12 The Bulletin. 



RELATION BETWEEN FLASH-POINT AND DANGER. 



Danger from explosions is always present when inflammable vapors 

 and air are mixed together. This condition may arise in the bowl 

 of any lamp, for above the liquid kerosene there is always kerosene 

 vapor and there is always air, the proportions of each depending 

 upon the temperature of the oil. The higher the temperature, the 

 greater the proportion of the oil vapor. The explosion is most violent 

 when the amount of air present is exactly sufficient to burn the vapor 

 completely. This proportion is about 50 volumes of air to one volume 

 of oil vapor. An excess of either air or oil vapor above this propor- 

 tion serves as a cushion to moderate the force of whatever explosion 

 does occur. Of course, an explosion cannot take place unless the 

 flame reaches the inflammable mixture. Contact between the ex- 

 plosive mixture and the flame is frequently brought about by the 

 use of a wick too small for the burner. 



The danger of explosion in lamps having metal reservoirs is in- 

 finitely less than in glass lamps. The reason for this lies in the 

 fact that glass being a poor conductor of heat, the oil in the lamp 

 does not get as hot as in the metal vessels, consequently an explosive 

 mixture of oil vapor and air (one volume to fifty) would be more 

 readily reached in the glass lamp than in the metal lamp, where the 

 proportion of oil vapor is much greater. When the oil vapor is in 

 great excess the mixture is not explosive. 



If low-flash oils be spilled and a flame applied, the fire spreads 

 much more rapidly than with an oil of high flash-point, and thus 

 the upsetting of a lamp containing low-flash oil is more dangerous 

 than if it contained oil of higher flash, especially if the temperature 

 of the oil be somewhat raised, as is usually the case. If a lighted 

 lamp filled with high-flash oil is upset, it will most probably be ex- 

 tinguished, for this kind of oil will not onlv not ignite at ordinary 

 temperatures, but will extinguish flame. 



ILLUMINATING POWER. 



In securing a safe oil, we must not lose sight of the fact that heavy 

 oil does not give good light except with burners of strong draught. 

 As already stated, it causes charring of the wick. It is the purpose 

 of the oil-inspection law to secure for the State oil of good illuminat- 

 ing power as well as safe oil, and the Board of Agriculture is au- 

 thorized to adopt such standards for luminosity as may be deemed 

 necessary to insure this. It has been thought advisable not to adopt 

 at present a fixed standard for luminosity in candle power, although 

 this may be done later. 



Newberry & Cutter in an article on The Safety of Commercial 

 Kerosene Oil (Amer. Chemical Journal, vol. 10, p. ^^Gl), say: "If 



