Chemistry and Physics. 305 
which concentrates toward one end of the fractionations; (2) the 
crimson line is not due to alumina, but is due to the presence of 
an accompanying earth concentrating toward the other end of 
the fractionations; (3) the crimson line belongs to alumina, but 
its full development requires certain precautions to be observed 
in the time and intensity of ignition, degree of exhaustion, or its 
absolute freedom from alkaline and other bodies carried down by 
precipitated alumina and difficult to remove by washing; experi- 
ence not having yet shown which of these precautions are essen- 
tial to the full development of the crimson line and which are 
unessential; and (4) the earth alumina is a compound molecule, 
one of its constituent molecules giving the crimson line. Accord- 
ing to this hypothesis alumina would be analogous to yttria.”— 
Nature, xxxv, 310, Jan., 1887. G. F. B. 
3. On Phosphorus pentafluoride.—Motssan has continued his 
researches on phosphorus pentafluoride. He finds that when this 
gas is submitted to the action of the electric spark, employing 
Berthelot’s arrangement of apparatus, great care being taken to 
have it absolutely dry, there is no decomposition with sparks 
which in air do not exceed four centimeters in length; thus con- 
firming the observation of Thorpe. But when sparks were em- 
ployed which were 15 to 20 centimeters in air, then the walls of 
the glass vessel were attacked and became dim and the mercury 
lost its brilliancy. After an hour, the experiment was concluded 
and the apparatus allowed to cool; the voiume had diminished. 
On adding water, silica was produced, showing the presence of 
silicium fluoride. The remaining gas, in some cases 15 per cent 
of the whole, is not absorbed by water and gives the reactions of 
phosphorus terfluoride. It appears therefore, that under the in- 
fluence of powerful electric discharges, phosphorus pentafluoride 
is decomposed into the terfluoride and free fluorine, the latter 
attacking both the mercury and the glass. Heated in a recurved 
bell jar to a red heat in presence of an excess of phosphorus 
_ vapor, the pentafluoride yields no terfluoride. It is not decom- 
posed by sulphur at 440° nor by iodine at 500°; but preserved 
in glass vessels, it attacks the glass if a trace of moisture be pres- 
ent, forming silicium fluoride and phosphoryl] fluoride. The anal- 
ysis of the pentafluoride was effected by the author in two ways: 
(1) a measured volume of the gas was absorbed by an alkaline 
solution, the filtered solution precipitated by molybdic acid, the 
precipitate filtered off, washed, dissolved, and the phosphoric acid 
precipitated as ammonium-magnesium phosphate. (2) the alka- 
line solution, after absorbing the gas, is decanted into a capsule, 
and, with the wash waters, is evaporated to dryness on the water 
bath with the addition of a little pure silica. The saline residue 
1s treated with sulphuric acid and evaporated till white fumes of 
the acid appear. After cooling, the whole is diluted, neutralized 
with ammonia and in the filtrate, the phosphoric acid is deter- 
mined as ammonium-magnesium phosphate.—C. &., ciii, 1257, 
Dec., 1886. Gu eB 
