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THE ROYAL SOCIETY OF CANADA 



Our first experiment therefore gives a figure of about 26% above 

 which it would not be safe to dilute with hydrogen. 



We next mixed helium, hydrogen and air in known proportions, 

 and expelled the mixture into an eudiometer tube standing over 

 mercury and sparked. Sometimes an explosion occurred. After 

 sparking, the mixture was passed back into the Brodie apparatus and 

 its volume measured. It was hard to decide on the amount of spark- 

 ing. Varying the percentage of air within wide limits did not seem 

 to have much effect upon the results. Thirty or forty experiments 

 were tried with the eudiometer method. The results, however, were 

 indecisive, though it seems as if the first spark causes no perceptible 

 combustion (as measured by a contraction of the total volume), if 

 the hydrogen is not greater than 10% of the mixture, but if sufficient 

 air is present a continued sparking burns up practically all the hydro- 

 gen and also some of the nitrogen, though much seems to depend on 

 the relative proportions of the gases. 



Mixtures of hydrogen and helium were next used to blow soap 

 bubbles upon a tube to be described presently, and a white hot 

 spiral was used to burn a hole through the film but these experiments 

 used up too much helium and were not continued. 



