270 RECENTLY DISCOVERED GASES. 



Such an operation demands much time. In the first place, the nec- 

 essary apparatus is not to be found in any ordinary chemical laboratory; 

 the preparation can not be carried out in glass tubes in an ordinary 

 furnace, but requires iron tubes of large size and an especial furnace; 

 in the second place, the operation must be repeated several times, for 

 it is not convenient to work with an excessively large quantity of mag- 

 nesium. As before, we removed the oxygen from the air by means of 

 copper at a red heat; the atmospheric nitrogen remaining was collected 

 in a large gasometer holding about 200 liters; after drying over concen- 

 trated sulphuric acid and phosphorous pentoxid, the gas was passed 

 through an iron tube of 5 centimeters diameter filled with magnesium 

 filings; the gas was then passed through a second copper oxid tube to 

 remove the hydrogen; it then entered a galvanized-iron gasometer, 

 which was constructed like an ordinary illuminating-gas gasometer, in 

 order that the argon should come in contact with as little water as pos- 

 sible, since argon is quite appreciably soluble in water, and, had the 

 ordinary form of gasometer been used, much would have been lost in 

 this way. Again, the gas had to be led over hot magnesium to reduce 

 still further the quantity of nitrogen; and, at last, it was circulated 

 between the gasometers, passing on its way through a mixture of thor- 

 oughly heated lime and magnesia at a red heat. This is a means of 

 absorption, recommended by Maquenne, to remove the last of nitrogen. 

 Since, however, it is not j>ossible to dry the lime absolutely, hydrogen 

 is taken up by the gas, and this must again be removed by copper 

 oxid, in order that all the hydrogen may be burned, after which the 

 water must again be removed by drying tubes. 



These operations required several months and were chiefly directed 

 by Dr. Travers. 



Meanwhile, it seemed to be worth while to make an examination as 

 to whether the desired gas might possibly form compounds and be 

 united with the magnesium, by which the nitrogen had been removed. 

 Miss Emily Aston assisted me to settle this question. 



Some 700 grams of the magnesium nitrid were, for this purpose, 

 treated with water in a large exhausted flask, in such a manner that 

 the evolved ammonia was absorbed in dilute sulphuric acid which had 

 been thoroughly boiled ; all the other gases were collected by a 

 Topler pump. The total volume of this gas was hardly 50 cubic cen- 

 timeters; it proved to be chiefly hydrogen, with a trace of hydrocar- 

 bons, arising from the small quantity of metallic magnesium present in 

 the magnesium nitrid. After the hydrogen had been removed by 

 explosion, an excess of oxygen was passed into the tube and the nitro- 

 gen removed in the usual manner by sparking over alkali. The pres- 

 ence of nitrogen here was undoubtedly due to the impossibility of per- 

 fectly exhausting all the air from so large a flask; the volume of 

 nitrogen was about 10 cubic centimeters. There now remained but a 

 minute bubble of gas, and on transferring this to a vacuum tube at 



