Prof. Guthrie on the Conduction of Heat by Liquids. 283 



iodide was subjected to the action of two molecules of the hy- 

 drated oxide of silver. 



In distilling the product of the foregoing reaction, I observed 

 that a small quantity of hydrochloric acid passed over after the 

 water. The production of this acid I could not account for ex- 

 cept by supposing that the chloriodide decomposed the water 

 which was present, as well as the oxide of silver (of which there 

 was only one molecule) , and that both reactions gave the same 

 product. The following equation will make this intelligible : — 



C 2 H 4 " { f l + 2^f } O) = C 2 H<" { | g + AgCl + Agl, 



C 2 H 4 " { P+^ji } O) = C 2 H 4 " {^ + HC1 + HI. 



In order to determine this point I exposed one part by weight 

 of the chloriodide and five parts by weight of distilled water, in 

 a sealed tube, to a temperature ranging between 160° and 

 220° C. till all the chloriodide had disappeared. I then opened 

 the tube and neutralized the product (which contained hydro- 

 chloric and hydriodic acids coloured with a little free iodine) with 

 dilute potash. On subjecting this to distillation I obtained a 

 syrupy liquid as before, which passed over between 180° and 

 220° C., and had all the characters of glycol. The quantity ob- 

 tained was small, a portion of it having been converted into 

 iodide of ethylene by the hydriodic acid formed in the reaction. 



XXXII. Note of Experiments upon the Conduction of Heat by Li- 

 quids. By Frederick Guthrie, Ph.D.,F.R.S.E., Professor 

 of Physics and Chemistry, Royal College, Mauritius*. 



IN the numerous and excellent studies which have been made 

 of conductivity, the attention of physicists has been hitherto 

 mainly directed to solids. Yet it must be admitted that, in 

 regard to their conductive powers, as well as in their other ther- 

 mal relations, gases and liquids present both theoretically and 

 practically many points of preeminent interest. 



No solid body can be said to be without structure. Definite 

 chemical compounds in the solid form, notoriously and perhaps 

 without exception possess crystalline form. Even such bodies, 

 simple or complex, as appear without crystalline form (that is, 

 which are amorphous) are nevertheless not without structure. 

 They show, on fracture, surfaces of least resistance ; and though 

 these surfaces may be so irregular as to defy mathematical for- 

 mulization, they yet prove that the cohesion is not uniform — that 

 * Communicated by the Author. 



