332 Dr. Andrews on a new Aspirator. 



had passed througli the tubes, but afterwards it began rapidly 

 to increase in weight. 



With well-di'ied, but not fused, chloride of calcium, as recom- 

 mended long ago by Liebig for organic analysis, in T, and sul- 

 phuric acid in T', some interesting results were obtained. To 

 ascertain whether the absorption of moisture by T' was complete, 

 a third tube containing sulphuric acid vras placed between it and 

 the aspirator. Sixty measures of the aspirator were passed in 

 succession through this series of tubes, which were only removed 

 from time to time for the purpose of being weighed. The gain 

 of tube T after this operation amounted to no less than 12'252 

 grms. (189-08 grs.) ; that of T' to 0-141 grm. (2-17 grs.) ; and of 

 the tube next the aspirator to 0-21 grm. (0'32gr.). It is import- 

 ant to remark that the gain of T' was a uniform quantity from 

 the beginning to the end of the experiment ; its average increase 

 of weight for each elevation of the aspirator from the first to the 

 twenty-fifth time being 0-0024 grm. (0-037 gr.), and from the 

 twenty-fifth to the sixtieth time 0-0023 grm. (0-035 gr.). The 

 gain of the third tube is quite insignificant, not amounting to 

 ■^^ydth part of the whole quantity of aqueous vapour, and ]5ro- 

 bably arising from moisture derived from the air in the aspirator, 

 or from some accidental cause. The experiment in this case was 

 continued till the stream of air was arrested by the liquefaction 

 of the chloride of calcium in the further end of T from the aspi- 

 rator ; yet the desiccating power of the chloride of calcium in the 

 other limb continued unimpaired till the end. It appears, then, 

 that the whole of the moisture may be absorbed from 1296 litres 

 (or nearly 80,000 cubic inches) of atmospheric air in its ordi- 

 nary state in this country by means of a chloride of calcium tube 

 weighing about 90 grms. (1400 grs.), aided by a supplementary 

 tube containing sulphuric acid, and of about half the weight. 

 As these tubes may be placed at the same time on the balance, 

 no additional trouble is incurred by employing them both. 

 Further experiments are, however, required to determine whether 

 the small increase of weight sustained by the sulphuric acid tube 

 arose actually from the absorption of aqueous vapour, or whether 

 it may not have been due to the absorption by the sulphuric acid 

 of a part of the carbonic acid existing in the air*. If this latter 

 view prove to be correct, dry chloride of calcium should be sub- 

 stituted for sulphuric acid in the tube T. 



A slight modification of the apparatus would give the quan- 

 tity of moisture in the air for shorter intei-vals of time ; and 

 there can be no doubt that the tubes would continue to absorb 

 all the moisture from air passing with much greater velocity than 



* See the observations on this subject of Prof. Rogers in the Chemical 

 Gazette, vol. vii. p. 477. 



