SCIENTIFIC SUMMARY. 
427 
while it is evident from the above that it is in reality carbonic oxide which 
enters into the reaction. — ( Compt . rend ., 1879. lxxxviii. 1204.) 
Reduction of Potassium Perchlorate. — Tommasi finds that this substance 
is not reduced by zinc, cadmium, magnesium, or aluminium, either in acid 
or in alkaline solution, at ordinary temperature or at 100°. Moreover it 
is not acted upon by sodium amalgam, nor reduced by ferrous hydrate. 
When the acetate of lead or copper is reduced by these metals, this salt, if 
present, undergoes no change. The perchlorate is, however, converted into 
chloride readily and at moderate temperatures, if mixed with sodium bisul- 
phite, and acted upon with rods of zinc. The hydrosulphite produced by 
this reaction is converted into sulphite at the expense of the oxygen of the 
perchlorate, in accordance with the following reaction — 
4SHNa0 2 + 01K0 4 = OIK + 4SHNaO,. 
No hydrogen is evolved. Towards the end of the reaction hyposulphite is. 
also found — 
2SHNa0 2 = H 3 0 + SNa 2 0 3 S. 
— (. Per . deut. chem. Gesell., 1879, xii. 1701.) 
The Direct Combination of Cyanogen and Hydrogen . — Gay-Lussac was 
unable to cause these substances to unite directly, either by the application 
of heat, or by the electric spark. In his day the influence of time on certain 
chemical reactions had not been studied. Berthelot therefore has repeated 
the experiment. It is now many years since the author showed that in a 
mixture of cyanogen and hydrogen, through which electric sparks had been 
passed, acetylene and hydrocyanic acid were formed. It cannot be clearly 
seen from this whether the substances directly unite, or whether acetylene 
be not first formed, and nitrogen separated, and hydrocyanic acid is not 
subsequently produced. A quantity of dry cyanogen and hydrogen in equal 
volumes were passed through a tube heated to 500°-550°, and a partial 
combination was at once noticed. The escaping gas contained 47 to 48 per- 
cent., instead of 50 per cent., of free hydrogen. In closed tubes this reaction 
took place more readily. After they had been heated for several hours, 
and were opened over mercury, a contraction of volume amounting to one- 
seventh was reached, due probably to the formation of paracyanogen. 
Potash quickly absorbed five-sevenths, and the remaining seventh consisted 
of nearly pure hydrogen. The reaction, therefore, had taken place in accor- 
dance with the equation : Cy + H = HCy. The process is quite analogous to 
that by which hydrochloric acid is produced, with the difference that it 
takes place more slowly, and at a higher temperature. At lower tempera- 
tures it goes more slowly j at higher, nitrogen is set free. Zinc, cadmium, 
and iron, heated with C} r anogen in tubes to 300°, formed cyanides of those 
metals, and no cyanogen was decomposed. Zinc, even at ordinary tempera- 
tures, is acted upon by cyanogen after several days exposure to it ; at 100°, 
after the lapse of some hours, an absorption of the gas is remarked. Cad- 
mium is passive in the cold, and at 100° only traces of cyanogen are ab- 
sorbed. Iron is passive at 100° ; silver and mercury are passive at all 
temperatures. The synthetic formation of hydrocyanic acid, whether by the 
combination of cyanogen and hydrogen in equal volumes without condensa- 
