PROFESSOR GRAHAM ON THE MOTION OF GASES. 
375 
The time of air was 970, 970 seconds; of sulphurous acid, 714 and 711 seconds; 
ratio of latter to air, 07345. Multiplying by 0-9, we obtain — 
Transpiration time of sulphurous acid 0’6610 
(2.) With the long capillary M, 52‘5 inches in length, this gas was transpired into 
the two-pint jar: thermometer 60°‘5, barometer 29'880 to 29*878 inches. 
The time of air was 1120, 1120 and 1120 seconds; the time of sulphurous acid 
814, 811 and 812 seconds. Using the two last observations only for sulphurous acid, 
we obtain the transpiration time 0*7245 for that gas, air being 1 ; or multiplying 
by 0-9,— 
Transpiration time of sulphurous acid 0’6520 
In a second series of experiments with the same capillary, thermometer 58° and 
barometer from 29'880 to 29*886, the following observations were made. Time of 
air, 1105, 1111, 1105 and 1111 seconds; time of sulphurous acid, 798, 797 and 798 
seconds, and ratio to air 0*7199. This gives — 
Transpiration time of sulphurous acid 0*6479 
The mean of the two results by this capillary gives — 
Transpiration time of sulphurous acid 0*6500 
9. Sulphuric Acid. 
Both air and oxygen gas saturated with the vapour of anhydrous sulphuric acid 
were transpired under the pressure of the atmosphere into an air-pump vacuum, by 
the short capillary K, 8*75 inches in length. Certain new arrangements of the appa- 
ratus, however, were required in operating upon so highly corrosive a vapour as that 
of sulphuric acid. Two ounces of the solid sulphuric acid were melted by heat in a 
U-tube stuffed with asbestos, and having while liquid impregnated the asbestos, were 
allowed to cool and become solid again before the air or other gas to be saturated 
with sulphuric acid vapour was conducted through the U-tube. For the tin conduct- 
ing tubes of the former arrangements, glass tubes were substituted, and the air-pump 
was employed to exhaust a stout globular glass globe of six pints in capacity and 
provided with three openings, which was employed as the aspirator cavity. Two of 
the openings of the globular receiver were in the sides and one at the bottom of the 
receiver ; by one of the former openings the globular receiver was connected with 
the transpiring capillary and by the other with the air-pump ; a tube containing 
carbonate of potash being interposed between the receiver and the air-pump, to arrest 
the acid vapours and prevent them from reaching the air-pump, when the latter was 
used for exhausting the globular receiver. The third and lower opening* communi- 
cated with a gauge barometer, by which the tension of the gas or vapour within the 
globular receiver was observed. The mercury in this barometer was found to adhere 
slightly to the glass and not to descend with an entirely level surface in the transpira- 
tion experiments, owing to a slight chemical action of the acid vapour upon the 
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