookes. It is a heavy metal, bearing a remarkable resemblance to lead 
in its physical properties. Its specific gravity is about twelve. It has a 
brilliant metallic lustre, but tarnishes very readily. It is very soft, and 
may be easily cut with a knife or scratched with the nail ; it may also be 
hammered out and drawn into wire ; it fuses below redness, and several 
pieces may with care be melted together and cast into one lump. The 
metal is not sensibly volatile below a red heat ; its atomic weight is very 
high. Thallium is readily soluble in nitric acid, and forms well-defined 
crystalline compounds with oxygen, chlorine, and various acids. The 
most characteristic property of the new element is, however, the mag- 
nificent green colour which it communicates to a flame : this light is 
perfectly homogeneous and gives a spectrum consisting of only one green 
line. Thallium, therefore, produces the simplest spectrum of any known 
element. The line appears to be identical in refrangibility with a well- 
defined line in the barium spectrum. Guided by this delicate test, the 
discoverer has found that thallium is by no means a sparingly-diffused 
metal — several pyrites from different parts of the world contain it ; and 
in a paper which the author read before the Royal Society last session he 
pointed out several sources and localities from which thallium might be 
obtained by the hundredweight at a time. 
Morren has examined the phenomena of phosphorescence when the in- 
duction spark is passed through rarefied gases. No simple or compound 
gas singly presents the phenomenon of phosphorescence ; but when a mix- 
ture of sulphurous acid and atmospheric air is placed in a tube, and the 
induction spark passed through the rarefied mixture, a splendid and per- 
