SCIENTIFIC SUMMARY. 
253 
of calcium, is acted on with dilute and cooled hydrochloric acid, and the 
scales resulting from this process are heated in a tube. These scales, 
which are of a nacreous colour, and which are separated from the mixture 
of silicide and hydrochloric acid by means of filtration, and then washed 
and dried in a vacuum over sulphuric acid, burn spontaneously on 
coming into contact with air, and leave a deposit of brown silica. The 
action of the hydrochloric acid on the silicide is much modified by the 
influence of sulphurous acid, although the latter has of itself no effect 
on either the silicide or silicon. When a large excess of aqueous sul- 
phurous acid plus a small quantity of dilute hydrochloric acid is poured 
on powdered silicide, the latter is quickly changed, without any evolution 
of gas, into a reddish-brown substance, which is composed of copper- 
coloured scales. This new substance, when prepared, dried, and heated in 
the air, burns like gunpowder, and when enclosed in a tube and heated, 
it explodes, giving off an odour of sulphuretted hydrogen. When heated 
gradually it gives off sulphuretted hydrogen without exploding ; and 
when placed in water, sulphuretted hydrogen is also formed, owing pos- 
sibly to the formation of sulphide of silicium. These novel compounds 
have been discovered and investigated by M. F. Wohler, who details his 
observations in the Annalen der Chimie und Pharmacie for September, 
1863. 
The New Notation. — The modification of Berzelius’s views proposed by 
Gerhardt, and introduced into this country by Williamson, Odling, and 
others, has been rather severely analysed in a communication of Mr. 
Waterston’s to the Philosophical Magazine (October). The writer consi- 
ders that now fashionable scheme in great measure an empirical one, 
and that so-called rational formula merely temporary, inasmuch as 
there may be several for an individual body ; that they are, in fact, 
possibilities ; chemical evidence to determine the correct one being as 
yet insufficient. He considers that the decomposition of water by potas- 
sium does not indicate that the aqueous molecule is composed of two 
atoms of hydrogen, as he believes that in the experiment referred to, two 
molecules are really affected. The dynamical theory of heat and gases 
has not been brought to bear in an adequate manner upon the theory of 
chemical combinations. In conclusion, the writer observes : “ Such con- 
siderations must enter into any system of classification of chemical 
compounds that is not quite artificial and arbitrary. To include under 
the same type a liquid of which the elements are in a burnt condition, 
with another the major part of which is in an unburnt condition, is 
simply to ignore the dynamical theory of heat, to reject as a guide a 
principle that has never failed to yield rich returns to those w T lio have 
resigned themselves entirely to its guidance in the study of Nature.” 
Explosive Gases of Gunpowder. — These are not, as some suppose, related 
to the mode in which combustion takes place, but are directly dependent 
on the composition of the powder. In such powder as Bunsen’s, which 
contains nitrate of potash in large quantities, as much as four per cent, of 
this substance is found in the residue. As a rule, it may be stated that 
ordnance powder develops a greater volume of explosive gases than that 
em ph>yed for sporting purposes. Hence, it is easy to understand that it is 
YOL. Ill, — NO. X. S 
