418 Prof. A De la Rive's Researches on the Magnetic 



C 5 H 13 N. Unfortunately isoamylamine readily absorbs carbonic 

 acid from the air and forms a solid carbonate — which slightly 

 dulls its transparency, so that I had some difficulty in determi- 

 ning its magneto-rotatory power very exactly. This was not the 

 case with the amylamine ; the first three series of observation s 

 gave the following results : — 



Amylamine. "Water. Ratio. 



10° 56 10 40 1-025 



9 35 9 20 1-026 



9 20 9 5 ]-027 



Mean . . 1-026 



Three other series, less concordant, gave: — 



9 44 9 33 1-019 



9 40 9 30 1-017 



9 40 9 15 1-042 



Mean . . 1-026 



Thus 1*026 may be regarded as expressing very accurately 

 the magneto-rotatory power of amylamine. 



As to the isoamylamine, I think its magneto-rotatory power 

 may, without great error, be set down as 1*017; but the diffi- 

 culty of observation renders this number rather uncertain. At 

 all events I am able to conclude from my experiments that this 

 substance has a lower magneto-rotatory power than amylamine. 

 Its boiling-point is 78°*5, while that of amylamine is 95°. The 

 density of isoamylamine (0*815 at 0°) is less than that of amyl- 

 amine (0*826 at 0°). 



To sum up, isomeric bodies, notwithstanding the identity of 

 their elementary composition, have not the same magneto-rota- 

 tory power ; between some the difference is great, between others 

 little. This difference does not appear to have any connexion 

 with their different densities, but rather with the difference of 

 their boiling-points ; for, in each group of isomers, that which 

 has the highest boiling-point has the greatest magneto-rotatory 

 power. 



Conclusions. 



From the experiments I have above related, I think the fol- 

 lowing conclusions may be drawn : — 



1. The magneto-rotatory power of bodies does not appear to 

 be connected with their other physical properties. Although in 

 general the densest and most refracting substances are those 

 which possess this power in the highest degree, there are some 

 notable exceptions ; and sulphuric acid is one of the most re- 



