M. Wurtz on Propyle-glycol. SJ93 



' ben/ In a note referring to these crystals, Dr. Percy observes 

 that, apart from the testimony of the tinder, he is convinced by 

 the appearance of the specimen that it must have come tromthe 

 bear of a blast furnace. Other instances of the occurrence ot 

 garnet in furnace products were observed by v. Kobell and &tuder 

 (Gurlt Uebersicht der pyrogenneten kilnstlichen Minerahen, p. bl). 

 No attempt was made to analyse the crystals, or to determine 

 their specific gravity, the whole quantity being very small, and 

 apparently mixed up with much foreign matter. 



Silicium. 

 Among some crystals of silicium given to me by T. H. Henry, 

 Esq by whom they were prepared, are several twins, the indi- 

 viduals of which are octahedrons, having a face of the octahe- 

 dron for the twin face, and, as frequently happens, excessively 

 thin in the direction of the twin axis. One of these, about fi 

 millim. long, 0-6 millim. wide, and 0-08 millim. thick in the 

 direction of the twin axis, enabled me to obtain an approximate 

 value of its index of refraction, by observing the polarizing angle 

 of lisht reflected from its two largest faces. By a mean ot six- 

 teen observations, this angle appeared to be 75° 1'. The result- 

 ing index of refraction is 3-736. 



XXXII. Chemical Notices from Foreign Journals. 



By E. Atkinson, Ph.D. 



[Continued from p, 219.] 



IN his first paper on glycol*, Wurtz indicated the existence of 

 the higher homologues of that body; that as glycol corresponds 

 to alcohol, so propyle-glycol corresponds to propylic alcohol, and 

 amylc-glycol to amylic alcohol; and, in general, that to each 

 monoatomic alcohol there corresponds a biatomic glycol. He 

 has now described more fully the propylef and amyle J glycols. 

 Propvle-glycol is obtained by synthesis from propylene gas. 

 According to Wurtz, the method of obtaining this gas described 

 by DusartS is not very productive. The best method is that ot 

 Kevnolds, which consists in passing the vapour of aniylic alcohol 

 throu-h a porcelain tube heated to dull redness, and collecting 

 the gas, after passing it through caustic potash solutiou, over 

 watS. The crude propylene gas is then treated with bromine, 

 by which it is readily absorbed: the liquid product ot the action 

 consists of the bromides of ethylene, propylene, together with 

 small quantities of bromide of butylene. These are separated 



* Phil. Mae. Supplement, January, 1857- ^ ^, , , , , . „. . 

 t Omples RenL, vol. xlv. p. 30G. J Ib.d. vol. xlvi. p. 244. 



§ Phil. Mag. vol. xi. p. 372. 



