of Edinburgh, Session 1879-80. 
7 0 O 
oo 
12. Further Note on Graphitoid Boron and the Production 
of Nitride of Boron. By K. Sydney Marsden, D.Sc. 
F.R.S.E., &c. 
This note is a continuation of the paper on the “ Preparation and 
Properties of Pure Graphitoid and Adamantine Boron,” by Dr R. 
M. Morrison and myself, published in the Transactions of this 
Society, vol. xxviii. p. 689, and its object is to correct a mistake 
which we have made in giving the properties of this substance. 
We say — 
1st, It is not oxidised by air at a white heat, even superficially. 
2d, It does not alloy with platinum at a white heat. 
I have again prepared a quantity of this substance and examined 
its properties under Professor Wohler, and I find that the above 
statements are wrong. A very fine film of oxide does form on the 
surface of this substance when heated on platinum foil over the 
blowpipe, and this film, although very thin and difficult to observe, 
is sufficient to prevent all further action of the air, and also to pre- 
vent its combining with the platinum. This misled us when we 
previously examined it. If, however, a quantity of it be placed on 
a piece of platinum foil, and the foil folded over it and pressed down 
so as to exclude all the air, then on heating it intensely before the 
blow-pipe the boron at once combines with the platinum and per- 
forates it. 
In that paper also we mention a slatish-grey powder which we 
found surrounding the metal on opening the porcelain crucible. 
I have made an examination of this powder, and find, it consists 
of a mixture of nitride of boron and amorphous boron, chiefly, 
however, of nitride of boron, which is formed by the superfluous 
boron uniting with the nitrogen of the air. If the experiment is 
prolonged over many hours the whole of the amorphous boron is 
converted into this nitride, and the powder is then white. The way 
in which I tested for the nitride was as follows : — A portion of the 
powder was heated in a hard glass-tube, with solid caustic potash to 
convert the nitrogen into ammonia, when the following reaction 
takes place — 
2BN + 6KH0 = 2NH 3 + B 2 0 3 + 3K 2 G . 
