PROFESSOR GRAHAM ON MOTION OF GASES. 
r«)9 
rect to take the first and second times together, or the whole fall from 30 to 16 inches, 
which gives — 
Air =1. 
Oxygen =1. 
Transpiration time of olefiant gas 
0-5659 
0-5093 
The times from 30 to 14 inches, 0'5093 and 0*5054, will thus closely approach to 
the average time obtained by the other method. But under 14 inches of pressure, 
where the transpiration becomes extremely slow as the resistance is greatly increased, 
the times rise to 0*5145 and 0*5199. In the present state of our knowledge respecting 
transpiration, it is difficult to decide upon the comparative value of these results, and 
to say which represents best the true transpiration time of olefiant gas. An unex- 
plained variation of 1|^ per cent, in the transpiration time of this gas must at present 
be admitted, which is a much greater latitude in the results than was observed with 
nitrogen, hydrogen, protocarburetted hydrogen, or even with carbonic acid. 
3. Ammonia. 
This gas is supposed to have certain chemical relations to olefiant gas, although 
differing very widely from the latter in its physical properties. The theoretical 
density of ammonia is 8*5, that of oxygen being 16; or 539*6 to oxygen 1000. It is 
therefore considerably lighter than olefiant gas ; it is also liquefied by pressure, and 
highly soluble in water, which the latter is not. 
This gas was always dried by passing over fragments of fused hydrate of potash. 
The mode of operating with gases like ammonia, which cannot be retained over 
water, found most convenient was to maintain a continued and copious evolution of 
the gas during the whole period of the transpiration experiments, conveying the gas 
into an empty bottle in the first instance, of which the cork was perforated by three 
tubes. By one of these tubes the gas entered this bottle, by another the portion of 
gas required for transpiration was condueted to the capillary, and the third, which 
was bent downwards and its extremity allowed to dip a line or two into a little cup 
of water, formed a waste-pipe or relief tube, by which the excess of gas evolved 
escaped into the atmosphere. The same method was equally applicable to hydrogen, 
carbonic acid, chlorine, &c., and does away with the necessity of collecting these 
gases over water, and so exposing them to contamination. 
(1.) This gas was transpired by capillary K, 8*5 inches in length, into the six-pint 
aspirator-jar upon the plate of the air-pump, through the usual range of 28*5 to 23*5 
inches on the gauge barometer ; thermometer 54°, barometer 29*772 inches. In two 
experiments with air the times were 982 and 981 seconds ; in three experiments with 
ammonia 546, 546, and 546 seconds. This gives 0*5563 for the time of ammonia 
referred to air, or multiplying this number by 0*9 to reduce it to the scale of 
oxygen -= 1 , we have, — 
Transpiration time of ammonia . 
0*5007 
