1905.] on New Low Temperature Phenomena. 191 



kept in the dark for months, and at the end of the time are quite 

 active when cooled as described. A manometer attached to the side 

 of the oxygen bulb shows that the oxygen pressure at the moment 

 phosphorescence begins is only a fraction of a millimetre of mercury. 

 From these results it appears that perfectly dry oxygen below 1 mm. 

 pressure combines with phosphorus. 



The following experiment proving the absorption of carbonic acid, 

 at a small partial pressure, by charcoal is very striking. A continuous 

 stream of ordinary atmospheric air, containing three volumes of car- 

 bonic acid in ten thousand, is made to enter the apparatus, Fig. 4, at 

 A and leave at H. It first passes through the jar B, which contains 

 some strong sulphuric acid, by which it is thoroughly dried. On 

 leaving B the stream of air is divided at C into two portions, one of 

 which passes through the jars D, E, the other through the jars F, G, 

 the two finally uniting and passing out at H. D and F are vacuum 

 vessels containing solid carbonic acid, which maintains a temperature 

 of — 78° C. The air passes through a U-tube in D, the arms of 

 which are filled with coils of copper gauze to ensure the complete re- 

 duction of its temperature to — 78° 0. It next passes through the 

 jar E, containing some baryta water, which absorbs the carbonic acid 

 remaining in it, before it emerges at H. The other stream of air 

 passes in like manner through a U-tube in F, in one arm of which is 

 a quantity of dry charcoal in small lumps ; thence, after bubbling 

 through some baryta water in the jar G, it passes to H, where it 

 escapes. Now, the streams of air entering D and F are in exactly the 

 same state, but while E shows by the milky deposit taking place that 

 the one stream is still fully charged with carbonic acid after being 

 thoroughly cooled to — 78° 0. in D, G shows by remaining per- 

 manently clear that a similar cooling of air to — 78° C. in the presence 

 of charcoal causes, for a time, complete absorption of the carbonic 

 acid from the air, and this goes on until the charcoal absorbs about 

 1 per cent, of its weight of carbonic acid. 



The absorptive power of charcoal for hydro-carbons is shown in a 

 similar manner by the following experiment : common coal gas enters 

 the apparatus in Fig. 5 by the tube at A, and after being dried by 

 bubbling through strong sulphuric acid in the jar B, has the less 

 volatile gases condensed by passing through a vessel C cooled with 

 carbonic acid snow, isolated in the vacuum vessel D. The gas is 

 further purified by percolating through the two copper coils contained 

 in the arms of the U-tube F F, immersed also in solid carbonic acid 

 in the vacuum vessel E, after which it passes on to H, where its path 

 is bifurcated, one branch leading to I, where the issuing gas is hghted, 

 while by the other branch the purified gas passes over charcoal in the 

 U-tube G, also at the temperature of solid carbonic acid, before pro- 

 ceeding to J, where it in turn is lighted. The difference between the 

 two flames is very noticeable, that at I being quite luminous, while 

 the other at J is non-luminous, like a Bunsen flame. The explana- 

 tion is, that the charcoal at the temperature of —78° C. completely 



