126 [May 22, 



tion of a superficial coating of boracic acid, which envelopes the par- 

 ticles of carbon and prevents their combustion. Suddenly mixed 

 with atmospheric air or oxygen, boric methide explodes with great 

 violence. In contact with atmospheric air, both boric methide and 

 the vapour of boric ethide exhibit two distinct kinds of spontaneous 

 combustion. Thus when these bodies issue very slowly from a glass 

 tube into the air, they burn with a lambent blue flame invisible in 

 daylight, and the temperature of which is so low that a finger may 

 be held in it for some time without much inconvenience. Under 

 these circumstances partial oxidation only takes place, and it is to 

 the products thus formed that the peculiar pungent odour of boric 

 ethide and boric methide is due. When, on the other hand, these 

 bodies issue into the air more rapidly, the lambent blue and nearly 

 cold flame changes to the green and hot flame above mentioned. I 

 have not examined the spectra of the two differently-coloured flames 

 from the same compound ; but they doubtless present a widely different 

 appearance, thus affording another instance of the dependence of the 

 spectra of bodies upon temperature, a phenomenon to which I re- 

 cently called attention in the case of lithium*. 



Boric methide is not acted upon by binoxide of nitrogen or by 

 iodine. Solution of bichromate of potash scarcely affects it, but the 

 addition of concentrated sulphuric acid at once determines the re- 

 duction of the chromic acid. When boric methide is allowed to 

 bubble through water into chlorine, each bubble burns explosively 

 with a bright flash of light and the separation of carbon : it has no 

 tendency to unite with acids. Concentrated sulphuric acid has no 

 action upon it ; when mixed with hydriodic acid gas, it suffers no 

 change ; but, on the other hand, it is freely absorbed by solutions of 

 the fixed alkalies and by ammonia. If a very rapid current of the 

 gas mixed with half its volume of marsh-gas be passed through a 

 stratum of strong solution of ammonia only half an inch deep, not a 

 trace of boric methide escapes absorption. 



Ammonia Boric Methide. 



When dry ammoniacal gas is mixed with an equal volume of dry 

 boric methide, both gases instantly disappear, with the evolution of a 

 considerable amount of heat and the production of a white, volatile, 

 * Phil. Mag. Dec. 1861, p. 472. 



