192 AP. Cooke, Jr., on Lecture Experiments. 
behind the jar, will make the line between the colored gas and 
the air visible to a considerable distance. When the’ jars are 
full, the qualities of the two gases may be made evident by > 
propriate experiments. As is well known, the gases will not 
elivered in atomic proportions, until the liquid acid is saturated 
with chlorine. It is best therefore not to empty the cell after 
the experiments, but, having removed the rubber stoppers with 
their attachments, to close the mouth with the ground glass 
stoppers, and the apparatus will then be ready for the next oc 
casio t is also best to interpose a small wash bottle contain- 
ing sulphuric acid, between the cell and the chlorine jar, for 
this will not only dry the gas but also equalize the hydrostatic 
pressure on the two delivery tubes. Decomposing cells like 
that represented in fig. 1, and all other forms of glassware de: 
scribed in this paper are made by the New England Glass 00, 
of East Cambridge, and can be ordered through any of the 
: rption tube whose construction is shown 1n 0 
tail by fig. 6. As the gaseous mixture is decidedly lighter than 
air, it Is conducted to the top of the absorption tube throug? 
the small quill tube, and overflows through the short tube be- 
low. Both of these should pass air-tight through the rubber, 
stopper, which closes the mouth of the large absorption tube and : } | 
* We here of course leave out of view the small difference which arises from 
ea that the gases do not absolutely obey Mariotte’s law and are therefore U 
camany condensed even by the atmospheric pressure. e vo 
a vie es undoubtedly be exactly equal under greatly diminished 
er ecary Prcserre of the air, the volume of the molecular wei , 
ms ‘by no means reciable in accurate experiments. re 
