of Determining Moisture and Carbonic Acid in Air. 311 



several days. The differences found are shown in the follow- 

 ing Table : — 



Intervals between weighings 



Counter- j Ordinary 



poise tube 1 (66*9230 grms.) 

 ( Ordinary 



(77-7075) 



Tube 1 



1 Comparative. 



(10-7840) 



{Ordinary .... 

 (87-6274) 

 Comparative. 

 (20-7041) 

 (Ordinary .... 

 (69-6367) 

 Comparative. 

 (2-7136) 



20 hours. 



3 hours. 



4£ hours. 



42 hours. 



+0-0012 



+0-0010 



+ 0-0008 



+0-0024 





+0-0009 



+0-0008 



+0-0018 





±0-0000 



±0-0000 



- 0-0004 



4-0-0007 



+0-0015 





+0-0023 



-o-oooi 



+0-0002 





+0-0002 



+00009 



+0-0010 



+00006 



+0-0018 



+0-0000 



-0-0002 



±0-0000 



-0-0005 



With regard, secondly, to the rate of aspiration possible 

 and the lasting powers of the tubes, we made a number of 

 experiments. 



When a single absorption-tube was used, instead of the 

 double ones described above, the absorption in the first tube 

 was perfect (at least with rates up to two litres per minute) 

 for a considerable time, as shown by the following expe- 

 riments. 



Experiment No. 1. 



90 litres of air were aspirated at a rate of 1 litre per 

 minute through two single absorption-tubes connected to- 

 gether by a very short piece of rubber tubing. The aspirator 

 in this and the following experiment was a glass filter-pump, 

 the air being measured by a gas meter : — 



Tube 1 



Tube 2 



+ 0-5142. 



+ 0-0000. 



Experiment No. 2. 



90 litres aspirated at 1 litre per minute. 



Tube 1 . . . . +0-4712. 

 Tube 2 .... +0-0002. 



Experiment No. 3. 



50 litres aspirated at If litres per minute. 



Tube 1 . . . . +0-4057. 

 Tube 2 .... +0-0001. 

 2B2 



