HYDROGEN GA$. 5°9 



weights are added to the other scale, till it is ex- 

 actly poised i let these weights, as before, be b, 



we have m this case x — . In this process 



a 



no correction is necessary for temperature, nor the 

 state of the barometer ; because air and all gases 

 undergo the same change of bulk, by changing 

 the temperature and the pressure. The gas is al- 

 ways weighed, saturated with moisture. This 

 is corrected when requisite by the table of Dalton. 

 In this way the flask may,be easily weighed, true 

 to the T ^-dth part of a grain ; so that you are al- 

 ways sure of the specific gravity of the gas, to the 

 3d decimal figure. The specific gravity of com- 

 mon air is always taken 1.000, and at the tempe- 

 rature of 6o*, barometer at 30 inches; 100 cubic 

 inches of it weigh 3c. 5 grains. These data enable 

 us to determine the weight of ico cubic inches of 

 any gas whose specific gravity is known. Mr 

 Dalton found the specific gravity of this gas 0.600. 

 I took its specific gravity more than once, and col- 

 lected at different times, but never found it hea- 

 vier than c.5554. 



6. The gas from stagnant water bums with a 

 yellow flame, more readily, and with a larger 

 flame, than any other combustible gas, except ole- 

 riant gas, and the vapour of ether. 



7. When mixed with oxygen gas, and kindled 

 by an electric spark, it detonates loudly, and 

 undergoes a considerable diminution of bulic. Its 



