ORGAJS'IC COMTOIJNDS CONTAINING BORON. 
175 
in water, alcohol, and ether. It possesses an agreeable ethereal odour, and a most 
intensely sweet taste. Exposed to the air, it evaporates at ordinary temperatures, 
undergoing at the same time partial decomposition, and invariably leaving a slight resi- 
due of boracic acid. It may be sublimed without change at about 40° C. in a current 
of dry carbonic acid, and it then condenses in magnificent crystalline plates resembling 
naphthaline. It fuses at a gentle heat, and at a higher temperature boils with partial 
decomposition. Its vapour tastes intensely sweet. 
Boric dioxyethide might be regarded as the anhydride of a bibasic acid ; the diethylate 
of boric dioxyethide would then be the ether of this acid, whilst the volatile crystalline 
body just described would be the hydrated acid itself. The latter does in fact redden 
litmus paper, but in other respects its acid qualities are very obscure, and I have not 
been able to form definite salts with it. It therefore scarcely possesses a valid claim 
to a place amongst the acids. 
Considering boric ethide to be formed by the substitution of the ethyl in zincethyl for 
the oxygen in boracic acid, Mr. Duppa and myself expressed the reaction as follows : — 
fC,H,0, fC,H, 
IB C.HjO, + 8ZnJ^ » = 2B + 6 
y 
Boracic ether. 
Zincethyl. 
T 
Boric ethide. 
“V"" 
Ethylate of zinc. 
Another but less probable view of the change presents itself in the supposition that 
the three atoms of ethyl in boric ethide were already present in the boracic ether, the 
action of the zincethyl being simply to remove the whole of the oxygen from the boracic 
ether. KjEKULEf has in fact adopted this latter view of the reaction. 
So long as the organic radical of the zinc compound and that of the boracic ether are 
identical, it is impossible to prove whether the three individual atoms of ethyl in boric 
ethide were originally present in the boracic ether, or have been derived from the zinc- 
ethyl. Indicating by an asterisk the atoms of ethyl which finally become part of the 
boric ethide, it is impossible to prove conclusively whether the reaction takes place 
according to the first or second of the following equations : — 
rQ H5 O2 
(1) 2B^C,H5 0, + 3Zn2|; 
J: 
C4H5O 
C.H * O. 
C4H5* 
C4H5* 
)C4H5* 
(2) + 
rc4H/ 
= 2B<^C4H5* -f 6 
Zn 
Oo 
Although we cannot thus label, as it were, the atoms taking part in the reaction, we 
can unerringly trace the movements of the alcohol radicals, if we secure their identifica- 
tion by varying their composition in the two compounds used in the process. The 
t Lehrbucli der org. Chemie, p. 489. 
