Constitution of the Atmosphere. 



245 



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In this way it may be shown, that sulphurous acid will pass 

 instantaneously into atmospheric air, against a pressure equi- 

 valent to two hundred and twenty inches of mercury, or seven 

 atmospheres and a third. 



The curved form of the instrument just described was 

 found to present certain inconveniences when pi-essures up- 

 wards of 6 or 7 atmospheres were made use of. The volume 

 of air, which at the beginning of the experiment occupied the 

 greater part of the extent of the shorter limb, had now col- 

 lapsed much in its dimensions, and owing to the unavoidable 

 giving way of the India-rubber and silk cover, had retreated 

 beneath it out of sight. It was not found expedient to lengthen 

 this limb, for that entailed a corresponding increase in the 

 dimensions of the battery, in order to produce a given con- 

 densation in a given time. A straight tube was therefore 

 taken, about three sevenths of an inch in bore, and a rim 

 turned on it at a a ; at the closed extremity the 

 platina wires b c entered ; a gauge tube d was 

 dropped in between them; water was then 

 poured to the height e e ; and lastly, a tube^, 

 containing an appropriate chemical test, was 

 inserted, its bottom resting on the top of the 

 gauge tube. Nothing remained but to tie on 

 the India-rubber with its silken support, and 

 by the voltaic battery to proceed to condense. 

 In this instrument the test fluid was never out 

 of sight, nor did the volume of the gas suffer 

 any inconvenient change ; the gauge too was 

 well located for observation, and a given con- 

 densation could be produced in less time, and 

 by a less amount of electricity, than with the 

 siphon tube. It is to be observed, however, that * ^ 



the gaseous matter evolved from the water mingles with the 

 atmospheric air in the upper part of the tube, and therefore 

 the passage of the gases tried, does not take place into at- 

 mospheric air, but into a mixture of oxygen, hydrogen, and 

 nitrogen. 



The tube f being filled with lime water, and a pressure 

 amounting to ten atmospheres being produced in the vessel, 

 it was exposed to an atmosphere of carbonic acid gas, at 

 ordinary pressures. In this course of a few minutes, the upper 

 part of the tube containing the lime-water began to look 

 milky, and in an hour a cloud of particles of carbonate of 

 lime had fallen to the bottom. 



Again, having filled the test tube f, with a solution of ace- 

 tate of lead, and produced a pressure amounting to twelve 



a 



