1823.] On the Ratio of Expansion of Gases, 415 



Article IV. , 

 On the Ratio of Expansion of Gases. By Mr. Matthew Biggs. 

 (To the Editor of the Annals of Philosophy .) 



SIR, ()3, Great RusselUstreet, Nov . S, 18^3. 



Having had occasion lately to turn my attention to the nature 

 of gaseous bodies generally, and particularly to their conduct 

 under varying temperature, I referred to the works of Dr. Henry 

 and Mr. Brande for information. We are told by both these 

 gentlemen that all aeriform bodies possess the same mechanical 

 properties ; that the rate of expansion and contraction under 

 increased or diminished temperature is common to all, and that, 

 according to the experiments of M. Gay-Lussac, which they 

 consider as the most correct, the expansion on increase of tem- 

 perature is :f i-g- of the volume for every degree of Fahrenheit's 

 scale, between 32° and 212°. I then proceeded to the rules 

 which are given for reducing any volume at any temperature to 

 such other temperature as may be required, and I found them 

 so defective that 1 doubt not I shall prove to you, that all calcu- 

 lations made from the data there laid down, must have produced 

 erroneous results. 



After having informed us as above that the increase is -^^ of 

 the volume for every degree of the thermometer, they proceed to 

 say, that in order to reduce any given volume at any known 

 temperature to any other that may be required, we must divide 

 the whole volume by 480, multiply the quotient by the number 

 of degrees between that at which the gas is, and that to which 

 it is to be reduced, and then add this product to the volume, if 

 the reduction be made from a lower to a higher temperature ; 

 subtract it if from a higher to a lower ; the number now found will 

 be the volume at the temperature required. Thus I have 100 

 cubic inches of gas at 32°; and my object is to ascertain what 

 space they would occupy at 60°, 



100 -r- 480 = -208 ; -208 x 28 = 5-824; 5-824+ 100= 105- 824- 

 they will have become 105*824 C. I. by an elevation of 28° ; but 

 suppose the reverse to be the state of the inquiry, having 

 105-824 C. I. at 60°, I wish to know their volume at 32°, 

 105-824-480= -220; -220 x 28 = 6-16 ; 105-824-6-16=99-664. 



This cannot be correct, because we know that although 

 bodies expand by the application of heat, they regain their 

 - former dimensions when reduced to their former temperature. 

 If I find that 100 C. L of any gaseous body become 105-824 by 

 an addition of 28° to their temperature, I know that by abstract- 

 ing the 28° they are again reduced to 100 ; but not lower, as this 

 mode of calculation would show. 



