

312 Messrs. Haldane and Pembrey on an Improved Method 



Experiment No. 4. 

 21 litres aspirated at 2 litres per minute. 



Tnbel .... +0*2334. 

 Tube 2 .... +0-0000. 



Experiment No. 5. 

 50 litres aspirated at 1 litre per minute. 



Tubel .... +0-4163. 

 Tube 2 .... -0-0003. 

 The same tubes were not used through all these experi- 

 ments, as tube No. 1 had become spent in the middle of the 

 series. The use of double tubes enormously increases the 

 lasting powers, so that, as shown by the following experi- 

 ment, a double tube may be used for 300 determinations or 

 more without being recharged. 



Experiment No. 6. 



The number of analyses possible without refilling a double 

 absorption-tube was determined by aspirating air through 

 two of them at a rate of 1 litre a minute, and weighing the 

 second pair at intervals. 120 litres had previously passed 

 through pair No. 1. 



Litres of Air 



Variation in We 



Aspirated through Pair 1. 



of Pair 2. 



235 



-0-0005* 



354 



-0-0002 



418 



+ 0-0000 



568 



-o-oooi 



753 



-0-0003 



1046 



+ 0-0000 



1225 





1346 



+ 0-0001 



1588 



+ 0-0003 



1767 



-0-0002 



1994 



+ 0-0000 



2200 



-o-oooi 



At the end of the experiment the first pair had absorbed 

 12*8255 grammes from 2320 litres of air. Although this 

 pair was still absorbing moisture completely we did not con- 

 tinue the experiment further, on account of the inconvenient 

 accumulation of dilute acid in the first tube. 



As in determining moisture we have generally made a 

 carbonic-acid determination simultaneously, our usual rate of 



* Weighed by mistake five minutes after experiment. 



