An important paper is contributed by M. Moissan to the current number
of the _Comptes Rendus_, describing two interesting new compounds
containing boron, phosphorus, and iodine. A few months ago M. Moissan
succeeded in preparing the iodide of boron, a beautiful substance of
the composition BI_{3}, crystallizing from solution in carbon bisulphide
in pearly tables, which melt at 43° to a liquid which boils
undecomposed at 210°. When this substance is brought in contact with
fused phosphorus an intense action occurs, the whole mass inflames
with evolution of violet vapor of iodine. Red phosphorus also reacts
with incandescence when heated in the vapor of boron iodide. The
reaction may, however, be moderated by employing solutions of
phosphorus and boron iodide in dry carbon bisulphide. The two
solutions are mixed in a tube closed at one end, a little phosphorus
being in excess, and the tube is then sealed. No external application
of heat is necessary. At first the liquid is quite clear, but in a few
minutes a brown solid substance commences to separate, and in three
hours the reaction is complete. The substance is freed from carbon
bisulphide in a current of carbon dioxide, the last traces being
removed by means of the Sprengel pump. The compound thus obtained is a
deep red amorphous powder, readily capable of volatilization. It melts
between 190° and 200°. When heated _in vacuo_ it commences to
volatilize about 170°, and the vapor condenses in the cooler portion
of the tube in beautiful red crystals. Analyses of these crystals
agree perfectly with the formula BPI_{2}. Boron phospho-di-iodide is a
very hygroscopic substance, moisture rapidly decomposing it. In
contact with a large excess of water, yellow phosphorus is deposited,
and hydriodic, boric, and phosphorus acids formed in the solution. A
small quantity of phosphureted hydrogen also escapes. If a small
quantity of water is used, a larger deposit of yellow phosphorus is
formed, together with a considerable quantity of phosphonium iodide.
Strong nitric acid oxidizes boron phospho-di-iodide with
incandescence. Dilute nitric acid oxidizes it to phosphoric and boric
acids. It burns spontaneously in chlorine, forming boron chloride,
chloride of iodine, and pentachloride of phosphorus. When slightly
warmed in oxygen it inflames, the combustion being rendered very
beautiful by the fumes of boric and phosphoric anhydrides and the
violet vapors of iodine. Heated in contact with sulphureted hydrogen,
it forms sulphides of boron and phosphorus and hydriodic acid, without
liberation of iodine. Metallic magnesium when slightly warmed reacts
with it with incandescence. When thrown into vapor of mercury, boron
phospho-di-iodide instantly takes fire.
The second phospho-iodide of boron obtained by M. Moissan is
represented by the formula BPI. It is formed when sodium or magnesium
in a fine state of division is allowed to act upon a solution of the
di-iodide just described in carbon bisulphide; or when boron
phospho-di-iodide is heated to 160° in a current of hydrogen. It is
obtained in the form of a bright red powder, somewhat hygroscopic. It
volatilizes _in vacuo_ without fusion at a temperature about 210°, and
the vapor condenses in the cooler portion of the tube in beautiful
orange colored crystals. When heated to low redness it decomposes into
free iodine and phosphide of boron, BP. Nitric acid reacts
energetically with it, but without incandescence, and a certain amount
of iodine is liberated. Sulphuric acid decomposes it upon warming,
without formation of sulphurous and boric acids and free iodine. By
the continued action of dry hydrogen upon the heated compound the
iodine and a portion of the phosphorus are removed, and a new phosphide
of boron, of the composition B_{5}P_{3}, is obtained.--_Nature_.
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