238 EXPERIMENTS OF GASES ABSORBED BY WATER; 



was then filled completely with mercury, which rof'e to its 

 correfponding level in the tube B. A given quantity of water^ 

 of a known temperature, and afterwards a meafured volume 

 of gas, were transferred into the vefl'el, in the mode already 

 defcnbed ; and, as the mercury, by opening the cock b, was 

 brought to the fame level in both legs of the fyphon, the gas> 

 it i* evident, mull have been tinder the ordinary weight of th« 

 atmofphere. A quantity of mercury was next poured into 

 the leg B, fufficient to lorm a column 28 inches higher thai* 

 the level of the mercury in A, afler this addition ; and the 

 bulk of the gas was again noted. This Was found to be, pretty 

 exaclly, f, -£-, &c. of the fpace occupied before, when one, 

 two, or more additional atmofpheres were applied* Britk 

 agitation was now ufed, as long as any abforplion took place; 

 and, into the tube B an affiftant poured mercury, fo as to pre- 

 ferve in it the excefs of 28 inches above the level of the mer* 

 cury in A. The degree of abforption was known by the fcal* 

 on A, or, more accurately, by the quantity of mercury re- 

 quired to fupport the elevation of 28 inches in B, 



By lengthening the column in B to 56 inches, the preflur© 

 of two additional atmofpheres was obtained ; and this was the 

 utmoft extent to which the addition of weight could be carried) 

 without forcing the joint at D. 



When the cock b was opened, and the column in each leg 

 thus fuddenly fell to the fame level, the water, which had been 

 previoufly charged with gas, under a preflure of three atmo- 

 fpheres, effervefced violently ; but fome time elapfed before 

 the additional gas, forced in by compreffion, was wholly 

 evolved. Thefe appearances are very ftriking and amufing; 

 and are well calculated for exhibition in a chemical le&ure. 

 The apparatus, however, I have no doubt, may be greatly 

 improved; but, at the diftance of nearly 200 miles from the 

 metropolis, I was under the neceffity of uling fuch an one as 

 could be conitructed by my own hands. 

 Improved appa- A confiderable improvement in the conftru&ion of the ap* 

 *«us. paratus, which would obviate the expediency of the flexible 



tube D, would be the following. To the lower neck of the 

 veflel A, Fig. 1, let a cap and cock, with a female fcrew, be 

 cemented ; and let the upper end of the pipe C be terminated 

 by a cock with a male fcrew. Introduce the gas and water, 



