382 



SCIENCE. 



[N. S. Vol. III. No. 63. 



An important question then is to be an- 

 swered before we can compare the lighting 

 power of gas and acetylene. Is an acety- 

 lene light more tolerant of lack of care in 

 the burners and of variations in the pres- 

 sure than is the case with common gas? 

 The most superficial obsei'vation shows that 

 the two gases must be burnt in a very dif- 

 ferent way. 



Gas burnt in an acetylene jet gives less 

 than one-tenth of its true lighting power, 

 and acetylene burnt in a common gas burner 

 gives a yellow, smoky flame, and when 

 turned down to a small flame it deposits 

 soot on the jet, clogging the burner, if the 

 opening consists of a straight slit. Even 

 the very fine fishtail burners with a straight 

 slit intended for oil gas suffer from this de- 

 fect when the acetj'lene flame is turned down. 



It appears then from the last experiments 

 that the choice of burner and the mode of 

 using it are very important factors in de- 

 termining the value of any kind of illumi- 

 nant, and hundreds of pages have been 

 published on this subject with reference to 

 oil and gas light, and it may be added that 

 the results are not yet concordant. 



Acetylene can not well be burnt in an 

 Argand burner nor with the devices that 

 succeed with petroleum lamps. A fishtail 

 flame with a good exposure to the air must 

 be used, and the best form of burner is that 

 which throws the swiftest stream of acetylene 

 into the air in the form of a very thin sheet. 



A lava-tip burner has long been used for 

 gas in which the opening is not a slit, but 

 two small holes. The construction of these 

 burners can be well shown by passing gas 

 through two blowpipe jets, and when the 

 two long jets of flame are made to impinge 

 on each other at nearly a right angle they 

 spread out into a fishtail form. Acetylene 

 can be burnt in very small lava tip jets of 

 this class, and gives about 30-candle power, 

 but the light can not be turned low without 

 losing its efficiency and smoking. 



An experiment can easily be made which 

 shows how large a quantity of air is re- 

 quired to render acetylene flames smoke- 

 less. Mix acetylene gas with measured 

 quantities of air up to IJ volumes of air 

 and burn the mixtures in a slit fishtail 

 burner. It will be found that the acetylene 

 does not diminish notably in illuminating 

 power. Larger proportions of air begin to 

 destroy the brilliancy of the fiame. The 

 same trials with common gas show that a 

 very small proportion of air renders the 

 flame less luminous. Suitable burners must 

 be chosen in each case. 



Acetylene can even be burnt mixed with 

 one-third its volume of oxygen, giving a 

 very brilliant flame. These experiments are 

 only of practical value in indicating the 

 kind of burner which should be chosen for 

 acetylene. Another quality of the flame 

 is very instructive from the same point of 

 view. The acetylene flame clings to the 

 burner in an extraordinary way, so that it 

 is difficult to blow it out, and the luminous 

 part of the fishtail flame almost touches the 

 jet, while in a gas flame a large blue zone 

 separates the luminous part from the jet. 

 An instantaneous photograph shows well 

 the character of the two flames and also 

 their comparative actinic powers.* 



By exploring the flame with a bit of 

 platinum wire, it is easy to see, by the in- 



* In the reproduction the gas flame appears rela- 

 tively too bright. — Ed. 



