﻿New Form of Sulphuric- Acid Drying- Vessel. 611 



joins it to the pentoxide tube. The four horizontal branches 

 (each 22 cm. long with an external diameter of 2 cm.) 

 are about half filled with acid, which is thus contained in four 

 separate compartments, so that the moisture from the wet-air 

 stream is nearly all absorbed in the first compartment. A 

 long series of experiments, which need not be detailed here, 

 have proved that with such a vessel containing 70 c.c. of acid 

 (10 c.c. in the first compartment), 20 c.c. of water can be 

 abstracted from an air-current without allowing any to pass 

 — or put in another way, air saturated with moisture at 

 30° C. will be completely dehydrated, although passed for 5 

 days at a rate such that 0*15 gramme of water is taken up 

 per hour. 



In the first experiment, a current of moist air was drawn 

 through a soda-lime tube * to remove the greater part of 

 the moisture and then through a Winkler sulphuric-acid 

 drying-vessel of large size connected to the pentoxide tube. 

 The air-bubbles were formed in the Winkler at the rate of 

 50 in 14 seconds. After 52 hours the pentoxide tube was 

 weighed and had gained *0010 gramme. As no special 

 precautions had been taken to dry the tube connecting the 

 Winkler to the pentoxide, the same experiment was repeated 

 immediately after the above weighing, and the air passed for 

 160 hours. The gain in weight of the phosphorus pentoxide 

 was now only '0002 gramme, showing that the sulphuric 

 acid had allowed practically no moisture to pass by. 



In all these experiments the pentoxide tube was weighed 

 against a glass counterpoise of about the same external area, 

 and, before weighing, both vessels were washed and dried 

 in as near a similar manner as possible, the weighings being 

 reduced to a vacuum. 



In the next experiment the Winkler was replaced by the 

 new form of sulphuric-acid vessel. After a week's run, when 

 about 600 litres of air had passed, the sulphuric acid had 

 absorbed 5*52 grammes of water while the pentoxide tube 

 had gained only '0001 gramme. 



Further evidence of the efficacy of this form of vessel 

 is found in a great number of experiments in which air was 

 passed over water, in a weighed vessel, and then over the 

 sulphuric acid. The loss in the former should equal the gain 

 in the latter. Without entering into lengthy details the 

 following gives some idea as to the magnitudes involved — 

 the vessels were similar to those described by us in Free. 

 Roy. Soc. A. vol. Ixxvii. p. 158 (1906). 



* Cp. note cm page 618. 

 2 R 2 



