Mr. Northcote on the Constitution of Thermophyllite. 263 



allyle. Crystals of bromide of ammonium were formed, but by 

 no means in so great quantity as when the terbromide was 

 employed, although 1 heated the tube containing the reacting 

 bodies' for a much longer time. On opening the tube and add- 

 ing water to the alcoholic solution, a heavy oil separated, nearly 

 equal in quantity to that originally employed. This oil proved 

 to be quite insoluble in hydrochloric acid. Its boiling-point I 

 found to be greatly inferior to that of the brominated bromide of 

 propylene, the greater part of it passing over between 107° 

 and 120^ C. Nevertheless analysis showed that it did not 

 differ much in composition from that body. 



The following numbers were obtained on analysis : — 



I. 0-3066 grm. of oil gave 0-1579 grm. carbonic acid and 

 0-0481 water. 



II. 0-4081 grm. of oil gave 0-8052 grm. bromide of silver. 

 These numbers agree tolerably with the empirical formula 



(312 JJ9 Br5, or -T^s Ss ^^> as the following Table shows :— 



Experiment. 

 11. 



Carbon . 

 Hydrogen 

 Bromine . . . 83-17 ... 83-94 



100-00 



XXVIII. On the Constitution of Thermophyllite. % Augustus 

 Beauchamp Northcote, F.C.S., Demonstrator to the Pro- 

 fessor of Chemistry at Oxford*. 

 AMONG several new and rare minerals recently given by M. 

 Nordenskiold to Dr. Percy, was a specimen of the sub- 

 stance which M. Nordenskiold has named Thermophyllite. No 

 record of the composition of this mineral being in existence, I 

 am indebted to Dr. Percy's kindness in furnishing me with the 

 requisite specimen for what I believe to be the first statement of 

 its composition. 



The mineral came from Hoponsuo ; it is disseminated in ag- 

 gregated masses of a brownish-grey colour and seuii-transluccnt, 

 through a rock which consists essentially of the same constituents 

 as itself. In some parts, where disposed in thin laminre (the 

 faces of the only perfect cleavage which it presents), it possesses 

 a decidedly micaceous appearance. Notwithstanding this, how- 

 ever, attempts to ascertain its crystalline form have failed, and 



* Communicated by the Autlior. 



