174 
T)i;. .M. TEAYEES, ME. G. SENTEE, AND DE. A. JAQUEEOD 
stop-cock P] for a moment, about 70 cub. centims. of the gas passed into the jjump. 
P’bis fraction (2) was probably as pure as fraction 1, for the additional cooling produced 
by its sudden expansion would compensate for the tendency of any light impurity 
to eya])orate : it u’as, howe^'er, kept sepaiute (fraction 2). 
AYheii fraction 2 liad l)een pumped otf and collected, the stop-cock E was again 
opened, and the remaining volatile gas Avas pumped off and collected. It formed 
fraction 2, and consisted of about 25 cub. centims. of gas. Finally the liquid 
hydrogen was removed, and the residue in tlie coil, Avhicli volatilised and ^Jassed into 
the })um]), was collected as fraction 4. 
Fraction 4 was found to consist largely of nitrogen, Avhich had jDrobably entered 
the tube in Avhich the gas had been stored since 1898 at the time it Avas last 
handled. This gas aavis sparked AAutli oxygen ovei' lAotash for some houis, and after 
remoAud of tlie excess of oxygen about O'o cub. "ventini. of gas AA'as left; it AA'as 
found on spectroscopic examination to consist of argon and krypton only, shoAA'ing tlie 
spectrum of the latter AA'ith brilliancy. 
The fact that cleA'eite helium yields krypton indicates that that gas must be present 
ill the original mineral. As krypton is present in air to an extent not greater than 
I part in 1,000,000, the presence of that gas in the helium could not possibly be due 
to leakage of air into the apparatus. The quantity of kryjkon, like mercury A apour, 
AA liich is necessary to giA’e a brilliant specti’um in presence of argon, is exceedingly 
small, and possibly the total quantity of kiypton in the gas might not exceed 
O'Ol cub. centim., or 0‘005 per cent, on the original helium. It is interesting to 
note that AA’hen Olszeavski attempted to liquefy helium by compressing it at 
— 210° C., and alloAving it to expand (‘ Nature ’ 1896, Ami. 62, p. 244), a small quantity 
of a AA’hite substance separated. It is intended on another occasion to inAmstigate 
tlie lieaA'v fraction of gas obtained in 1898 bv tlie diffusion of helium. 
Tlie tirst fraction of gas, aaTucIi we called fraction 1, aavis used in the first series of 
measurements of the boiling-point and A'apour pressures of liquid hydrogen doAAm to 
15°‘5 abs. ITrictions 1 and 2 AAmre subsequently mixed and passed a second time 
through a coil immersed in liquid hydrogen directly into the large constant-A'olume 
thermometer for the measurement of the pressure coethcient (p. 129), AAdiich AA’as 
tound to be 0t)0366255. 
For the second series of measurements of the A’apour pressures of liquid hydrogen 
the helium Aias further purified by passing it through a coil immersed in liquid 
liydrogen boiling under reduced pressure. For this purpose the coil c, through 
Avhich the helium Avas jiassed (fig. 3), AA’as enclosed AA’ithin an apparatus similar to 
that employed in determining the A’apour jire.ssure of hydrogen. The arrangement 
which is shoAA’n in fig. 4 requires little description. 'The \ acuuni A'essel containing the 
liquid hydrogen aahs introduced from beloAA’ into the AA’ide (p. 160) tidie so as to 
sui'rouiid the coil and the hnlb A\ hich contained the pure hydrogen, and \A as connected 
w ith a manometer hy A\ hich the A’apour pressure on the pure liA'drogen, and from this 
