218 On the confinement of Dry Gases over Mercury. [1826. 



illustration it affords of the difficulty of confining dry gases 

 over mercury alone. Two volumes of hydrogen gas were 

 mixed with one volume of oxygen gas, in a jar over the mer- 

 curial trough, and fused chloride of lime introduced, for the 

 purpose of removing hygrometric water. Three glass bottles, 

 of about three ounces capacity each, were selected for the 

 accuracy with which their glass stoppers had been ground into 

 them; they were well cleaned and dried, no grease being 

 allowed upon the stopper. The mixture of gases was trans- 

 ferred into these bottles over the mercurial trough, until they 

 were about four-fifths full, the rest of the space being occupied 

 by the mercury. The stoppers were then replaced as tightly 

 as could be, the bottles put into glasses in an inverted position, 

 and mercury poured round the stoppers and necks, until it 

 rose considerably above them, though not quite so high as the 

 level of the mercury within. Thus arranged they were put 

 into a cupboard, which happened to be dark, and were sealed 

 up. This was done on June 28, 1825, and on September the 

 15th, 1826, after a lapse of fifteen months, they were examined. 

 The seals were unbroken, and the bottles found exactly as 

 they were left, the mercury still being higher on the inside 

 than the outside. One of them was taken to the mercurial 

 trough, and part of its gaseous contents transferred ; upon ex- 

 amination it proved to be common air, no traces of the original 

 mixture of oxygen and hydrogen remaining in the bottle. A 

 second was examined in the same manner ; it proved to contain 

 an explosive mixture. A portion of the gas introduced into a 

 tube, with a piece of spongy platina, caused dull ignition of 

 the platina; no explosion took place, but a diminution to 

 rather less than one-half. The residue supported combustion 

 a little better than common air. It would appear, therefore, 

 that nearly a half of the mixture of oxygen and hydrogen had 

 escaped from it, and been replaced by common air. The third 

 bottle, examined in a similar manner, yielded also an explosive 

 mixture, and upon trial was found to contain nearly two-fifths 

 of a mixture of oxygen and hydrogen, the rest being very little 

 better in oxygen than common air. 



There is no good reason for supposing that this capability 

 of escape between glass and mercury is confined to the mixture 

 here experimented with ; probably every other gas, having no 



