39x O?? CAftBUUETTKU HIDROGE^ GAS. 



aUer. I have a large flask fitted with a stop-cock. 1 

 weigh this flask very accurately, then exhaust it, and 

 weigh it again. Let the loss of weight be a, I then fill 

 the flask with the gas, the specific gravity of which I want, 

 and weigh it again. If the weight of the flask be the same 

 as at first, it is obvious, that the gas has exactly the speci- 

 fic gravity of common air. If it be heavier than at first, 

 the gas is heavier than common air; if lighter, the gas is 

 iig^hter than common air. Suppose the flask lighter than at 

 first, I add weights till the flask is exactly poised. Let the 

 weight added be b. We have the weight of comm6n air to 

 that of the gas as a to a—b. And to find the specific gra- 

 vity, we have this proportion, aia^b : : I :a;= specific 



gravity wanted, or x = - — . If the flask is heavier than 



at first, weights are added to the other scale, till it is 

 (Kxabtly poised ; let these Weights, as before, be 6, we have 



ip this csLse x = r-. In this process no correction is ne- 

 cessary for temperature, or the state of the barometer;, 

 because air and all gasses undergo the same change of bulk, 

 by changing the temperature and the pressure. The gas is 

 always 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^^^dth part of a 

 grain; so that you are always sure of the specific gravity 

 of the gas, to the 3d decimal figure. The specific gravity 

 of common air is always taken 1*000, and at the tempera- 

 ture of eo*-', barometer at 30 inches, 100 cubic inches of it 

 weigh 30*5 grains. These data enable us to determine the 

 weight of 100 cubic inches of any gas the specific gravity 

 of which is known, Mr. Dalton found the specific gravity 

 of this gas 0*600. I t'ook its specific gravity more than 

 once, and collected at diflerent times, but never found it 

 heavier than 0*5554. 

 Farther proper- 6. The gas from stagnant water burns with a yellow flame, 



ties of the gas more readily, and with y, lari^er flame, than any other com* 

 from stagnant - ... ^ • ' •' 



wat«r. bustible gas, except olehant gas, and the vapour of ether. 



7. When mi\ed with oxigen gas, and kindled by an elec- 

 tric spark, it detonates loudly, and undei^goes a considera- 



bk 



