1824.] Mr. Biggs on the Expansion of Gases. 133 



clean blade of the knife ; and when six different portions of this 

 substance were projected on a poker, heated to a dull red, each 

 gave a distinctly visible white smoke, and decided alliaceous 

 odour; although each portion could only have contained about 

 l-78th of a grain of the metal. 



I may add, that if a clean knife be held in the fumes, a portion 

 of a white powder will be condensed on the blade, even from the 

 most minute portions of arsenic which I have thus volatilized. 

 I am, dear Sir, very truly yours, 



Thomas Stewart Traill. 



Article XVI. 



On the Expansion of Gases. By Mr. Matthew Bi°-o- s . 

 (To the Editor of the Annals of Philosophy.) 



DEAR SIR, j an . | 5 , 1824. 



A gentleman signing himself X. has, in the Philosophical 

 Magazine for December, given some algebraic formula? for cal- 

 culating the expansion of gaseous fluids under increasing tem- 

 perature, which, he says, prove the accuracy of certain rules for 

 the same purpose, which I referred to in a paper you were o- od 

 enough to insert for me in the Annals of Philosophy for Decem- 

 ber, and the inaccuracy of some which I proposed to substitute 

 for them. It is so evident that he is wrong, that I had not 

 intended to take any notice of what he says, but having been 

 told that some answer ought to be made, I may just observe, that 

 any person who will take the trouble of working the same sum 

 by his method, at one operation and at several, may satisfy him- 

 self that no dependance whatever is to be placed upon it ; thus, 

 let 100 volumes of gas at 32° be raised to 212°, 



100(480 + 180) 10 „ , 



— So =137-5, 



This is correct according to Gay-Lussac and others. 



Now let 100 volumes of gas at 32° be raised to 212° by four 

 several additions of 45°, 



,00(480 + 45 l = 109-375, 



480 

 109-375(480 + 45) 



4s0 

 119-6289(480 + 45) 



= 119-6289, 



= 130-8441, 

 = 143-1107, 



480 

 1.10 8441 (480 4 45) 



upwards of 5| volumes more than the truth ; and if the elevation 



