198 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. lviii. 



i r 



absorption, the stoppers of the tubes E and F were 

 removed ; F was connected with an aspirator, and E with 

 an apparatus for purifying the air and saturating it with 

 moisture. About 1 litre of air was drawn through each 

 tube at one time, the operation occupying about ten 

 minutes. The stoppers were then 

 replaced, and the volume of the con- 

 tained air immediately ascertained. 



The quantity of carbonic anhydride, 

 produced by the seeds, was found at 

 the end of the experiment in the 

 following way : — The contents of the 

 two boats B and B\ from each of the 

 two tubes, were washed into two small 

 flasks, like A in Fig. 4, with distilled 

 water. 



Each flask was, in turn, fitted with 

 an indiarubber cork, B, perforated 

 by the wide tube C, which was con- 

 nected with a Sprengel's mercury 

 pump. A tap funnel, E, containing 

 recently boiled dilute sulphuric acid 

 tinged with litmus communicated with the interior 

 of the flask by the narrow tube, D, which passes down 

 the axis of the broad tube C. As soou as a vacuum 

 had been obtained, the acid solution in the funnel was 

 cautiously run into the flask till the contents were pink 

 in colour. The pump was then worked, and the flask 

 exhausted as far as possible, the carbonic anhydride being 

 collected in a tube over mercury. Gentle heat was then 

 applied to the liquid, which caused it to boil briskly. 

 It was found very advantageous to put a small piece of 

 platinum foil, previously ignited, into the flask to prevent 

 bumping. The source of heat was then withdrawn, and 

 the pump worked till a vacuum was again produced, at 

 which stage heat was applied once more, and the pump 

 was set in action as previously. This operation was 

 repeated until a vacuum was obtained within a few seconds 

 after boiling the liquid. By proper attention to these 

 details, the carbonic anhydride expelled from the liquid 

 can be obtained nearly free from water in the collecting 



Fior. 4. 



