408 



Mr. J. B. Hannay. 



[June 16, 



This I find to be the case, and to a very remarkable extent. I am still 

 investigating this matter, but as I have so much on hand it may be 

 some time before I can finish the work, so I wish to place on record 

 the results so far as I have proceeded. I find that glass, when at a 

 temperature of about 200°, absorbs a large quantity of gas when the 

 latter is under a pressure of 200 atmospheres. Oxygen and carbon 

 dioxide have been used, and have been found to be largely absorbed, 

 and on cooling the glass under pressure the gas is retained per- 

 manently fixed. So much is absorbed that, on quickly raising the 

 temperature to the softening temperature of the glass, the sudden 

 escape of gas drives the glass into foam. On slowly raising the tem- 

 perature and retaining it at 300°, most of the absorbed gas is given off 

 without any visible action. 



The frothing up of the glass by the outrush of gas is very striking. 

 Other silicates, and also borates and phosphates, absorb gas, especially 

 carbon dioxide, under great pressure. Metals absorb hydrogen and 

 some of its compounds with carbon. As the treatment of quantities 

 of matter sufficient for analysis at these high press ares and tempera- 

 tares is a matter of great difficulty, the majority of experiments being 

 failures, the work proceeds but slowly ; but I hope during the summer 

 and autumn to be able to elucidate the subject quantitatively, when I 

 shall detail the results to the Society. 



XV. " On the States of Matter." By J. B. Hannay, F.R.S.E., 

 F.C.S. Communicated by Professor G. G. Stokes, D.C.L., 

 &c, Sec. R.S. Received June 4, 1881. 



The conception which had been held from the earliest times that the 

 three recognised states of matter were clearly separated from each 

 other received a rude blow from the interpretation put upon the work 

 of Andrews, that the liquid and gaseous states were really continuous, 

 and that the two states could only be classified under one head — the 

 fluid state. Andrews demonstrated that by placing a liquid under a 

 pressure greater than the critical, and then raising the temperature, 

 the liquid might be made to pass to an undoubtedly gaseous state 

 without any sudden change having been visible. Thus the continuity 

 of the liquid and gaseous states seemed established. I say seemed, 

 because I have shown in former papers that under any pressure the 

 fluid passes at a given temperature from a state where it possesses 

 cohesion, capillarity, or surface tension — the distinguishing property 

 of liquid, which prevents it freely mixing with a true gas — to a state 

 where it possesses no cohesion, capillarity, nor surface tension, and 

 where it mixes freely with any gas — in fact, to the gaseous state ; and 

 this change takes place at a fixed temperature . independent of pressure. 



