Prof. Graham on the Law of the Diffusion of Gases. 275 



instrument, corrected from the standard, was 6 measures; in 

 four hours and a half, 13 measures; in fifteen hours, 29 mea- 

 sures; in twenty hours, 34 measures; in twenty-nine hours, 

 41 measures; in thirty-eight hours, the expansion was at a 

 maximum, namely, 43 measures. In explanation of the long 

 duration of this and the following experiments, it may be. 

 stated, that the plug was fully half an inch in thickness. 



795 measures oxygen and vapour have therefore been re- 

 placed by 838 measures air and vapour. 



795 



-— = 0*9487 = diffusion-volume of oxygen by experiment. 



This is the exact theoretic number; a coincidence, however, 

 which we must view as accidental. 



Exp, 2. — In a careful repetition of this experiment with 

 another specimen of oxygen gas, the results approached very 

 closely to the preceding; but the return-air was in slight ex- 

 cess above the theoretical quantity. Thus, 



1 oxygen was replaced by 1*056 air, by experiment. 

 1 1*054 air, by theory. 



Oxygen, therefore, affords a most striking confirmation of the 

 law. 



11. Nitrogen. — Prepared by burning an excess of phos- 

 phorus in a confined portion of air, and allowing the residuary 

 gas to stand over water for several days. 



Specific gravity, 0*9722. Root, 0*9860. Reciprocal of 

 root, 1*0140. 100 nitrogen should be replaced by 98*60; and 

 100 air should replace 101*40 nitrogen. 



Thermometer, 66°. Barometer, 29*23. Diffusion into moist 

 air as in the preceding experiments. 



836 measures contracted 3 measures in two hours and forty 

 minutes, as corrected by standard ; and 13 measures in eigh- 

 teen hours, which was the maximum contraction; for in 

 twenty-three hours and a half from the beginning of experi- 

 ment, a contraction of 12 measures was indicated. Taking 

 the last as the true result, 



r—- = 1*0143 = diffusion-volume of nitrogen by experiment. 



1*0140 = diffusion-volume of nitrogen by theory. 



12. Olefiant Gas. — Specific gravity likewise 0*972, &c. as 

 in nitrogen. The gas was carefully made, collected in a low 

 receiver, allowed to stand over water for twenty-four hours, 

 and finally washed with caustic ley. 



Thermometer, 59°. Barometer, 29*83. 800 measures of 

 this gas were replaced by 785 measures of air, in twenty-five 

 hours, correcting from standard. 



2 N2 



