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SCIENCE. 



[N. S. Vol. IX. No. 217. 



der that the argon should come in contact 

 with as little water as possible, 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 

 thoroughly 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 

 possible to dry the lime absolutely, hydro- 

 gen 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 

 drj'ing 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 sulfuric acid which had been thor- 

 oughly boiled ; all the other gases were 

 collected by a Topler pump. The total 

 volume of this gas was hardly 50 ccm.; it 

 proved to be chiefly hydrogen, with a trace 

 of hydrocarbons, arising from the small 

 quantity of metallic magnesium present in 

 the magnesium nitrid. After the hydro- 

 gen had been reoioved by explosion, an 

 excess of oxygen was passed into the tube 

 and the nitrogen removed in the usual 

 manner by sparking over alkali. The 

 presence of nitrogen here was undoubt- 



edly due to the impossibility of perfectly 

 exhausting all the air from so large a flask ; 

 the volume of nitrogen was about 10 ccm. 

 There now remained but a minute bubble 

 of gas, and on transferring this to a vacuum 

 tube at very low pressure the spectrum of 

 argon appeared. There was here, there- 

 fore, no trace of a new gas to be found. 



It was not deemed worth while to investi- 

 gate the ammonia, since I had already 

 prepared nitrogen out of this and Lord 

 Rayleigh had determined its density ; he 

 found this to be exactly the same as the 

 density of nitrogen from different chemical 

 sources. It remained, however, possible 

 that the sought-for gas could combine with 

 hydrogen, and that such a compound might 

 possess an acid character ; in this case it 

 might have entered into combination with 

 the magnesium. On account of the possi- 

 bility that such a compound might be solu- 

 ble, the magnesia was extracted with water, 

 the solution evaporated and treated with 

 sulfuric acid in a vacuum. A gas was 

 evolved, but it proved to be exclusively 

 carbon dioxid. We should have carried the 

 treatment of the magnesium further had 

 not the argon at last become sufficiently 

 pure to subject it to the refrigerating action 

 of liquid air ; and it seemed to me there 

 was more hope of finding the new substance 

 in the argon from the atmosphere than in 

 this residue of magnesia, which it would 

 requii-e much time and labor to work up. 



Dr. Hampson, the inventor of a very 

 simple and practical machine for the prepa- 

 ration of liquid air, which is based upon the 

 same principle as that of Herr Linde, was 

 so kind as to place large quantities of liquid 

 air at my disposal. In order to become 

 acquainted with the art of working with so 

 unusual a material, I asked Dr. Hampson 

 for a liter ; with this Dr. Travers and I 

 practiced and made different little experi- 

 ments to prepare ourselves for the great 

 experiment of liquefying argon. 



