PREPARATION OF GASES 73 



enough to ignite the stream of gas, which for a moment 

 would probably be directed towards the lantern. I once 

 knew this happen, and should such a flame reach an oxygen 

 bag with any quantity of gas in it, the result would probably 

 be a combustion of the bag itself so furious as to be almost 

 explosive, and highly dangerous. 



With care the mixed jet can easily be used with only 

 oxygen in a bag, and gas from the main, instead of employing 

 an oxy-gas jet. In this case the bag must be lightly weighted 

 only fifty- six pounds being placed on. I often use the jet 

 thus in experiments ; but it should only be thus used by ex- 

 perienced persons. 



CHAPTER V 



PBEPARATION OF GASES 



88. Hydrogen. It is unadvisable to make this gas. It 

 has been often stated to give a better light, but careful 

 experiments made at the old Polytechnic proved that this 

 was a delusion, even with similar-sized nipples. No difference 

 could be perceived; and double the quantity of oxygen is 

 needed, besides the expense of the hydrogen. A bag of gas 

 can easily be sent by rail, if necessary ; or a bottle of com- 

 pressed coal-gas, at the present low prices, will be less trouble 

 and cheaper than making pure hydrogen, besides saving half 

 the oxygen. There are also the oxy-spirit jet, and the oxy- 

 ether and oxy-carbon lights (Chapter VII.) to fall back upon. 

 There are however a few out-of-the-way places where it may 

 be necessary to use hydrogen for lack of other materials. 



A glass bottle may be used as a generator, but a leaden one 

 is more usual. It is furnished with a movable cap, bearing 

 a long tube reaching nearly to the bottom and with a funnel 

 at the top, and a delivery-tube coming from the cap ; the 

 general arrangement resembling an ordinary wash- bottle, or 



