A Comprehensive Treatise on Inorganic and Theoretical Chemistry

212 INORGANIC AND THEORETICAL CHEMISTRY
this compound is stable only below 1364°, decomposing at that temp, into crystals
of platinum, and a fused mass containing about 80 per cent, of that metal. M. Podkopajeff
gave 1266° for the m.p. of this compound. According to F. Doerinckel,
the break in the curve at 846° represents the interaction of platinum stannide and
the fused alloy to form what is probably platinum hemitristannide, Pt2Sn8.
H. St. C. Deville and H. Debray obtained this same compound by slowly cooling an
alloy of platinum with six times its "weight of tin, and then treating the product
with hydrochloric acid ; and P. Schutzenberger, by the action of hydrogen on
Pt2Sn3O2(OH)2, or on Pt2(SnO)2SnO2. The greyish-white powder contains cubic
or rhombohedral crystals. F. Doerinckel said that it exists in two allotropic
forms, one stable below 738°, and the other stable between 738° and 846°.
P. Schutzenberger observed that when oxidized in air, it forms Pt2(SnO)3 ; and
when heated in chlorine, stannous chloride distils off. F. Doerinckel observed that
the f.p. curve at 538° has a break corresponding with a reaction between the hemitristannide
and the fused alloy, to form what is probably platinum tritaoctostannide,
Pt3Sn8. The compound forms long needles, and it decomposes when
melted. The diagram was discussed by W. Guertler, and K. Bornemann.
Three other compounds have been reported although the f.p. curve does
not indicate their existence. M. Levy and Xi. Bourgeois observed that when
PtO2.4SnO2 is reduced by hydrogen at a red-heat, and the product is treated with
hydrochloric acid, platinum tetritatristannide, Pt4Sn3, is formed in lustrous
plates with a black reflex. J. W. Mallet reported platinum distannide, PtSn2,
or Pt4Sn7, to be formed as a hard brittle mass which is easily pulverized. The
sp. gr. is 10-72. Mercury amalgamated with a little sodium attacks this product.
If an alloy with 2 per cent, of platinum is treated with very dil. hydrochloric
acid, lustrous plates appear on the surface, and these are easily detached by a glass
rod. A more cone, acid, or the application of heat, destroys the crystals. The
analysis corresponds with platinum tetrastannide, PtSn4. N. Podkopajeff also
prepared this compound. With sodium chloride and chlorine at a red-heat, there
is formed sodium chloroplatinate, and volatile stannous chloride ; and at a redheat,
hydrogen chloride removes all the tin as stannous chloride. Gr. Tammann
studied the subject.
A. F. Gehlen said that the alloy is tin-white, brittle, and with a laminated
texture. F. Doerinckel observed that alloys with up to 20 per cent, of platinum
arc coarsely crystalline, and tin-white ; alloys with 30 per cent, of platinum have
a finer structure and are pale grey ; alloys with between 40 and 55 per cent, of
platinum have a fine crystalline structure, and are somewhat darker in colour ;
alloys with about 62-5 per cent, of platinum have a more lustrous fracture with
with the same texture and colour ; and with more platinum, the lustre decreases,
and the colour becomes darker. According to F. M. Jager and J. A. Bottema, the
crystals of the monostannide, PtSn, are hexagonal with the same type of structure
as NiAs, and the lattice has two mols. of PtSn per cell. The lattice parameters are
a=4-103 A., and c==5-428 A. The calculated sp. gr. is 13-9. W. Lewis gave for
the sp. gr. of the tin-platinum alloys :
Tin . . 50-4 66-3 8OO 88-9 92-3 96 1OO per cent.
Sp. gr. . 10-827 8-972 7-794 7-705 7-613 7-471 7-180
F. Doerinckel found that the alloys with up to 30 per cent, of platinum are scarcely
harder than their components, but beyond this point, the hardness rapidly increases,
and attains a maximum with 80 per cent, of platinum. G. Wertheim found that
an alloy with the proportions Sn : Pt=50*l, has a sp. gr. 7*578 ; an elasticity coeff.
of 5309 kgrms. per sq. mm., a tensile strength of 4-75 kgrms. per sq. mm. ; and
the velocity of sound 7-89O (air unity). F. M. Jager and J. A. Bottema gave 1281°
to 1330° for the limits of the m.p. ; this estimate is based on F. Doerinekel's
1281° ; and N. Podkopajeff's, 1330°. The heat capacity, Q cals., between B and 0° is :
0 . . 189-74° 221-88° 418-67° 644-90° 718-30° 80206° 1044-80°
Q . . 7-3728 8-6419 16-5282 25-8917 28-9991 32-5927 43-4606