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SCIENCE. 



[N. S. Vol. IX 'So. 217. 



collected by itself, and the remaiuder was 

 evaporated into another gasometer. 



You can well imagine how eager we were 

 to know what the density of this purified gas 

 would prove to be. It was immediately 

 weighed. Our satisfaction can well be re- 

 alized when we found that its density was 

 9.76. Since, however, its spectrum at low 

 pressure still showed argon lines, though 

 weak, we were compelled to admit that this 

 number was certainly too high. It was 

 impossible that this gas should not contain 

 argon, since at the temperature used argon 

 possessed a measurable vapor pressure. 



"We have, therefore, estimated that the 

 density of the pure gas is 9 65. Here our 

 work for the time was ended by the begin- 

 ing of the summer holidays. 



On our return we resumed the study of 

 this gas, which we will hereafter designate 

 by its name of ' neon.' Its spectrum was 

 photographed by Mr. Baly, one of my as- 

 sistants, by means of a spectrometer which 

 we had constructed during the vacation. 

 To our astonishment, the lines of helium 

 were easily recognized. A comparison 

 photograph showed this beyond all ques- 

 tion. Hence the density of the gas was in 

 all probability too low, owing to the pres- 

 ence of the helium. Since now the temper- 

 atui-e used was insuflBcient to liquefy the 

 neon, and since the argon had been removed 

 as far as possible, we had to face the problem 

 of how one could free neon from its accom- 

 panying impurities. A means was found 

 in its solubility. It is well known that the 

 solubility of those gases which do not react 

 chemically with the solvent follows in gen- 

 eral the same order as their condensibility. 

 According to this helium should have a lesser 

 solubility than neon, and neon than argon. 

 The solubility of these gases in water is, 

 however, too slight to be available for their 

 separation. We have, therefore, used liquid 

 oxygen as a solvent. This mixes with all 

 three gases and boils at a temperature not 



far from the boiling point of argon. "We, 

 therefore, mixed the gas with sufficient oxy- 

 gen to be almost wholly condensed at the 

 temperature attained by boiling air at the 

 lowest possible pressure. The uncondensed 

 portion, about one fifth of the whole, was 

 separated and collected as that richest in 

 helium ; the middle portion we considered 

 as purified neon, while the remainder con- 

 sisted of a mixture of argon and neon ; 

 naturally, all these portions contained oxy- 

 gen in larger or smaller quantities. 



After the removal of the oxygen, which 

 was accomplished by passage over hot cop- 

 per filings, we determined the density and 

 refractivity of the middle portion. The 

 density in two determinations was 10.04 

 and 10.19; the second figure was obtained 

 after passing the electric spark through the 

 gas mixed with oxygen in the presence of 

 caustic potash and subsequent removal of 

 the oxygen by phosphorus. The entire 

 quantity weighed was only 30 cubic centi- 

 meters at a pressure of 250 millimeters. 

 The weight was 0.0095 gram. I mention 

 these figures in order to show with what 

 an exceedingly small quantity of gas it is 

 possible to carry out a very satisfactory 

 density determination. 



The refractivity of this portion with refer- 

 ence to the air as unity was 0.338. This 

 portion still showed the spectra of argon 

 and helium, and was, therefore, submitted to 

 a second purification, in which the heavier 

 part was more completely removed than 

 the lighter. Even this purification, how- 

 ever, did not remove all the argon, but its 

 quantity was decidedly diminished. The 

 density was somewhat diminished, and 

 helium was stronger in the spectrum. The 

 entire amount of neon had become, by these 

 operations, so divided up that it was not 

 possible to carry out a further purification 

 without preparing a greater quantity of 

 crude neon. On this Dr. Travers and I 

 are at present engaged. 



