174 
POPULAR SCIENCE REVIEW. 
to 141*6. The solutions are precipitated green "by alkalies, "but the precipitate 
dissolves in excess with a "blue colour. Sulphuretted hydrogen gives a 
"brown precipitate which does not redissolve ; zinc reduces the sulphate first to 
a brown liquid, and, on boiling, to metal. Before the blowpipe it gives yellow 
glasses, which turn blue on cooling, and upon charcoal with soda there is 
formed a yellowish-green coating. 
Cause of the Poisonous Character of Arsenic Oxides. — According to a 
paper on this subject by C. Binz and H. Schultz ( Ber . deutsch. chem. Gesell- 
schaft, xii. 2199), the poisonous character of these oxides depends on their 
easy conversion and re-conversion within the organism from the higher to 
the lower stage of oxidation, whereby the tissues are destroyed owing to the 
violent vibration of the atoms of oxygen. For the same reason they con- 
sider the other members of the nitrogen group are also poisonous. 
Carbonic Acid Explosion in a Coal Mine. — An explosion of this kind took 
place on the 28th July, 1879, in a coal-mine at Rochabelle, Gard. Two sharp 
and quickly following detonations were heard, without flame, and caused by 
compressed carbonic acid. Three workmen were killed, and during the course 
of the day the gas spread itself throughout the whole of the workings, so 
that the lamps were extinguished. By the explosion which occurred at the 
end of a gallery, the latter was closed up for the space of nine metres with 
dislodged fragments. The gas which escaped is estimated to have amounted 
to 4596 cubic metres. The escape of gas continued after the accident hap- 
pened. Delesse who reports the occurrence ( Compt . Rend, lxxxix. 814), 
ascribes it to the generation of acid by the action of water on beds of pyrites, 
and the action of this acid on the beds of Jurassic limestone lying adjacent. 
Dumas finds that if 2000 cubic metres, or 4000 kilogrammes of carbonic acid 
were enclosed, about 8000 kilogr. of limestone and 6000 kilogr. of acid would 
suffice for its production. Considering the great surface. which the much- 
fissured pyrites presents to the air, the production of such a quantity appears 
quite probable. 
A new Silicium Hydride. — Ogier has submitted siliciuretted hydrogen to 
the action of the electric effluvium, and decomposed it entirely. A yellow 
substance is deposited in the tube, and the volume of the hydrogen increases 
to a constant limit. In five experiments where the volume taken was 
originally =1, it increased to 121, 1-22, 1-21, 1*29, and 1*26, from which the 
formation of the solid product, which must contain the whole of the silicium, 
may be reckoned. It must be, — 
^i*58 ^ H V56 Si Hj.gg Si Hi .42 Si H x . 48 
or about Si 2 H 8 . This body corresponds with the suboxide of carbon or the 
crotonylene in the series of the hydro-carbons. When gently heated in air, 
it burns giving off sparks ; when struck it takes fire, in chlorine it burns 
with flame ; carefully heated in an atmosphere of nitrogen or hydrogen it 
evolves ordinary siliciuretted hydrogen, which spontaneously inflames in air. 
If strongly heated, it is decomposed into silicium and hydrogen. Siliciuretted 
hydrogen under the action of the electric effluvium conducts itself in an 
exactly analogous way to methane, which is resolved into acetylene and a 
condensible hydro-carbon, which has the odour of turpentine. The analogy 
is further borne out by the fixation of nitrogen, if equal volumes of siliciu- 
