Chemistry and Physics. 315 



lene bromide however though dissociated, does not conduct. 

 Nitrogen dioxide is not a conductor. — Zeitschr. physikal. Chem., 

 xii, 244, August, 1893. G. F. b. 



2. On the Electrolysis of Steam. — The action of electric sparks 

 on steam has been made the subject of investigation by J. J. 

 Thomson. The steam was passed through the middle limb of a 

 T tube, its closed side limbs being provided with delivery tubes 

 and also with gold or platinum electrodes between which sparks 

 might be passed through the steam. By means of the delivery 

 tubes the gases were conducted into two eudiometers, in which 

 the gaseous mixture which had been formed by the action of the 

 sparks upon the steam, could be exploded. It was noticed that 

 when the sparks were from 1*5 to 4 mm long, the volumes of the 

 excess of hydrogen in the one tube and of oxygen in the other, 

 remaining after the explosion of the mixed gases, were, within 

 the limit of error of the experiment, equal respectively to the 

 volumes of the oxygen and hydrogen liberated in a water vol- 

 tameter placed in series with the steam tube; and further that 

 the excess of hydrogen appeared in the tube which was in connec- 

 tion with the positive electrode, and the excess of oxygen in 

 that which was connected with the Negative electrode. If the 

 spark-length be greater than 4 mm , the first of the preceding results 

 ceases to hold; and when it reaches il mm or over, the excess of 

 hydrogen instead of appearing at the positive electrode changes 

 over to the negative ; the excess of oxygen at the same time go- 

 ing over to the positive. Reversal- again takes place when the 

 length of the sparks is increased to 22 mm . The author has further 

 observed that on passing the arc discharge through hydrogen 

 and oxygen respectively, the hydrogen acts as if it had a nega- 

 tive charge and the oxygen as if it had a positive one. — Proc. 

 Roy. Soc, liii, 90; J. Chem. Soc., lxiv, ii, 515, November, 1893. 



G. F. B. 



3. On the Temperature of Ignition of Gaseous Explosive Mix- 

 tures. — An investigation has been recently made by V. Meyer 

 and Munch to determine the precise point of temperature at 

 which the explosion or silent combination of gaseous mixtures 

 occurs. The mixture to be exploded is contained in a small bulb, 

 placed inside the larger bulb of an air thermometer which was 

 made use of to determine the temperature, this larger bulb being 

 placed in a bath of a fused alloy of lead and tin. The tempera- 

 ture was determined by displacing the air of the thermometer, 

 its volume being known, by hydrogen chloride gas, and measur- 

 ing this volume over distilled water. As the result of several 

 series of experiments made with four distinct sets of apparatus, 

 the temperature of explosion of electrolytic hydrogen and oxygen 

 was found to vary from 612° to 686°; confirming the theoretical 

 conclusion of Van't Hoff that this mixture does not possess a 

 sharply defined explosion-point. It makes no difference appar- 

 ently whether the gases are moist or dry ; for if dry, silent com- 

 bination appears to take place to a small extent, thus rendering 



