OE&ANIC COMPOUNDS CONTAININO BOEON. 
181 
condensation which is usually considered to be abnormal, and which, where it occurs, is 
generally explained by the assumption of a decomposition of the body at the moment of 
conversion into vapour. The proof of the disunion or integrity of the vaporous mole- 
cule of ammonia-boric methide would be interesting in connexion with these so-called 
anomalous vapour-densities, but I have to regret my inability to offer any sufficiently 
decisive solution of this problem. The difficulty to be overcome is the finding of a 
reagent that will not decompose ammonia-boric methide at elevated temperatures, but 
which would absorb ammonia only, out of a mixture of this gas with boric methide, at a 
temperature above the boiling-point of ammonia-boric methide. Chloride of calcium 
does not decompose ammonia-boric methide ; but although it readily absorbs ammonia 
at ordinary temperatures, yet it allows the whole of it to escape again at 110° C. Chlo- 
ride of zinc decomposes ammonia-boric methide before the latter volatilizes. The same 
effect is produced by all the strong acids, which are therefore also inadmissible, whilst 
dry boracic acid does not absorb ammonia even at ordinary temperatures. The sub- 
stance which appeared to be best adapted for this reaction was dry and recently fused 
chloride of copper. This salt does not decompose ammonia-boric methide below the 
boiling-point of the latter, whilst it readily absorbs ammonia, and retains it at a tempe- 
rature of 160° C. I will now describe the mode in which an experiment with this sub- 
stance was conducted, and the results which were obtained. A quantity of ammonia- 
boric methide was introduced into a graduated tube filled with mercury, and inverted in 
a vessel containing the same metal. The whole was now immersed in an oil-bath, and 
heat applied until the boron compound was converted into vapour, the volume of which, 
at a known temperature and pressure, was then observed. After the apparatus had been 
allowed to cool, a fragment of chloride of copper was passed up into the tube, and heat 
again applied. The boron compound soon melted and enveloped the fragment of chlo- 
ride of copper: as the temperature approached the boiling-point of am m onia-boric 
methide, the latter slowly boiled off from the chloride of copper, and the vapour then 
occupied the same volume as that read off before the introduction of the chloride of 
copper. The mercm-y in the tube remained steady for two or three minutes ; it then 
gradually ascended, and the contraction of the vapour-volume continued until it was 
reduced to exactly one-half, as indicated by the following numbers : — 
Corrected volume of vapour before treatment 
with chloride of copper 35 ‘6 7 cub. centims. 
Ditto after treatment with chloride of copper 17‘85 cub. centims. 
By treatment with chloride of copper, 100 volumes of vapour were therefore reduced 
to 50‘04 vols., the residue consisting of pure boric methide gas. It is obvious that this 
absorption may be due either to decomposition of the vapour of ammonia-boric methide 
hy chloride of cojyjper at an elevated temperature, or to the decomposition hy heat of 
the boric compound into equal volumes of boric methide and ammonia, the latter being 
then absorbed by the chloride of copper. Unfortunately, the result of the experiment 
