CHEMISTRY. 401 



In a note following Mr. Dixon's paper. Professor Armstrong suggests 

 that in a mixture of carbon monoxide and oxygen, the former is oxidized 

 and the latter hjdrogenized simultaneously by the steam present, a 

 view which Mr. Dixon remarks is not opposed to any of the observed 

 facts. The explanation offered by Professor Armstrong involves the 

 simultaneous occurrence of two re-actions, which Mr. Dixon regards as 

 taking place successively. (J. Chem. Soc. [London], 1886, 94.) 



Oil the Combustiou of Cyanogen, by Harold B. Dixon. — The author has 

 examined the conditions under which a mixture of cyanogen and oxygen 

 gases explodes, and comes to the conclusion that the explosion depends 

 solely upon the nature of the spark itself. The spark from a Holtz 

 machine failed entirely to explode dry mixtures of these gases. The 

 induction spark failed to explode the mixture in the eudiometer, where 

 the wires were 0.25 to 1"'™ apart; but the explosion was violent in the 

 tubes when the wires were 1 to S™"" apart, and this was the case where the 

 gases were moist. He then compared the explosion rate of this mixture 

 with that of carbon monoxide and. oxygen, using for the purpose a tube 

 10 feet long and recording the time on a pendulum chronograph. The 

 velocities obtained were as follows in meters per second : Cyanogen and 

 oxygen, dried with phosphoric anhydride, 813; dried with KHO, 

 808; saturated with moisture at 15^ C, 752. Carbon monoxide and 

 oxygen dried with phosphoric anhydride, 36; dried with H2SO4, 119; 

 saturated with moisture at 10^ C, 175; at 35° C, 244; and at 60°, 317. 

 It is notable that in the latter case the rate of explosion increases 

 rapidly by the addition of moisture, while with the cyanogen moisture 

 produces an opposite effect. When a platinum wire is heated to dull 

 redness in the mixture of cyanogen and oxygen, the coil cooled without 

 result M'hen the circuit was o])ened ; but when raised to full redness it 

 glowed brightly for half a minute after the current was broken, and 

 orange fumes appeared in the tube. On opening the tube it was found 

 that about three-fourths of the cyanogen had been converted into car- 

 bon dioxide, and one-fourth into carbon monoxide. (J. Chem. Soc, 

 XLix, 384.) 



Preparation of Hydrogen Dioxide, by James Kennedy. — The author 

 points out the difficulty of removing the barium chloride by means of 

 silver sulphate when preparing hydrogen dioxide by Regnault's method, 

 and the uncertainties of Fownes's method, and proposes the following, 

 for which he claims simplicity and economy. 



Place any convenient quantity of tribasic phosphoric acid in a shal- 

 low porcelain vessel immersed in a freezing mixture (ice and salt), and 

 when the temperature has fallen to 40° F. or below, saturate with per- 

 oxide of barium previously made into moderately thick paste with dis- 

 tilled water; when completely saturated filter through pure filter paper. 



Certain precautions are to be observed in this process in order to in- 

 H. Mis. 600 26 



