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The absorption of gas by quartz vacuum tubes
July, Jg~6.]
(_'tRb~EXT TOPICS,
13I
The Ignition of Gases by Impulsive Electrical Discharge. W. ~I. THORNTON. IProceedinys of the Royal Society, Series A, vol. 92, No. A64I, May 6, I9I 6 . ) - - T h e ignition of gases by impulsive discharge is considered first as a function of sparking distance. It is shown that the shorter the distance the greater the spark, so that the volumes of the least igniting spark are, in a typical case, the same for all spark lengths, lgnition may occur with intense m o m e n t a r y brush discharge, generally with the true disruptive sparks. T h e products of combustion are found to be ionized and to carry a positive charge. The gases examined were mixtures in air of hydrogen, methane,. propane, and pentane ; ethylene and acetylene ; carbon monoxide and cyanogen; coal gas and a mixture of equal volumes of hydrogen and methane. Hydrogen, propane, pentane, and carbon monoxide rise gradually in difficulty as the percentage of oxygen is reduced; methane is ignited by the same spark, whatever the percentage of gas may be ; acetylene and cyanogen have the stepped atomic type of ignition; ethylene is more inflammable in rich mixtures. Hydrogen and methane in equal volumes are ignited as methane in type, hydrogen in magnitude. The limits of inflammability of the paraffins are shown to be reached: the upper limit when there is twice the volume of combustible gas to that in the mixture for perfect combustion, the lower limit when the volume of oxygen is twice that for perfect combustion, less I atom to the molecule. The ignition of coal gas is through~ methane. Four types of electric ignition are given, covering all fromthe most rapid to the slowest rate of discharge from the poles. The: work gives direct evidence that ignition begins by ionization of theoxygen in the mixture.
The Absorption of Gas by Quartz Vacuum Tubes.
R.S.
WILLOWS and H. T. GEORGE. (Proceedings of the Physical Society of London, vol. xxviii, part iii, April ~5, I 9 1 6 . ) - - I t is a common experience to those who work with vacuum tubes, once the electrodes are freed from gas, the continued passage of the discharge lowers the pressure, and the tube eventually evacuates itself to such an extent that further discharge is impossible. This gives rise to much trouble in X-ray technic, and, as gas pressure regulators have to be added, complicates the construction of the tubes. These disadvantages have only recently been surmounted in the well-known but costly Coolidge tube. It is, therefore, a matter of great practical importance to gain some knowledge of this process of self-evacuation. The experiments are a continuation of those of Willows and Hill on the absorption of gas which is brought about by the electrical discharges. A new quartz bulb does not absorb air, but if it be fed with repeated doses of hydrogen--which are absorbed when an electrodeless discharge is passed--it then becomes very active. If dis-
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CURRENT TOPICS.
[J. F. I.
charges in hydrogen are alternated with those in air the bulb can be made to absorb large quantities of either gas, and the activity with each gradually increases. The authors reject the theory of surface absorption and, in their own experiments at least, also Swinton's theory that the gas is shot into the walls and held there. It is supposed that chemical actions occur with air, and oxidation products are formed ; these are reduced by hydrogen. The process is compared with the formation of the plates in a Plant6 cell. Attempts to produce the same effects by chemical treatment are partially successful, particularly in fatiguing the bulb so that no further absorption takes place. The conditions under which the primary and secondary" hydrogen spectra appear are also described.
Effects of Atmospheres Deficient in Oxygen on Small Animals and on Men. G. A. ~LrRELI. and G. G. OBERFELL. (Bureau off Mines, Technical Paper I22, November, I 9 I S . ) - - I n studies of the composition of mine atmospheres as related to the health and safety of miners, the writers of this paper have observed that small animals, such as mice and canaries, are not quickly sensitive to atmospheres deficient in oxygen, and hence may not indicate to exploring parties in mines that the oxygen content of an atmosphere is dangerously low. For this reason a series of tests was conducted to determine the sensitiveness of canaries and mice to such atmospheres; also, some information was obtained as to the effects of such atmospheres on men. Deprivation of oxygen was found to cause collapse in men about the same time as it does in mice and canaries. The animals may collapse in atmospheres of different composition, and presumably the same is true of men. The fact is evident that birds and mice cannot be used safely as indicators of atmospheres low in oxygen by exploring parties in mines. Canaries are slightly more susceptible to " oxygen want " than are mice, and are chiefly valuable for indicating the presence of carbon monoxide, to which they are much more susceptible than man. In mixtures of air and nitrogen containing about 7.6 to 7.8 per cent. oxygen, canaries show pronounced distress. When the oxygen content is about 7 per cent. mice show considerable distress, and a man is in grave danger of dying; hence canaries and mice should not be used by exploring parties in mines to show when men unequipped with breathing helmets should retreat, because the atmosphere is low in oxygen. Mice and canaries, especially the latter, are chiefly of value for indicating to exploring parties the presence of dangerous proportions of carbon monoxide. In an atmosphere in which oil-fed lamps will not burn, an exploring party should not depend upon canaries for further guidance, but should use breathing apparatus in advancing into the atmosphere.
(_'tRb~EXT TOPICS,
13I
The Ignition of Gases by Impulsive Electrical Discharge. W. ~I. THORNTON. IProceedinys of the Royal Society, Series A, vol. 92, No. A64I, May 6, I9I 6 . ) - - T h e ignition of gases by impulsive discharge is considered first as a function of sparking distance. It is shown that the shorter the distance the greater the spark, so that the volumes of the least igniting spark are, in a typical case, the same for all spark lengths, lgnition may occur with intense m o m e n t a r y brush discharge, generally with the true disruptive sparks. T h e products of combustion are found to be ionized and to carry a positive charge. The gases examined were mixtures in air of hydrogen, methane,. propane, and pentane ; ethylene and acetylene ; carbon monoxide and cyanogen; coal gas and a mixture of equal volumes of hydrogen and methane. Hydrogen, propane, pentane, and carbon monoxide rise gradually in difficulty as the percentage of oxygen is reduced; methane is ignited by the same spark, whatever the percentage of gas may be ; acetylene and cyanogen have the stepped atomic type of ignition; ethylene is more inflammable in rich mixtures. Hydrogen and methane in equal volumes are ignited as methane in type, hydrogen in magnitude. The limits of inflammability of the paraffins are shown to be reached: the upper limit when there is twice the volume of combustible gas to that in the mixture for perfect combustion, the lower limit when the volume of oxygen is twice that for perfect combustion, less I atom to the molecule. The ignition of coal gas is through~ methane. Four types of electric ignition are given, covering all fromthe most rapid to the slowest rate of discharge from the poles. The: work gives direct evidence that ignition begins by ionization of theoxygen in the mixture.
The Absorption of Gas by Quartz Vacuum Tubes.
R.S.
WILLOWS and H. T. GEORGE. (Proceedings of the Physical Society of London, vol. xxviii, part iii, April ~5, I 9 1 6 . ) - - I t is a common experience to those who work with vacuum tubes, once the electrodes are freed from gas, the continued passage of the discharge lowers the pressure, and the tube eventually evacuates itself to such an extent that further discharge is impossible. This gives rise to much trouble in X-ray technic, and, as gas pressure regulators have to be added, complicates the construction of the tubes. These disadvantages have only recently been surmounted in the well-known but costly Coolidge tube. It is, therefore, a matter of great practical importance to gain some knowledge of this process of self-evacuation. The experiments are a continuation of those of Willows and Hill on the absorption of gas which is brought about by the electrical discharges. A new quartz bulb does not absorb air, but if it be fed with repeated doses of hydrogen--which are absorbed when an electrodeless discharge is passed--it then becomes very active. If dis-
t32
CURRENT TOPICS.
[J. F. I.
charges in hydrogen are alternated with those in air the bulb can be made to absorb large quantities of either gas, and the activity with each gradually increases. The authors reject the theory of surface absorption and, in their own experiments at least, also Swinton's theory that the gas is shot into the walls and held there. It is supposed that chemical actions occur with air, and oxidation products are formed ; these are reduced by hydrogen. The process is compared with the formation of the plates in a Plant6 cell. Attempts to produce the same effects by chemical treatment are partially successful, particularly in fatiguing the bulb so that no further absorption takes place. The conditions under which the primary and secondary" hydrogen spectra appear are also described.
Effects of Atmospheres Deficient in Oxygen on Small Animals and on Men. G. A. ~LrRELI. and G. G. OBERFELL. (Bureau off Mines, Technical Paper I22, November, I 9 I S . ) - - I n studies of the composition of mine atmospheres as related to the health and safety of miners, the writers of this paper have observed that small animals, such as mice and canaries, are not quickly sensitive to atmospheres deficient in oxygen, and hence may not indicate to exploring parties in mines that the oxygen content of an atmosphere is dangerously low. For this reason a series of tests was conducted to determine the sensitiveness of canaries and mice to such atmospheres; also, some information was obtained as to the effects of such atmospheres on men. Deprivation of oxygen was found to cause collapse in men about the same time as it does in mice and canaries. The animals may collapse in atmospheres of different composition, and presumably the same is true of men. The fact is evident that birds and mice cannot be used safely as indicators of atmospheres low in oxygen by exploring parties in mines. Canaries are slightly more susceptible to " oxygen want " than are mice, and are chiefly valuable for indicating the presence of carbon monoxide, to which they are much more susceptible than man. In mixtures of air and nitrogen containing about 7.6 to 7.8 per cent. oxygen, canaries show pronounced distress. When the oxygen content is about 7 per cent. mice show considerable distress, and a man is in grave danger of dying; hence canaries and mice should not be used by exploring parties in mines to show when men unequipped with breathing helmets should retreat, because the atmosphere is low in oxygen. Mice and canaries, especially the latter, are chiefly of value for indicating to exploring parties the presence of dangerous proportions of carbon monoxide. In an atmosphere in which oil-fed lamps will not burn, an exploring party should not depend upon canaries for further guidance, but should use breathing apparatus in advancing into the atmosphere.