ARGON AND HELIUM. 123 



than i/i2oth of the nitrogen. At this point Lord Rayleigh was 

 assisted in his investigations by Prof. Ramsay. They succeeded 

 in isolating the heavier constituent of atmospheric nitrogen, to 

 which they have given the name of " Argon." One of the 

 methods used by them for this purpose was the same as that used 

 by Cavendish. They used a very powerful induction coil and 

 alternating dynamo currents. The air was mixed with oxygen, 

 and sparked for several hours in contact with strong caustic alkali. 

 The excess of oxygen was removed by ordinary methods. The 

 other method which they used was to remove the oxygen from air 

 with red-hot copper, and then absorb the nitrogen by red-hot 

 magnesium. 



Separation of Argon on a large scale. — To prepare argon on a 

 large scale a quantity of air was first freed from oxygen by means of 

 red-hot copper, and the atmospheric nitrogen remaining was stored 

 in a gas-holder. The gas was passed from the gas-holder through 

 sulphuric acid to indicate the rate of flow, and then dried over soda- 

 lime and phosphorus pentoxide. It then passed through a com- 

 bustion tube packed with magnesium turnings and heated to 

 redness in a furnace. The current of gas and heat were carefully 

 regulated so as not to soften the glass tube. The gas was then 

 passed over a mixture of copper and copper oxide, again over soda- 

 lime and phosphorus pentoxide, and then into a system of tubes 

 containing red-hot magnesium turnings. It was kept circulating till 

 no further absorption took place, and was then pumped out of the 

 tubes and transferred to a mercury gas-holder. The removal of the 

 last portions of nitrogen is very slow, but circulation for two days 

 usually effects it, as far as can be shown by the spectrum. As this 

 test will show the presence of i^A per cent, of nitrogen it is 

 certain that the argon so obtained did not contain more than i ^ 

 per cent, of nitrogen. The oxygen method is the slower one of 

 the two, but at the same time it requires less attention than the 

 magnesium one. If an alternating current can be readily obtained, 

 then the oxygen method would be the easier to work. 



Properties. — That argon is a very inert gas is proved by the 

 method used for its isolation. Nitrogen itself is generally considered 

 inert, but it will combine under certain circumstances with oxygen 

 and magnesium, whereas argon will not. Titanium at a red heat 



